G2Cdb::Gene report

Gene id
G00001435
Gene symbol
FYN (HGNC)
Species
Homo sapiens
Description
FYN oncogene related to SRC, FGR, YES
Orthologue
G00000186 (Mus musculus)

Databases (8)

Curated Gene
OTTHUMG00000016305 (Vega human gene)
Gene
ENSG00000010810 (Ensembl human gene)
2534 (Entrez Gene)
241 (G2Cdb plasticity & disease)
FYN (GeneCards)
Literature
137025 (OMIM)
Marker Symbol
HGNC:4037 (HGNC)
Protein Sequence
P06241 (UniProt)

Synonyms (3)

  • MGC45350
  • SLK
  • SYN

Literature (355)

Pubmed - other

  • The role of Fyn kinase in the release from metaphase in mammalian oocytes.

    Levi M and Shalgi R

    Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel-Aviv University, Ramat-Aviv, Tel-Aviv, Israel.

    Meiosis in mammalian oocytes starts during embryonic life and arrests for the first time before birth, at prophase of the first meiotic division. The second meiotic arrest occurs after spindle formation at metaphase of the second meiotic division (MII) in selected oocytes designated for ovulation. The fertilizing spermatozoon induces the release from MII arrest only after the oocyte's spindle assembly checkpoint (SAC) was deactivated. Src family kinases (SFKs) are nine non-receptor protein tyrosine kinases that regulate many key cellular functions. Fyn is an SFK expressed in many cell types, including oocytes. Recent studies, including ours, imply a role for Fyn in exit from meiotic and mitotic metaphases. Other studies demonstrate that SFKs, particularly Fyn, are required for regulation of microtubules polymerization and spindle stabilization. Altogether, Fyn is suggested to play an essential role in signaling events that implicate SAC pathway and hence in regulating the exit from metaphase in oocytes and zygote.

    Molecular and cellular endocrinology 2010;314;2;228-33

  • Alternative splicing modulates autoinhibition and SH3 accessibility in the Src kinase Fyn.

    Brignatz C, Paronetto MP, Opi S, M, Audebert S, Feuillet V, Bismuth G, Roche S, Arold ST, Sette C and Collette Y

    UMR891 INSERM, Centre de Recherche sur le Cancer de Marseille, 27 Boulevard Leï Roure, 13009 Marseille, France.

    Src family kinases are central regulators of a large number of signaling pathways. To adapt to the idiosyncrasies of different cell types, these kinases may need a fine-tuning of their intrinsic molecular control mechanisms. Here, we describe on a molecular level how the Fyn kinase uses alternative splicing to adapt to different cellular environments. Using structural analysis, site-directed mutagenesis, and functional analysis, we show how the inclusion of either exon 7A or 7B affects the autoinhibition of Fyn and how this changes the SH3-dependent interaction and tyrosine phosphorylation of Sam68, with functional consequences for the Sam68-regulated survival of epithelial cells. Our results illustrate a novel mechanism of evolution that may contribute to the complexity of Src kinase regulation.

    Funded by: Worldwide Cancer Research: 08-0822

    Molecular and cellular biology 2009;29;24;6438-48

  • The G protein betagamma subunit mediates reannealing of adherens junctions to reverse endothelial permeability increase by thrombin.

    Knezevic N, Tauseef M, Thennes T and Mehta D

    Center for Lung and Vascular Biology, Department of Pharmacology, University of Illinois, Chicago, IL 60612, USA.

    The inflammatory mediator thrombin proteolytically activates protease-activated receptor (PAR1) eliciting a transient, but reversible increase in vascular permeability. PAR1-induced dissociation of Galpha subunit from heterotrimeric Gq and G12/G13 proteins is known to signal the increase in endothelial permeability. However, the role of released Gbetagamma is unknown. We now show that impairment of Gbetagamma function does not affect the permeability increase induced by PAR1, but prevents reannealing of adherens junctions (AJ), thereby persistently elevating endothelial permeability. We observed that in the naive endothelium Gbeta1, the predominant Gbeta isoform is sequestered by receptor for activated C kinase 1 (RACK1). Thrombin induced dissociation of Gbeta1 from RACK1, resulting in Gbeta1 interaction with Fyn and focal adhesion kinase (FAK) required for FAK activation. RACK1 depletion triggered Gbeta1 activation of FAK and endothelial barrier recovery, whereas Fyn knockdown interrupted with Gbeta1-induced barrier recovery indicating RACK1 negatively regulates Gbeta1-Fyn signaling. Activated FAK associated with AJ and stimulated AJ reassembly in a Fyn-dependent manner. Fyn deletion prevented FAK activation and augmented lung vascular permeability increase induced by PAR1 agonist. Rescuing FAK activation in fyn(-/-) mice attenuated the rise in lung vascular permeability. Our results demonstrate that Gbeta1-mediated Fyn activation integrates FAK with AJ, preventing persistent endothelial barrier leakiness.

    Funded by: NHLBI NIH HHS: HL71794, HL84153, R01 HL071794, R01 HL084153

    The Journal of experimental medicine 2009;206;12;2761-77

  • Synapse formation regulated by protein tyrosine phosphatase receptor T through interaction with cell adhesion molecules and Fyn.

    Lim SH, Kwon SK, Lee MK, Moon J, Jeong DG, Park E, Kim SJ, Park BC, Lee SC, Ryu SE, Yu DY, Chung BH, Kim E, Myung PK and Lee JR

    Brain Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Republic of Korea.

    The receptor-type protein tyrosine phosphatases (RPTPs) have been linked to signal transduction, cell adhesion, and neurite extension. PTPRT/RPTPrho is exclusively expressed in the central nervous system and regulates synapse formation by interacting with cell adhesion molecules and Fyn protein tyrosine kinase. Overexpression of PTPRT in cultured neurons increased the number of excitatory and inhibitory synapses by recruiting neuroligins that interact with PTPRT through their ecto-domains. In contrast, knockdown of PTPRT inhibited synapse formation and withered dendrites. Incubation of cultured neurons with recombinant proteins containing the extracellular region of PTPRT reduced the number of synapses by inhibiting the interaction between ecto-domains. Synapse formation by PTPRT was inhibited by phosphorylation of tyrosine 912 within the membrane-proximal catalytic domain of PTPRT by Fyn. This tyrosine phosphorylation reduced phosphatase activity of PTPRT and reinforced homophilic interactions of PTPRT, thereby preventing the heterophilic interaction between PTPRT and neuroligins. These results suggest that brain-specific PTPRT regulates synapse formation through interaction with cell adhesion molecules, and this function and the phosphatase activity are attenuated through tyrosine phosphorylation by the synaptic tyrosine kinase Fyn.

    Funded by: PHS HHS: R01-2007-000-11499-0

    The EMBO journal 2009;28;22;3564-78

  • Identification of SH3 domain interaction partners of human FasL (CD178) by phage display screening.

    Voss M, Lettau M and Janssen O

    Institute of Immunology, Christian-Albrechts-University of Kiel, D-24105 Kiel, Germany. matthias.voss@med.uni-muenchen.de

    Background: Fas ligand is a cytotoxic effector molecule of T and NK cells which is characterized by an intracellular N-terminal polyproline region that serves as a docking site for SH3 and WW domain proteins. Several previously described Fas ligand-interacting SH3 domain proteins turned out to be crucial for the regulation of storage, expression and function of the death factor. Recent observations, however, indicate that Fas ligand is also subject to posttranslational modifications including shedding and intramembrane proteolysis. This results in the generation of short intracellular fragments that might either be degraded or translocate to the nucleus to influence transcription. So far, protein-protein interactions that specifically regulate the fate of the intracellular fragments have not been identified.

    Results: In order to further define the SH3 domain interactome of the intracellular region of Fas ligand, we now screened a human SH3 domain phage display library. In addition to known SH3 domains mediating binding to the Fas ligand proline-rich domain, we were able to identify a number of additional SH3 domains that might also associate with FasL. Potential functional implications of the new binding proteins for the death factor's biology are discussed. For Tec kinases and sorting nexins, the observed interactions were verified in cellular systems by pulldown experiments.

    Conclusion: We provide an extended list of putative Fas ligand interaction partners, confirming previously identified interactions, but also introducing several novel SH3 domain proteins that might be important regulators of Fas ligand function.

    BMC immunology 2009;10;53

  • Fyn and SRC are effectors of oncogenic epidermal growth factor receptor signaling in glioblastoma patients.

    Lu KV, Zhu S, Cvrljevic A, Huang TT, Sarkaria S, Ahkavan D, Dang J, Dinca EB, Plaisier SB, Oderberg I, Lee Y, Chen Z, Caldwell JS, Xie Y, Loo JA, Seligson D, Chakravari A, Lee FY, Weinmann R, Cloughesy TF, Nelson SF, Bergers G, Graeber T, Furnari FB, James CD, Cavenee WK, Johns TG and Mischel PS

    Department of Pathology and Laboratory Medicine, University of California-Los Angeles David Geffen School of Medicine, USA.

    Activating epidermal growth factor receptor (EGFR) mutations are common in many cancers including glioblastoma. However, clinical responses to EGFR inhibitors are infrequent and short-lived. We show that the Src family kinases (SFK) Fyn and Src are effectors of oncogenic EGFR signaling, enhancing invasion and tumor cell survival in vivo. Expression of a constitutively active EGFR mutant, EGFRvIII, resulted in activating phosphorylation and physical association with Src and Fyn, promoting tumor growth and motility. Gene silencing of Fyn and Src limited EGFR- and EGFRvIII-dependent tumor cell motility. The SFK inhibitor dasatinib inhibited invasion, promoted tumor regression, and induced apoptosis in vivo, significantly prolonging survival of an orthotopic glioblastoma model expressing endogenous EGFRvIII. Dasatinib enhanced the efficacy of an anti-EGFR monoclonal antibody (mAb 806) in vivo, further limiting tumor growth and extending survival. Examination of a large cohort of clinical samples showed frequent coactivation of EGFR and SFKs in glioblastoma patients. These results establish a mechanism linking EGFR signaling with Fyn and Src activation to promote tumor progression and invasion in vivo and provide rationale for combined anti-EGFR and anti-SFK targeted therapies.

    Funded by: NCI NIH HHS: 5T32CA09056, CA097257, CA108633, CA119347, P50 CA097257, R01 CA108633, T32 CA009056, U54 CA119347; NINDS NIH HHS: NS049720, NS050151, R01 NS049720, R01 NS049720-06, R01 NS050151, R01 NS050151-05

    Cancer research 2009;69;17;6889-98

  • Decreased expression of Fyn protein and disbalanced alternative splicing patterns in platelets from patients with schizophrenia.

    Hattori K, Fukuzako H, Hashiguchi T, Hamada S, Murata Y, Isosaka T, Yuasa S and Yagi T

    KOKORO Biology Group, Laboratories for Integrated Biology, Graduate School of Frontier Biosciences, Osaka University, Yamadaoka 1-3, Suita 565-0871, Japan.

    Fyn, a Src-family kinase, is highly expressed in brain tissue and blood cells. In the mouse brain, Fyn participates in brain development, synaptic transmission through the phosphorylation of N-methyl-d-aspartate (NMDA) receptor subunits, and the regulation of emotional behavior. Recently, we found that Fyn is required for the signal transduction in striatal neurons that is initiated by haloperidol, an antipsychotic drug. To determine whether Fyn abnormalities are present in patients with schizophrenia, we analyzed Fyn expression in platelet samples from 110 patients with schizophrenia, 75 of the patients' first-degree relatives, and 130 control subjects. A Western blot analysis revealed significantly lower levels of Fyn protein among the patients with schizophrenia and their relatives, compared with the level 19b3 in the control group. At the mRNA level, the splicing patterns of fyn were altered in the patients and their relatives; specifically, the ratio of fynDelta7, in which exon 7 is absent, was elevated. An expression study in HEK293T cells revealed that FynDelta7 had a dominant-negative effect on the phosphorylation of Fyn's substrate. These results suggest novel deficits in Fyn function, manifested as the downregulation of Fyn protein or the altered transcription of the fyn gene, in patients with schizophrenia.

    Psychiatry research 2009;168;2;119-28

  • Gene expression profiling of imatinib and PD166326-resistant CML cell lines identifies Fyn as a gene associated with resistance to BCR-ABL inhibitors.

    Grosso S, Puissant A, Dufies M, Colosetti P, Jacquel A, Lebrigand K, Barbry P, Deckert M, Cassuto JP, Mari B and Auberger P

    INSERM U895, Cell Death, Differentiation and Cancer Team, Faculté de Médecine de Nice, Nice Cedex 2, France.

    Imatinib is used to treat chronic myelogenous leukemia (CML), but resistance develops in all phases of this disease. The purpose of the present study was to identify the mode of resistance of newly derived imatinib-resistant (IM-R) and PD166326-resistant (PD-R) CML cells. IM-R and PD-R clones exhibited an increase in viability and a decrease in caspase activation in response to various doses of imatinib and PD166326, respectively, as compared with parental K562 cells. Resistance involved neither mutations in BCR-ABL nor increased BCR-ABL, MDR1 or Lyn expression, all known modes of resistance. To gain insight into the resistance mechanisms, we used pangenomic microarrays and identified 281 genes modulated in parental versus IM-R and PD-R cells. The gene signature was similar for IM-R and PD-R cells, accordingly with the cross-sensitivity observed for both inhibitors. These genes were functionally associated with pathways linked to development, cell adhesion, cell growth, and the JAK-STAT 3af cascade. Especially relevant were the increased expression of the tyrosine kinases AXL and Fyn as well as CD44 and HMGA2. Small interfering RNA experiments and pharmacologic approaches identified FYN as a candidate for resistance to imatinib. Our findings provide a comprehensive picture of the transcriptional events associated with imatinib and PD166326 resistance and identify Fyn as a new potential target for therapeutic intervention in CML.

    Molecular cancer therapeutics 2009;8;7;1924-33

  • The association study of three FYN polymorphisms with prophylactic lithium response in bipolar patients.

    Szczepankiewicz A, Skibinska M, Suwalska A, Hauser J and Rybakowski JK

    Department of Pediatric Pulmonology, Allergy and Clinical Immunology, IIIrd Department of Pediatrics, Poznan University of Medical Sciences, Poznan, Poland. alszczep@amp.edu.pl

    FYN belongs to the protein kinase family that phosphorylates NMDA receptor subunits, participating in the regulation of ion transmission and BDNF/TrkB signal transduction pathway. Lithium inhibits glutamatergic transmission via NMDA receptors, exerting neuroprotective effect against excitotoxicity. The aim of this study was to find possible association of three polymorphisms of FYN gene with prophylactic lithium response in the group of bipolar patients. We analyzed 101 bipolar patients treated with lithium carbonate for 5-27 years (mean 15 years). Twenty-four patients were identified as excellent lithium responders (ER), 51 patients as partial responders (PRs), and 26 patients were non-responders. Genotypes of the three analyzed polymorphisms were established by PCR-RFLP. Statistical analysis was done with Statistica. No significant differences in genotype distribution and allele frequencies were observed between T/G and A/G FYN polymorphisms and lithium response. We observed a trend toward association of TT genotype and T allele of T/C polymorphism with worse lithium response. The results of the study demonstrated only marginal association between FYN polymorphisms and prophylactic lithium response in bipolar patients. The results are discussed in light of our previous studies on FYN gene in bipolar illness and BDNF gene in lithium response.

    Human psychopharmacology 2009;24;4;287-91

  • Differential trafficking of Src, Lyn, Yes and Fyn is specified by the state of palmitoylation in the SH4 domain.

    Sato I, Obata Y, Kasahara K, Nakayama Y, Fukumoto Y, Yamasaki T, Yokoyama KK, Saito T and Yamaguchi N

    Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan.

    Src-family tyrosine kinases (SFKs), which participate in a variety of signal transduction events, are known to localize to the cytoplasmic face of the plasma membrane through lipid modification. Recently, we showed that Lyn, an SFK member, is exocytosed to the plasma membrane via the Golgi region along the secretory pathway. We show here that SFK trafficking is specified by the palmitoylation state. Yes is also a monopalmitoylated SFK and is biosynthetically transported from the Golgi pool of caveolin to the plasma membrane. This pathway can be inhibited in the trans-Golgi network (TGN)-to-cell surface delivery by temperature block at 19 degrees C or dominant-negative Rab11 GTPase. A large fraction of Fyn, a dually palmitoylated SFK, is directly targeted to the plasma membrane irrespective of temperature block of TGN exit. Fyn(C6S), which lacks the second palmitoylation site, is able to traffic in the same way as Lyn and Yes. Moreover, construction of Yes(S6C) and chimeric Lyn or Yes with the Fyn N-terminus further substantiates the importance of the dual palmitoylation site for plasma membrane targeting. Taken together with our recent finding that Src, a nonpalmitoylated SFK, is rapidly exchanged between the plasma membrane and late endosomes/lysosomes, these results suggest that SFK trafficking is specified by the palmitoylation state in the SH4 domain.

    Journal of cell science 2009;122;Pt 7;965-75

  • Endocytosis of flotillin-1 and flotillin-2 is regulated by Fyn kinase.

    Riento K, Frick M, Schafer I and Nichols BJ

    MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.

    Flotillin-1 and flotillin-2 co-assemble into plasma membrane microdomains that are involved in the endocytosis of molecules such as glycosyl phosphatidylinositol (GPI)-linked proteins. Previous studies suggest that budding of flotillin microdomains from the plasma membrane is a tightly regulated process. Here, we demonstrate that endocytosis of flotillins is regulated by the Src family kinase Fyn. The Src kinase inhibitor PP2 prevents EGF-induced flotillin internalisation, and EGF-induced internalisation does not occur in SYF cells lacking Src, Yes and Fyn. Expression of Fyn, but not Src or Yes, restores EGF-induced internalisation in SYF cells. Expression of an active form of Fyn but not other Src kinases is sufficient to induce redistribution of flotillins from the plasma membrane to late endosomes and lysosomes. Using two partial Fyn constructs that form a functional kinase upon addition of rapamycin to cells, we show that flotillin internalisation from the plasma membrane occurs shortly after Fyn activation. Tyr160 in flotillin-1 and Tyr163 in flotillin-2 are directly phosphorylated by Fyn, and mutation of these residues to phenylalanine prevents Fyn-induced flotillin internalisation. Uptake of the GPI-linked protein CD59 is reduced by expression of the phenylalanine-mutated flotillins. These data establish uptake of flotillin microdomains as a tyrosine-kinase-regulated endocytic process.

    Funded by: Medical Research Council: MC_U105178778

    Journal of cell science 2009;122;Pt 7;912-8

  • Genetic association between -93A/G polymorphism in the Fyn kinase gene and alcohol dependence in Spanish men.

    Pastor IJ, Laso FJ, Inés S, Marcos M and González-Sarmiento R

    Unidad de Medicina Molecular, Departamento de Medicina, Universidad de Salamanca, Avda. de Alfonso X el Sabio s/n, 37007 Salamanca, Spain.

    Background: Fyn tyrosine kinase is a member of the Scr family that phosphorylates the NR2A and NR2B subunits of 15a7 the NMDA receptors reducing the inhibitory effects of ethanol and therefore may regulate the individual sensitivity to ethanol.

    Objectives: To investigate whether there is any relationship between the polymorphism at position -93 of the Fyn kinase gene and the susceptibility to develop alcoholism.

    Methods: We studied the distribution of genotypes and alleles of the polymorphism -93A/G (137346 T/C) in the 5' UTR region of the fyn gene in 207 male heavy drinkers (119 with alcohol dependence and 88 with alcohol abuse) and 100 control subjects from Castilla y León (Spain).

    Results: The frequency of G allele carriers was higher in alcohol dependents than in alcohol abusers (47.9% vs 30.6%; p=0.015; OR=2.077; 95% CI 1.165-3.704).

    Conclusion: Our results show that the -93G allele of Fyn kinase gene is associated with higher risk to develop alcohol dependence in Spanish men.

    European psychiatry : the journal of the Association of European Psychiatrists 2009;24;3;191-4

  • Oxidative stress promotes transcriptional up-regulation of Fyn in BCR-ABL1-expressing cells.

    Gao Y, Howard A, Ban K and Chandra J

    Department of Pediatrics Research, Unit 853, Children's Cancer Hospital at M. D. Anderson, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.

    Signaling initiated by the BCR-ABL1 kinase causes chronic myelogenous leukemia (CML). Recently, we reported that expression of Fyn, a Src kinase, is heightened in CML cells and patient specimens and confers in vitro and in vivo proliferative advantages. Fyn is regulated by redox, and because BCR-ABL1 raises intracellular oxidant levels, which have been implicated in CML progression, we explored the molecular regulation of Fyn. Here we identify the transcription factors that drive redox- and BCR-ABL1-dependent Fyn expression. Promoter deletion analysis in 293T, BaF3, BaF3-p210, and K562 cells identified the region essential for basal transcriptional activity. Mutation of Sp1 and Egr1 binding sites within the e 1a39 ssential region diminished Fyn promoter activity and identified Egr1 as conferring redox sensitivity. Gel shift and chromatin immunoprecipitation assays confirmed the binding of Sp1 and Egr1 to the promoter fragments. Importantly, knockdown of Sp1 or Egr1 with small interference RNA or inhibition of Sp1 binding by mithramycin A repressed Fyn protein expression. Our work is the first to define transcription factors that are responsible for endogenous, oxidative stress-dependent and BCR-ABL1-dependent Fyn expression.

    Funded by: NCI NIH HHS: R01 CA 115811

    The Journal of biological chemistry 2009;284;11;7114-25

  • FYN kinase gene: another glutamatergic gene associated with bipolar disorder?

    Szczepankiewicz A, Rybakowski JK, Skibinska M, Dmitrzak-Weglarz M, Leszczynska-Rodziewicz A, Wilkosc M and Hauser J

    Department of Psychiatry, Poznan University of Medical Sciences, Poznan, Poland. alszczep@amp.edu.pl

    Several genes of the glutamatergic system have been implicated in both schizophrenia and bipolar disorder. The Src family tyrosine kinase FYN plays a key role in the interaction between brain-derived neurotrophic factor and glutamatergic receptor N-methyl-D-aspartate. Although no association between FYN gene polymorphisms and schizophrenia has been demonstrated, in our previous paper we found an association between FYN polymorphisms and cognitive test performance in schizophrenic patients. The aim of this study was to find a possible association of three polymorphisms of the FYN gene with bipolar diso 1f40 rder. We analyzed 425 bipolar patients and 518 control subjects. Genotypes of three analyzed polymorphisms, i.e. rs706895 (-93A/G in the 5'-flanking region), rs6916861 (Ex12+894T/G in the 3'-UTR) and rs3730353 (IVS10+37T/C in intron 10) were established by PCR-RFLP. A significant association was found between rs6916861 T/G and rs3730353 T/C polymorphisms of the FYN gene and bipolar disorder. These results were also significant in the subgroups of bipolar I and early-onset (<18 years) bipolar disorder patients. No association with -93 A/G polymorphism was found. Haplotype analysis revealed that rs6916861 T/G and rs3730353 T/C polymorphisms are in linkage disequilibrium (r(2) = 0.86, D' = 0.93 with 95% CI = 0.9-0.97). The results suggest that the glutamatergic FYN gene may be associated with bipolar disorder, particularly with type I illness and early age of onset.

    Neuropsychobiology 2009;59;3;178-83

  • Ischemic injury to kidney induces glomerular podocyte effacement and dissociation of slit diaphragm proteins Neph1 and ZO-1.

    Wagner MC, Rhodes G, Wang E, Pruthi V, Arif E, Saleem MA, Wean SE, Garg P, Verma R, Holzman LB, Gattone V, Molitoris BA and Nihalani D

    Department of Medicine, Division of Nephrology, Indiana University, Indianapolis, Indiana 46202, USA.

    Glomerular injury is often characterized by the effacement of podocytes, loss of slit diaphragms, and proteinuria. Renal ischemia or the loss of blood flow to the kidneys has been widely associated with tubular and endothelial injury but rarely has been shown to induce podocyte damage and disruption of the slit diaphragm. In this study, we have used an in vivo rat ischemic model to demonstrate that renal ischemia induces podocyte effacement with loss of slit diaphragm and proteinuria. Biochemical analysis of the ischemic glomerulus shows that ischemia induces rapid loss of interaction between slit diaphragm junctional proteins Neph1 and ZO-1. To further understand the effect of ischemia on molecular interactions between slit diaphragm proteins, a cell culture model was employed to study the binding between Neph1 and ZO-1. Under physiologic conditions, Neph1 co-localized with ZO-1 at cell-cell contacts in cultured human podocytes. Induction of injury by ATP depletion resulted in rapid loss of Neph1 and ZO-1 binding and redistribution of Neph1 and ZO-1 proteins from cell membrane to the cytoplasm. Recovery resulted in increased Neph1 tyrosine phosphorylation, restoring Neph1 and ZO-1 binding and their localization at the cell membrane. We further demonstrate that tyrosine phosphorylation of Neph1 mediated by Fyn results in significantly increased Neph1 and ZO-1 binding, suggesting a critical role for Neph1 tyrosine phosphorylation in reorganizing the Neph1-ZO-1 complex. This study documents that renal ischemia induces dynamic changes in the molecular interactions between slit diaphragm proteins, leading to podocyte damage and proteinuria.

    Funded by: NIDDK NIH HHS: K01 DK072047-03, K08 DK081403, K08 DK081403-01, P50 DK061594, R01 DK069408

    The Journal of biological chemistry 2008;283;51;35579-89

  • Inhibition of DNA methyltransferase activity upregulates Fyn tyrosine kinase expression in Hut-78 T-lymphoma cells.

    Kozłowska A and Jagodziński PP

    Department of Biochemistry and Molecular Biology, Poznań University of Medical Sciences, Poznan, Poland.

    Tyrosine kinase Fyn, the expression of which is epigenetically regulated, has been proposed to be a tumour suppressor gene. A frequent deletion at the 6q chromosomal region encoding the Fyn gene in lymphomas has been reported. Therefore, we assessed the impact of 5-Aza-2'-deoxycytidine (5-dAzaC), a DNA methyltransferase (DNMTs) inhibitor on Fyn expression in Hut-78 T-lymphoma cells. Using reverse transcription, real-time quantitative PCR (RQ-PCR), and western blot analyses, we found that 5-dAzaC significantly increased transcript and protein levels of Fyn in Hut-78 T-lymphoma cells. However, bisulfite sequencing revealed that Hut-78 T-lymphoma cells cultured in the absence of 5-dAzaC contained unmethylated cytosine in the cytosine-guanosine dinucleotide island of the Fyn promoter. Our results suggest that the DNMTs activity may have an indirect influence on the expression of Fyn without altering the methylation level of its promoter in Hut-78 T-lymphoma cells.

    Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie 2008;62;10;672-6

  • Role of Fyn and PI3K in H2O2-induced inhibition of apical Cl-/OH- exchange activity in human intestinal epithelial cells.

    Saksena S, Gill RK, Tyagi S, Alrefai WA, Ramaswamy K and Dudeja PK

    Department of Medicine, University of Illinois at Chicago, Jesse Brown VA Medical Center, Chicago, IL 60612, USA.

    H(2)O(2) is a highly reactive oxygen metabolite that has been implicated as an important mediator of inflammation-induced intestinal injury associated with ischaemia/reperfusion, radiation and inflammatory bowel disease. Previous studies have shown that H(2)O(2) inhibits NaCl absorption and activates Cl(-) secretion in the rat and rabbit colon. To date, however, almost no information is available with respect to its effect on the human intestinal apical anion exchanger Cl(-)/OH(-) (HCO(3)(-)). The present studies were, therefore, undertaken to examine the direct effects of H(2)O(2) on OH(-) gradient-driven DIDS (4,4'-di-isothiocyanostilbene-2,2'-disulfonate)-sensitive (36)Cl(-) uptake utilizing a post-confluent transformed human intestinal epithelial cell line, Caco-2. Our results demonstrate that H(2)O(2) (1 mM for 60 min) significantly inhibited (approx. 60%; P<0.05) Cl(-)/OH(-) exchange activity in Caco-2 cells. H(2)O(2)-mediated inhibition of Cl(-)/OH(-) exchange activity involved the Src kinase Fyn and PI3K (phosphoinositide 3-kinase)-dependent pathways. H(2)O(2) also induced phosphorylation of Fyn and p85 (the regulatory subunit of PI3K) in Caco-2 cells. Moreover, an increased association of Fyn and p85 was observed in response to H(2)O(2), resulting in the activation of the downstream target PLCgamma1 (phospholipase Cgamma1). Elevated intracellular Ca(2+) levels and PKCalpha (protein kinase Calpha) functioned as downstream effectors of H(2)O(2)-induced PLCgamma1 activation. Our results, for the first time, provide evidence for H(2)O(2)-induced Src kinase Fyn/PI3K complex association. This complex association resulted in the subsequent activation of PLCgamma1 and Ca(2+)-dependent PKCalpha, resulting in the inhibition of Cl(-)/OH(-) exchange activity. These findings suggest that H(2)O(2)-induced inhibition of the Cl(-)/OH(-) exchange process may play an important role in the pathophysiology of diarrhoea associated with inflammatory disorders, where the amount of reactive oxygen species is markedly elevated.

    Funded by: NIDDK NIH HHS: DK 33349, DK 54016, DK 67990, DK 71596, P01 DK 067887, P01 DK067887, P01 DK067887-030001, R01 DK033349, R01 DK054016, R01 DK054016-11, R01 DK067990, R01 DK071596, R56 DK071596

    The Biochemical journal 2008;416;1;99-108

  • Quantifying information transfer by protein domains: analysis of the Fyn SH2 domain structure.

    Lenaerts T, Ferkinghoff-Borg J, Stricher F, Serrano L, Schymkowitz JW and Rousseau F

    SWITCH laboratory, VIB, Brussels, Belgium. tlenaert@vub.ac.be

    Background: Efficient communication between distant sites within a protein is essential for cooperative biological response. Although often associated with large allosteric movements, more subtle changes in protein dynamics can also induce long-range correlations. However, an appropriate formalism that directly relates protein structural dynamics to information exchange between functional sites is still lacking.

    Results: Here we introduce a method to analyze protein dynamics within the framework of information theory and show that signal transduction within proteins can be considered as a particular instance of communication over a noisy channel. In particular, we analyze the conformational correlations between protein residues and apply the concept of mutual information to quantify information exchange. Mapping out changes of mutual information on the protein structure then allows visualizing how distal communication is achieved. We illustrate the approach by analyzing information transfer by the SH2 domain of Fyn tyrosine kinase, obtained from Monte Carlo dynamics simulations. Our analysis reveals that the Fyn SH2 domain forms a noisy communication channel that couples residues located in the phosphopeptide and specificity binding sites and a number of residues at the other side of the domain near the linkers that connect the SH2 domain to the SH3 and kinase domains. We find that for this particular domain, communication is affected by a series of contiguous residues that connect distal sites by crossing the core of the SH2 domain.

    Conclusion: As a result, our method provides a means to directly map the exchange of biological information on the structure of protein domains, making it clear how binding triggers conformational changes in the protein structure. As such it provides a structural road, next to the existing attempts at sequence level, to predict long-range interactions within protein structures.

    BMC structural biology 2008;8;43

  • Candidate gene/loci studies in cleft lip/palate and dental anomalies finds novel susceptibility genes for clefts.

    Vieira AR, McHenry TG, Daack-Hirsch S, Murray JC and Marazita ML

    Department of 1Oral Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA. arv11@dental.pitt.edu

    Purpose: We revisited 42 families with two or more cleft-affected siblings who participated in previous studies. Complete dental information was collected to test the hypothesis that dental anomalies are part of the cleft phenotype spectrum, and can provide new opportunities for identification of cleft susceptibility genes.

    Methods: Genotypes from 1489 single nucleotide polymorphism markers located in 150 candidate genes/loci were reanalyzed. Two sets of association analyses were carried out. First, we ran the analysis solely on the cleft status. Second, we assigned affection to any cleft or dental anomaly (tooth agenesis, supernumerary teeth, and microdontia) and repeated the analysis.

    Results: Significant over-transmission was seen for a single nucleotide polymorphism in ankyrin repeat and sterile alpha motif domain containing 6 (rs4742741, 9q22.33; P = 0.0004) when a dental anomaly phenotype was included in the analysis. Significant over-transmission was also seen for a single nucleotide polymorphism in ERBB2 (rs1810132, 17q21.1; P = 0.0006). In the clefts only data, the most significant result was also for ERBB2 (P = 0.0006). Other markers with suggestive P values included interferon regulatory factor 6 and 6q21-q23 loci. In contrast to the above results, suggestive over-transmission of markers in GART, DPF3, and neurexin 3 were seen only when the dental anomaly phenotype was included in the analysis.

    Conclusions: These findings support the hypothesis that some loci may contribute to both clefts and congenital dental anomalies. Thus, including dental anomalies information in the genetics analysis of cleft lip and palate will provide new opportunities to map susceptibility loci for clefts.

    Funded by: NHGRI NIH HHS: N01HG65403; NIDCR NIH HHS: P50 DE016215, P50 DE016215-04, P50 DE016215-05, P50-DE016215, R01 DE016148, R01-DE016148, R21 DE016718, R21-DE016718, R37 DE008559, R37 DE008559-18, R37 DE008559-19, R37-DE08559

    Genetics in medicine : official journal of the American College of Medical Genetics 2008;10;9;668-74

  • Mechanotransduction in an extracted cell model: Fyn drives stretch- and flow-elicited PECAM-1 phosphorylation.

    Chiu YJ, McBeath E and Fujiwara K

    Aab Cardiovascular Research Institute, University of Rochester School of Medicine and Dentistry, West Henrietta, NY 14586, USA.

    Mechanosensing followed by mechanoresponses by cells is well established, but the mechanisms by which mechanical force is converted into biochemical events are poorly understood. Vascular endothelial cells (ECs) exhibit flow- and stretch-dependent responses and are widely used as a model for studying mechanotransduction in mammalian cells. Platelet EC adhesion molecule 1 (PECAM-1) is tyrosine phosphorylated when ECs are exposed to flow or when PECAM-1 is directly pulled, suggesting that it is a mechanochemical converter. We show that PECAM-1 phosphorylation occurs when detergent-extracted EC monolayers are stretched, indicating that this phosphorylation is mechanically triggered and does not require the intact plasma membrane and soluble cytoplasmic components. Using kinase inhibitors and small interfering RNAs, we identify Fyn as the PECAM-1 kinase associated with the model. We further show that stretch- and flow-induced PECAM-1 phosphorylation in intact ECs is abolished when Fyn expression is down-regulated. We suggest that PECAM-1 and Fyn are essential components of a PECAM-1-based mechanosensory complex in ECs.

    Funded by: NHLBI NIH HHS: HL69041, R01 HL069041

    The Journal of cell biology 2008;182;4;753-63

  • Neither replication nor simulation supports a role for the axon guidance pathway in the genetics of Parkinson's disease.

    Li Y, Rowland C, Xiromerisiou G, Lagier RJ, Schrodi SJ, Dradiotis E, Ross D, Bui N, Catanese J, Aggelakis K, Grupe A and Hadjigeorgiou G

    Celera, Alameda, California, United States of America. yonghong.li@celera.com

    Susceptibility to sporadic Parkinson's disease (PD) is thought to be influenced by both genetic and environmental factors and their interaction with each other. Statistical models including multiple variants in axon guidance pathway genes have recently been purported to be capable of predicting PD risk, survival free of the disease and age at disease onset; however the specific models have not undergone independent validation. Here we tested the best proposed risk panel of 23 single nucleotide polymorphisms (SNPs) in two PD sample sets, with a total of 525 cases and 518 controls. By single marker analysis, only one marker was significantly associated with PD risk in one of our sample sets (rs6692804: P = 0.03). Multi-marker analysis using the reported model found a mild association in one sample set (two sided P = 0.049, odds ratio for each score change = 1.07) but no significance in the other (two sided P = 0.98, odds ratio = 1), a stark contrast to the reported strong association with PD risk (P = 4.64x10(-38), odds ratio as high as 90.8). Following a procedure similar to that used to build the reported model, simulated multi-marker models containing SNPs from randomly chosen genes in a genome wide PD dataset produced P-values that were highly significant and indistinguishable from similar models where disease status was permuted (3.13x10(-23) to 4.90x10(-64)), demonstrating the potential for overfitting in the model building process. Together, these results challenge the robustness of the reported panel of genetic markers to predict PD risk in particular and a role of the axon guidance pathway in PD genetics in general.

    PloS one 2008;3;7;e2707

  • Fyn modulation of Dab1 effects on amyloid precursor protein and ApoE receptor 2 processing.

    Hoe HS, Minami SS, Makarova A, Lee J, Hyman BT, Matsuoka Y and Rebeck GW

    Department of Neuroscience, Georgetown University Medical Center, 3970 Reservoir Road NW, Washington, DC 20057, USA.

    Dab1 is an intracellular adaptor protein that interacts with amyloid precursor protein (APP) and apoE receptor 2 (apoEr2), increases their levels on the cell surface, and increases their cleavage by alpha-secretases. To investigate the mechanism underlying these alterations in processing and trafficking of APP and apoEr2, we examined the effect of Fyn, an Src family-tyrosine kinase known to interact with and phosphorylate Dab1. Co-immunoprecipitation, co-immunostaining, and fluorescence lifetime imaging demonstrated an association between Fyn and APP. Fyn induced phosphorylation of APP at Tyr-757 of the (757)YENPTY(762) motif and increased cell surface expression of APP. Overexpression of Fyn alone did not alter levels of sAPPalpha or cytoplasmic C-terminal fragments, although it significantly decreased production of Abeta. However, in the presence of Dab1, Fyn significantly increased sAPPalpha and C-terminal fragments. Fyn-induced APP phosphorylation and cell surface levels of APP were potentiated in the presence of Dab1. Fyn also induced phosphorylation of apoEr2 and increased its cell surface levels and, in the presence of Dab1, affected processing of its C-terminal fragment. In vivo studies showed that sAPPalpha was decreased in the Fyn knock-out, supporting a role for Fyn in APP processing. These data demonstrate that Fyn, due in part to its effects on Dab1, regulates the phosphorylation, trafficking, and processing of APP and apoEr2.

    Funded by: NIA NIH HHS: AG 022455, AG 14473, P01 AG030128

    The Journal of biological chemistry 2008;283;10;6288-99

  • BCR-ABL1 mediates up-regulation of Fyn in chronic myelogenous leukemia.

    Ban K, Gao Y, Amin HM, Howard A, Miller C, Lin Q, Leng X, Munsell M, Bar-Eli M, Arlinghaus RB and Chandra J

    Department of Pediatrics Research, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.

    Chronic myelogenous leukemia (CML) invariably progresses to blast crisis, which represents the most proliferative phase of the disease. The BCR-ABL1 oncogene stimulates growth and survival pathways by phosphorylating numerous substrates, including various Src family members. Here we describe up-regulation, in contrast to activation, of the ubiquitously expressed Src kinase, Fyn, by BCR-ABL1. In a tissue microarray, Fyn expression was significantly increased in CML blast crisis compared with chronic phase. Cells overexpressing BCR-ABL1 in vitro and in vivo display an up-regulation of Fyn protein and mRNA. Knockdown of Fyn with shRNA slows leukemia cell growth, inhibits clonogenicity, and leads to increased sensitivity to imatinib, indicating that Fyn mediates CML cell proliferation. In severe combined immunodeficient (SCID) mice injected with Fyn shRNA-expressing cells, myeloid-derived cell numbers dropped by 50% and death from leukemia was delayed. Taken together, these results encourage the development of therapies targeting Fyn expression.

    Funded by: NCI NIH HHS: R01 CA 115811, R01 CA115811

    Blood 2008;111;5;2904-8

  • Hepatitis C virus NS5A protein binds the SH3 domain of the Fyn tyrosine kinase with high affinity: mutagenic analysis of residues within the SH3 domain that contribute to the interaction.

    Shelton H and Harris M

    Institute of Molecular and Cellular Biology, Faculty of Biological Sciences and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK. h.a.shelton@reading.ac.uk

    Background: The hepatitis C virus (HCV) non-structural 5A protein (NS5A) contains a highly conserved C-terminal polyproline motif with the consensus sequence Pro-X-X-Pro-X-Arg that is able to interact with the Src-homology 3 (SH3) domains of a variety of cellular proteins.

    Results: To understand this interaction in more detail we have expressed two N-terminally truncated forms of NS5A in E. coli and examined their interactions with the SH3 domain of the Src-family tyrosine kinase, Fyn. Surface plasmon resonance analysis revealed that NS5A binds to the Fyn SH3 domain with what can be considered a high affinity SH3 domain-ligand interaction (629 nM), and this binding did not require the presence of domain I of NS5A (amino acid residues 32-250). Mutagenic analysis of the Fyn SH3 domain demonstrated the requirement for an acidic cluster at the C-terminus of the RT-Src loop of the SH3 domain, as well as several highly conserved residues previously shown to participate in SH3 domain peptide binding.

    Conclusion: We conclude that the NS5A:Fyn SH3 domain interaction occurs via a canonical SH3 domain binding site and the high affinity of the interaction suggests that NS5A would be able to compete with cognate Fyn ligands within the infected cell.

    Funded by: Wellcome Trust

    Virology journal 2008;5;24

  • Chromosomal deletion, promoter hypermethylation and downregulation of FYN in prostate cancer.

    Sørensen KD, Borre M, Ørntoft TF, Dyrskjøt L and Tørring N

    Molecular Diagnostics Laboratory, Department of Clinical Biochemistry, Aarhus University Hospital, Skejby, Aarhus N, Denmark.

    Loss of heterozygosity (LOH) at 6q is a frequent chromosomal aberration in prostate adenocarcinoma; however, a possible target gene remains to be identified. Findings in this study indicate that the FYN tyrosine kinase gene at 6q21 is a new candidate tumor suppressor in prostate cancer. Initially, single nucleotide polymorphism microarray analysis of 40 microdissected prostate adenocarcinoma samples revealed 25% LOH at the FYN locus. Furthermore, Western blot analysis and real-time reverse transcriptase PCR (RT-PCR) showed significantly lower FYN expression in prostate cancer tissue than in benign prostate hyperplasia (BPH), as well as in 6 prostate adenocarcinoma cell lines compared with that in BPH-1 cells. By immunohistochemistry, FYN protein was detected in nonmalignant prostate epithelium, but not in cancerous glands. Moreover, genomic bisulfite sequencing revealed frequent aberrant methylation of a large CpG island in the FYN promoter region in both adenocarcinoma cell lines (3 of 5 cell lines tested) and primary prostate cancer (12 of 18 tumors). Methylation was generally of moderate density, affecting preferentially the 3' region of the CpG island. Dense hypermethylation of the entire CpG island, consistent with gene silencing, was detected in 2 of 18 tumors (11%). No methylation was found in BPH-1 cells or nonmalignant prostate tissue samples (0 of 7). These results indicate that FYN is downregulated in prostate cancer by both chromosomal deletion and promoter hypermethylation, and therefore is a novel prostate tumor suppressor gene candidate.

    International journal of cancer 2008;122;3;509-19

  • Regulation of FynT function by dual domain docking on PAG/Cbp.

    Solheim SA, Torgersen KM, Taskén K and Berge T

    Biotechnology Centre of Oslo and Centre for Molecular Medicine Norway, Nordic EMBL Partnership, University of Oslo, Gaustadalléen 21, Blindern, Oslo, Norway.

    In resting T-cells, the transmembrane adaptor protein PAG (phosphoprotein associated with glycosphingolipid-enriched microdomains) is constitutively tyrosine-phosphorylated, a state maintained by the Src family kinase FynT. PAG has a role in negative regulation of Src family kinases in T-cells by recruitment of Csk (C-terminal Src kinase) to the membrane via binding to PAG phosphotyrosine 317. The interaction between FynT and PAG is essential for PAG function; however, so far the FynT binding mode has been unknown. Here, we demonstrate that the FynT-PAG complex formation is a dual domain docking process, involving SH2 domain binding to PAG phosphotyrosines as well as an SH3 domain interaction with the first proline-rich region of PAG. This binding mode affects FynT kinase activity, PAG phosphorylation, and recruitment of FynT and Csk, demonstrated in Jurkat TAg cells after antibody stimulation of the T cell receptor. Furthermore, we show that TCR-induced tyrosine phosphorylation is regulated by SH3 domain modulation of the FynT-PAG interaction in human primary T-cells. Although FynT SH3 domain association is shown to be crucial for efficiently initiating PAG phosphorylation, we suggest that engagement of the SH2 domain on PAG renders FynT insensitive to Csk negative regulation. Thus, in T-cells, PAG is involved in positive as well as negative regulation of FynT activity.

    The Journal of biological chemistry 2008;283;5;2773-83

  • Association of polymorphisms in complement component C3 gene with susceptibility to systemic lupus erythematosus.

    Miyagawa H, Yamai M, Sakaguchi D, Kiyohara C, Tsukamoto H, Kimoto Y, Nakamura T, Lee JH, Tsai CY, Chiang BL, Shimoda T, Harada M, Tahira T, Hayashi K and Horiuchi T

    Department of Medicine and Biosystemic Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.

    Objective: Identification of the genes responsible for systemic lupus erythematosus (SLE).

    Methods: All the exons and putative promoter regions of 53 candidate genes (TNFRSF6/Fas, TNFSF6/FasL, Fli1, TNFSF10/TRAIL, TNFSF12/TWEAK, Bcl-2, PTEN, FADD, TRADD, CDKN1A, TNFRSF1A/TNFR1, TNFRSF4/OX40, TNFSF4/OX40L, TNFSF5/CD40L, TNFSF13B/BAFF, ICOS, CTLA4, CD28, FYN, G2A, CR2, PTPRC/CD45, CD22, CD19, Lyn, PDCD1, PTPN6, TGFB1, TGFB2, TGFB3, TGFBR1, TGFBR2, TGFBR3, CD3Z, DNASE1, APCS, MERTK, C3, C1QA, C1QB, C1QG, C2, MBL2, IGHM, IL-2, IL-4, IL-10, IFNG, TNFA, MAN2A1, TNFRSF11A/RANK, TNFRSF11B/OPG, TNFSF11/OPGL) were screened for single nucleotide polymorphisms (SNPs) and their association with SLE was assessed by case-control studies. A total of 509 cases and 964 controls of Japanese descent were enrolled.

    Results: A total of 316 SNPs was identified. When analysed in the Japanese population, the allele frequencies of T at rs7951 and G at rs2230201 of the C3 gene were 0.110 and 0.626, respectively, in SLE patients; significantly higher than the frequencies of 0.081 and 0.584, respectively, in controls [odds ratio (OR) = 1.40, 95% confidence interval (CI) = 1.05-1.86, P = 0.016 and OR=1.19, 95% CI = 1.01-1.41, P = 0.038, respectively]. The mean serum C3 level of carriers of the rs7951 T allele was significantly lower than that of non-carriers of the T allele in 87 SLE patients whose medical records were available (P = 0.0018).

    Conclusion: rs7951 T allele of the C3 gene was significantly associated with SLE, and decreased serum level of C3 seems to be correlated with this allele.

    Rheumatology (Oxford, England) 2008;47;2;158-64

  • Association analysis of tyrosine kinase FYN gene polymorphisms in asthmatic children.

    Szczepankiewicz A, Breborowicz A, Skibińska M, Wiłkość M, Tomaszewska M and Hauser J

    Department of Pediatric Pulmonology, Allergy and Clinical Immunology, Poznan University of Medical Sciences, Poznan, Poland. alszczep@amp.edu.pl

    Background: FYN is nonreceptor tyrosine kinase that represents the earliest detectable signaling response after antigen-activated inflammatory cells. Studies in animal models of allergic asthma have shown that inhibitors of tyrosine kinases exert an anti-inflammatory effect. In the FYN gene, several polymorphisms have been described. There have, however, been no studies analyzing the impact of FYN gene polymorphisms on the course and severity of asthma. The aim of this study was to analyze the possible relationship between three polymorphisms (-93A/G, Intron10+37C/T and Ex12+894T/G) in the FYN gene and asthma.

    Methods: We analyzed 120 pediatric asthmatic patients aged from 6 to 18 years. The diagnosis of allergic asthma was based on clinical manifestation, lung function test and positive skin prick tests and/or an increased IgE level. The control group consisted of 187 healthy subjects. The polymorphisms were genotyped with use of the PCR-RFLP method.

    Results: We observed an association of the -93A/G polymorphism and the presence of asthma (p = 0.014 for genotypes and p = 0.019 for alleles) and in the subgroup of 55 patients with severe asthma (p = 0.042 for genotypes and p = 0.021 for alleles). We also found an association of the Ex12+894T/G polymorphism in the whole group analyzed (p = 0.067 for genotypes and p = 0.024 for alleles), but not in the subgroup with severe asthma. For the Intron10+37T/C polymorphism, we did not find a significant difference between the whole group of asthmatic patients and the control group nor between the subgroup with severe asthma and the control group. In the linkage disequilibrium analysis, we observed a modest linkage between -93A/G and Intron10+37T/C polymorphisms (lod = 18.7, D' = 0.62, 95% CI: 0.51-0.71, r2 = 0.29); however, it was not strong enough to generate any haplotypes.

    Conclusions: The results may suggest a relationship between the FYN polymorphisms and allergic asthma.

    International archives of allergy and immunology 2008;145;1;43-7

  • Signaling status of IgG B cell receptor (IgG BCR) is indicative for an activated state of circulating B cells in multiple myeloma.

    Ilić V, Milosević-Jovcić N, Petrović S, Marković D, Bila J, Bosković D, Stefanović G, Marković O and Glibetić M

    Institute for Medical Research, University of Belgrade, Belgrade, Serbia. vesnai@imi.bg.ac.yu

    Circulating post-switch B cells have been proposed as proliferative and disseminating progenitors in multiple myeloma. It is unclear whether the class-switched antigen receptor expressed at the surface of these cells plays a role in their expansion. In this work, the signaling status of IgG B cell receptor (BCR) isolated from the lysates of peripheral blood lymphocytes of 32 patients with IgG multiple myeloma, at the time of diagnosis, was investigated by examining whether phosphorylation of BCR Igalpha and Igbeta signal transducer factors (co-receptors) or other signaling molecules was abnormal in these cells when compared with healthy controls. In IgG BCR of normal controls, weak phosphorylation of 56 and 61 kDa Src kinase-related proteins and unphosphorylated co-receptors were found. In myeloma, p56 and p61 kDa proteins, co-receptors, and other IgG BCR-associated proteins from the signal cascade were phosphorylated. Myeloma patients can be classified into subgroups by IgG BCR phosphorylation profiles which characteristically coordinated with the level of IgG paraprotein in serum and the stage of disease. There was a correlative trend between the extent of phosphorylation reduction and advanced stage of disease. Reduced phosphorylation was more pronounced with advanced stages of multiple myeloma.

    Annals of hematology 2007;86;12;905-12

  • Direct and indirect interactions of the cytoplasmic region of CD244 (2B4) in mice and humans with FYN kinase.

    Clarkson NG, Simmonds SJ, Puklavec MJ and Brown MH

    Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom.

    Engagement of the receptor CD244 (2B4) by its ligand CD48 has inhibitory and activating potential, and this differs depending on experimental systems in mouse and human. c6d We show that, in both mouse and human upon engagement of its ligand CD48, CD244 can give a negative signal to natural killer cells, implying conservation of function between the two species. The signaling mechanisms used by CD244 in both human and mouse are conserved as shown by quantitative analyses of the direct molecular interactions of the SH2 domains of the adaptors SLAM-associated protein (SAP) and EAT-2 and of FYN kinase with CD244 together with the indirect interactions of the FYN SH2 domain with EAT-2. Functional experiments support the biochemical hierarchy of interactions and show that EAT-2 is not inhibitory per se. The data are consistent with a model in which the mechanism of signal transduction by CD244 is to regulate FYN kinase recruitment and/or activity and the outcome of CD48/CD244 interactions is determined by which other receptors are engaged.

    Funded by: Medical Research Council: G0400808

    The Journal of biological chemistry 2007;282;35;25385-94

  • Polymorphisms of the Fyn kinase gene and a performance on the Wisconsin Card Sorting Test in schizophrenia.

    Rybakowski JK, Borkowska A, Skibinska M and Hauser J

    Department of Adult Psychiatry, University of Medical Sciences, Poznan, Poland. rybakows@wlkp.top.pl

    The glutamatergic system has been implicated in the pathogenesis and prefrontal cortex dysfunctions in schizophrenia. The Src-family tyrosine kinase Fyn plays a key role in the interaction between brain-derived neurotrophic factor and glutamatergic receptor N-methyl-D-aspartate, in prefrontal cortex. We estimated an association between three polymorphisms of Fyn gene and performance on the Wisconsin Card Sorting Test, measuring prefrontal cortex functions, in 188 schizophrenic patients. Patients with T/T genotype of IVS10+T/C polymorphism and T/T genotype of Ex12+894T/G polymorphism made significantly less perseverative errors in the Wisconsin Card Sorting Test compared with patients with remaining genotypes, and obtained numerically better results in other Wisconsin Card Sorting Test domains. No significant differences in Wisconsin Card Sorting Test performance were found as to -93 A/G polymorphism. The main finding of the study is showing a relationship between polymorphisms of the Fyn gene, related to the function of glutamatergic system, and a performance on neuropsychological test of prefrontal cortex activity in schizophrenic patients.

    Psychiatric genetics 2007;17;3;201-4

  • Systematic identification of SH3 domain-mediated human protein-protein interactions by peptide array target screening.

    Wu C, Ma MH, Brown KR, Geisler M, Li L, Tzeng E, Jia CY, Jurisica I and Li SS

    Department of Biochemistry and the Siebens-Drake Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.

    Systematic identification of direct protein-protein interactions is often hampered by difficulties in expressing and purifying the corresponding full-length proteins. By taking advantage of the modular nature of many regulatory proteins, we attempted to simplify protein-protein interactions to the corresponding domain-ligand recognition and employed peptide arrays to identify such binding events. A group of 12 Src homology (SH) 3 domains from eight human proteins (Swiss-Prot ID: SRC, PLCG1, P85A, NCK1, GRB2, FYN, CRK) were used to screen a peptide target array composed of 1536 potential ligands, which led to the identification of 921 binary interactions between these proteins and 284 targets. To assess the efficiency of the peptide array target screening (PATS) method in identifying authentic protein-protein interactions, we examined a set of interactions mediated by the PLCgamma1 SH3 domain by coimmunoprecipitation and/or affinity pull-downs using full-length proteins and achieved a 75% success rate. Furthermore, we characterized a novel interaction between PLCgamma1 and hematopoietic progenitor kinase 1 (HPK1) identified by PATS and demonstrated that the PLCgamma1 SH3 domain negatively regulated HPK1 kinase activity. Compared to protein interactions listed in the online predicted human interaction protein database (OPHID), the majority of interactions identified by PATS are novel, suggesting that, when extended to the large number of peptide interaction domains encoded by the human genome, PATS should aid in the mapping of the human interactome.

    Proteomics 2007;7;11;1775-85

  • Association of gene polymorphisms with blood pressure and the prevalence of hypertension in community-dwelling Japanese individuals.

    Yamada Y, Ando F and Shimokata H

    Department of Human Functional Genomics, Life Science Research Center, Mie University, Mie 514-8507, Japan. yamada@gene.mie-u.ac.jp

    Hypertension is a complex multifactorial disorder that is thought to result from an interaction between genetic background and environmental factors. Although various loci and genes have been implicated in predisposition to hypertension by genetic linkage analyses and candidate gene association studies, the genes that confer susceptibility to this condition remain to be identified definitively. We examined the relations of nine candidate gene polymorphisms to blood pressure (BP) and the prevalence of hypertension in a population-based study. The 2238 subjects (1110 women, 1128 men) were aged 40 to 79 years and were randomly recruited for a population-based prospective cohort study of aging and age-related diseases in Japan. BP was measured with subjects having rested in a sitting position for at least 15 min. Genotypes for the 160C-->T (Arg54Trp) polymorphism of QPCT, the C-->T (Pro198Leu) polymorphism of GPX1, the 137,346T-->C polymorphism of FYN, the -344C-->T polymorphism of CYP11B2, and the A-->G (Ser49Gly) polymorphism of ADRB1 were determined with a fluorescence-based allele-specific DNA primer assay system; those for the A-->G polymorphism of CNR2, the I/D (22,375delAC) polymorphism of CAV1, and the -1213T-->C polymorphism of ESR2 by melting curve analysis, and that for the (GT)n polymorphism of COL1A2 were determined by DNA fragment analysis. The polymorphism of FYN was associated with systolic and diastolic BP in women. In men, polymorphisms of CNR2, QPCT, GPX1, COL1A2, CYP11B2, and ESR2 were associated with systolic and diastolic BP, those of CAV1 and FYN with systolic BP, and that of ADRB1 with diastolic BP. The polymorphisms of QPCT and CYP11B2 were also associated with the prevalence of hypertension in men. These results suggest that polymorphisms of QPCT and CYP11B2 are determinants of BP and the development of hypertension in Japanese men.

    International journal of molecular medicine 2007;19;4;675-83

  • Evidence of LAT as a dual substrate for Lck and Syk in T lymphocytes.

    Jiang Y and Cheng H

    Department of Medicine and Pennstate Cancer Institute, Penn State University College of Medicine, Hershey, PA 17033, United States.

    LAT is a linker protein essential for activation of T lymphocytes. Its rapid tyrosine-phosphorylation upon T cell receptor (TCR) stimulation recruits downstream signaling molecules for membrane targeting and activation. LAT is physically concentrated in cholesterol-enriched membrane microdomains and is known a substrate for Syk/Zap70 kinase. In this study, we demonstrate that LAT serves as a dual substrate for both Lck and Syk kinases. LAT phosphorylation is absent in Lck-deficient J.CaM1.6 cells and Lck is co-precipitated with LAT in pervanadate-activated Jurkat cells. Further, the in vitro kinase assay using purified Lck and LAT shows that Lck directly phosphorylates LAT. Both Lck and Syk, phosphorylate the ITAM-like motifs on LAT at Y171Y191, which is essential for induction of the interaction of LAT with downstream signaling molecules such as Grb2, PLC-gamma1 and c-Cbl, and for activation of MAPK-ERK. Collectively, our data indicate that LAT is an immediate substrate for Lck in one of the earliest events of T cell activation.

    Funded by: NIAID NIH HHS: P30 AI2774

    Leukemia research 2007;31;4;541-5

  • Proteomics analysis of protein kinases by target class-selective prefractionation and tandem mass spectrometry.

    Wissing J, Jänsch L, Nimtz M, Dieterich G, Hornberger R, Kéri G, Wehland J and Daub H

    Department of Cell Biology, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, 38124 Braunschweig, Germany.

    Protein kinases constitute a large superfamily of enzymes with key regulatory functions in nearly all signal transmission processes of eukaryotic cells. However, due to their relatively low abundance compared with the vast majority of cellular proteins, currently available proteomics techniques do not permit the comprehensive biochemical characterization of protein kinases. To address these limitations, we have developed a prefractionation strategy that uses a combination of immobilized low molecular weight inhibitors for the selective affinity capture of protein kinases. This approach resulted in the direct purification of cell type-specific sets of expressed protein kinases, and more than 140 different members of this enzyme family could be detected by LC-MS/MS. Furthermore the enrichment technique combined with phosphopeptide fractionation led to the identification of more than 200 different phosphorylation sites on protein kinases, which often remain occluded in global phosphoproteome analysis. As the phosphorylation states of protein kinases can provide a readout for the signaling activities within a cellular system, kinase-selective phosphoproteomics based on the procedures described here has the potential to become an important tool in signal transduction analysis.

    Molecular & cellular proteomics : MCP 2007;6;3;537-47

  • The novel cellular mechanism of human 5-HT6 receptor through an interaction with Fyn.

    Yun HM, Kim S, Kim HJ, Kostenis E, Kim JI, Seong JY, Baik JH and Rhim H

    Biomedical Research Center, Korea Institute of Science and Technology, Seoul 136-791, Korea.

    The human 5-HT(6) receptor (5-HT(6)R) is one of the latest cloned receptors among the known 5-HT receptors. Its abundant distribution in the limbic region, which participates in the control of mood and emotion and is involved in nervous system diseases such as depression and Alzheimer disease, has caused it to generate much interest. However, the cellular mechanisms of 5-HT(6)R are poorly understood. In the present study we found, using a yeast two-hybrid assay, that the carboxyl-terminal region of 5-HT(6)R interacts with the Fyn-tyrosine kinase. We also determined using a glutathione S-transferase pulldown assay that this interaction was mediated through the SH3 domain of Fyn and confirmed this by co-immunoprecipitation assays in two different transfected cell lines as well as in adult rat brains. Immunocyto(histo)chemistry also showed prominent co-localization between 5-HT(6)R and Fyn in transfected cells and a similar distribution between 5-HT(6)R and Fyn in the rat brain. Based on this interaction, we further examined the modulation of 5-HT(6)R by Fyn and vice versa. In addition, we demonstrated that the activation of 5-HT(6)R activated the extracellular signal-regulated kinase1/2 via an Fyn-dependent pathway. These findings suggest that Fyn may play an important role in 5-HT(6)R- mediated signaling pathways in the central nervous system.

    The Journal of biological chemistry 2007;282;8;5496-505

  • A novel, non-immunogenic Fyn SH3-derived binding protein with tumor vascular targeting properties.

    Grabulovski D, Kaspar M and Neri D

    ETH Zürich, Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland.

    The generation of novel binding molecules based on protein frameworks ("scaffolds") represents an emerging field in protein engineering, with the potential to replace antibodies for many research and clinical applications. Here, we describe the design, construction, characterization, and use of a novel human Fyn SH3 phage library, containing 1.2 x 10(9) individual clone members. We also present the isolation and in vitro characterization of Fyn SH3-derived proteins binding to the extra-domain B of fibronectin, a marker of angiogenesis. One specific binding clone, named D3, was further evaluated and showed a remarkable ability to stain vascular structures in tumor sections. Furthermore, quantitative biodistribution studies in tumor-bearing mice revealed the ability of D3 to selectively accumulate in the tumor. In contrast to human scFv antibody fragments administered to mice, neither Fyn SH3 WT nor the D3 mutant was immunogenic in mice after four intravenous injections. The extra-domain B binding D3 protein opens new biomedical opportunities for the in vivo imaging of solid tumors and for the delivery of toxic agents to the tumoral vasculature.

    The Journal of biological chemistry 2007;282;5;3196-204

  • Sorting of Fas ligand to secretory lysosomes is regulated by mono-ubiquitylation and phosphorylation.

    Zuccato E, Blott EJ, Holt O, Sigismund S, Shaw M, Bossi G and Griffiths GM

    Sir William Dunn School of Pathology, South Parks Rd, Oxford, OX1 3RE, UK.

    Fas ligand (FasL), a potent mediator of apoptosis expressed by CTL and NK cells, is sorted into the inner vesicles of secretory lysosomes for release via exosome-like vesicles. Previous studies identified a proline-rich domain in the cytoplasmic tail required for sorting FasL to secretory lysosomes, but the mechanisms by which this occurs have not been identified. Here we demonstrate that the PRD of FasL binds Fgr, Fyn and Lyn tyrosine kinases, leading to phosphorylation of FasL. Loss of phosphorylation reduces internalisation of FasL into multivesicular bodies. FasL is also directly mono-ubiquitylated at lysines flanking the PRD and mutation of these lysines reduces MVB localisation of FasL. Phosphorylation is not required for ubiquitylation because FasL lacking all tyrosines undergoes mono-ubiquitylation. These studies show that phosphorylation and ubiquitin signals regulate the sorting of FasL to secretory lysosomes by controlling entry into multivesicular bodies.

    Funded by: Wellcome Trust

    Journal of cell science 2007;120;Pt 1;191-9

  • Force sensing by mechanical extension of the Src family kinase substrate p130Cas.

    Sawada Y, Tamada M, Dubin-Thaler BJ, Cherniavskaya O, Sakai R, Tanaka S and Sheetz MP

    Department of Biological Sciences, Columbia University, Sherman Fairchild Center Room 715, MC-2416, 1212 Amsterdam Avenue, New York, NY 10027, USA. ys454-ind@umin.ac.jp

    How physical force is sensed by cells and transduced into cellular signaling pathways is poorly understood. Previously, we showed that tyrosine phosphorylation of p130Cas (Cas) in a cytoskeletal complex is involved in force-dependent activation of the small GTPase Rap1. Here, we mechanically extended bacterially expressed Cas substrate domain protein (CasSD) in vitro and found a remarkable enhancement of phosphorylation by Src family kinases with no apparent change in kinase activity. Using an antibody that recognized extended CasSD in vitro, we observed Cas extension in intact cells in the peripheral regions of spreading cells, where higher traction forces are expected and where phosphorylated Cas was detected, suggesting that the in vitro extension and phosphorylation of CasSD are relevant to physiological force transduction. Thus, we propose that Cas acts as a primary force sensor, transducing force into mechanical extension and thereby priming phosphorylation and activation of downstream signaling.

    Funded by: NIBIB NIH HHS: R01 EB001480, R01 EB001480-03

    Cell 2006;127;5;1015-26

  • TNF-alpha increases tyrosine phosphorylation of vascular endothelial cadherin and opens the paracellular pathway through fyn activation in human lung endothelia.

    Angelini DJ, Hyun SW, Grigoryev DN, Garg P, Gong P, Singh IS, Passaniti A, Hasday JD and Goldblum SE

    Division of Infectious Disease and Pulmonary, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.

    Tumor necrosis factor (TNF)-alpha is a key mediator of sepsis-associated multiorgan failure, including the acute respiratory distress syndrome. We examined the role of protein tyrosine phosphorylation in TNF-alpha-induced pulmonary vascular permeability. Postconfluent human lung microvascular and pulmonary artery endothelial cell (EC) monolayers exposed to human recombinant TNF-alpha displayed a dose- and time-dependent increase in transendothelial [(14)C]albumin flux in the absence of EC injury. TNF-alpha also increased tyrosine phosphorylation of EC proteins, and several substrates were identified as the zonula adherens proteins vascular endothelial (VE)-cadherin, and beta-catenin, gamma-catenin, and p120 catenin (p120(ctn)). Prior protein tyrosine kinase (PTK) inhibition protected against the TNF-alpha effect. TNF-alpha activated multiple PTKs, including src family PTKs. Prior PTK inhibition with the src-selective agents PP1 and PP2 each protected against approximately 60% of the TNF-alpha-induced increment in [(14)C]albumin flux. PP2 also blocked TNF-alpha-induced tyrosine phosphorylation of VE-cadherin, gamma-catenin, and p120(ctn). To identify which src family kinase(s) was required for TNF-alpha-induced vascular permeability, small interfering RNA (siRNA) targeting each of the three src family PTKs expressed in human EC, c-src, fyn, and yes, were introduced into the barrier function assay. Only fyn siRNA protected against the TNF-alpha effect, whereas the c-src and yes siRNAs did not. These combined data suggest that TNF-alpha regulates the pulmonary vascular endothelial paracellular pathway, in part, through fyn activation.

    Funded by: NHLBI NIH HHS: HL-58064, HL-70155

    American journal of physiology. Lung cellular and molecular physiology 2006;291;6;L1232-45

  • Perlecan proteolysis induces an alpha2beta1 integrin- and Src family kinase-dependent anti-apoptotic pathway in fibroblasts in the absence of focal adhesion kinase activation.

    Laplante P, Raymond MA, Labelle A, Abe J, Iozzo RV and Hébert MJ

    Centre de Recherche du Centre Hospitalier de l'Université de Montreal, University of Montreal, 1560 Sherbrooke East, Montreal, Quebec H2L 4M1, Canada.

    Dysregulation of apoptosis in endothelial cells (EC) and fibroblasts contributes to fibrosis. We have shown previously that apoptosis of EC triggers the proteolysis of extracellular matrix components and the release of a C-terminal fragment of perlecan, which in turn inhibits apoptosis of fibroblasts. Here we have defined the receptors and pathways implicated in this anti-apoptotic response in fibroblasts. Neutralizing alpha2beta1 integrin activity in fibroblasts exposed to either medium conditioned by apoptotic EC (SSC) or a recombinant perlecan C-terminal fragment (LG3) prevented resistance to apoptosis and is associated with decreased levels of Akt phosphorylation. Co-incubation of fibroblasts for 24 h with SSC or LG3 in the presence of PP2 (AG1879), a biochemical inhibitor of Src family kinases (SFKs) and focal adhesion kinase, showed a significantly decreased anti-apoptotic response. However, focal adhesion kinase gene silencing with RNA interference did not inhibit the anti-apoptotic response in fibroblasts. Src phosphorylation was increased in fibroblasts exposed to SSC, and transfection of fibroblasts with constitutively active Src mutants induced an anti-apoptotic response that was not further increased by SSC. Also, Src(-/-)Fyn(-/-) fibroblasts failed to mount an anti-apoptotic response in presence of SSC for 24 h but developed a complete anti-apoptotic response when exposed to SSC for 7 days. These results suggest that extracellular matrix fragments produced by apoptotic EC initiate a state of resistance to apoptosis in fibroblasts via an alpha2beta1 integrin/SFK (Src and Fyn)/phosphatidylinositol 3-kinase (PI3K)-dependent pathway. In the long term, additional SFK members are recruited for sustaining the anti-apoptotic response, which could play crucial roles in abnormal fibrogenic healing.

    The Journal of biological chemistry 2006;281;41;30383-92

  • Glucocorticoids cause rapid dissociation of a T-cell-receptor-associated protein complex containing LCK and FYN.

    Löwenberg M, Verhaar AP, Bilderbeek J, Marle Jv, Buttgereit F, Peppelenbosch MP, van Deventer SJ and Hommes DW

    Laboratory of Experimental Internal Medicine, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. m.lowenberg@amc.uva.nl

    Although glucocorticoid (GC)-induced nongenomic effects have been reported, the underlying mechanisms remain unexplained. We previously described that lymphocyte-specific protein tyrosine kinase (LCK) and FYN oncogene related to SRC, FGR, YES (FYN) mediate GC-induced inhibition of T-cell-receptor (TCR) signalling. Here we characterize the underlying molecular mechanism. The present study shows that the GC receptor is part of a TCR-linked multiprotein complex containing heat-shock protein (HSP)90, LCK and FYN, which is essential for TCR-dependent LCK/FYN activation. Experiments with cells transfected with GC-receptor short interfering RNA (siRNA) showed that the GC receptor is an essential component of the TCR signalling complex. Short-term GC treatment induces dissociation of this protein complex, resulting in impaired TCR signalling as a consequence of abrogated LCK/FYN activation. HSP90siRNA-transfected cells are not able to assemble this TCR-associated multiprotein complex, and accordingly HSP90siRNA treatment mimics GC effects on LCK/FYN activities. These observations support a model for nongenomic GC-induced immunosuppression on the basis of dissolution of membrane-bound GC-receptor multiprotein complexes after GC-receptor ligation.

    EMBO reports 2006;7;10;1023-9

  • Magicin associates with the Src-family kinases and is phosphorylated upon CD3 stimulation.

    Lee MF, Beauchamp RL, Beyer KS, Gusella JF and Ramesh V

    Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA 02114, USA.

    We recently identified a novel actin cytoskeleton-associated protein magicin, for merlin and Grb2 interacting cytoskeletal protein. To unravel the cellular functions of magicin, we used a yeast two-hybrid system and identified Fyn tyrosine kinase as a specific binding partner for magicin. Fyn phosphorylates magicin in vitro. In addition to Fyn, Src and Lck also interact with magicin. Upon stimulation with anti-CD3 antibody, magicin is phosphorylated in the T lymphocyte leukemia Jurkat cell line. Magicin phosphorylation is not observed in an Lck-deficient line, J.CaM1.6, indicating that Lck is the major Src family kinase for phosphorylating magicin in Jurkat cells. Employing site-directed mutagenesis along with in vitro kinase assays, we found that Y64 of magicin is phosphorylated by Lck creating a SH2-Grb2 binding motif. Magicin has also been identified as a Mediator subunit (MED28) in the nucleus involved in transcriptional regulation, therefore we propose that magicin may serve as a multi-faceted adaptor/scaffold to relay cellular signaling to the cytoskeleton and from the cytoskeleton to the nucleus.

    Funded by: NINDS NIH HHS: NS24279

    Biochemical and biophysical research communications 2006;348;3;826-31

  • Mast cell costimulation by CD226/CD112 (DNAM-1/Nectin-2): a novel interface in the allergic process.

    Bachelet I, Munitz A, Mankutad D and Levi-Schaffer F

    Deparment of Pharmacology, The School of Pharmacy, The Faculty of Medicine, The Hebrew University of Jerusalem, and Department of Obstetrics and Gynecology, Hadassah University Hospital, Israel.

    Mast cells have critical effector functions in various immune reactions. In allergic inflammation, mast cells interact with tissue-infiltrating eosinophils, forming a regulatory unit in the late and chronic phases of the allergic process. However, the pathways and molecules within this unit are still largely undefined. Here, we show that human mast cells and eosinophils express DNAX accessory molecule 1 (DNAM-1, CD226) and its ligand Nectin-2 (CD112). CD226 synergizes with FcepsilonRI on mast cells, and its engagement augments degranulation through a pathway involving Fyn, linker of activation of T-cells, phospholipase C gamma2, and CD18. This pathway is subject to negative interference by inhibitory receptors and is completely inhibited by linking IgE with IRp60 (CD300a) using a bispecific antibody. Moreover, blocking CD112 expressed on eosinophils using neutralizing antibodies normalized the hyperactivity resulting from IgE-dependent activation of mast cells co-cultured with eosinophils. Our findings demonstrate a novel interface between these two effector cells, implicating relevance for in vivo allergic states. Moreover, costimulatory responses might be a critical component in allergic reactions and may therefore become novel targets for anti-allergic therapy.

    The Journal of biological chemistry 2006;281;37;27190-6

  • A role for Fyn in Trk receptor transactivation by G-protein-coupled receptor signaling.

    Rajagopal R and Chao MV

    Molecular Neurobiology Program, Skirball Institute of Biomolecular Medicine, Department of Cell Biology and Physiology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA.

    Signaling through Trk receptor tyrosine kinases can occur in the absence of neurotrophins through certain G-protein-coupled receptors (GPCRs). It has previously been suggested that GPCR-mediated Trk activation occurs on intracellular membranes and involves several second messengers, including Src family kinases and intracellular calcium. Here, we describe a novel role for the Src family kinase, Fyn, in regulating signaling events between GPCRs and Trk. We find that Fyn expression is sufficient to allow transactivation of Trk by adenosine and that Fyn and Trk are colocalized in a juxtanuclear membrane compartment. Adenosine activation of Fyn results in direct phosphorylation of Trk in vitro and follows a delayed time course that coincides with Trk activation. These results indicate that Fyn is activated by GPCR stimulation and is responsible for transactivation of Trk receptors on intracellular membranes.

    Funded by: NICHD NIH HHS: HD23315; NINDS NIH HHS: NS21072

    Molecular and cellular neurosciences 2006;33;1;36-46

  • Physical and functional interaction of Fyn tyrosine kinase with a brain-enriched Rho GTPase-activating protein TCGAP.

    Liu H, Nakazawa T, Tezuka T and Yamamoto T

    Division of Oncology, Department of Cancer Biology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.

    Fyn, a member of the Src family of tyrosine kinases, is implicated in both brain development and adult brain function. In the present study, we identified a Rho GTPase-activating protein (GAP), TCGAP (Tc10/Cdc42 GTPase-activating protein), as a novel Fyn substrate. TCGAP interacted with Fyn and was phosphorylated by Fyn, with Tyr-406 in the GAP domain as a major Fyn-mediated phosphorylation site. Fyn suppressed the GAP activity of wild-type TCGAP but not the Y406F mutant of TCGAP in a phosphorylation-dependent manner, suggesting that Fyn-mediated Tyr-406 phosphorylation negatively regulated the TCGAP activity. In situ hybridization analyses showed that TCGAP mRNA was expressed prominently in both immature and adult mouse brain, with high levels in cortex, corpus striatum, hippocampus, and olfactory bulb. Overexpression of wild-type TCGAP in PC12 cells suppressed nerve growth factor-induced neurite outgrowth, whereas a GAP-defective mutant of TCGAP enhanced the neurite outgrowth. Nerve growth factor enhanced tyrosine phosphorylation of TCGAP through activation of Src family kinases. These results suggest that TCGAP is involved in Fyn-mediated regulation of axon and dendrite outgrowth.

    The Journal of biological chemistry 2006;281;33;23611-9

  • Structure of human Fyn kinase domain complexed with staurosporine.

    Kinoshita T, Matsubara M, Ishiguro H, Okita K and Tada T

    Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Gakuencho 1-1, Sakai, Osaka 599-8531, Japan. kinotk@b.s.osakafu-u.ac.jp

    The tyrosine kinase Fyn is a member of the Src kinase family. Besides the role of Fyn in T cell signal transduction in concert with Lck, its excess activity in the brain is involved with conditions such as Alzheimer's and Parkinson's diseases. Therefore, inhibition of Fyn kinase may help counteract these nervous system disorders. Here, we solved the crystal structure of the human Fyn kinase domain complexed with staurosporine, a potent kinase inhibitor, at 2.8 A resolution. Staurosporine binds to the ATP-binding site of Fyn in a similar manner as in the Lck- and Csk-complexes. The small structural differences in the staurosporine-binding and/or -unbinding region among the three kinase domains may help obtaining the selective inhibitors against the respective kinases.

    Biochemical and biophysical research communications 2006;346;3;840-4

  • Grb2 and Gads exhibit different interactions with CD28 and play distinct roles in CD28-mediated costimulation.

    Watanabe R, Harada Y, Takeda K, Takahashi J, Ohnuki K, Ogawa S, Ohgai D, Kaibara N, Koiwai O, Tanabe K, Toma H, Sugamura K and Abe R

    Research Institute for Biological Sciences, Faculty of Science and Technology, Tokyo University of Science, 1669 Yamazaki, Noda, Chiba 278-0022, Japan.

    Although both CD28 and ICOS bind PI3K and provide stimulatory signal for T cell activation, unlike CD28, ICOS does not costimulate IL-2 secretion. CD28 binds both PI3K and Grb2, whereas ICOS binds only PI3K. We have generated an ICOS mutant, which can bind Grb2 by replacement of its PI3K binding motif YMFM with the CD28 YMNM motif, and shown that it induces significant activation of the IL-2 promoter. However, this mutant ICOS was insufficient to activate the NF-kappaB pathway. In this study, we show that Gads, but not Grb2, is essential for CD28-mediated NF-kappaB activation, and its binding to CD28 requires the whole CD28 cytoplasmic domain in addition to the YMNM motif. Mutagenesis experiments have indicated that mutations in the N-terminal and/or C-terminal PXXP motif(s) of CD28 significantly reduce their association with Gads, whereas their associations with Grb2 are maintained. They induced strong activity of the NFAT/AP-1 reporter comparable with the CD28 wild type, but weak activity of the NF-kappaB reporter. Grb2- and Gads-dominant-negative mutants had a strong effect on NFAT/AP-1 reporter, but only Gads-dominant-negative significantly inhibited NF-kappaB reporter. Our data suggest that, in addition to the PI3K binding motif, the PXXP motif in the CD28 cytoplasmic domain may also define a functional difference between the CD28- and ICOS-mediated costimulatory signals by binding to Gads.

    Journal of immunology (Baltimore, Md. : 1950) 2006;177;2;1085-91

  • Fibronectin rigidity response through Fyn and p130Cas recruitment to the leading edge.

    Kostic A and Sheetz MP

    Department of Biological Sciences, Columbia University, New York, NY 10027, USA.

    Cell motility on extracellular matrices critically depends on matrix rigidity, which affects cell adhesion and formation of focal contacts. Receptor-like protein tyrosine phosphatase alpha (RPTPalpha) and the alphavbeta3 integrin form a rigidity-responsive complex at the leading edge. Here we show that the rigidity response through increased spreading and growth correlates with leading edge recruitment of Fyn, but not endogenous c-Src. Recruitment of Fyn requires the palmitoylation site near the N-terminus and addition of that site to c-Src enables it to support a rigidity response. In all cases, the rigidity response correlates with the recruitment of the Src family kinase to early adhesions. The stretch-activated substrate of Fyn and c-Src, p130Cas, is also required for a rigidity response and it is phosphorylated at the leading edge in a Fyn-dependent process. A possible mechanism for the fibronectin rigidity response involves force-dependent Fyn phosphorylation of p130Cas with rigidity-dependent displacement. With the greater displacement of Fyn from p130Cas on softer surfaces, there will be less phosphorylation. These studies emphasize the importance of force and nanometer-level movements in cell growth and function.

    Molecular biology of the cell 2006;17;6;2684-95

  • A protein-protein interaction network for human inherited ataxias and disorders of Purkinje cell degeneration.

    Lim J, Hao T, Shaw C, Patel AJ, Szabó G, Rual JF, Fisk CJ, Li N, Smolyar A, Hill DE, Barabási AL, Vidal M and Zoghbi HY

    Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.

    Many human inherited neurodegenerative disorders are characterized by loss of balance due to cerebellar Purkinje cell (PC) degeneration. Although the disease-causing mutations have been identified for a number of these disorders, the normal functions of the proteins involved remain, in many cases, unknown. To gain insight into the function of proteins involved in PC degeneration, we developed an interaction network for 54 proteins involved in 23 inherited ataxias and expanded the network by incorporating literature-curated and evolutionarily conserved interactions. We identified 770 mostly novel protein-protein interactions using a stringent yeast two-hybrid screen; of 75 pairs tested, 83% of the interactions were verified in mammalian cells. Many ataxia-causing proteins share interacting partners, a subset of which have been found to modify neurodegeneration in animal models. This interactome thus provides a tool for understanding pathogenic mechanisms common for this class of neurodegenerative disorders and for identifying candidate genes for inherited ataxias.

    Funded by: NICHD NIH HHS: HD24064; NINDS NIH HHS: NS27699

    Cell 2006;125;4;801-14

  • Stromal-cell-derived factor-1/CXCL12-induced chemotaxis of a T cell line involves intracellular signaling through Cbl and Cbl-b and their regulation by Src kinases and CD45.

    Okabe S, Tauchi T, Ohyashiki K and Broxmeyer HE

    Department of Microbiology/Immunology and Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA.

    Stromal-cell-derived factor-1alpha (SDF-1alpha/CXCL12) is a potent chemoattractant for T cells. We report that Cbl family members, Cbl and Cbl-b, are tyrosine-phosphorylated after SDF-1alpha/CXCL12 stimulation of Jurkat T cells. Enhanced phosphorylation of Cbl and Cbl-b was regulated by src family kinases, and perhaps Fyn. Activated Cbl and Cbl-b interacted with Crk-L, Zap-70, Nck, PLC-gamma and Fyb after SDF-1alpha/CXCL12 stimulation, implicating association of these proteins in SDF-1alpha/CXCL12 actions. SDF-1alpha/CXCL12 did not induce tyrosine phosphorylation of Cbl or Cbl-b in Lck-deficient T cell line J.CaM1.6 or CD45-deficient T cell line J45.01. Thus, Lck Src kinase and tyrosine phosphatase CD45 are likely involved in regulating activation of Cbl family members. A functional role for Cbl and Cbl-b in migration was demonstrated by the decrease in SDF-1/CXCL12-induced migration in a T cell line in which transfected small interfering RNA for Cbl and Cbl-b decreased expression of Cbl and Cbl-b, but not MAPK activity. SDF-1alpha/CXCL12-induced chemotaxis was greatly reduced in the CD45-deficient T cell line. Our results implicate CD45, Cbl, Cbl-b, src kinases and potentially other associated proteins as mediators of SDF-1alpha/CXCL12-induced cell m 11cf igration of Jurkat T cells.

    Funded by: NHLBI NIH HHS: R01 HL67384; NIDDK NIH HHS: R01 DK53674

    Blood cells, molecules & diseases 2006;36;2;308-14

  • IgE-dependent activation of sphingosine kinases 1 and 2 and secretion of sphingosine 1-phosphate requires Fyn kinase and contributes to mast cell responses.

    Olivera A, Urtz N, Mizugishi K, Yamashita Y, Gilfillan AM, Furumoto Y, Gu H, Proia RL, Baumruker T and Rivera J

    Molecular Inflammation Section, Molecular Immunology and Inflammation Branch, NIAMS, National Institutes of Health, Bethesda, Maryland 20892, USA.

    Engagement of the high affinity receptor for IgE (FcepsilonRI) on mast cells results in the production and secretion of sphingosine 1-phosphate (S1P), a lipid metabolite present in the lungs of allergen-challenged asthmatics. Herein we report that two isoforms of sphingosine kinase (SphK1 and SphK2) are expressed and activated upon FcepsilonRI engagement of bone marrow-derived mast cells (BMMC). Fyn kinase is required for FcepsilonRI coupling to SphK1 and -2 and for subsequent S1P production. Normal activation of SphK1 and -2 was restored by expression of wild type Fyn but only partly with a kinase-defective Fyn, indicating that induction of SphK1 and SphK2 depended on both catalytic and noncatalytic properties of Fyn. Downstream of Fyn, the requirements for SphK1 activation differed from that of SphK2. Whereas SphK1 was considerably dependent on the adapter Grb2-associated binder 2 and phosphatidylinositol 3-OH kinase, SphK2 showed minimal dependence on these molecules. Fyn-deficient BMMC were defective in chemotaxis and, as previously reported, in degranulation. These functional responses were partly reconstituted by the addition of exogenous S1P to FcepsilonRI-stimulated cells. Taken together with our previous study, which demonstrated delayed SphK activation in Lyn-deficient BMMC, we propose a cooperative role between Fyn and Lyn kinases in the activation of SphKs, which contributes to mast cell responses.

    Funded by: NIAID NIH HHS: AI51612

    The Journal of biological chemistry 2006;281;5;2515-25

  • Identification of preferred protein interactions by phage-display of the human Src homology-3 proteome.

    Kärkkäinen S, Hiipakka M, Wang JH, Kleino I, Vähä-Jaakkola M, Renkema GH, Liss M, Wagner R and Saksela K

    Institute of Medical Technology, University of Tampere and Tampere University Hospital, Biokatu 8, Tampere 33014, Finland.

    We have determined the human genome to contain 296 different Src homology-3 (SH3) domains and cloned them into a phage-display vector. This provided a powerful and unbiased system for simultaneous assaying of the complete human SH3 proteome for the strongest binding to target proteins of interest, without the limitations posed by short linear peptide ligands or confounding variables of more indirect methods for protein interaction screening. Studies involving three ligand proteins, human immunodeficiency virus-1 Nef, p21-activated kinase (PAK)2 and ADAM15, showed previously reported as well as novel SH3 partners with nanomolar affinities specific for them. This argues that SH3 domains may have a more dominant role in directing cellular protein interactions than has been assumed. Besides showing potentially important new SH3-directed interactions, these studies also led to the discovery of novel signalling proteins, such as the PAK2-binding adaptor protein POSH2 and the ADAM15-binding sorting nexin family member SNX30.

    EMBO reports 2006;7;2;186-91

  • Modelling thymic HIV-1 Nef effects.

    Stove V and Verhasselt B

    Department of Clinical Chemistry, Microbiology and Immunology, Ghent University, Ghent University Hospital, 9000 Ghent, Belgium.

    The nef gene is conserved among primate lentiviruses and is one of the first viral genes that is transcribed following infection. This suggests a critical role for Nef in the virus life cycle and in the pathogenesis of lentiviral infections. In vitro, several functions have been described, including down regulation of CD4 and MHC class I surface expression, altered T-cell signaling and activation, and enhanced viral infectivity. However, the impact of these individual functions on viral pathogenicity in general, and thymic T cell production in particular, remains elusive. Here, we review the observations from experimental models that have been used to study the pathogenic effect of HIV-1 Nef on the thymus. These in vitro and in vivo studies have led to a better understanding of Nef's mechanism of action, although there still exists discord as to the contribution of Nef-mediated disturbance of thymopoiesis in the pathogenesis of AIDS.

    Current HIV research 2006;4;1;57-64

  • Disease-related modifications in tau affect the interaction between Fyn and Tau.

    Bhaskar K, Yen SH and Lee G

    Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA.

    Microtubule-associated protein tau is the major component of the neurofibrillary tangles of Alzheimer disease (AD) and is genetically linked to frontotemporal dementias (FTDP-17). We have recently shown that tau interacts with the SH3 domain of Fyn, an Src family non-receptor tyrosine kinase, and is tyrosine-phosphorylated by Fyn on Tyr-18. Also, tyrosine-phosphorylated tau is present in the neuropathology of AD. To determine whether alterations in the tau-Fyn interaction might correlate with disease-related factors in AD and FTDP-17, we have performed real-time surface plasmon resonance studies on a panel of 21 tau constructs with Fyn SH3. We report that the interaction between Fyn SH3 and 3R-tau was 20-fold higher than that with 4R-tau. In addition, the affinity between 4R-tau and Fyn SH3 was increased 25-45-fold by phosphorylation-mimicking mutations or by FTDP-17 mutations. In vitro kinase reactions show that tau, with lower affinity SH3 interactions, exhibited a lower level of Tyr-18 phosphorylation under our reaction conditions. Lastly, we have demonstrated that tau is phosphorylated on Tyr-18 in the tau P301L mouse model for tauopathy (JNPL3). In summary, our results suggest that disease-related phosphorylation and missense mutations of tau increase association of tau with Fyn. Because these effects are mediated through the 4R component of the tau population, these results also have implications for the FTDP-17 diseases caused by increased expression of 4R-tau. Our data support a role for the Fyn-tau interaction in neurodegeneration.

    Funded by: NIA NIH HHS: AG17753

    The Journal of biological chemistry 2005;280;42;35119-25

  • Towards a proteome-scale map of the human protein-protein interaction network.

    Rual JF, Venkatesan K, Hao T, Hirozane-Kishikawa T, Dricot A, Li N, Berriz GF, Gibbons FD, Dreze M, Ayivi-Guedehoussou N, Klitgord N, Simon C, Boxem M, Milstein S, Rosenberg J, Goldberg DS, Zhang LV, Wong SL, Franklin G, Li S, Albala JS, Lim J, Fraughton C, Llamosas E, Cevik S, Bex C, Lamesch P, Sikorski RS, Vandenhaute J, Zoghbi HY, Smolyar A, Bosak S, Sequerra R, Doucette-Stamm L, Cusick ME, Hill DE, Roth FP and Vidal M

    Center for Cancer Systems Biology and Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street, Boston, Massachusetts 02115, USA.

    Systematic mapping of protein-protein interactions, or 'interactome' mapping, was initiated in model organisms, starting with defined biological processes and then expanding to the scale of the proteome. Although far from complete, such maps have revealed global topological and dynamic features of interactome networks that relate to known biological properties, suggesting that a human interactome map will provide insight into development and disease mechanisms at a systems level. Here we describe an initial version of a proteome-scale map of human binary protein-protein interactions. Using a stringent, high-throughput yeast two-hybrid system, we tested pairwise interactions among the products of approximately 8,100 currently available Gateway-cloned open reading frames and detected approximately 2,800 interactions. This data set, called CCSB-HI1, has a verification rate of approximately 78% as revealed by an independent co-affinity purification assay, and correlates significantly with other biological attributes. The CCSB-HI1 data set increases by approximately 70% the set of available binary interactions within the tested space and reveals more than 300 new connections to over 100 disease-associated proteins. This work represents an important step towards a systematic and comprehensive human interactome project.

    Funded by: NCI NIH HHS: R33 CA132073; NHGRI NIH HHS: P50 HG004233, R01 HG001715, RC4 HG006066, U01 HG001715; NHLBI NIH HHS: U01 HL098166

    Nature 2005;437;7062;1173-8

  • Fyn kinase induces synaptic and cognitive impairments in a transgenic mouse model of Alzheimer's disease.

    Chin J, Palop JJ, Puoliväli J, Massaro C, Bien-Ly N, Gerstein H, Scearce-Levie K, Masliah E and Mucke L

    Gladstone Institute of Neurological Disease, University of California, San Francisco, California 94158, USA.

    Human amyloid precursor protein (hAPP) transgenic mice with high levels of amyloid-beta (Abeta) develop behavioral deficits that correlate with the depletion of synaptic activity-related proteins in the dentate gyrus. The tyrosine kinase Fyn is altered in Alzheimer's disease brains and modulates premature mortality and synaptotoxicity in hAPP mice. To determine whether Fyn also modulates Abeta-induced behavioral deficits and depletions of synaptic activity-dependent proteins, we overexpressed Fyn in neurons of hAPP mice with moderate levels of Abeta production. Compared with nontransgenic controls and singly transgenic mice expressing hAPP or FYN alone, doubly transgenic FYN/hAPP mice had striking depletions of calbindin, Fos, and phosphorylated ERK (extracellular signal-regulated kinase), impaired neuronal induction of Arc, and impaired spatial memory retention. These deficits were qualitatively and quantitatively similar to those otherwise seen only in hAPP mice with higher Abeta levels. Surprisingly, levels of active Fyn were lower in high expresser hAPP mice than in NTG controls and lower in FYN/hAPP mice than in FYN mice. Suppression of Fyn activity may result from dephosphorylation by striatal-enriched phosphatase, which was upregulated in FYN/hAPP mice and in hAPP mice with high levels of Abeta. Thus, increased Fyn expression is sufficient to trigger prominent neuronal deficits in the context of even relatively moderate Abeta levels, and inhibition of Fyn activity may help counteract Abeta-induced impairments.

    Funded by: NIA NIH HHS: AG022074; NINDS NIH HHS: NS41787

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2005;25;42;9694-703

  • Disruption of the actin network enhances MAP-2c and Fyn-induced process outgrowth.

    Zamora-Leon SP and Shafit-Zagardo B

    Department of Pathology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.

    We investigated the interaction of MAP-2c and Fyn in the initiation of process outgrowth in COS7 cells. Single transfections of Fyn and MAP-2c resulted in a dramatic decrease in flat, rounded COS7 cells, and a significant increase in both the number of cells with multiple short, spike-like processes, and cells with longer processes. Co-transfection of Fyn and MAP-2c resulted in an additive increase in the number of cells with more than two processes and discrete sites of co-localization within processes. When single or double transfected cells were treated with cytochalasin D or lantrunculin there was a dramatic increase in the number of cells with more than two processes. In addition, there was an increase in the length of the processes, both in single and double transfected cells, suggesting that the actin meshwork provides a barrier for MT-based process extension. When co-transfected cells were post-treated with nocodazole, Fyn was not associated with MAP-2c and acetylated, stable tubulin. Although some Fyn/MAP-2c co-localization was retained, punctate staining of MAP-2c and Fyn were observed at the cell periphery, in areas devoid of stable MTs. Mutations in either tyrosine 67 (Tyr67), a site on human MAP-2c phosphorylated by Fyn, or a second tyrosine residue (Tyr50), did not alter the ability of MAP-2c and Fyn to induce process outgrowth. These studies suggest that independent of one another MAP-2c and Fyn are able to induce process outgrowth and in concert can initiate and enhance process outgrowth in an additive manner.

    Cell motility and the cytoskeleton 2005;62;2;110-23

  • Tyrosine 394 is phosphorylated in Alzheimer's paired helical filament tau and in fetal tau with c-Abl as the candidate tyrosine kinase.

    Derkinderen P, Scales TM, Hanger DP, Leung KY, Byers HL, Ward MA, Lenz C, Price C, Bird IN, Perera T, Kellie S, Williamson R, Noble W, Van Etten RA, Leroy K, Brion JP, Reynolds CH and Anderton BH

    Department of Neuroscience, Institute of Psychiatry, King's College London, London SE5 8AF, United Kingdom.

    Tau is a major microtubule-associated protein of axons and is also the principal component of the paired helical filaments (PHFs) that comprise the neurofibrillary tangles found in Alzheimer's disease and other tauopathies. Besides phosphorylation of tau on serine and threonine residues in both normal tau and tau from neurofibrillary tangles, Tyr-18 was reported to be a site of phosphorylation by the Src-family kinase Fyn. We examined whether tyrosine residues other than Tyr-18 are phosphorylated in tau and whether other tyrosine kinases might phosphorylate tau. Using mass spectrometry, we positively identified phosphorylated Tyr-394 in PHF-tau from an Alzheimer brain and in human fetal brain tau. When wild-type human tau was transfected into fibroblasts or neuroblastoma cells, treatment with pervanadate caused tau to become phosphorylated on tyrosine by endogenous kinases. By replacing each of the five tyrosines in tau with phenylalanine, we identified Tyr-394 as the major site of tyrosine phosphorylation in tau. Tyrosine phosphorylation of tau was inhibited by PP2 (4-amino-5-(4-chlorophenyl-7-(t-butyl)pyrazolo[3,4-d]pyrimidine), which is known to inhibit Src-family kinases and c-Abl. Cotransfection of tau and kinases showed that Tyr-18 was the major site for Fyn phosphorylation, but Tyr-394 was the main residue for Abl. In vitro, Abl phosphorylated tau directly. Abl could be coprecipitated with tau and was present in pretangle neurons in brain sections from Alzheimer cases. These results show that phosphorylation of tau on Tyr-394 is a physiological event that is potentially part of a signal relay and suggest that Abl could have a pathogenic role in Alzheimer's disease.

    Funded by: Wellcome Trust

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2005;25;28;6584-93

  • Fyn is a downstream target of the pleiotrophin/receptor protein tyrosine phosphatase beta/zeta-signaling pathway: regulation of tyrosine phosphorylation of Fyn by pleiotrophin.

    Pariser H, Ezquerra L, Herradon G, Perez-Pinera P and Deuel TF

    Department of Molecular and Experimental Medicine, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.

    Pleiotrophin (PTN the protein, Ptn the gene) signals downstream targets through inactivation of its receptor, the transmembrane receptor protein tyrosine phosphatase (RPTP)beta/zeta, disrupting the balanced activity of RPTPbeta/zeta and the activity of a constitutively active tyrosine kinase. As a consequence of the inactivation of RPTPbeta/zeta, PTN stimulates a sharp increase in the levels of tyrosine phosphorylation of the substrates of RPTPbeta/zeta in PTN-stimulated cells. We now report that the Src family member Fyn interacts with the intracellular domain of RPTPbeta/zeta in a yeast two-hybrid system. We further demonstrate that Fyn is a substrate of RPTPbeta/zeta, and that tyrosine phosphorylation of Fyn is sharply increased in PTN-stimulated cells. In previous studies, we demonstrated that beta-catenin and beta-adducin are targets of the PTN/RPTPbeta/zeta-signaling pathway and defined the mechanisms through which tyrosine phosphorylation of beta-catenin and beta-adducin disrupts cytoskeletal protein complexes. We conclude that Fyn is a downstream target of the PTN/RPTPbeta/zeta-signaling pathway and suggest that PTN coordinately regulates tyrosine phosphorylation of beta-catenin, beta-adducin, and Fyn through the PTN/RPTPbeta/zeta-signaling pathway and that together Fyn, beta-adducin, and beta-catenin may be effectors of the previously described PTN-stimulated disruption of cytoskeletal stability, increased cell plasticity, and loss of cell-cell adhesion that are characteristic of PTN-stimulated cells and a feature of many human malignant cells in which mutations have established constitutive expression of the Ptn gene.

    Funded by: NCI NIH HHS: CA66029, CA88440; NHLBI NIH HHS: NHLBI 31102; NIDDK NIH HHS: DK 53557

    Biochemical and biophysical research communications 2005;332;3;664-9

  • Calcium-induced human keratinocyte differentiation requires src- and fyn-mediated phosphatidylinositol 3-kinase-dependent activation of phospholipase C-gamma1.

    Xie Z, Singleton PA, Bourguignon LY and Bikle DD

    Endocrine Unit, Veterans Affairs Medical Center, Northern California Institute for Research and Education and University of California-San Francisco, San Francisco, CA 94121, USA. zjxie@itsa.ucsf.edu

    We have previously demonstrated that phospholipase C (PLC)-gamma1 is required for calcium-induced human keratinocyte differentiation. In the present study, we investigated whether the activation of PLC-gamma1 by nonreceptor kinases such as src and fyn plays a role in mediating this process. Our results showed that the combination of dominant negative src and fyn blocked calcium-stimulated PLC-gamma1 activity and human keratinocyte differentiation, whereas each separately has little effect. However, unlike the activation of PLC-gamma1 by epidermal growth factor, calcium-induced activation of PLC-gamma1 was not a result of direct tyrosine phosphorylation. Therefore, we examined an alternative mechanism, in particular phosphatidylinositol 3,4,5-triphosphate (PIP3) formed as a product of phosphatidylinositol 3-kinase (PI3K) activity. PIP3 binds to and activates PLC-gamma1. The combination of dominant negative src and fyn blocked calcium-induced tyrosine phosphorylation of the regulatory subunit of PI3K, p85alpha, and the activity of the catalytic subunit of PI3K. PI3K inhibitors blocked calcium activation of PLC-gamma1 as well as the induction of keratinocyte differentiation markers involucrin and transglutaminase. These data indicate that calcium activates PLC-gamma1 via increased PIP3 formation mediated by c-src- and fyn-activated PI3K. This activation is required for calcium-induced human keratinocyte differentiation.

    Molecular biology of the cell 2005;16;7;3236-46

  • Altered p59Fyn kinase expression accompanies disease progression in Alzheimer's disease: implications for its functional role.

    Ho GJ, Hashimoto M, Adame A, Izu M, Alford MF, Thal LJ, Hansen LA and Masliah E

    Department of Neurosciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0624, USA.

    Alzheimer's disease (AD) is characterized by progressive decline in memory and other cognitive domains, accompanied by early loss of presynaptic terminals, amyloid-bearing neuritic plaques and neurofibrillary tangles containing hyperphosphorylated tau. The mechanisms leading to neurodegeneration are not completely understood, however, recent evidence suggests that alterations in p59Fyn kinase, an Src family tyrosine kinase, might contribute to AD pathogenesis. In this context, the main objective of the present study was to investigate the relationship between Fyn protein levels and the neurological and neuropathological alterations in AD. We found, by quantitative immunoblotting, that in AD, Fyn levels were increased in the insoluble fraction and decreased in the soluble fraction. Soluble Fyn levels were directly correlated with the cognitive scores and levels of synaptophysin immunoreactivity, and inversely correlated with neurofibrillary tangle counts in the frontal cortex. Consistent with these findings, the immunocytochemical analysis showed that in AD cases, Fyn levels were decreased in the synapses and increased in the neuronal cell bodies where it was colocalized with neurofibrillary tangles. Taken together, these findings suggest that alterations in Fyn localization might be associated with neurofibrillary pathology and synapse loss in AD.

    Funded by: NIA NIH HHS: AG00975, AG18440, P50 AG05131

    Neurobiology of aging 2005;26;5;625-35

  • Interactions of TOM1L1 with the multivesicular body sorting machinery.

    Puertollano R

    Laboratory of Cell Signaling, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA. puertolr@mail.nih.gov

    Tom1L1 (Tom1-like1) and related proteins Tom1 (Target of Myb1) and Tom1L2 (Tom1-like2) constitute a new protein family characterized by the presence of a VHS (Vps27p/Hrs/Stam) domain in the N-terminal portion followed by a GAT (GGA and Tom) domain. Recently it was demonstrated that the GAT domain of both Tom1 and Tom1L1 binds ubiquitin, suggesting that these proteins might participate in the sorting of ubiquitinated proteins into multivesicular bodies (MVBs). Here we report a novel interaction between Tom1L1 and members of the MVB sorting machinery. Specifically, we found that the VHS domain of Tom1L1 interacts with Hrs (Hepatocyte growth factor-regulated tyrosine kinase substrate), whereas a PTAP motif, located between the VHS and GAT domain of Tom1L1, is responsible for binding to TSG101 (tumor susceptibility gene 101). Myc epitope-tagged Tom1L1 showed a cytosolic distribution but was recruited to endosomes following Hrs expression. In addition, Tom1L1 possesses several tyrosine motifs at the C-terminal region that mediate interactions with members of the Src family kinases and other signaling proteins such as Grb2 and p85. We showed that a fraction of Fyn kinase localizes at endosomes and that this distribution becomes more evident after epidermal growth factor internalization. Moreover, expression of a constitutive active form of Fyn also promoted the recruitment of Tom1L1 to enlarged endosomes. Taken together, we propose that Tom1L1 could act as an intermediary between signaling and degradative pathways.

    The Journal of biological chemistry 2005;280;10;9258-64

  • Nonsteroidal anti-inflammatory drugs inhibit a Fyn-dependent pathway coupled to Rac and stress kinase activation in TCR signaling.

    Paccani SR, Patrussi L, Ulivieri C, Masferrer JL, D'Elios MM and Baldari CT

    Department of Evolutionary Biology, University of Siena, Siena, Via Aldo Moro 2, 53100 Siena, Italy.

    In addition to their anti-inflammatory properties, nonsteroidal anti-inflammatory drugs (NSAIDs) harbor immunosuppressive activities related to their capacity both to inhibit cyclooxygenases (COXs) and to act as peroxisome proliferator-activated receptor (PPAR) ligands. We have previously shown that the stress-activated kinase p38 is a selective target of NSAIDs in T cells. Here we have investigated the effect of NSAIDs on the signaling pathway triggered by the T-cell antigen receptor (TCR) and leading to stress kinase activation. The results show that nonselective and COX-1-selective NSAIDs also block activation of the stress kinase c-Jun N-terminal kinase (JNK) and that prostaglandin-E2 (PGE2) reverses this block and enhances TCR-dependent JNK activation. Analysis of the activation state of the components upstream of p38 and JNK showed that NSAIDs inhibit the serine-threonine kinase p21-activated protein kinase 1 (Pak1) and the small guanosine 5'-triphosphatase (GTPase) Rac, as well as the Rac-specific guanine nucleotide exchanger, Vav. Furthermore, activation of Fyn, which controls Vav phosphorylation, is inhibited by NSAIDs, whereas activation of lymphocyte-specific protein tyrosine kinase (Lck) and of the Lck-dependent tyrosine kinase cascade is unaffected. Accordingly, constitutively active Fyn reverses the NSAID-dependent stress kinase inhibition. The data identify COX-1 as an important early modulator of TCR signaling and highlight a TCR proximal pathway selectively coupling the TCR to stress kinase activation.

    Funded by: Telethon: E.1161

    Blood 2005;105;5;2042-8

  • Pigment epithelium-derived factor inhibits fibroblast-growth-factor-2-induced capillary morphogenesis of endothelial cells through Fyn.

    Kanda S, Mochizuki Y, Nakamura T, Miyata Y, Matsuyama T and Kanetake H

    Department of Molecular Microbiology and Immunology, Division of Endothelial Cell Biology, Nagasaki University Graduate School of Biomedical Science, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan. shigeruk@net.nagasaki-u.ac.jp

    Pigment epithelium-derived factor (PEDF) exerts anti-angiogenic actions. However, the signal-transduction pathways regulated by PEDF remain to be elucidated. We show here that PEDF inhibited fibroblast growth factor 2 (FGF-2) induced capillary morphogenesis of a murine brain capillary endothelial cell line (IBE cells) and of human umbilical-vein endothelial cells (HUVECs) cultured on growth-factor-reduced Matrigel. We previously showed that FGF-2-mediated capillary morphogenesis was blocked by the Src-kinase inhibitor PP2 and that expression of dominant negative Fyn in IBE cells inhibited capillary morphogenesis. We examined the effect of PEDF on kinase activity of Fyn and found that PEDF downregulated FGF-2-promoted Fyn activity by tyrosine phosphorylation at the C-terminus in a Fes-dependent manner. In a stable IBE cell line expressing kinase-inactive Fes (KE5-15 Fes cells), PEDF failed to inhibit FGF-2-induced capillary morphogenesis or Fyn activity. PEDF induced the colocalization of Fyn and Fes in IBE cells expressing wild-type Fes, but not in KE5-15 Fes cells. In addition, wild-type Fes increased the tyrosine phosphorylation of Fyn in vitro, suggesting that Fes might directly phosphorylate Fyn. Expression of constitutively active Fyn (Y531F) in IBE cells exhibited capillary morphogenesis in the absence of FGF-2 and was resistant for PEDF treatment. Our results suggest that PEDF downregulates Fyn through Fes, resulting in inhibition of FGF-2-induced capillary morphogenesis of endothelial cells.

    Journal of cell science 2005;118;Pt 5;961-70

  • The adaptor protein 3BP2 associates with VAV guanine nucleotide exchange factors to regulate NFAT activation by the B-cell antigen receptor.

    Foucault I, Le Bras S, Charvet C, Moon C, Altman A and Deckert M

    Institut National de la Santé et de la Recherche Médicale Unité 576, Nice, France.

    Engagement of the B-cell antigen receptor (BCR) activates kinases of the Src and Syk families and signaling complexes assembled by adaptor proteins, which dictate B-cell fate and function. The adaptor 3BP2/SH3BP2, an Abl Src homology domain 3 (SH3)-binding and Syk-kinases interacting protein, exhibits positive regulatory roles in T, natural killer (NK), and basophilic cells. However, its involvement in BCR signaling is completely unknown. Here we show that 3BP2 is tyrosine phosphorylated following BCR aggregation on B lymphoma cells, and that 3BP2 is a substrate for Syk and Fyn, but not Btk. To further explore the function of 3BP2 in B cells, we screened a yeast 2-hybrid B-lymphocyte library and found 3BP2 as a binding partner of Vav proteins. The interaction between 3BP2 and Vav proteins involved both constitutive and inducible mechanisms. 3BP2 also interacted with other components of the BCR signaling pathway, including Syk and phospholipase C gamma (PLC-gamma). Furthermore, overexpression and RNAi blocking experiments showed that 3BP2 regulated BCR-mediated activation of nuclear factor of activated T cells (NFATs). Finally, evidence was provided that 3BP2 functionally cooperates with Vav proteins and Rho GTPases to activate NFATs. Our results show that 3BP2 may regulate BCR-mediated gene activation through Vav proteins.

    Blood 2005;105;3;1106-13

  • Regulation of ultraviolet B-induced phosphorylation of histone H3 at serine 10 by Fyn kinase.

    He Z, Cho YY, Ma WY, Choi HS, Bode AM and Dong Z

    Hormel Institute, University of Minnesota, Austin, Minnesota 55912, USA.

    Ultraviolet B (UVB) induces phosphorylation of histone H3 at serine 10, and mitogen-activated protein kinases are involved in this signal transduction pathway. Here we provide evidence that Fyn kinase, a member of the Src kinase family, is involved in the UVB-induced phosphorylation of histone H3 at serine 10. UVB distinctly increased Fyn kinase activity and phosphorylation. Fyn kinase inhibitors 4-amino-5-(4-chlorophenyl)-7(t-butyl)pyrazol(3,4-d)pyramide and leflunomide, an Src kinase inhibitor, suppressed both UVB-induced phosphorylation of histone H3 at serine 10 and Fyn kinase activity and phosphorylation. UVB-induced phosphorylation of histone H3 at serine 10 was blocked by either a dominant-negative mutant of Fyn (DNM-Fyn) kinase or small interfering RNA of Fyn kinase. UVB-induced phosphorylation and activities of ERKs and protein kinase B/Akt were markedly inhibited by DNM-Fyn kinase. However, DNM-Fyn kinase did not inhibit UVB-induced phosphorylation of p38 MAPK or c-Jun N-terminal kinases. Active Fyn kinase phosphorylated histone H3 at serine 10 in vitro, and the phosphorylated Fyn kinase could translocate into the nucleus of HaCaT cells. These results indicate that Fyn kinase plays a key role in the UVB-induced phosphorylation of histone H3 at serine 10.

    Funded by: NCI NIH HHS: CA27502, CA77646

    The Journal of biological chemistry 2005;280;4;2446-54

  • Fyn phosphorylates human MAP-2c on tyrosine 67.

    Zamora-Leon SP, Bresnick A, Backer JM and Shafit-Zagardo B

    Department of Pathology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.

    The Src homology 3 (SH3) domain of Fyn binds to a conserved PXXP motif on microtubule-associated protein-2. Co-transfections into COS7 cells and in vitro kinase assays performed with Fyn and wild-type, or mutant MAP-2c, determined that Fyn phosphorylated MAP-2c on tyrosine 67. The phosphorylation generated a consensus sequence for the binding of the SH2 domain of Grb2 (pYSN). Pull-down assays with SH2-Grb2 from human fetal brain homogenates, and co-immunoprecipitation of Grb2 and MAP-2 confirmed the interaction in vivo, and demonstrated that MAP-2c is tyrosine-phosphorylated in human fetal brain. Filter overlay assays confirmed that the SH2 domain of Grb2 binds to human MAP-2c following incubation with active Fyn. Enzyme-linked immunosorbent assays confirmed the interaction between the SH2 domain of Grb2 and a tyrosine-phosphorylated MAP-2 peptide spanning the pY(67)SN motif. Thus, MAP-2c can directly recruit multiple signaling proteins important for central nervous system development.

    Funded by: NIGMS NIH HHS: GM55692; NINDS NIH HHS: NS38102

    The Journal of biological chemistry 2005;280;3;1962-70

  • Stromal cell-derived factor-1alpha/CXCL12-induced chemotaxis of T cells involves activation of the RasGAP-associated docking protein p62Dok-1.

    Okabe S, Fukuda S, Kim YJ, Niki M, Pelus LM, Ohyashiki K, Pandolfi PP and Broxmeyer HE

    Department of Microbiology/Immunology and the Walther Oncology Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA.

    Events mediating stromal cell-derived factor-1 (SDF-1alpha/CXCL12) chemotaxis of lymphocytes are not completely known. We evaluated intracellular signaling through RasGAP-associated protein p62Dok-1 (downstream of tyrosine kinase [Dok-1]) and associated proteins. SDF-1alpha/CXCL12 stimulated Dok-1 tyrosine phosphorylation and association with RasGAP, adaptor protein p46Nck, and Crk-L in Jurkat T cells. The phosphorylation of Dok-1 was blocked by pretreatment of cells with the src kinase inhibitor PP2. Src kinase family member Lck was implicated. SDF-1alpha/CXCL12 did not phosphorylate Dok-1 in J.CaM1.6 cells, a Jurkat derivative not expressing Lck, but did phosphorylate Dok-1 in J.CaM1.6 cells expressing Lck. SDF-1alpha/CXCL12 induced the tyrosine phosphorylation of Pyk2 and the association of Pyk2 with zeta chain-associated protein-70 kilodaltons (Zap-70) and Vav. SDF-1alpha/CXCL12 enhanced the association of RasGAP with Pyk2. CXCR4-expressing NIH3T3 and Baf3 cells transfected with full-length Dok-1 cDNA were suppressed in their responses to SDF-1alpha/CXCL12-induced chemotaxis; mitogen-activated protein (MAP) kinase activity was also decreased. Chemotaxis to SDF-1/CXCL12 was significantly enhanced in Dok-1(-/-) CD4+ and CD8+ splenic T cells. These results implicate Dok-1, Nck, Crk-L, and Src kinases-especially Lck, Pyk2, Zap-70, Vav, and Ras-GAP-in intracellular signaling by SDF-1alpha/CXCL12, and they suggest that Dok-1 plays an important role in SDF-1alpha/CXCL12-induced chemotaxis in T cells.

    Funded by: NHLBI NIH HHS: R01 HL67384, R01 HL69669; NIDDK NIH HHS: R01 DK536764

    Blood 2005;105;2;474-80

  • Nef: "necessary and enforcing factor" in HIV infection.

    Joseph AM, Kumar M and Mitra D

    National Centre for Cell Science, Ganeshkhind, Pune-411007, India.

    The Human Immunodeficiency Virus -1 (HIV-1) Nef protein that was originally identified as a viral negative factor is a 27kDa myristoylated protein. However, this so called dispensable viral protein has emerged as one of the most important proteins for viral life cycle. Nef not only establishes the host cell environment suitable for viral replication and pathogenesis but also facilitates the progression of the infection into disease. Previous efforts have been focussed to explain how Nef down modulates host cell receptors like CD4 and MHC-1 molecules, thereby helping the virus to evade host defense and to increase viral infectivity. Nef also ably modulates specific processes like apoptosis in favour of viral life cycle other than being the stimulus for cell activation and signal transduction pathways. After much maligning over its reported positive or negative functions on the HIV-1 Long Terminal Repeat (LTR) promoter, the Nef protein is now perceived to enhance viral replication and infection through a combination of different effector functions. Recent reports emphasize a role for Nef in viral gene expression and place it in a prime position to oversee and optimize viral replication. Nef may do so by enhancing Tat mediated gene expression from the LTR by activating signalling pathways that result in a concomitant increase in the activation of general transcription factors, and also by mediating translocation of repression factors from the nucleus. Thus, Nef not only enhances infection but also plays an important role in viral replication and pathogenesis.

    Current HIV research 2005;3;1;87-94

  • Substrate-trapping techniques in the identification of cellular PTP targets.

    Blanchetot C, Chagnon M, Dubé N, Hallé M and Tremblay ML

    McGill Cancer Centre, McGill University, 3655 Sir William-Osler, Room 715, Montreal, Quebec, H3G1Y6 Canada. christophe.blanchetot@mcgill.ca

    Tyrosine phosphorylation is negatively regulated by the protein-tyrosine phosphatases (PTPs). In order to find the physiological substrates of these enzymes, diverse PTP mutants that do not possess any catalytic activities but appear to bind tightly to their tyrosine phosphorylated substrates have been designed. Hence, they can be used as tools to pull out their respective substrates from heterogeneous extracts. Named PTP "substrate-trapping" mutants by the Tonks laboratory, they represent a diverse variety of defective PTPs that are epitomized by the Cys to Ser mutant (C/S) where the active cysteine residue of the signature motif is mutated to a serine residue. In addition, new mutants have been developed which are expected to help characterize novel and less abundant substrates. In this article, we review and describe all the different substrate-trapping mutants that have successfully been used or that hold interesting promises. We present their methodology to identify substrates in vivo (co-immunoprecipitation) and in vitro (GST pulldown), and provide a current list of substrates that have been identified using these technologies.

    Methods (San Diego, Calif.) 2005;35;1;44-53

  • Src, Fyn and Yes play differential roles in VEGF-mediated endothelial cell events.

    Werdich XQ and Penn JS

    Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.

    Widely coexpressed Src family kinase (SFK) members Src, Fyn and Yes are involved in various cellular events, often acting downstream of receptor tyrosine kinases, such as vascular endothelial growth factor (VEGF) receptors. They are well known for their functional redundancy; any unique features remain largely undefined. Utilizing RNA interference, we have selectively knocked down Src, Fyn and Yes in human retinal microvascular endothelial cells (HRMECs). Cells with single SFK knockdown showed that all three kinases were required for VEGF mitogenic signaling. VEGF-induced cell migration was significantly increased in Fyn-deficient cells and decreased in Yes-deficient cells. Selective interference of Fyn, but not Src or Yes, impaired VEGF-induced tube formation in HRMECs. Cells in which all three SFKs were targeted showed significant inhibition of all three cellular events. In addition, interference of Src, Fyn and Yes did not affect the anti-apoptotic effect of VEGF in HRMECs, as determined by DNA fragmentation analysis. These results provide direct evidence that Src, Fyn and Yes maintain distinct properties in the regulation of VEGF-mediated endothelial cell events.

    Funded by: NEI NIH HHS: EY07533, EY08126

    Angiogenesis 2005;8;4;315-26

  • Phosphorylation of DCC by Fyn mediates Netrin-1 signaling in growth cone guidance.

    Meriane M, Tcherkezian J, Webber CA, Danek EI, Triki I, McFarlane S, Bloch-Gallego E and Lamarche-Vane N

    Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, H3A 2B2, Canada.

    Netrin-1 acts as a chemoattractant molecule to guide commissural neurons (CN) toward the floor plate by interacting with the receptor deleted in colorectal cancer (DCC). The molecular mechanisms underlying Netrin-1-DCC signaling are still poorly characterized. Here, we show that DCC is phosphorylated in vivo on tyrosine residues in response to Netrin-1 stimulation of CN and that the Src family kinase inhibitors PP2 and SU6656 block both Netrin-1-dependent phosphorylation of DCC and axon outgrowth. PP2 also blocks the reorientation of Xenopus laevis retinal ganglion cells that occurs in response to Netrin-1, which suggests an essential role of the Src kinases in Netrin-1-dependent orientation. Fyn, but not Src, is able to phosphorylate the intracellular domain of DCC in vitro, and we demonstrate that Y1418 is crucial for DCC axon outgrowth function. Both DCC phosphorylation and Netrin-1-induced axon outgrowth are impaired in Fyn(-/-) CN and spinal cord explants. We propose that DCC is regulated by tyrosine phosphorylation and that Fyn is essential for the response of axons to Netrin-1.

    The Journal of cell biology 2004;167;4;687-98

  • Netrin requires focal adhesion kinase and Src family kinases for axon outgrowth and attraction.

    Liu G, Beggs H, Jürgensen C, Park HT, Tang H, Gorski J, Jones KR, Reichardt LF, Wu J and Rao Y

    Department of Anatomy, Washington University School of Medicine, 660 South Euclid Ave., St. Louis, Missouri 63110, USA.

    Although netrins are an important family of neuronal guidance proteins, intracellular mechanisms that mediate netrin function are not well understood. Here we show that netrin-1 induces tyrosine phosphorylation of proteins including focal adhesion kinase (FAK) and the Src family kinase Fyn. Blockers of Src family kinases inhibited FAK phosphorylation and axon outgrowth and attraction by netrin. Dominant-negative FAK and Fyn mutants inhibited the attractive turning response to netrin. Axon outgrowth and attraction induced by netrin-1 were significantly reduced in neurons lacking the FAK gene. Our results show the biochemical and functional links between netrin, a prototypical neuronal guidance cue, and FAK, a central player in intracellular signaling that is crucial for cell migration.

    Funded by: NCI NIH HHS: CA107193, R01 CA107193, R01 CA107193-03; NINDS NIH HHS: NS19090, R01 NS019090

    Nature neuroscience 2004;7;11;1222-32

  • The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).

    Gerhard DS, Wagner L, Feingold EA, Shenmen CM, Grouse LH, Schuler G, Klein SL, Old S, Rasooly R, Good P, Guyer M, Peck AM, Derge JG, Lipman D, Collins FS, Jang W, Sherry S, Feolo M, Misquitta L, Lee E, Rotmistrovsky K, Greenhut SF, Schaefer CF, Buetow K, Bonner TI, Haussler D, Kent J, Kiekhaus M, Furey T, Brent M, Prange C, Schreiber K, Shapiro N, Bhat NK, Hopkins RF, Hsie F, Driscoll T, Soares MB, Casavant TL, Scheetz TE, Brown-stein MJ, Usdin TB, Toshiyuki S, Carninci P, Piao Y, Dudekula DB, Ko MS, Kawakami K, Suzuki Y, Sugano S, Gruber CE, Smith MR, Simmons B, Moore T, Waterman R, Johnson SL, Ruan Y, Wei CL, Mathavan S, Gunaratne PH, Wu J, Garcia AM, Hulyk SW, Fuh E, Yuan Y, Sneed A, Kowis C, Hodgson A, Muzny DM, McPherson J, Gibbs RA, Fahey J, Helton E, Ketteman M, Madan A, Rodrigues S, Sanchez A, Whiting M, Madari A, Young AC, Wetherby KD, Granite SJ, Kwong PN, Brinkley CP, Pearson RL, Bouffard GG, Blakesly RW, Green ED, Dickson MC, Rodriguez AC, Grimwood J, Schmutz J, Myers RM, Butterfield YS, Griffith M, Griffith OL, Krzywinski MI, Liao N, Morin R, Morrin R, Palmquist D, Petrescu AS, Skalska U, Smailus DE, Stott JM, Schnerch A, Schein JE, Jones SJ, Holt RA, Baross A, Marra MA, Clifton S, Makowski KA, Bosak S, Malek J and MGC Project Team

    The National Institutes of Health's Mammalian Gene Collection (MGC) project was designed to generate and sequence a publicly accessible cDNA resource containing a complete open reading frame (ORF) for every human and mouse gene. The project initially used a random strategy to select clones from a large number of cDNA libraries from diverse tissues. Candidate clones were chosen based on 5'-EST sequences, and then fully sequenced to high accuracy and analyzed by algorithms developed for this project. Currently, more than 11,000 human and 10,000 mouse genes are represented in MGC by at least one clone with a full ORF. The random selection approach is now reaching a saturation point, and a transition to protocols targeted at the missing transcripts is now required to complete the mouse and human collections. Comparison of the sequence of the MGC clones to reference genome sequences reveals that most cDNA clones are of very high sequence quality, although it is likely that some cDNAs may carry missense variants as a consequence of experimental artifact, such as PCR, cloning, or reverse transcriptase errors. Recently, a rat cDNA component was added to the project, and ongoing frog (Xenopus) and zebrafish (Danio) cDNA projects were expanded to take advantage of the high-throughput MGC pipeline.

    Funded by: PHS HHS: N01-C0-12400

    Genome research 2004;14;10B;2121-7

  • Cbl-mediated degradation of Lyn and Fyn induced by constitutive fibroblast growth factor receptor-2 activation supports osteoblast differentiation.

    Kaabeche K, Lemonnier J, Le Mée S, Caverzasio J and Marie PJ

    Laboratory of Osteoblast Biology and Pathology, INSERM U606, University Paris 7, Hôpital Lariboisière, 2 rue Ambroise Paré, 75475 Paris Cedex 10, France.

    Fibroblast growth factors (FGFs) play an important regulatory role in skeletal development and bone formation. However, the FGF signaling mechanisms controlling osteoblast function are poorly understood. Here, we identified a role for the Src family members Lyn and Fyn in osteoblast differentiation promoted by constitutive activation of FGF receptor-2 (FGFR2). We show that the overactive FGFR2 S252W mutation induced decreased Src family kinase tyrosine phosphorylation and activity associated with decreased Lyn and Fyn protein expression in human osteoblasts. Pharmacological stimulation of Src family kinases or transfection with Lyn or Fyn vectors repressed alkaline phosphatase (ALP) up-regulation induced by overactive FGFR2. Inhibition of proteasome activity restored normal Lyn and Fyn expression and ALP activity in FGFR2 mutant osteoblasts. Immunoprecipitation studies showed that Lyn, Fyn, and FGFR2 interacted with the ubiquitin ligase c-Cbl and ubiquitin. Transfection with c-Cbl in which the RING finger was disrupted or with c-Cbl with a point mutation that abolishes the binding ability of the Cbl phosphotyrosine-binding domain restored Src kinase activity and Lyn, Fyn, and FGFR2 levels and reduced ALP up-regulation in mutant osteoblasts. Thus, constitutive FGFR2 activation induces c-Cbl-dependent Lyn and Fyn proteasome degradation, resulting in reduced Lyn and Fyn kinase activity, increased ALP expression, and FGFR2 down-regulation. This reveals a common Cbl-mediated negative feedback mechanism controlling Lyn, Fyn, and FGFR2 degradation in response to overactive FGFR2 and indicates a role for Cbl-dependent down-regulation of Lyn and Fyn in osteoblast differentiation induced by constitutive FGFR2 activation.

    The Journal of biological chemistry 2004;279;35;36259-67

  • The intranuclear localization and function of YT521-B is regulated by tyrosine phosphorylation.

    Rafalska I, Zhang Z, Benderska N, Wolff H, Hartmann AM, Brack-Werner R and Stamm S

    University of Erlangen, Institute for Biochemistry, Germany.

    YT521-B is a ubiquitously expressed nuclear protein that changes alternative splice site usage in a concentration dependent manner. YT521-B is located in a dynamic nuclear compartment, the YT body. We show that YT521-B is tyrosine phosphorylated by c-Abl in the nucleus. The protein shuttles between nucleus and cytosol, where it can be phosphorylated by c-Src or p59(fyn). Tyrosine phosphorylation causes dispersion of YT521-B from YT bodies to the nucleoplasm. Whereas YT bodies are soluble in non-denaturing buffers, the phosphorylated, dispersed form is non-soluble. Non-phosphorylated YT521-B changes alternative splice site selection of the IL-4 receptor, CD44 and SRp20, but phosphorylation of c-Abl minimizes this concentration dependent effect. We propose that tyrosine phosphorylation causes sequestration of YT521-B in an insoluble nuclear form, which abolishes the ability of YT521-B to change alternative splice sites.

    Human molecular genetics 2004;13;15;1535-49

  • Tyrosine phosphorylation of calponins. Inhibition of the interaction with F-actin.

    Abouzaglou J, Bénistant C, Gimona M, Roustan C, Kassab R and Fattoum A

    Centre de Recherches de Biochimie Macromoléculaire du CNRS, Montpellier, France.

    The phosphorylation-dephosphorylation of serine and threonine residues of calponin is known to modulate in vitro its interaction with F-actin and is thought to regulate several biological processes in cells, involving either of the calponin isoforms. Here, we identify, for the first time, tyrosine-phosphorylated calponin h3 within COS 7 cells, before and after their transfection with the pSV vector containing cDNA encoding the cytoplasmic, Src-related, tyrosine kinase, Fyn. We then describe the specific tyrosine phosphorylation in vitro of calponin h1 and calponin h3 by this kinase. 32P-labeling of tyrosine residues was monitored by combined autoradiography, immunoblotting with a specific phosphotyrosine monoclonal antibody and dephosphorylation with the phosphotyrosine-specific protein phosphatase, YOP. PhosphorImager analyses showed the incorporation of maximally 1.4 and 2.0 mol of 32P per mol of calponin h3 and calponin h1, respectively. As a result, 75% and 68%, respectively, of binding to F-actin was lost by the phosphorylated calponins. Furthermore, F-actin, added at a two- or 10-fold molar excess, did not protect, but rather increased, the extent of 32P-labeling in both calponins. Structural analysis of the tryptic phosphopeptides from each 32P-labeled calponin revealed a single, major 32P-peptide in calponin h3, with Tyr261 as the phosphorylation site. Tyr261 was also phosphorylated in calponin h1, together with Tyr182. Collectively, the data point to the potential involvement, at least in living nonmuscle cells, of tyrosine protein kinases and the conserved Tyr261, located in the third repeat motif of the calponin molecule, in a new level of regulation of the actin-calponin interaction.

    European journal of biochemistry 2004;271;13;2615-23

  • Robust phosphoproteomic profiling of tyrosine phosphorylation sites from human T cells using immobilized metal affinity chromatography and tandem mass spectrometry.

    Brill LM, Salomon AR, Ficarro SB, Mukherji M, Stettler-Gill M and Peters EC

    Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, USA. lbrill@gnf.org

    Protein tyrosine phosphorylation cascades are difficult to analyze and are critical for cell signaling in higher eukaryotes. Methodology for profiling tyrosine phosphorylation, considered herein as the assignment of multiple protein tyrosine phosphorylation sites in single analyses, was reported recently (Salomon, A. R.; Ficarro, S. B.; Brill, L. M.; Brinker, A.; Phung, Q. T.; Ericson, C.; Sauer, K.; Brock, A.; Horn, D. M.; Schultz, P. G.; Peters, E. C. Proc. Natl. Acad. Sci. U.S.A. 2003, 100, 443-448). The technology platform included the use of immunoprecipitation, immobilized metal affinity chromatography (IMAC), liquid chromatography, and tandem mass spectrometry. In the present report, we show that when using complex mixtures of peptides from human cells, methylation improved the selectivity of IMAC for phosphopeptides and eliminated the acidic bias that occurred with unmethylated peptides. The IMAC procedure was significantly improved by desalting methylated peptides, followed by gradient elution of the peptides to a larger IMAC column. These improvements resulted in assignment of approximately 3-fold more tyrosine phosphorylation sites, from human cell lysates, than the previous methodology. Nearly 70 tyrosine-phosphorylated peptides from proteins in human T cells were assigned in single analyses. These proteins had unknown functions or were associated with a plethora of fundamental cellular processes. This robust technology platform should be broadly applicable to profiling the dynamics of tyrosine phosphorylation.

    Analytical chemistry 2004;76;10;2763-72

  • Regulation of TRPC6 channel activity by tyrosine phosphorylation.

    Hisatsune C, Kuroda Y, Nakamura K, Inoue T, Nakamura T, Michikawa T, Mizutani A and Mikoshiba K

    Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute (BSI), 2-1 Hirosawa, Wako City, Saitama 351-0198, Japan. chihiro@brain.riken.go.jp

    Various hormonal stimuli and growth factors activate the mammalian canonical transient receptor potential (TRPC) channel through phospholipase C (PLC) activation. H 64d owever, the precise mechanism of the regulation of TRPC channel activity remains unknown. Here, we provide the first evidence that direct tyrosine phosphorylation by Src family protein-tyrosine kinases (PTKs) is a novel mechanism for modulating TRPC6 channel activity. We found that TRPC6 is tyrosine-phosphorylated in COS-7 cells when coexpressed with Fyn, a member of the Src family PTKs. We also found that Fyn interacts with TRPC6 and that the interaction is mediated by the SH2 domain of Fyn and the N-terminal region of TRPC6 in a phosphorylation-independent manner. In addition, we demonstrated the physical association of TRPC6 with Fyn in the mammalian brain. Moreover, we showed that stimulation of the epidermal growth factor receptor induced rapid tyrosine phosphorylation of TRPC6 in COS-7 cells. This epidermal growth factor-induced tyrosine phosphorylation of TRPC6 was significantly blocked by PP2, a specific inhibitor of Src family PTKs, and by a dominant negative form of Fyn, suggesting that the direct phosphorylation of TRPC6 by Src family PTKs could be caused by physiological stimulation. Furthermore, using single channel recording, we showed that Fyn modulates TRPC6 channel activity via tyrosine phosphorylation. Thus, our findings demonstrated that tyrosine phosphorylation by Src family PTKs is a novel regulatory mechanism of TRPC6 channel activity.

    The Journal of biological chemistry 2004;279;18;18887-94

  • No genetic association between Fyn kinase gene polymorphisms (-93A/G, IVS10+37T/C and Ex12+894T/G) and Japanese sporadic Alzheimer's disease.

    Watanabe T, Ohnuma T, Shibata N, Ohtsuka M, Ueki A, Nagao M and Arai H

    Department of Psychiatry, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 343-0032, Japan. tomoko-w@med.juntendo.ac.jp

    Several groups have reported that abnormal phosphorylation of tau by Fyn, a protein-tyrosine kinase, may play a role in the neuropathogenesis of Alzheimer's disease (AD). In the present study, three common Japanese polymorphisms of the Fyn gene (-93A/G in the 5'-flanking region, IVS10+37T/C in intron 10 and Ex12+894T/G in the 3'-untranslated region) were studied in 127 healthy controls and 182 sporadic AD cases using a polymerase chain reaction restriction fragment length polymorphism method. A comparison of the allelic and genotypic frequencies of these polymorphisms between controls and sporadic AD cases failed to show any significant difference. These results suggest that the Fyn polymorphisms (-93A/G, IVS10+37T/C and Ex12+894T/G) investigated here have no genetic association with sporadic AD.

    Neuroscience letters 2004;360;1-2;109-11

  • Regulation of the type 1 inositol 1,4,5-trisphosphate receptor by phosphorylation at tyrosine 353.

    Cui J, Matkovich SJ, deSouza N, Li S, Rosemblit N and Marks AR

    Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.

    The inositol 1,4,5-trisphosphate receptor (IP3R) plays an essential role in Ca2+ signaling during lymphocyte activation. Engagement of the T cell or B cell receptor by antigen initiates a signal transduction cascade that leads to tyrosine phosphorylation of IP3R by Src family nonreceptor protein tyrosine kinases, including Fyn. However, the effect of tyrosine phosphorylation on the IP3R and subsequent Ca2+ release is poorly understood. We have identified tyrosine 353 (Tyr353) in the IP3-binding domain of type 1 IP3R (IP3R1) as a phosphorylation site for Fyn both in vitro and in vivo. We have developed a phosphoepitope-specific antibody and shown that IP3R1-Y353 becomes phosphorylated during T cell and B cell activation. Furthermore, tyrosine phosphorylation of IP3R1 increased IP3 binding at low IP3 concentrations (<10 nm). Using wild-type IP3R1 or an IP3R1-Y353F mutant that cannot be tyrosine phosphorylated at Tyr353 or expressed in IP3R-deficient DT40 B cells, we demonstrated that tyrosine phosphorylation of Tyr353 permits prolonged intracellular Ca2+ release during B cell activation. Taken together, these data suggest that one function of tyrosine phosphorylation of IP3R1-Y353 is to enhance Ca2+ signaling in lymphocytes by increasing the sensitivity of IP3R1 to activation by low levels of IP3.

    Funded by: NIAID NIH HHS: R01 AI39794

    The Journal of biological chemistry 2004;279;16;16311-6

  • HIV/SIV escape from immune surveillance: focus on Nef.

    Tolstrup M, Ostergaard L, Laursen AL, Pedersen SF and Duch M

    Department of Infectious Disease Q, Skejby Hospital, Denmark.

    During a progressive HIV-1 infection, the gradual decrease in functional CD4+ T(helper) cells leads to immunodeficiency and eventually death in the untreated patient. The virulence role of the lentiviral accessory gene nef was first reported from deletion studies in the macaque model, and research during the past decade has revealed a pluripotent protein capable of multiple points of interference with cellular mechanisms. Importantly, Nef has the capacity to modify the plasma membrane signalling by regulation of receptor/ligand endocytosis as well as to modulate cellular regulation such as apoptosis and lymphocyte activation. This effective defence against an apparent vigorous and specific immune response is crucial for the ability of HIV-1 to persist in the host. Here we review the multitude of functions exerted by Nef and discuss the functional domains of the protein in terms of cellular interaction partners and the effect of nef mutations in the course of AIDS disease progression.

    Current HIV research 2004;2;2;141-51

  • Protein tyrosine phosphatase epsilon activates Yes and Fyn in Neu-induced mammary tumor cells.

    Granot-Attas S and Elson A

    Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel.

    The receptor-type form of protein tyrosine phosphatase epsilon (RPTP) is among the few tyrosine phosphatases that can support the transformed phenotype of tumor cells. Accordingly, cells from mammary epithelial tumors induced by activated Neu in mice genetically lacking RPTP appear morphologically less transformed and exhibit reduced proliferation. The effect of RPTP in these cells is mediated at least in part by its ability to activate Src, the prototypic member of a family of related kinases. We show here that RPTP is a physiological activator of two additional Src family kinases, Yes and Fyn. Activities of both kinases are inhibited in mammary tumor cells lacking RPTP, and phosphorylation at their C-terminal inhibitory tyrosines is increased. In agreement, opposite effects on activities and phosphorylation of Yes and Fyn are observed following increased expression of PTP. RPTP also forms stable complexes with either kinase, providing physical opportunity for their activation by RPTP. Surprisingly, expression of Yes or of Fyn does not rescue the morphological phenotype of RPTP-deficient tumor cells in contrast with the strong ability of Src to do so. We conclude that RPTP activates Src, Yes, and Fyn, but that these related kinases play distinct roles in Neu-induced mammary tumor cells.

    Experimental cell research 2004;294;1;236-43

  • Phosphorylation of tau by fyn: implications for Alzheimer's disease.

    Lee G, Thangavel R, Sharma VM, Litersky JM, Bhaskar K, Fang SM, Do LH, Andreadis A, Van Hoesen G and Ksiezak-Reding H

    Department of Internal Medicine, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, Iowa 52242, USA. gloria-lee@uiowa.edu

    The abnormal phosphorylation of tau protein on serines and threonines is a hallmark characteristic of the neurofibrillary tangles of Alzheimer's disease (AD). The discovery that tau could be phosphorylated on tyrosine and evidence that Abeta signal transduction involved tyrosine phosphorylation led us to question whether tyrosine phosphorylation of tau occurred during the neurodegenerative process. In this study we determined that human tau tyr18 was phosphorylated by the src family tyrosine kinase fyn. By developing both polyclonal and monoclonal probes specific for phospho-tyr18, we found that the phosphorylation of tau at tyr18 occurred at early developmental stages in mouse but was absent in the adult. Our phosphospecific probes also revealed that paired helical filament preparations exhibited phospho-tyr18 reactivity that was sensitive to phosphotyrosine-specific protein phosphatase treatment. Moreover, immunocytochemical studies indicated that tyrosine phosphorylated tau was present in the neurofibrillary tangles in AD brain. However, the staining pattern excluded neuropil threads and dystrophic neurites indicating that tyrosine phosphorylated tau was distributed in AD brain in a manne 1f40 r dissimilar from other abnormally phosphorylated tau. We also found evidence suggesting that differentially phosphorylated tau existed within degenerating neurons. Our data add new support for a role for fyn in the neurodegenerative process.

    Funded by: NIA NIH HHS: AG17753

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2004;24;9;2304-12

  • The hepatitis C virus NS5A protein binds to members of the Src family of tyrosine kinases and regulates kinase activity.

    Macdonald A, Crowder K, Street A, McCormick C and Harris M

    Division of Microbiology, School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK.

    The hepatitis C virus (HCV) non-structural NS5A protein has been shown to associate with a variety of cellular signalling proteins. Of particular interest is the observation that a highly conserved C-terminal polyproline motif in NS5A was able to interact with the Src-homology 3 (SH3) domains of the adaptor protein Grb2. As it has previously been shown that specific polyproline motifs can interact with a range of SH3 domains, we investigated whether NS5A was capable of interacting with other SH3 domain-containing proteins. We show here that NS5A interacts with the SH3 domains of members of the Src family of tyrosine kinases: a combination of in vitro binding assays and co-immunoprecipitation experiments revealed an interaction between NS5A and Hck, Lck, Lyn and Fyn, but interestingly not Src itself. Mutational analysis confirmed that the polyproline motif responsible for binding to Grb2 also bound to the SH3 domains of Hck, Lck, Lyn and Fyn. Furthermore, a previously unidentified polyproline motif, adjacent to the first motif, was also able to mediate binding to the SH3 domain of Lyn. Using transient transfections and Huh-7 cells harbouring a persistently replicating subgenomic HCV replicon we demonstrate that NS5A bound to native Src-family kinases in vivo and differentially modulated kinase activity, inhibiting Hck, Lck and Lyn but activating Fyn. Lastly, we show that signalling pathways controlled by Src-family kinases are modulated in replicon cells. We conclude that the interactions between NS5A and Src-family kinases are physiologically relevant and may play a role in either virus replication or pathogenesis.

    The Journal of general virology 2004;85;Pt 3;721-9

  • Unc119, a novel activator of Lck/Fyn, is essential for T cell activation.

    Gorska MM, Stafford SJ, Cen O, Sur S and Alam R

    Division of Allergy and Immunology, Department of Internal Medicine, University of Texas Medical Branch, Galveston 77555, USA.

    The first step in T cell receptor for antigen (TCR) signaling is the activation of the receptor-bound Src kinases, Lck and Fyn. The exact mechanism of this process is unknown. Here, we report that the novel Src homology (SH) 3/SH2 ligand-Uncoordinated 119 (Unc119) associates with CD3 and CD4, and activates Lck and Fyn. Unc119 overexpression increases Lck/Fyn activity in T cells. In Unc119-deficient T cells, Lck/Fyn activity is dramatically reduced with concomitant decrease in interleukin 2 production and cellular proliferation. Reconstitution of cells with Unc119 reverses the signaling and functional outcome. Thus, Unc119 is a receptor-associated activator of Src-type kinases. It provides a novel mechanism of signal generation in the TCR complex.

    Funded by: NIAID NIH HHS: AI46004, AI50179, R01 AI050179

    The Journal of experimental medicine 2004;199;3;369-79

  • [Analysis of the fyn kinase gene in Alzheimer's disease and schizophrenia].

    Nakano Y, Akahane A, Tanaka H, Ueno M, Kunugi H and Nanko S

    Department of Psychiatry, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8606, Japan.

    Reelin is a protein which plays an important role in cell construction and proliferation of neurons during the development of the central nervous system. Several lines of evidence suggest a possible role for reelin-related genes in the etiology of neurodevelopmental as well as neurodegenerative diseases. It is possible that variations in reelin-related genes (Reelin, VLDLR, FYN, CNRs, a3b1INTEGRIN, mDAB1) may be involved in the pathogenesis of schizophrenia and Alzheimer's disease. We have been conducting a systematic survey of the association of reelin-related gene polymorphisms with these disorders. Previously, we examined the association of the triplet repeats of the reelin and VLDLR gene with schizophrenia. We found no significant association of schizophrenia with the trinucleotide repeat polymorphism of the reelin nor VLDLR genes (Akahane et al. 2002). In this study, we performed an allelic association analysis in Alzheimer's disease and schizophrenia with three polymorphisms of the fyn gene reported by Ishiguro et al (2000). Diagnosis was based on DSM-IV and NINCDS-ADRDA. We found no significant differences in genotype distribution or allelic frequency between patient and control groups. Thus, it is unlikely that these polymorphisms play an important role in the pathogenesis of Alzheimer's disease or schizophrenia.

    No to shinkei = Brain and nerve 2004;56;2;153-6

  • Interactions of HIV-1 proteins gp120 and Nef with cellular partners define a novel allosteric paradigm.

    Leavitt SA, SchOn A, Klein JC, Manjappara U, Chaiken IM and Freire E

    Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA. ef@jhu.edu

    During the course of infection, a subset of HIV-1 proteins interacts with multiple cellular partners, sometimes in a hierarchical or sequential way. These proteins include those associated with the initial infection event, with the preparation of the cell for the replicative cycle of the virus and with the exit of new virions from the infected cell. It appears that the interactions of viral proteins with multiple cellular partners are mediated by the occurrence of ligand-induced conformational changes that direct the binding of these proteins to subsequent partners. Two of the most studied HIV-1 proteins that are known to interact with different cellular partners are gp120 and Nef. Here we discuss the interactions of these two proteins with their cellular partners and present new results indicating that the conformational changes undergone by these proteins define a novel allosteric paradigm. In the traditional view, conformational changes are thought to occur between well defined structural conformations of a protein. In gp120 and Nef, those changes involve conformations characterized by the presence of large regions devoid of stable secondary or tertiary structure. Those unstructured regions contain the binding determinants for subsequent partners and only become functionally competent by ligand-induced structuring or un-structuring of those regions. By switching binding epitopes between structured and unstructured conformations the binding affinity can be modulated by several orders of magnitude, thus effectively precluding binding against unwanted partners. A better understanding of these interactions would lead to improved strategies for inhibitor design against these viral targets.

    Funded by: NIGMS NIH HHS: GM 57144, GM56550

    Current protein & peptide science 2004;5;1;1-8

  • Complete sequencing and characterization of 21,243 full-length human cDNAs.

    Ota T, Suzuki Y, Nishikawa T, Otsuki T, Sugiyama T, Irie R, Wakamatsu A, Hayashi K, Sato H, Nagai K, Kimura K, Makita H, Sekine M, Obayashi M, Nishi T, Shibahara T, Tanaka T, Ishii S, Yamamoto J, Saito K, Kawai Y, Isono Y, Nakamura Y, Nagahari K, Murakami K, Yasuda T, Iwayanagi T, Wagatsuma M, Shiratori A, Sudo H, Hosoiri T, Kaku Y, Kodaira H, Kondo H, Sugawara M, Takahashi M, Kanda K, Yokoi T, Furuya T, Kikkawa E, Omura Y, Abe K, Kamihara K, Katsuta N, Sato K, Tanikawa M, Yamazaki M, Ninomiya K, Ishibashi T, Yamashita H, Murakawa K, Fujimori K, Tanai H, Kimata M, Watanabe M, Hiraoka S, Chiba Y, Ishida S, Ono Y, Takiguchi S, Watanabe S, Yosida M, Hotuta T, Kusano J, Kanehori K, Takahashi-Fujii A, Hara H, Tanase TO, Nomura Y, Togiya S, Komai F, Hara R, Takeuchi K, Arita M, Imose N, Musashino K, Yuuki H, Oshima A, Sasaki N, Aotsuka S, Yoshikawa Y, Matsunawa H, Ichihara T, Shiohata N, Sano S, Moriya S, Momiyama H, Satoh N, Takami S, Terashima Y, Suzuki O, Nakagawa S, Senoh A, Mizoguchi H, Goto Y, Shimizu F, Wakebe H, Hishigaki H, Watanabe T, Sugiyama A, Takemoto M, Kawakami B, Yamazaki M, Watanabe K, Kumagai A, Itakura S, Fukuzumi Y, Fujimori Y, Komiyama M, Tashiro H, Tanigami A, Fujiwara T, Ono T, Yamada K, Fujii Y, Ozaki K, Hirao M, Ohmori Y, Kawabata A, Hikiji T, Kobatake N, Inagaki H, Ikema Y, Okamoto S, Okitani R, Kawakami T, Noguchi S, Itoh T, Shigeta K, Senba T, Matsumura K, Nakajima Y, Mizuno T, Morinaga M, Sasaki M, Togashi T, Oyama M, Hata H, Watanabe M, Komatsu T, Mizushima-Sugano J, Satoh T, Shirai Y, Takahashi Y, Nakagawa K, Okumura K, Nagase T, Nomura N, Kikuchi H, Masuho Y, Yamashita R, Nakai K, Yada T, Nakamura Y, Ohara O, Isogai T and Sugano S

    Helix Research Institute, 1532-3 Yana, Kisarazu, Chiba 292-0812, Japan.

    As a base for human transcriptome and functional genomics, we created the "full-length long Japan" (FLJ) collection of sequenced human cDNAs. We determined the entire sequence of 21,243 selected clones and found that 14,490 cDNAs (10,897 clusters) were unique to the FLJ collection. About half of them (5,416) seemed to be protein-coding. Of those, 1,999 clusters had not been predicted by computational methods. The distribution of GC content of nonpredicted cDNAs had a peak at approximately 58% compared with a peak at approximately 42%for predicted cDNAs. Thus, there seems to be a slight bias against GC-rich transcripts in current gene prediction procedures. The rest of the cDNAs unique to the FLJ collection (5,481) contained no obvious open reading frames (ORFs) and thus are candidate noncoding RNAs. About one-fourth of them (1,378) showed a clear pattern of splicing. The distribution of GC content of noncoding cDNAs was narrow and had a peak at approximately 42%, relatively low compared with that of protein-coding cDNAs.

    Nature genetics 2004;36;1;40-5

  • Analysis of genetic variations of protein tyrosine kinase fyn and their association with alcohol dependence in two independent cohorts.

    Schumann G, Rujescu D, Kissling C, Soyka M, Dahmen N, Preuss UW, Wieman S, Depner M, Wellek S, Lascorz J, Bondy B, Giegling I, Anghelescu I, Cowen MS, Poustka A, Spanagel R, Mann K, Henn FA and Szegedi A

    Department of Psychiatry, Central Institute of Mental Health, Mannheim, Germany.

    Background: Decreased sensitivity to and increased tolerance for the effects of alcohol is a phenotype, which was shown to be associated with an increased risk for alcoholism in humans and was observed in protein tyrosine kinase (PTK) fyn knockout mice.

    Methods: We performed an association study of genetic variations of PTK fyn in 430 alcohol-dependent patients and 365 unrelated control subjects from two independent samples.

    Results: In a combined analysis, we found an association of alcohol dependence with the single nucleotide polymorphism (SNP) T137346C in the 5' untranslated region (UTR) of the gene. A relevant association could be excluded for the remaining two informative SNPs. Selection by phenotype showed that a high number of withdrawal symptoms, high amount of alcohol intake, and high maximum number of drinks compared with unrelated control subjects was associated with the SNP in the 5'-UTR region but not with the remaining SNPs.

    Conclusions: Our results indicate a possible association of alcohol dependence with a genotype of the SNP T137346C of the PTK fyn, with C being the risk allele.

    Biological psychiatry 2003;54;12;1422-6

  • Identification and activation of Src family kinases in primary megakaryocytes.

    Lannutti BJ, Shim MH, Blake N, Reems JA and Drachman JG

    Puget Sound Blood Center, 921 Terry Avenue, Seattle, WA 98104-1256, USA. brianl@psbc.org

    Objectives: We have recently shown that the Src family of tyrosine kinases (SFKs) are activated by TPO stimulation in both primary megakaryocytic progenitors and a hematopoietic cells line (BaF3) expressing the TPO receptor (Mpl). In this study, we examine which of the eight Src family members are expressed in primary megakaryocytes (MKs) and determine which of these become activated in response to TPO.

    High-density oligonucleotide microarrays were used to compare the gene expression profiles of Src kinases from undifferentiated hematopoietic progenitors (CD34+/CD38(lo)) and after in vitro megakaryocytic differentiation. Western blot analysis of lysates from purified, mature murine MKs identified which of SFKs are present. Finally, in vitro kinase assays determined which of the SFKs in primary MKs are activated by TPO stimulation.

    Results: Array profiles demonstrate that Fyn, Lyn, Fgr, Hck, Src, and Yes are all expressed in cultured human MKs (Fyn, Lyn>Src, Yes, Fgr, Hck). Similarly, Western blots of murine MKs identified the same six SFKs (Fyn, Fgr, Hck, Lyn, Src, and Yes). Of these, only Fyn and Lyn demonstrate increased kinase activity after TPO stimulation. Interestingly, gene expression analysis indicates that, among the SFKs, Fyn expression is uniquely upregulated during MK development.

    Conclusion: These results provide the first direct evidence that two Src kinases are activated in primary MKs, Fyn and Lyn. The fact that only Fyn expression is significantly upregulated during MK differentiation suggests variable gene regulation. Specificity of the TPO signaling cascade is demonstrated by the selective activation of Fyn and Lyn.

    Funded by: NHLBI NIH HHS: R01 HL 65498

    Experimental hematology 2003;31;12;1268-74

  • Biochemical properties of the Cdc42-associated tyrosine kinase ACK1. Substrate specificity, authphosphorylation, and interaction with Hck.

    Yokoyama N and Miller WT

    Department of Physiology and Biophysics, School of Medicine, State University of New York at Stony Brook, Stony Brook, New York 11794-8661, USA.

    ACK1 (activated Cdc42-associated kinase 1) is a nonreceptor tyrosine kinase and the only tyrosine kinase known to interact with Cdc42. To characterize the enzymatic properties of ACK, we have expressed and purified active ACK using the baculovirus/Sf9 cell system. This ACK1 construct contains (from N to C terminus) the kinase catalytic domain, SH3 domain, and Cdc42-binding Cdc42/Rac interactive binding (CRIB) domain. We characterized the substrate specificity of ACK1 using synthetic peptides, and we show that the specificity of the ACK1 catalytic domain most closely resembles that of Abl. Purified ACK1 undergoes autophosphorylation, and autophosphorylation enhances kinase activity. We identified Tyr284 in the activation loop of ACK1 as the primary autophosphorylation site using mass spectrometry. When expressed in COS-7 cells, the Y284F mutant ACK1 showed dramatically reduced levels of tyrosine phosphorylation. Although the SH3 and CRIB domains of purified ACK1 are able to bind ligands (a polyproline peptide and Cdc42, respectively), the addition of ligands did not stimulate tyrosine kinase activity. To characterize potential interacting partners for ACK1, we screened several SH2 and SH3 domains for their ability to bind to full-length ACK1 or to the catalytic-SH3-CRIB construct. ACK1 interacts most strongly with the SH3 domains of Src family kinases (Src or Hck) via its C-terminal proline-rich domain. Co-expression of Hck with kinase-inactive ACK1(K158R) in mammalian cells resulted in tyrosine phosphorylation of ACK1, suggesting that ACK1 is a substrate for Hck. Our data suggest that Hck is a novel binding partner for ACK1 that can regulate ACK1 activity by phosphorylation.

    Funded by: NCI NIH HHS: CA 28146

    The Journal of biological chemistry 2003;278;48;47713-23

  • Tr-kit promotes the formation of a multimolecular complex composed by Fyn, PLCgamma1 and Sam68.

    Paronetto MP, Venables JP, Elliott DJ, Geremia R, Rossi P and Sette C

    Department of Public Health and Cell Biology, Section of Anatomy, University of Rome 'Tor Vergata', Rome, Italy.

    Tr-kit is a truncated form of the tyrosine kinase receptor c-kit expressed in the haploid phase of spermatogenesis. Upon microinjection, tr-kit triggers metaphase-to-anaphase transition in mouse eggs by the sequential activation of Fyn and PLCgamma1. Here, we show that tr-kit promotes the interaction of several tyrosine-phosphorylated proteins with the SH3 domain of PLCgamma1. Western blot analysis indicates that one of these proteins is Sam68, an RNA-binding protein that is known to interact with and be phosphorylated by Src-like kinases in mitosis. tr-kit promotes the association of Sam68 with PLCgamma1 and Fyn in a multimolecular complex, as demonstrated by co-immunoprecipitation of the phosphorylated forms of these proteins using antibodies directed to anyone of the partners of the complex. Expression of tr-kit potentiates the interaction of endogenous Sam68 also with the SH3 domain of Fyn. Furthermore, the subcellular localization of Sam68 is affected by tr-kit through activation of Fyn in live cells. Lastly, we show that interaction with the SH3 domain of Fyn triggers the release of Sam68 from bound RNA. Thus, our data suggest that tr-kit promotes the formation of a multimolecular complex composed of Fyn, PLCgamma1 and Sam68, which allows phosphorylation of PLCgamma1 by Fyn, and may modulate RNA metabolism.

    Oncogene 2003;22;54;8707-15

  • Alphavbeta6-Fyn signaling promotes oral cancer progression.

    Li X, Yang Y, Hu Y, Dang D, Regezi J, Schmidt BL, Atakilit A, Chen B, Ellis D and Ramos DM

    Department of Stomatology, University of California-San Francisco, San Francisco, CA 94143-0512, USA.

    We have previously shown that the integrin beta6 is neo-expressed in invasive oral squamous cell carcinoma (SCC) and is correlated with oral tumor progression. However, the mechanism by which the integrin beta6 promotes oral tumor progression is not well understood. The purpose of the present study was to determine whether integrin beta6 signaling activates Fyn and thus promotes oral squamous cell carcinoma progression. We analyzed the integrin beta6 signaling complex and investigated the function of these signaling molecules in oral SCC cells. We found that, upon ligation of the integrin beta6 with fibronectin, beta6 complexed with Fyn and activated it. The activation of Fyn recruited and activated focal adhesion kinase to this complex. This complex was necessary to activate Shc and to couple beta6 signaling to the Raf-ERK/MAPK pathway. This pathway transcriptionally activated the matrix metalloproteinase-3 gene and promoted oral SCC cell proliferation and experimental metastasis in vivo. These findings indicate that integrin beta6 signaling activates Fyn and thus promotes oral cancer progression.

    Funded by: NIDCR NIH HHS: P01 DE 13904, R01 DE 12856, R29/R01 DE 11930

    The Journal of biological chemistry 2003;278;43;41646-53

  • The DNA sequence and analysis of human chromosome 6.

    Mungall AJ, Palmer SA, Sims SK, Edwards CA, Ashurst JL, Wilming L, Jones MC, Horton R, Hunt SE, Scott CE, Gilbert JG, Clamp ME, Bethel G, Milne S, Ainscough R, Almeida JP, Ambrose KD, Andrews TD, Ashwell RI, Babbage AK, Bagguley CL, Bailey J, Banerjee R, Barker DJ, Barlow KF, Bates K, Beare DM, Beasley H, Beasley O, Bird CP, Blakey S, Bray-Allen S, Brook J, Brown AJ, Brown JY, Burford DC, Burrill W, Burton J, Carder C, Carter NP, Chapman JC, Clark SY, Clark G, Clee CM, Clegg S, Cobley V, Collier RE, Collins JE, Colman LK, Corby NR, Coville GJ, Culley KM, Dhami P, Davies J, Dunn M, Earthrowl ME, Ellington AE, Evans KA, Faulkner L, Francis MD, Frankish A, Frankland J, French L, Garner P, Garnett J, Ghori MJ, Gilby LM, Gillson CJ, Glithero RJ, Grafham DV, Grant M, Gribble S, Griffiths C, Griffiths M, Hall R, Halls KS, Hammond S, Harley JL, Hart EA, Heath PD, Heathcott R, Holmes SJ, Howden PJ, Howe KL, Howell GR, Huckle E, Humphray SJ, Humphries MD, Hunt AR, Johnson CM, Joy AA, Kay M, Keenan SJ, Kimberley AM, King A, Laird GK, Langford C, Lawlor S, Leongamornlert DA, Leversha M, Lloyd CR, Lloyd DM, Loveland JE, Lovell J, Martin S, Mashreghi-Mohammadi M, Maslen GL, Matthews L, McCann OT, McLaren SJ, McLay K, McMurray A, Moore MJ, Mullikin JC, Niblett D, Nickerson T, Novik KL, Oliver K, Overton-Larty EK, Parker A, Patel R, Pearce AV, Peck AI, Phillimore B, Phillips S, Plumb RW, Porter KM, Ramsey Y, Ranby SA, Rice CM, Ross MT, Searle SM, Sehra HK, Sheridan E, Skuce CD, Smith S, Smith M, Spraggon L, Squares SL, Steward CA, Sycamore N, Tamlyn-Hall G, Tester J, Theaker AJ, Thomas DW, Thorpe A, Tracey A, Tromans A, Tubby B, Wall M, Wallis JM, West AP, White SS, Whitehead SL, Whittaker H, Wild A, Willey DJ, Wilmer TE, Wood JM, Wray PW, Wyatt JC, Young L, Younger RM, Bentley DR, Coulson A, Durbin R, Hubbard T, Sulston JE, Dunham I, Rogers J and Beck S

    The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK. ajm@sanger.ac.uk

    Chromosome 6 is a metacentric chromosome that constitutes about 6% of the human genome. The finished sequence comprises 166,880,988 base pairs, representing the largest chromosome sequenced so far. The entire sequence has been subjected to high-quality manual annotation, resulting in the evidence-supported identification of 1,557 genes and 633 pseudogenes. Here we report that at least 96% of the protein-coding genes have been identified, as assessed by multi-species comparative sequence analysis, and provide evidence for the presence of further, otherwise unsupported exons/genes. Among these are genes directly implicated in cancer, schizophrenia, autoimmunity and many other diseases. Chromosome 6 harbours the largest transfer RNA gene cluster in the genome; we show that this cluster co-localizes with a region of high transcriptional activity. Within the essential immune loci of the major histocompatibility complex, we find HLA-B to be the most polymorphic gene on chromosome 6 and in the human genome.

    Nature 2003;425;6960;805-11

  • Tyrosine phosphorylation of plakoglobin causes contrary effects on its association with desmosomes and adherens junction components and modulates beta-catenin-mediated transcription.

    Miravet S, Piedra J, Castaño J, Raurell I, Francí C, Duñach M and García de Herreros A

    Unitat de Biofísica, Departament de Bioquímica i Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain.

    Plakoglobin is a protein closely related to beta-catenin that links desmosomal cadherins to intermediate filaments. Plakoglobin can also substitute for beta-catenin in adherens junctions, providing a connection between E-cadherin and alpha-catenin. Association of beta-catenin with E-cadherin and alpha-catenin is regulated by phosphorylation of specific tyrosine residues; modification of beta-catenin Tyr654 and Tyr142 decreases binding to E-cadherin and alpha-catenin, respectively. We show here that plakoglobin can also be phosphorylated on tyrosine residues, but unlike beta-catenin, this modification is not always associated with disrupted association with junctional components. Protein tyrosine kinases present distinct specificities on beta-catenin and plakoglobin, and phosphorylation of beta-catenin-equivalent Tyr residues of plakoglobin affects its interaction with components of desmosomes or adherens junctions differently. For instance, Src, which mainly phosphorylates Tyr86 in beta-catenin, modifies Tyr643 in plakoglobin, decreasing the interaction with E-cadherin and alpha-catenin and increasing the interaction with the alpha-catenin-equivalent protein in desmosomes, desmoplakin. The tyrosine kinase Fer, which modifies beta-catenin Tyr142, lessening its association with alpha-catenin, phosphorylates plakoglobin Tyr549 and exerts the contrary effect: it raises the binding of plakoglobin to alpha-catenin. These results suggest that tyrosine kinases like Src or Fer modulate desmosomes and adherens junctions differently. Our results also indicate that phosphorylation of Tyr549 and the increased binding of plakoglobin to components of adherens junctions can contribute to the upregulation of the transcriptional activity of the beta-catenin-Tcf-4 complex observed in many epithelial tumor cells.

    Molecular and cellular biology 2003;23;20;7391-402

  • Lithium reduced N-methyl-D-aspartate receptor subunit 2A tyrosine phosphorylation and its interactions with Src and Fyn mediated by PSD-95 in rat hippocampus following cerebral ischemia.

    Ma J and Zhang GY

    Research Center for Biochemistry and Molecular Biology, Xuzhou Medical College, 84 West Huai-hai Road, Xuzhou, 221002 Jiangsu, PR China.

    Recently, the neuroprotective effects of lithium against excitotoxicity mediated by N-methyl-D-aspartate (NMDA) receptors have been demonstrated. Since brain ischemia results in NMDA receptor over-excitation and Src family protein tyrosine kinase-mediated tyrosine phosphorylation of NMDA receptor subunit 2A (NR2A) enhances NMDA receptor activity, we examined the effects of lithium on tyrosine phosphorylation of NR2A and its interactions with Src and Fyn (two members of the Src family of protein tyrosine kinases) mediated by PSD-95 (postsynaptic density protein 95 kDa) after 6 h of reperfusion following 15 min of ischemia (I/R), which was induced by occlusion of the four vessels in Sprague-Dawley rats. After abdominal injection of LiCl (2 mg/kg) for 7 days, the data showed that together with the significant decrease in I/R-induced tyrosine phosphorylation of NR2A, the interactions of NR2A with Src and Fyn mediated by PSD-95 were also decreased significantly. However, lithium pretreatment did not alter the total protein levels of NR2A, Src, Fyn and PSD-95. These results suggest that the inhibition of NR2A tyrosine phosphorylation and its interactions with Src and Fyn mediated by PSD-95 may contribute to the lithium-induced downregulation of NMDA receptor function and provide neuroprotection against excitotoxicity.

    Neuroscience letters 2003;348;3;185-9

  • Clustering-induced tyrosine phosphorylation of nephrin by Src family kinases.

    Lahdenperä J, Kilpeläinen P, Liu XL, Pikkarainen T, Reponen P, Ruotsalainen V and Tryggvason K

    Division of Matrix Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden.

    Background: Nephrin is a recently discovered protein of the immunoglobulin (Ig) superfamily. In the kidney, it is located at the slit diaphragm, which forms the decisive size-selective filter of glomerular ultrafiltration barrier and locates between the interdigitating foot processes of podocytes. Nephrin is mutated in congenital nephrosis of the Finnish type (NPHS1) and has been demonstrated to be an essential component of the slit diaphragm. Based on its domain structure, nephrin is likely to be a cell-cell or cell-matrix adhesion protein that may have a signaling function. In this study, we hypothesized that the clustering of nephrin with antibodies on cell surface mimics the situation where the interaction between nephrin and its extracellular ligand(s) is altered.

    Methods: Nephrin was clustered on the surface of stably transfected HEK293 cells by a monoclonal antinephrin antibody and polyclonal secondary antibody. Clusters were visualized by immunofluorescence microscopy. Changes in protein phosphorylation were studied employing immunoprecipitations and Western blot analysis. A specific inhibitor and cotransfection experiments were used to investigate role of Src family kinases in nephrin phosphorylation.

    Results: Clustering of nephrin induced its own tyrosine phosphorylation. This phosphorylation was inhibited by PP2, an inhibitor of Src family kinases. Several members of Src family kinases were able to induce nephrin phosphorylation when cotransfected to HEK293 cells with nephrin. Moreover, the Src family kinase Fyn was consistently found to be coimmunoprecipitated with nephrin. Interestingly, clustering of nephrin induced also tyrosine phosphorylation of a 46 kD protein that was as well found to be coimmunoprecipitated with nephrin.

    Conclusion: Nephrin is a signaling protein phosphorylated by Src family kinases.

    Funded by: NIDDK NIH HHS: DK54724

    Kidney international 2003;64;2;404-13

  • Two new substrates in insulin signaling, IRS5/DOK4 and IRS6/DOK5.

    Cai D, Dhe-Paganon S, Melendez PA, Lee J and Shoelson SE

    Joslin Diabetes Center and the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215, USA.

    We have identified two new human genes that encode proteins with tandem pleckstrin homology-phosphotyrosine binding (PH-PTB) domains at their amino termini. Because the other known PH-PTB proteins (insulin receptor substrates: IRS-1, IRS-2, IRS-3, and IRS-4, and the downstream of kinases: DOK-1, DOK-2, and DOK-3) are substrates of insulin and insulin-like growth factor (IGF)-1 receptors, we asked whether these new proteins, termed IRS5/DOK4 and IRS6/DOK5, might also have roles in insulin and IGF-1 signaling. Northern analyses indicate that IRS5/DOK4 is ubiquitously expressed but most abundant in kidney and liver. IRS6/DOK5 expression is highest in skeletal muscle. Both proteins are tyrosine-phosphorylated in response to insulin and IGF-1 in transfected cells, although the kinetics differ. Insulin receptor-phosphorylated IRS5/DOK4 associates with RasGAP, Crk, Src, and Fyn, but not phosphatidylinositol 3-kinase p85, Grb2, SHP-2, Nck, or phospholipase Cgamma Src homology 2 domains, and activates MAPK in cells. IRS6/DOK5 neither associates with these Src homology 2 domains nor activates MAPK. IRS5/DOK4 and IRS6/DOK5 represent two new signaling proteins with potential roles in insulin and IGF-1 action.

    Funded by: NIDDK NIH HHS: DK36836, F32 DK61187, R01 DK43123

    The Journal of biological chemistry 2003;278;28;25323-30

  • Dual regulation of neuronal morphogenesis by a delta-catenin-cortactin complex and Rho.

    Martinez MC, Ochiishi T, Majewski M and Kosik KS

    Dept. of Neurology, Brigham and Women's Hospital and Harvard Medical School, Harvard Institute of Medicine, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.

    Delta-catenin is a neuronal protein that contains 10 Armadillo motifs and binds to the juxtamembrane segment of classical cadherins. We report that delta-catenin interacts with cortactin in a tyrosine phosphorylation-dependent manner. This interaction occurs within a region of the delta-catenin sequence that is also essential for the neurite elongation effects. Src family kinases can phosphorylate delta-catenin and bind to delta-catenin through its polyproline tract. Under conditions when tyrosine phosphorylation is reduced, delta-catenin binds to cortactin and cells extend unbranched primary processes. Conversely, increasing tyrosine phosphorylation disrupts the delta-catenin-cortactin complex. When RhoA is inhibited, delta-catenin enhances the effects of Rho inhibition on branching. We conclude that delta-catenin contributes to setting a balance between neurite elongation and branching in the elaboration of a complex dendritic tree.

    The Journal of cell biology 2003;162;1;99-111

  • p250GAP, a novel brain-enriched GTPase-activating protein for Rho family GTPases, is involved in the N-methyl-d-aspartate receptor signaling.

    Nakazawa T, Watabe AM, Tezuka T, Yoshida Y, Yokoyama K, Umemori H, Inoue A, Okabe S, Manabe T and Yamamoto T

    Division of Oncology, Department of Cancer Biology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan.

    N-methyl-d-aspartate (NMDA) receptors regulate structural plasticity by modulating actin organization within dendritic spines. Herein, we report identification and characterization of p250GAP, a novel GTPase-activating protein for Rho family proteins that interacts with the GluRepsilon2 (NR2B) subunit of NMDA receptors in vivo. The p250GAP mRNA was enriched in brain, with high expression in cortex, corpus striatum, hippocampus, and thalamus. Within neurons, p250GAP was highly concentrated in the postsynaptic density and colocalized with the GluRepsilon2 (NR2B) subunit of NMDA receptors and with postsynaptic density-95. p250GAP promoted GTP hydrolysis of Cdc42 and RhoA in vitro and in vivo. When overexpressed in neuroblastoma cells, p250GAP suppressed the activities of Rho family proteins, which resulted in alteration of neurite outgrowth. Finally, NMDA receptor stimulation led to dephosphorylation and redistribution of p250GAP in hippocampal slices. Together, p250GAP is likely to be involved in NMDA receptor activity-dependent actin reorganization in dendritic spines.

    Molecular biology of the cell 2003;14;7;2921-34

  • H-Ras modulates N-methyl-D-aspartate receptor function via inhibition of Src tyrosine kinase activity.

    Thornton C, Dinh S and Ron D

    Ernest Gallo Clinic and Research Center, University of California San Francisco, San Francisco, California 94110-3518, USA.

    Tyrosine phosphorylation of the NR2A and NR2B subunits of the N-methyl-d-aspartate (NMDA) receptor by Src protein-tyrosine kinases modulates receptor channel activity and is necessary for the induction of long term potentiation (LTP). Deletion of H-Ras increases both NR2 tyrosine phosphorylation and NMDA receptor-mediated hippocampal LTP. Here we investigated whether H-Ras regulates phosphorylation and function of the NMDA receptor via Src family protein-tyrosine kinases. We identified Src as a novel H-Ras binding partner. H-Ras bound to Src but not Fyn both in vitro and in brain via the Src kinase domain. Cotransfection of H-Ras and Src inhibited Src activity and decreased NR2A tyrosine phosphorylation. Treatment of rat brain slices with Tat-H-Ras depleted NR2A from the synaptic membrane, decreased endogenous Src activity and NR2A phosphorylation, and decreased the magnitude of hippocampal LTP. No change was observed for NR2B. We suggest that H-Ras negatively regulates Src phosphorylation of NR2A and retention of NR2A into the synaptic membrane leading to inhibition of NMDA receptor function. This mechanism is specific for Src and NR2A and has implications for studies in which regulation of NMDA receptor-mediated LTP is important, such as synaptic plasticity, learning, and memory and addiction.

    Funded by: NIAAA NIH HHS: R01 AA013438, R01AA/MH13438-01A1

    The Journal of biological chemistry 2003;278;26;23823-9

  • p250GAP, a neural RhoGAP protein, is associated with and phosphorylated by Fyn.

    Taniguchi S, Liu H, Nakazawa T, Yokoyama K, Tezuka T and Yamamoto T

    Division of Oncology, Department of Cancer Biology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, 108-8639, Tokyo, Japan.

    Fyn is a member of the Src-family protein tyrosine kinases and plays important roles in both neurons and oligodendrocytes. Here we report association of Fyn with p250GAP, a RhoGAP protein that is expressed predominantly in brain. p250GAP interacts with Fyn both in vitro and in vivo. p250GAP is tyrosine phosphorylated by Fyn when co-expressed in HEK293T cells. This phosphorylation appears to enhance the interaction between p250GAP and Fyn. Furthermore, the level of tyrosine phosphorylation of p250GAP increases upon differentiation of the oligodendrocyte cell line CG4. Given that Fyn activity is up-regulated during oligodendrocyte maturation, the results argue that p250GAP is phosphorylated by Fyn in oligodendrocytes. Tyrosine phosphorylation of p250GAP by Fyn would regulate its RhoGAP activity, subcellular localization, or interactions with other proteins, leading to morphological and phenotypic changes of oligodendrocytes.

    Biochemical and biophysical research communications 2003;1;151-5

  • Fyn binds to and phosphorylates the kidney slit diaphragm component Nephrin.

    Verma R, Wharram B, Kovari I, Kunkel R, Nihalani D, Wary KK, Wiggins RC, Killen P and Holzman LB

    Department of Veterans Affairs, Ann Arbor, Michigan 48105, USA.

    Recent investigations have focused on characterizing the molecular components of the podocyte intercellular junction, because several of these components, including Nephrin, are functionally necessary for development of normal podocyte structure and filter integrity. Accumulating evidence suggests that the Nephrin-associated protein complex is a signaling nexus. As such, Nephrin-dependent signaling might be mediated in part through Nephrin phosphorylation. Described are biochemical and mouse genetics experiments demonstrating that membrane-associated Nephrin is tyrosine-phosphorylated by the Src family kinase Fyn. Nephrin fractionated in detergent-resistant glomerular membrane fractions with Fyn and Yes. Fyn directly bound Nephrin via its SH3 domain, and Fyn directly phosphorylated Nephrin. Glomeruli in which Fyn, Yes, or Fyn and Yes were genetically deleted in mice were characterized to explore the relationship between these kinases and Nephrin. Fyn deletion resulted in coarsening of podocyte foot processes and marked attenuation of Nephrin phosphorylation in isolated glomerular detergent-resistant membrane fractions. Yes deletion had no identifiable effect on podocyte morphology but dramatically increased Nephrin phosphorylating activity. Similar to Fyn deletion, simultaneous deletion of Fyn and Yes reduced Nephrin phosphorylating activity. These results demonstrate that endogenous Fyn catalyzes Nephrin phosphorylation in podocyte detergent-resistant membrane fractions. Although Yes appears to effect the regulation of Nephrin phosphorylation, the mechanism by which this occurs requires investigation.

    The Journal of biological chemistry 2003;278;23;20716-23

  • Transmodulation between phospholipase D and c-Src enhances cell proliferation.

    Ahn BH, Kim SY, Kim EH, Choi KS, Kwon TK, Lee YH, Chang JS, Kim MS, Jo YH and Min DS

    Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul, Korea.

    Phospholipase D (PLD) has been implicated in the signal transduction pathways initiated by several mitogenic protein tyrosine kinases. We demonstrate for the first time that most notably PLD2 and to a lesser extent the PLD1 isoform are tyrosine phosphorylated by c-Src tyrosine kinase via direct association. Moreover, epidermal growth factor induced tyrosine phosphorylation of PLD2 and its interaction with c-Src in A431 cells. Interaction between these proteins is via the pleckstrin homology domain of PLD2 and the catalytic domain of c-Src. Coexpression of PLD1 or PLD2 with c-Src synergistically enhances cellular proliferation compared with expression of either molecule. While PLD activity as a lipid-hydrolyzing enzyme is not affected by c-Src, wild-type PLDs but not catalytically inactive PLD mutants significantly increase c-Src kinase activity, up-regulating c-Src-mediated paxillin phosphorylation and extracellular signal-regulated kinase activity. These results demonstrate the critical role of PLD catalytic activity in the stimulation of Src signaling. In conclusion, we provide the first evidence that c-Src acts as a kinase of PLD and PLD acts as an activator of c-Src. This transmodulation between c-Src and PLD may contribute to the promotion of cellular proliferation via amplification of mitogenic signaling pathways.

    Molecular and cellular biology 2003;23;9;3103-15

  • Expression of Fyn, a non-receptor tyrosine kinase in prefrontal cortex from patients with schizophrenia and its correlation with clinical onset.

    Ohnuma T, Kato H, Arai H, McKenna PJ and Emson PC

    Department of Psychiatry, Juntendo University School of Medicine 2-1-1 Hongo, Bunkyo-ku, Tokyo, Japan. tohru.oonuma@nifty.ne.jp

    Fyn is a member of the non-receptor tyrosine kinase family, which is known to be closely involved in signal transduction in neurons and has an important role in the development and organisation of the central nervous system. In order to explore the possible role of Fyn in schizophrenia, the expression of Fyn messenger RNA (mRNA) and protein were investigated in the postmortem prefrontal cortex of brains from normal and 'schizophrenic' cases. There was an increase in both total area Fyn mRNA signal (17.7%, P<0.05) and cellular mRNA content (15.7%, P<0.05) in the schizophrenic group relative to controls. In parallel the content of Fyn protein detected by immuno-autoradiography was also increased in the schizophrenic cases (21.8% P<0.05). In addition, the cellular Fyn mRNA signal was negatively correlated with the age of onset (r=-0.94, P=0.0026). These results suggest that an increase in Fyn expression may contribute to the pathophysiology of schizophrenia.

    Brain research. Molecular brain research 2003;112;1-2;90-4

  • The role of PI3K in immune cells.

    Koyasu S

    Department of Microbiology and Immunology, Keio University School of Medicine, Tokyo 160-8582, Japan. koyasu@sc.itc.keio.ac.jp

    Members of the phosphoinositide-3 kinase (PI3K) family control several cellular responses including cell growth, survival, cytoskeletal remodeling and the trafficking of intracellular organelles in many different types of cell. In particular PI3K has important functions in the immune system. It has been difficult to evaluate the roles of distinct PI3Ks in cellular immune responses because no PI3K inhibitors are specific for individual family members and because most stimuli activate several PI3K enzymes. The development of gene-targeted mice now enables us to examine the physiological functions of individual PI3K enzymes in the immune system in vivo.

    2003;4;4;313-9

  • p120 Catenin-associated Fer and Fyn tyrosine kinases regulate beta-catenin Tyr-142 phosphorylation and beta-catenin-alpha-catenin Interaction.

    Piedra J, Miravet S, Castaño J, Pálmer HG, Heisterkamp N, García de Herreros A and Duñach M

    Unitat de Biofísica, Departament de Bioquímica i Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain.

    beta-Catenin has a key role in the formation of adherens junction through its interactions with E-cadherin and alpha-catenin. We show here that interaction of beta-catenin with alpha-catenin is regulated by the phosphorylation of beta-catenin Tyr-142. This residue can be phosphorylated in vitro by Fer or Fyn tyrosine kinases. Transfection of these kinases to epithelial cells disrupted the association between both catenins. We have also examined whether these kinases are involved in the regulation of this interaction by K-ras. Stable transfectants of the K-ras oncogene in intestinal epithelial IEC18 cells were generated which show little alpha-catenin-beta-catenin association with respect to control clones; this effect is accompanied by increased Tyr-142 phosphorylation and activation of Fer and Fyn kinases. As reported for Fer, Fyn kinase is constitutively bound to p120 catenin; expression of K-ras induces the phosphorylation of p120 catenin on tyrosine residues increasing its affinity for E-cadherin and, consequently, promotes the association of Fyn with the adherens junction complex. Yes tyrosine kinase also binds to p120 catenin but only upon activation, and stimulates Fer and Fyn tyrosine kinases. These results indicate that p120 catenin acts as a docking protein facilitating the activation of Fer/Fyn tyrosine kinases by Yes and demonstrate the role of these p120 catenin-associated kinases in the regulation of beta-catenin-alpha-catenin interaction.

    Molecular and cellular biology 2003;23;7;2287-97

  • Regulation of a transient receptor potential (TRP) channel by tyrosine phosphorylation. SRC family kinase-dependent tyrosine phosphorylation of TRPV4 on TYR-253 mediates its response to hypotonic stress.

    Xu H, Zhao H, Tian W, Yoshida K, Roullet JB and Cohen DM

    Division of Nephrology, Department of Medicine, Oregon Health & Science University and the Portland Veterans Affairs Medical Center, Portland, Oregon 97201, USA.

    The recently identified transient receptor potential (TRP) channel family member, TRPV4 (formerly known as OTRPC4, VR-OAC, TRP12, and VRL-2) is activated by hypotonicity. It is highly expressed in the kidney as well as blood-brain barrier-deficient hypothalamic nuclei responsible for systemic osmosensing. Apart from its gating by hypotonicity, little is known about TRPV4 regulation. We observed that hypotonic stress resulted in rapid tyrosine phosphorylation of TRPV4 in a heterologous expression model and in native murine distal convoluted tubule cells in culture. This tyrosine phosphorylation was sensitive to the inhibitor of Src family tyrosine kinases, PP1, in a dose-dependent fashion. TRPV4 associated with Src family kinases by co-immunoprecipitation studies and confocal immunofluorescence microscopy, and this interaction required an intact Src family kinase SH2 domain. One of these kinases, Lyn, was activated by hypotonic stress and phosphorylated TRPV4 in an immune complex kinase assay and an in vitro kinase assay using recombinant Lyn and TRPV4. Transfection of wild-type Lyn dramatically potentiated hypotonicity-dependent TRPV4 tyrosine phosphorylation whereas dominant negative-acting Lyn modestly inhibited it. Through mutagenesis studies, the site of tonicity-dependent tyrosine phosphorylation was mapped to Tyr-253, which is conserved across all species from which TRPV4 has been cloned. Importantly, point mutation of Tyr-253 abolished hypotonicity-dependent channel activity. In aggregate, these data indicate that hypotonic stress results in Src family tyrosine kinase-dependent tyrosine phosphorylation of the tonicity sensor TRPV4 at residue Tyr-253 and that this residue is essential for channel function in this context. This is the first example of direct regulation of TRP channel function through tyrosine phosphorylation.

    Funded by: NIDDK NIH HHS: DK52494

    The Journal of biological chemistry 2003;278;13;11520-7

  • Pituitary adenylate cyclase-activating polypeptide (PACAP(1-38)) enhances N-methyl-D-aspartate receptor function and brain-derived neurotrophic factor expression via RACK1.

    Yaka R, He DY, Phamluong K and Ron D

    Ernest Gallo Clinic and Research Center, University of California San Francisco, San Francisco, California 94110-3518, USA.

    We recently identified a novel mechanism for modulation of the phosphorylation state and function of the N-methyl-d-aspartate (NMDA) receptor via the scaffolding protein RACK1. We found that RACK1 binds both the NR2B subunit of the NMDA receptor and the nonreceptor protein-tyrosine kinase, Fyn. RACK1 inhibits Fyn phosphorylation of NR2B and decreases NMDA receptor-mediated currents in CA1 hippocampal slices (Yaka, R., Thornton, C., Vagts, A. J., Phamluong, K., Bonci, A., and Ron, D. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 5710-5715). Here, we identified the signaling cascade by which RACK1 is released from the NMDA receptor complex and identified the consequences of the dissociation. We found that activation of the cAMP/protein kinase A pathway in hippocampal slices induced the release of RACK1 from NR2B and Fyn. This resulted in the induction of NR2B phosphorylation and the enhancement of NMDA receptor-mediated activity via Fyn. We identified the neuropeptide, pituitary adenylate cyclase activating polypeptide (PACAP(1-38)), as a ligand that induced phosphorylation of NR2B and enhanced NMDA receptor potentials. Finally, we found that activation of the cAMP/protein kinase A pathway induced the movement of RACK1 to the nuclear compartment in dissociated hippocampal neurons. Nuclear RACK1 in turn was found to regulate the expression of brain-derived neurotrophic factor induced by PACAP(1-38). Taken together our results suggest that activation of adenylate cyclase by PACAP(1-38) results in the release of RACK1 from the NMDA receptor and Fyn. This in turn leads to NMDA receptor phosphorylation, enhanced activity mediated by Fyn, and to the induction of brain-derived neurotrophic factor expression by RACK1.

    Funded by: NIAAA NIH HHS: R01AA/MH13438-01A1

    The Journal of biological chemistry 2003;278;11;9630-8

  • Dual functional roles for the X-linked lymphoproliferative syndrome gene product SAP/SH2D1A in signaling through the signaling lymphocyte activation molecule (SLAM) family of immune receptors.

    Li C, Iosef C, Jia CY, Han VK and Li SS

    Department of Biochemistry, Faculty of Medicine and Dentistry, University of Western Ontario, London, Canada.

    The X-linked lymphoproliferative (XLP) syndrome gene encodes a protein named SAP or SH2D1A that is composed of a single Src homology 2 (SH2) domain. Two models have been proposed for its function in lymphocyte signaling. One postulates that it acts as an inhibitor of interactions between the phosphatase SHP-2 and the immune receptor SLAM. The other suggests that it functions as an adaptor to promote the recruitment of a kinase, FynT, to SLAM. Here, we provide evidence in support of both roles for SAP. Using an array of peptides derived from the SLAM family of receptors, we demonstrate that SAP binds with comparable affinities to the same sites in these receptors as do the SH2 domains of SHP-2 and SHIP, suggesting that these three proteins may compete against one another in binding to a given SLAM family receptor. Furthermore, in vitro and in vivo binding studies indicate that SAP is capable of binding directly to FynT, an interaction mediated by the FynT SH3 domain. In cells, FynT was shown to be indispensable for SLAM tyrosine phosphorylation, which, in turn, was drastically enhanced by SAP. Because SAP also blocked the recruitment of SHP-2 to SLAM in these cells, we propose a dual functional role for SAP in SLAM signaling by acting both as an adaptor for FynT and an inhibitor to SHP-2 binding. The physiological relevance of the dual functional role for SAP is underscored by the observation that disease-causing SAP mutants exhibited significantly reduced affinities to both FynT and SLAM.

    The Journal of biological chemistry 2003;278;6;3852-9

  • Integrin-mediated tyrosine phosphorylation of Shc in T cells is regulated by protein kinase C-dependent phosphorylations of Lck.

    Niu S, Xie H and Marcantonio EE

    Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.

    Integrin receptor signals are costimulatory for mitogenesis with the T-cell receptor during T-cell activation. A subset of integrin receptors can link to the adapter protein Shc and provide a mitogenic stimulus. Using a combination of genetic and pharmacological approaches, we show herein that integrin signaling to Shc in T cells requires the receptor tyrosine phosphatase CD45, the Src family kinase member Lck, and protein kinase C. Our results suggest a model in which integrin-dependent serine phosphorylation of Lck is the critical step that determines the efficiency of Shc tyrosine phosphorylation in T cells. Serine phosphorylation of Lck is dependent on PKC and is also linked to CD45 dephosphorylation. Mutants of Lck that cannot be phosphorylated on the critical serine residues do not signal efficiently to Shc and have greatly reduced kinase activity. This signaling from integrins to Lck may be an important step in the costimulation with the T-cell receptor during lymphocyte activation.

    Funded by: NIGMS NIH HHS: GM-44585

    Molecular biology of the cell 2003;14;2;349-60

  • SAP couples Fyn to SLAM immune receptors.

    Chan B, Lanyi A, Song HK, Griesbach J, Simarro-Grande M, Poy F, Howie D, Sumegi J, Terhorst C and Eck MJ

    Department of Cancer Biology, Dana-Farber Cancer Institute, 44 Binney Street, Boston, MA 02115, USA.

    SAP (SLAM-associated protein) is a small lymphocyte-specific signalling molecule that is defective or absent in patients with X-linked lymphoproliferative syndrome (XLP). Consistent with its single src homology 2 (SH2) domain architecture and unusually high affinity for SLAM (also called CD150), SAP has been suggested to function by blocking binding of SHP-2 or other SH2-containing signalling proteins to SLAM receptors. Additionally, SAP has recently been shown to be required for recruitment and activation of the Src-family kinase FynT after SLAM ligation. This signalling 'adaptor' function has been difficult to conceptualize, because unlike typical SH2-adaptor proteins, SAP contains only a single SH2 domain and lacks other recognized protein interaction domains or motifs. Here, we show that the SAP SH2 domain binds to the SH3 domain of FynT and directly couples FynT to SLAM. The crystal structure of a ternary SLAM-SAP-Fyn-SH3 complex reveals that SAP binds the FynT SH3 domain through a surface-surface interaction that does not involve canonical SH3 or SH2 binding interactions. The observed mode of binding to the Fyn-SH3 domain is expected to preclude the auto-inhibited conformation of Fyn, thereby promoting activation of the kinase after recruitment. These findings broaden our understanding of the functional repertoire of SH3 and SH2 domains.

    Nature cell biology 2003;5;2;155-60

  • Fyn tyrosine kinase is a critical regulator of disabled-1 during brain development.

    Arnaud L, Ballif BA, Förster E and Cooper JA

    Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, 98109, Seattle, WA, USA.

    Background: Disabled-1 (Dab1) is an intracellular adaptor protein that regulates migrations of various classes of neurons during mammalian brain development. Dab1 function depends on its tyrosine phosphorylation, which is stimulated by Reelin, an extracellular signaling molecule. Reelin increases the stoichiometry of Dab1 phosphorylation and downregulates Dab1 protein levels. Reelin binds to various cell surface receptors, including two members of the low-density lipoprotein receptor family that also bind to Dab1. Mutations in Dab1, its phosphorylation sites, Reelin, or the Reelin receptors cause a common phenotype. However, the molecular mechanism whereby Reelin regulates Dab1 tyrosine phosphorylation is poorly understood.

    Results: We found that Reelin-induced Dab1 tyrosine phosphorylation in neuron cultures is inhibited by acute treatment with pharmacological inhibitors of Src family, but not Abl family, kinases. In addition, Reelin stimulates Src family kinases by a mechanism involving Dab1. We analyzed the Dab1 protein level and tyrosine phosphorylation stoichiometry by using brain samples and cultured neurons that were obtained from mouse embryos carrying mutations in Src family tyrosine kinases. We found that fyn is required for proper Dab1 levels and phosphorylation in vivo and in vitro. When fyn copy number is reduced, src, but not yes, becomes important, reflecting a partial redundancy between fyn and src.

    Conclusions: Reelin activates Fyn to phosphorylate and downregulate Dab1 during brain development. The results were unexpected because Fyn deficiency does not cause the same developmental phenotype as Dab1 or Reelin deficiency. This suggests additional complexity in the Reelin signaling pathway.

    Funded by: NCI NIH HHS: R37 CA41072, T32 CA09657-11

    Current biology : CB 2003;13;1;9-17

  • Regulation of vascular endothelial growth factor receptor-2 activity by caveolin-1 and plasma membrane cholesterol.

    Labrecque L, Royal I, Surprenant DS, Patterson C, Gingras D and Béliveau R

    Centre de Cancérologie Charles-Bruneau, Hôpital Sainte-Justine, Montréal, Quebec, Canada H3T 1C5.

    The stimulation of vascular endothelial growth factor receptor-2 (VEGFR-2) by tumor-derived VEGF represents a key event in the initiation of angiogenesis. In this work, we report that VEGFR-2 is localized in endothelial caveolae, associated with caveolin-1, and that this complex is rapidly dissociated upon stimulation with VEGF. The kinetics of caveolin-1 dissociation correlated with those of VEGF-dependent VEGFR-2 tyrosine phosphorylation, suggesting that caveolin-1 acts as a negative regulator of VEGF R-2 activity. Interestingly, we observed that in an overexpression system in which VEGFR-2 is constitutively active, caveolin-1 overexpression inhibits VEGFR-2 activity but allows VEGFR-2 to undergo VEGF-dependent activation, suggesting that caveolin-1 can confer ligand dependency to a receptor system. Removal of caveolin and VEGFR-2 from caveolae by cholesterol depletion resulted in an increase in both basal and VEGF-induced phosphorylation of VEGFR-2, but led to the inhibition of VEGF-induced ERK activation and endothelial cell migration, suggesting that localization of VEGFR-2 to these domains is crucial for VEGF-mediated signaling. Dissociation of the VEGFR-2/caveolin-1 complex by VEGF or cyclodextrin led to a PP2-sensitive phosphorylation of caveolin-1 on tyrosine 14, suggesting the participation of Src family kinases in this process. Overall, these results suggest that caveolin-1 plays multiple roles in the VEGF-induced signaling cascade.

    Molecular biology of the cell 2003;14;1;334-47

  • Specific interactions of neuronal focal adhesion kinase isoforms with Src kinases and amphiphysin.

    Messina S, Onofri F, Bongiorno-Borbone L, Giovedì S, Valtorta F, Girault JA and Benfenati F

    Department of Experimental Medicine, Section of Human Physiology, University of Genova, Italy.

    Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that activates Src family kinases via SH2- and SH3-mediated interactions. Specific FAK isoforms (FAK+), responsive to depolarization and neurotransmitters, are enriched in neurons. We analyzed the interactions of endogenous FAK+ and recombinant FAK+ isoforms containing amino acid insertions (boxes 6,7,28) with an array of SH3 domains and the c-Src SH2/SH3 domain tandem. Endogenous FAK+ bound specifically to the SH3 domains of c-Src (but not n-Src), Fyn, Yes, phosphtidylinositol-3 kinase, amphiphysin II, amphiphysin I, phospholipase Cgamma and NH2-terminal Grb2. The inclusion of boxes 6,7 was associated with a significant decrease in the binding of FAK+ to the c-Src and Fyn SH3 domains, and a significant increase in the binding to the Src SH2 domain, as a consequence of the higher phosphorylation of Tyr-397. The novel interaction with the amphiphysin SH3 domain, involving the COOH-terminal proline-rich region of FAK, was confirmed by coimmunoprecipitation of the two proteins and a closely similar response to stimuli affecting the actin cytoskeleton. Moreover, an impairment of endocytosis was observed in synaptosomes after internalization of a proline-rich peptide corresponding to the site of interaction. The data account for the different subcellular distribution of FAK and Src kinases and the specific regulation of the transduction pathways linked to FAK activation in the brain and implicate FAK in the regulation of membrane trafficking in nerve terminals.

    Funded by: Telethon: 1131

    Journal of neurochemistry 2003;84;2;253-65

  • Src kinase becomes preferentially associated with the VEGFR, KDR/Flk-1, following VEGF stimulation of vascular endothelial cells.

    Chou MT, Wang J and Fujita DJ

    Department of Biochemistry and Molecular Biology, University of Calgary Health Sciences Center, 3330 Hospital Dr, N,W, Calgary, AB, Canada T2N 4N1. mthchou@ucalgary.ca

    Background: The cytoplasmic tyrosine kinase, Src, has been found to play a crucial role in VEGF (vascular endothelial growth factor) - dependent vascular permeability involved in angiogenesis. The two main VEGFRs present on vascular endothelial cells are KDR/Flk-1 (kinase insert domain-containing receptor/fetal liver kinase-1) and Flt-1 (Fms-like tyrosine kinase-1). However, t 1f40 o date, it has not been determined which VEGF receptor (VEGFR) is involved in binding to and activating Src kinase following VEGF stimulation of the receptors.

    Results: In this report, we demonstrate that Src preferentially associates with KDR/Flk-1 rather than Flt-1 in human umbilical vein endothelial cells (HUVECs), and that VEGF stimulation resulted in an increase of Src activity associated with activated KDR/Flk-1. These findings were determined through immunoprecipitation-kinase experiments and coimmunoprecipitation studies, and were further confirmed by GST-pull-down assays and Far Western studies. However, Fyn and Yes, unlike Src, were found to associate preferentially with Flt-1.

    Conclusions: Thus, Src preferentially associates with KDR/Flk-1, rather than with Flt-1, upon VEGF stimulation in endothelial cells. Our findings further highlight the potential significance of upregulated KDR/Flk-1-associated Src activity in the process of angiogenesis, and help to elucidate more clearly the specific roles and mechanisms involving Src family tyrosine kinase in VEGF-stimulated signal transduction events.

    BMC biochemistry 2002;3;32

  • Defective thymocyte maturation by transgenic expression of a truncated form of the T lymphocyte adapter molecule and Fyn substrate, Sin.

    Donlin LT, Roman CA, Adlam M, Regelmann AG and Alexandropoulos K

    Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.

    Adapter molecules that promote protein-protein interactions play a central role in T lymphocyte differentiation and activation. In this study, we examined the role of the T lymphocyte-expressed adapter protein and Src kinase substrate, Sin, on thymocyte function using transgenic mice expressing an activated, truncated allele of Sin (SinDeltaC). We found that SinDeltaC expression led to reduced numbers of CD4(+) and CD8(+) single-positive cells and reduced thymic cellularity due to increased thymocyte apoptosis. Because the adapter properties of Sin are mediated by tyrosine-based motifs and given that Sin is a substrate for Src tyrosine kinases, we examined the involvement of these kinases in the inhibitory effects of SinDeltaC. We found that in transgenic thymocytes, SinDeltaC was constitutively phosphorylated by the Src kinase Fyn, but not by the related kinase Lck. Using SinDeltaC and fyn(-/-) animals, we also found that the expression of Fyn was required for the inhibitory effect of SinDeltaC on thymocyte apoptosis but not for SinDeltaC-mediated inhibition of T cell maturation. The inhibitory effect of SinDeltaC on thymocyte maturation correlated with defective activation of the mitogen-activated protein kinase extracellular signal-regulated kinase. Our results suggest that the Sin mutant inhibits thymocyte differentiation through Fyn-dependent and -independent mechanisms and that endogenous Sin may be an important regulator of thymocyte development.

    Funded by: NIAID NIH HHS: 5 T32 AI07525, R01 AI49387-01; NIGMS NIH HHS: 5 T32 GM03767-26

    Journal of immunology (Baltimore, Md. : 1950) 2002;169;12;6900-9

  • Regulation of Lck and Fyn tyrosine kinase activities by transmembrane protein tyrosine phosphatase leukocyte common antigen-related molecule.

    Tsujikawa K, Ichijo T, Moriyama K, Tadotsu N, Sakamoto K, Sakane N, Fukada S, Furukawa T, Saito H and Yamamoto H

    Department of Immunology, Graduate School of Pharmaceutical Sciences, Osaka University, Yamadaoka, Suita, Osaka, Japan. tujikawa@phs.osaka-u.ac.jp

    Leukocyte common antigen-related molecule (LAR) is a receptor-like protein tyrosine phosphatase (PTPase) with two PTPase domains. In the present study, we detected the expression of LAR in the brain, kidney, and thymus of mice using anti-LAR PTPase domain subunit monoclonal antibody (mAb) YU1. In the thymus, LAR was expressed on CD4(-)CD8(-) and CD4(-)CD8(low) thymocytes. The development of thymocytes in CD45 knockout mice is blocked partially in the maturation of CD4(-)CD8(-) to CD4(+)CD8(+). We postulated that LAR regulates Lck and Fyn in the immature thymocytes. Transfection of wild-type LAR activated extracellular signal-regulated kinase signal transduction pathway in CD45-deficient Jurkat cells stimulated with anti-CD3 mAb. LAR mutants, with Cys to Ser mutation in the catalytic center of PTPase D1, bound to tyrosine-phosphorylated Lck and Fyn, and LAR PTPase domain 2 was tyrosine phosphorylated by Fyn tyrosine kinase. The phosphorylated LAR was associated with Fyn Src homology 2 domain. Moreover, LAR dephosphorylated phosphorylated tyrosine residues in both the COOH terminus and kinase domain of Fyn in vitro. Our results indicate that Lck and Fyn would be substrates of LAR in immature thymocytes and that each LAR PTPase domain plays distinct functional roles in phosphorylation and dephosphorylation.

    Molecular cancer research : MCR 2002;1;2;155-63

  • Activation of NMDA receptors and L-type voltage-gated calcium channels mediates enhanced formation of Fyn-PSD95-NR2A complex after transient brain ischemia.

    Hou XY, Zhang GY, Yan JZ, Chen M and Liu Y

    Research Center for Biochemistry and Molecular Biology, Xuzhou Medical College, 84 West Huai-hai Road, Xuzhou, Jiangsu 221002, China.

    Recent studies have indicated that tyrosine phosphorylation of NMDA receptor subunit 2A (NR2A) by Src family kinases (Src, Fyn, etc.) up-regulates NMDA receptors activity and postsynaptic density protein 95 kDa (PSD95) may mediate the regulation. To investigate whether the above processes are involved in brain ischemia-induced enhancement of NMDA receptors function, we examined the effects of transient (15 min) brain ischemia followed by reperfusion on interactions involving Fyn, NR2A and PSD95 in rat hippocampus by co-immunoprecipitation. Transient brain ischemia was induced by the method of four-vessel occlusion in Sprague-Dawley rats. Association between Fyn and NR2A increased immediately after brain ischemia and the increase was maintained for at least 24 h during followed reperfusion, up to about 1.7-1.8-fold relative to sham-groups. The 15-min reperfusion after brain ischemia induced enhanced co-immunoprecipitation of PSD95, Fyn and NR2A with one another. The associations of PSD95 with Fyn and NR2A increased at 0-24 h, 0-1 h of reperfusion, up to 6.9- and 2.1-fold relative to sham groups, respectively. Inhibiting activation of NMDA receptors or L-type voltage-gated calcium channels (L-VGCC) by ketamine or nifedipine attenuated the above increases of associations. These results suggest that stimulation of NMDA receptors and L-VGCC facilitates formation of a ternary complex: Fyn-PSD95-NR2A during transient brain ischemia followed by reperfusion, which may result in potentiation of NMDA receptor function and contribute to ischemic neuronal cell death.

    Brain research 2002;955;1-2;123-32

  • Dynamic interaction of CD2 with the GYF and the SH3 domain of compartmentalized effector molecules.

    Freund C, Kühne R, Yang H, Park S, Reinherz EL and Wagner G

    Protein Engineering Group and Molecular Modeling Group, Forschungsinstitut für Molekulare Pharmakologie and Freie Universität Berlin, Robert-Rössle-Strasse 10, D-13125 Berlin, Germany. freund@fmp-berlin.de

    Intracellular protein interaction domains are essential for eukaryotic signaling. In T cells, the CD2BP2 adaptor binds two membrane-proximal proline-rich motifs in the CD2 cytoplasmic tail via its GYF domain, thereby regulating interleukin-2 production. Here we present the structure of the GYF domain in complex with a CD2 tail peptide. Unlike SH3 domains, which use two surface pockets to accommodate proline residues of ligands, the GYF domain employs phylogenetically conserved hydrophobic residues to create a single interaction surface. NMR analysis shows that the Fyn but not the Lck tyrosine kinase SH3 domain competes with CD2BP2 GYF-domain binding to the same CD2 proline-rich sequence in vitro. To test the in vivo significance of this competition, we used co-immunoprecipitation experiments and found that CD2BP2 is the ligand of the membrane-proximal proline-rich tandem repeat of CD2 in detergent-soluble membrane compartments, but is replaced by Fyn SH3 after CD2 is translocated into lipid rafts upon CD2 ectodomain clustering. This unveils the mechanism of a switch of CD2 function due to an extracellular mitogenic signal.

    Funded by: NCRR NIH HHS: RR 00995; NIAID NIH HHS: AI 19807, AI 37581, R01 AI019807, R01 AI037581, R37 AI019807, R56 AI019807; NIGMS NIH HHS: GM 47467, P01 GM047467

    The EMBO journal 2002;21;22;5985-95

  • Identification of an alternatively spliced isoform of the fyn tyrosine kinase.

    Goldsmith JF, Hall CG and Atkinson TP

    Department of Pathology, University of Alabama-Birmingham School of Medicine, Birmingham, AL 35294, USA.

    Two isoforms of the src-family tyrosine kinase p59fyn have been shown to arise through alternative splicing of exon 7 of the fyn gene. These isoforms have been designated fynT, expressed in hematopoietic cells, and fynB, expressed in the brain. Here, we describe a novel isoform, fynDelta7, in which exon 7 is absent. FynDelta7 mRNA transcripts have been identified in peripheral blood mononuclear cells from all individuals tested thus far and semi-quantitative RT-PCR indicates that this fyn transcript is expressed at near wild-type levels. Transcripts coding for the fynDelta7 isoform can be detected in purified B cells, T cells, NK cells, and monocytes, indicating that it is not lineage specific. We further show that the message isolated is functional using an in vitro expression system and by its expression in COS cells.

    Biochemical and biophysical research communications 2002;298;4;501-4

  • Loss of a FYN-regulated different 5a8 iation and growth arrest pathway in advanced stage neuroblastoma.

    Berwanger B, Hartmann O, Bergmann E, Bernard S, Nielsen D, Krause M, Kartal A, Flynn D, Wiedemeyer R, Schwab M, Schäfer H, Christiansen H and Eilers M

    Tumor stage, age of patient, and amplification of MYCN predict disease outcome in neuroblastoma. To gain insight into the underlying molecular pathways, we have obtained expression profiles from 94 primary neuroblastoma specimens. Advanced tumor stages show a characteristic expression profile that includes downregulation of multiple genes involved in signal transduction through Fyn and the actin cytoskeleton. High expression of Fyn and high Fyn kinase activity are restricted to low-stage tumors. In culture, expression of active Fyn kinase induces differentiation and growth arrest of neuroblastoma cells. Expression of Fyn predicts long-term survival independently of MYCN amplification. Amplification of MYCN correlates with deregulation of a distinct set of genes, many of which are target genes of Myc. Our data demonstrate a causal role for Fyn kinase in the genesis of neuroblastoma.

    Cancer cell 2002;2;5;377-86

  • SKAP55 recruits to lipid rafts and positively mediates the MAPK pathway upon T cell receptor activation.

    Wu L, Yu Z and Shen SH

    Mammalian Cell Genetics, Biotechnology Research Institute, National Research Council Canada, 6100 Royalmount Avenue, Montreal, Quebec H4P 2R2, Canada.

    T cell receptor (TCR) engagement triggers a series of events including protein tyrosine kinase activation, tyrosine phosphorylation of adapter proteins, and multiple protein-protein interactions. We observed that adapter protein SKAP55, the Src kinase-associated phosphoprotein, formed homodimers through its SH3 domain and SK region. SKAP55 as a substrate interacted with Fyn kinase in vivo. In Jurkat cells, interaction between SKAP55 and Fyn kinase depended on TCR activation. Stable overexpression of SKAP55 in Jurkat cells caused mitogen-activated protein kinase activation following TCR engagement. Anti-CD3 stimulation also promoted the interaction of SKAP55 with Grb-2 in T cells. Mutational analysis revealed that tyrosine 271 in SKAP55 played a pivotal role for interaction with both Fyn kinase and adapter protein Grb-2, indicating that the Fyn-phosphorylated SKAP55 transiently associates with adapter Grb-2 to mediate mitogen-activated protein kinase activation. Intriguingly, T cell receptor engagement dramatically induced the translocation of endogenous SKAP55 to lipid rafts where SKAP55 was found to interact with Fyn kinase, suggesting that the positive function of SKAP55 via its association with Fyn and other signaling components may have been involved in raft-mediated T cell activation.

    The Journal of biological chemistry 2002;277;43;40420-7

  • The distinct capacity of Fyn and Lck to phosphorylate Sam68 in T cells is essentially governed by SH3/SH2-catalytic domain linker interactions.

    Feuillet V, Semichon M, Restouin A, Harriague J, Janzen J, Magee A, Collette Y and Bismuth G

    Département de Biologie Cellulaire, INSERM U.567, CNRS UMR 8104, Université René Descartes, Institut Cochin, 75014 Paris, France.

    Sam68 phosphorylation correlates with Fyn but not Lck expression in T cells. This substrate has been used here to explore the possible basis of the specificity of Fyn versus Lck. We show that this specificity is not based on a spatial segregation of the two kinases, since a chimeric Lck molecule containing the membrane anchoring domain of Fyn does not phosphorylate Sam68. Moreover, a Sam68 molecule targeted to the plasma membrane by the farnesylation signal of c-Ha-Ras remains poorly phosphorylated by Lck. In T cells, Fyn appears to be the active Src kinase in rafts, but Sam68 is not expressed in rafts, and its distinct phosphorylation by Fyn and Lck is not affected by raft dispersion. The Fyn/Lck specificity does not reflect a higher kinase activity of Fyn in general, as both Fyn and Lck are similarly recognized by an anti-active Src antibody. Both also strongly phosphorylate another Src substrate in vivo. Mainly, Lck phosphorylates Sam68 when the interaction between the SH3 domain and the SH2-catalytic domain linker is altered in heterologous Src molecules or after mutating key residues in the linker that increase the accessibility of the SH3 domain. Thus, the distinct potential of Fyn and Lck to phosphorylate Sam68 is likely controlled by the interaction of the kinase SH3 domain with the linker and Sam68, possibly on a competitive binding basis.

    Oncogene 2002;21;47;7205-13

  • Tr-kit-induced resumption of the cell cycle in mouse eggs requires activation of a Src-like kinase.

    Sette C, Paronetto MP, Barchi M, Bevilacqua A, Geremia R and Rossi P

    Department of Public Health and Cell Biology, Section of Anatomy, University of Rome Tor Vergata, Rome, Italy. claudio.sette@uniroma2.it

    Microinjection in mouse eggs of tr-kit, a truncated form of the c-kit tyrosine kinase present in mouse spermatozoa, causes resumption of meiosis through activation of phospholipase Cgamma1 (PLCgamma1) and Ca(2+) mobilization from intracellular stores. We show that the Src-like kinase Fyn phosphorylates Tyr161 in tr-kit and that this residue is essential for tr-kit function. Fyn is localized in the cortex region underneath the plasma membrane in mouse oocytes. Using several approaches, we demonstrate that Fyn associates with tr-kit and that the interaction requires Tyr161. The interaction between tr-kit and Fyn triggers activation of the kinase as monitored by both autophosphorylation and phosphorylation of PLCgamma1. Co-injection of tr-kit with the SH2 domain of Fyn, or pre-treatment with a Fyn inhibitor, impairs oocyte activation, suggesting that activation of Fyn by tr-kit also occurs in vivo. Finally, microinjection of constitutively active Fyn triggers oocyte activation downstream of tr-kit but still requires PLC activity. We suggest that the mechanism by which tr-kit triggers resumption of meiosis of mouse eggs requires a functional interaction with Fyn and phosphorylation of PLCgamma1.

    The EMBO journal 2002;21;20;5386-95

  • c-Cbl is involved in Met signaling in B cells and mediates hepatocyte growth factor-induced receptor ubiquitination.

    Taher TE, Tjin EP, Beuling EA, Borst J, Spaargaren M and Pals ST

    Department of Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.

    Hepatocyte growth factor/scatter factor (HGF) and its receptor tyrosine kinase Met are key regulators of epithelial motility and morphogenesis. Recent studies indicate that the HGF/Met pathway also plays a role in B cell differentiation, whereas uncontrolled Met signaling may lead to B cell neoplasia. These observations prompted us to explore HGF/Met signaling in B cells. In this study, we demonstrate that HGF induces strong tyrosine phosphorylation of the proto-oncogene product c-Cbl in B cells and increases Cbl association with the Src family tyrosine kinases Fyn and Lyn, as well as with phosphatidylinositol-3 kinase and CrkL. In addition, we demonstrate that c-Cbl mediates HGF-induced ubiquitination of Met. This requires the juxtamembrane tyrosine Y1001 (Y2) of Met, but not the multifunctional docking site (Y14/15) or any additional C-terminal tyrosine residues (Y13-16). In contrast to wild-type c-Cbl, the transforming mutants v-Cbl and 70Z/3 Cbl, which lack the ubiquitin ligase RING finger domain, suppress Met ubiquitination. Our findings identify c-Cbl as a negative regulator of HGF/Met signaling in B cells, mediating ubiquitination and, consequently, proteosomal degradation of Met, and suggest a role for Cbl in Met-mediated tumorigenesis.

    Journal of immunology (Baltimore, Md. : 1950) 2002;169;7;3793-800

  • P59(fyn) is upregulated in anergic CD8+ T cells.

    Welke J and Zavazava N

    Department of Internal Medicine, C51-F, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA 52242, USA.

    The ultimate goal in clinical transplantation is achievement of graft tolerance. Despite long-term immunosuppression, alloantigens on transplants elicit alloresponses that can initiate organ rejection. Acute rejection is mediated by CD8(+) cytotoxic T cells, whereas chronic rejection is a result of many factors including non-immunological events. The aim of this study was to examine the molecular requirements of T cell anergy, a cellular state that is an integral component of tolerance in vivo. In vitro, the tolerant state is usually best represented by T cell anergy, which is defined by loss of the ability of T cells to produce and secrete interleukin-2 upon restimulation. In the literature, molecular changes in anergic CD4(+) T cells have been studied in great detail, but only little is known about functional and biochemical characteristics of anergic CD8(+) T lymphocytes. In this study, we demonstrate, that CD8(+) T cells are rendered anergic by TCR stimulation without costimulation. They exhibit impaired interleukin-2 production and tyrosine-phosphorylation, but markedly upregulated p59(fyn) expression, which could be shown to be an early event during anergization. Anergic CD8(+) T lymphocytes show elevated surface expression of early activation markers as well as costimulatory molecules, especially that of CTLA4. These results, are an important component for the discovery of potential molecular targets, which contribute to the development and maintenance of tolerance.

    Human immunology 2002;63;10;834-43

  • QM, a putative tumor suppressor, regulates proto-oncogene c-yes.

    Oh HS, Kwon H, Sun SK and Yang CH

    Division of Chemistry and Molecular Engineering, Seoul National University, Seoul 151-742, Korea.

    The QM gene encodes a 24.5 kDa ribosomal protein L10 known to be highly homologous to a Jun-binding protein (Jif-1), which inhibits the formation of Jun-Jun dimers. Here we have carried out screening with the c-Yes protein and found that a QM homologous protein showed interactions with c-Yes and other Src family members. We have found that two different regions of QM protein were associated with the SH3 domain of c-Yes. The QM protein does not contain canonical SH3 binding motifs or previously reported amino acid fragments showing interaction with SH3 domains. Several c-Yes kinase activity assays indicated that the QM protein reduced c-Yes kinase activity by 70% and that this suppression is related not only to the two SH3 binding regions but also to the C-terminal region of QM. Moreover, our autophosphorylation assays clarified that this regulation resulted from the inhibition of c-Yes autophosphorylation. Immunofluorescence studies showed that the QM proteins and c-Yes are able to interact in various tumor cell lines in vivo. The increases of the c-Yes protein and mRNA levels were detected when the QM was transfected. These results suggest that the QM protein might be a regulator for various signal transduction pathways involving SH3 domain-containing membrane proteins.

    The Journal of biological chemistry 2002;277;39;36489-98

  • Cutting edge: Fyn is essential for tyrosine phosphorylation of Csk-binding protein/phosphoprotein associated with glycolipid-enriched microdomains in lipid rafts in resting T cells.

    Yasuda K, Nagafuku M, Shima T, Okada M, Yagi T, Yamada T, Minaki Y, Kato A, Tani-Ichi S, Hamaoka T and Kosugi A

    Department of Oncogenesis, Graduate School of Medicine, Osaka University, Osaka, Japan.

    In resting T cells, Csk is constitutively localized in lipid rafts by virtue of interaction with a phosphorylated adaptor protein, Csk-binding protein (Cbp)/phosphoprotein associated with glycolipid-enriched microdomains, and sets an activation threshold in TCR signaling. In this study, we examined a kinase responsible for Cbp phosphorylation in T cell membrane rafts. By analyzing T cells from Fyn-/- mice, we clearly demonstrated that Fyn, but not Lck, has its kinase activity in membrane rafts, and plays a critical role in Cbp phosphorylation, Cbp-Csk interaction, and Csk kinase activity. Naive CD44(low)CD62 ligand(high) T cells were substantially reduced in Fyn-/- mice, presumably due to the inhibition of Cbp phosphorylation. Thus, Fyn mediates Cbp-Csk interaction and recruits Csk to rafts by phosphorylating Cbp. Csk recruited to rafts would then be activated and inhibit the kinase activity of Lck to keep resting T cells in a quiescent state. Our results elucidate a negative regulatory role for Fyn in proximal TCR signaling in lipid rafts.

    Journal of immunology (Baltimore, Md. : 1950) 2002;169;6;2813-7

  • Biological activity of the thyroid TRK-T3 oncogene requires signalling through Shc.

    Roccato E, Miranda C, Ranzi V, Gishizki M, Pierotti MA and Greco A

    Department of Experimental Oncology, Istituto Nazionale Tumori, Via G. Venezian 1, 20133 Milan, Italy.

    The thyroid TRK-T3 oncogene, produced by a chromosomal translocation, is a chimeric, constitutively activated version of the NTRK1/NGF receptor and it is able to transform NIH3T3 cells and differentiate PC12 cells. TRK-T3 oncoprotein triggers multiple signal transduction pathways. Among others, TRK-T3 binds and phosphorylates the Shc and SNT1/FRS2 adaptor proteins both involved in coupling the receptor tyrosine kinase to the mitogen-activated protein kinase pathway by recruiting Grb2/SOS. We were interested in defining the role of Shc in the oncogenesis by TRK-T3. The mutation of TRK-T3 tyrosine 291, docking site for both Shc and FRS2, abrogates the oncogene biological activity. To directly explore the role of Shc we used the ShcY317F mutant, which carries the mutation of a tyrosine residue involved in Grb2 recruitment. We demonstrated that the ShcY317F mutant exerts an inhibitory effect on TRK-T3 transforming activity. Such effect can be modulated by the amount of ShcY317F protein and affects the viability of cells expressing TRK-T3 by means of a mechanism involving apoptosis. Our results indicate a definitive role of the adaptor protein Shc in TRK-T3 transforming activity.

    British journal of cancer 2002;87;6;645-53

  • Activation of phospholipase Cgamma2 by tyrosine phosphorylation.

    Ozdener F, Dangelmaier C, Ashby B, Kunapuli SP and Daniel JL

    Department of Pharmacology, Temple University Medical School, Philadelphia, Pennsylvania 19140, USA.

    Phospholipase Cgamma2 (PLCgamma2) has been implicated in collagen-induced signal transduction in platelets and antigen-dependent signaling in B-lymphocytes. It has been suggested that tyrosine kinases activate PLCgamma2. We expressed the full-length cDNA for human PLCgamma2 in bacteria and purified the recombinant enzyme. The recombinant enzyme was Ca(2+)-dependent with optimal activity in the range of 1 to 10 microM Ca(2+). In vitro phosphorylation experiments with recombinant PLCgamma2 and recombinant Lck, Fyn, and Lyn tyrosine kinases showed that phosphorylation of PLCgamma2 led to activation of the recombinant enzyme. Using site-directed mutagenesis, we investigated the role of specific tyrosine residues in activation of PLCgamma2. A mutant form of PLCgamma2, in which all three tyrosines at positions 743, 753, and 759 in the SH2-SH3 linker region were replaced by phenylalanines, exhibited decreased Lck-induced phosphorylation and completely abolished the Lck-dependent activation of PLCgamma2. Individual mutations of these tyrosine residues demonstrated that tyrosines 753 and 759, but not 743, were responsible for Lck-induced activation of PLCgamma2. To confirm these results, we procured a phosphospecific antibody to a peptide containing phosphorylated tyrosines corresponding to residues 753 and 759. This antibody recognized phosphorylated wild-type PLCgamma2 on Western blots but did not interact with unphosphorylated PLCgamma2 or with PLCgamma2 containing mutated tyrosine residues at 753 and 759. Using this antibody, we showed in intact platelets that collagen, a PLCgamma2-dependent agonist, induces phosphorylation of PLCgamma2 at Y753 and Y759. These studies demonstrate the importance of these two tyrosine residues in regulating the activity of PLCgamma2.

    Funded by: NHLBI NIH HHS: HL60683

    Molecular pharmacology 2002;62;3;672-9

  • Fyn and Cdk5 mediate semaphorin-3A signaling, which is involved in regulation of dendrite orientation in cerebral cortex.

    Sasaki Y, Cheng C, Uchida Y, Nakajima O, Ohshima T, Yagi T, Taniguchi M, Nakayama T, Kishida R, Kudo Y, Ohno S, Nakamura F and Goshima Y

    Department of Molecular Pharmacology and Neurobiology, Yokohama City University School of Medicine, Yokohama, Japan. yukio.sasaki@pharmac.med.yokohama-cu.ac.jp

    Semaphorin-3A (Sema3A), a member of class 3 semaphorins, regulates axon and dendrite guidance in the nervous system. How Sema3A and its receptors plexin-As and neuropilins regulate neuronal guidance is unknown. We observed that in fyn- and cdk5-deficient mice, Sema3A-induced growth cone collapse responses were attenuated compared to their heterologous controls. Cdk5 is associated with plexin-A2 through the active state of Fyn. Sema3A promotes Cdk5 activity through phosphorylation of Tyr15, a phosphorylation site with Fyn. A Cdk5 mutant (Tyr15 to Ala) shows a dominant-negative effect on the Sema3A-induced collapse response. The sema3A gene shows strong interaction with fyn for apical dendrite guidance in the cerebral cortex. We propose a signal transduction pathway in which Fyn and Cdk5 mediate neuronal guidance regulated by Sema3A.

    Neuron 2002;35;5;907-20

  • Fyn kinase initiates complementary signals required for IgE-dependent mast cell degranulation.

    Parravicini V, Gadina M, Kovarova M, Odom S, Gonzalez-Espinosa C, Furumoto Y, Saitoh S, Samelson LE, O'Shea JJ and Rivera J

    Molecular Inflammation Section, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892-1820, USA.

    Fc epsilon RI activation of mast cells is thought to involve Lyn and Syk kinases proximal to the receptor and the signaling complex organized by the linker for activation of T cells (LAT). We report here that Fc epsilon RI also uses a Fyn kinase-dependent pathway that does not require Lyn kinase or the adapter LAT for its initiation, but is necessary for mast cell degranulation. Lyn-deficiency enhanced Fyn-dependent signals and degranulation, but inhibited the calcium response. Fyn-deficiency impaired degranulation, whereas Lyn-mediated signaling and calcium was normal. Thus, Fc epsilon RI-dependent mast cell degranulation involves cross-talk between Fyn and Lyn kinases.

    Nature immunology 2002;3;8;741-8

  • Inhibition of Src family kinases blocks epidermal growth factor (EGF)-induced activation of Akt, phosphorylation of c-Cbl, and ubiquitination of the EGF receptor.

    Kassenbrock CK, Hunter S, Garl P, Johnson GL and Anderson SM

    Department of Pathology, University of Colorado Health Sciences Center, Denver 80262, USA.

    Stimulation of T47D cells with epidermal growth factor (EGF) results in the activation of the intrinsic tyrosine kinases of the receptor and the phosphorylation of multiple cellular proteins including the receptor, scaffold molecules such as c-Cbl, adapter molecules such as Shc, and the serine/threonine protein kinase Akt. We demonstrate that EGF stimulation of T47D cells results in the activation of the Src protein-tyrosine kinase and that the Src kinase inhibitor PP1 blocks the EGF-induced phosphorylation of c-Cbl but not the activation/phosphorylation of the EGF receptor itself. PP1 also blocks EGF-induced ubiquitination of the EGF receptor, which is presumably mediated by phosphorylated c-Cbl. Src is associated with c-Cbl, and we have previously demonstrated that the Src-like kinase Fyn can phosphorylate c-Cbl at a preferred binding site for the p85 subunit of phosphatidylinositol 3'-kinase. PP1 treatment blocks EGF-induced activation of the anti-apoptotic protein kinase Akt suggesting that Src may regulate activation of Akt, perhaps by a Src --> c-Cbl --> phosphatidylinositol 3'-kinase --> Akt pathway.

    Funded by: NIDDK NIH HHS: DK48879; NIGMS NIH HHS: GM55754

    The Journal of biological chemistry 2002;277;28;24967-75

  • Interactions between Eph kinases and ephrins provide a mechanism to support platelet aggregation once cell-to-cell contact has occurred.

    Prevost N, Woulfe D, Tanaka T and Brass LF

    Department of Medicine and Center for Experimental Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA.

    Eph kinases are receptor tyrosine kinases whose ligands, the ephrins, are also expressed on the surface of cells. Interactions between Eph kinases and ephrins on adjacent cells play a central role in neuronal patterning and vasculogenesis. Here we examine the expression of ephrins and Eph kinases on human blood platelets and explore their role in the formation of the hemostatic plug. The results show that human platelets express EphA4 and EphB1, and the ligand, ephrinB1. Forced clustering of EphA4 or ephrinB1 led to cytoskeletal reorganization, adhesion to fibrinogen, and alpha-granule secretion. Clustering of ephrinB1 also caused activation of the Ras family member, Rap1B. In platelets that had been activated by ADP and allowed to aggregate, EphA4 formed complexes with two tyrosine kinases, Fyn and Lyn, and the cell adhesion molecule, L1. Blockade of Eph/ephrin interactions prevented the formation of these complexes and caused platelet aggregation at low ADP concentrations to become more readily reversible. We propose that when sustained contacts between platelets have occurred in response to agonists such as collagen, ADP, and thrombin, the binding of ephrins to Eph kinases on adjacent platelets provides a mechanism to perpetuate signaling and promote stable platelet aggregation.

    Funded by: NCI NIH HHS: CA-16520, P30 CA016520; NHLBI NIH HHS: HL-40387, P01 HL040387; NIDDK NIH HHS: DK-19525, P30 DK019525

    Proceedings of the National Academy of Sciences of the United States of America 2002;99;14;9219-24

  • Striatal enriched phosphatase 61 dephosphorylates Fyn at phosphotyrosine 420.

    Nguyen TH, Liu J and Lombroso PJ

    Child Study Center, Yale University School of Medicine, New Haven, Connecticut 06520, USA. tnguyen@lumicyte.com

    A family of protein tyrosine phosphatases enriched within the central nervous system called striatal enriched phosphatase (STEP) has been implicated in the regulation of the N-methyl-d-aspartate receptor. STEP(61), a membrane-associated isoform located in the postsynaptic densities (PSDs) of striatal neurons, contains two transmembrane domains, two proline-rich domains, and a kinase-interacting motif. This study demonstrates that STEP(61) associates with Fyn, a member of the Src family kinases that is also enriched in PSDs. By using human embryonic kidney 293 cells for co-transfection, we determined that a substrate-trapping variant (STEP(61) CS) binds to Fyn but not to other members of the Src family present in PSDs. In a complementary experiment, myc-tagged Fyn immunoprecipitates STEP(61) CS. STEP(61) binds to Fyn through one of its proline-rich domains and the kinase-interacting motif domain, whereas Fyn binds to STEP(61) through its Src homology 2 domain and the unique N-terminal domain. STEP(61) CS pulls down Fyn when the Tyr(420) site is phosphorylated. In vitro, wild-type STEP(61) dephosphorylates Fyn at Tyr(420) but not at Tyr(531). These results suggest that STEP regulates the activity of Fyn by specifically dephosphorylating the regulatory Tyr(420) and may be one mechanism by which Fyn activity is decreased within PSDs.

    Funded by: NIMH NIH HHS: KO2 MH01527, MH18268, R01 MH52711

    The Journal of biological chemistry 2002;277;27;24274-9

  • Activation of Pyk2/RAFTK induces tyrosine phosphorylation of alpha-synuclein via Src-family kinases.

    Nakamura T, Yamashita H, Nagano Y, Takahashi T, Avraham S, Avraham H, Matsumoto M and Nakamura S

    Department of Clinical Neuroscience and Therapeutics, Hiroshima University Graduate School of Biomedical Sciences, Japan.

    alpha-Synuclein (alpha S) is a neuronal protein that has been implicated in the pathogenesis of Parkinson's disease. The present report demonstrates that the protein tyrosine kinase Pyk2/RAFTK is involved in cell stress-induced tyrosine phosphorylation of alpha S. Hyperosmotic stress induced tyrosine phosphorylation of alpha S via Pyk2/RAFTK at tyrosine residue 125. Pyk2/RAFTK-mediated phosphorylation of alpha S was primarily achieved with Src-family kinases. In addition, osmotic stress-induced phosphorylation of alpha S was dependent on Pyk2/RAFTK activation. Accordingly, such results indicate that Pyk2/RAFTK lies upstream of Src-family kinases in the signaling cascade by which osmotic stress induces tyrosine phosphorylation of alpha S.

    FEBS letters 2002;521;1-3;190-4

  • Association of Fyn and Lyn with the proline-rich domain of glycoprotein VI regulates intracellular signaling.

    Suzuki-Inoue K, Tulasne D, Shen Y, Bori-Sanz, Inoue O, Jung SM, Moroi M, Andrews RK, Berndt MC and Watson SP

    Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, United Kingdom. katsue.inoue@pharm.ox.ac.uk

    The glycoprotein VI (GPVI)-Fc receptor (FcR) gamma-chain complex, a key activatory receptor for collagen on platelet surface membranes, is constitutively associated with the Src family kinases Fyn and Lyn. Molecular cloning of GPVI has revealed the presence of a proline-rich domain in the sequence of GPVI cytoplasmic tail which has the consensus for interaction with the Src homology 3 (SH3) domains of Fyn and Lyn. A series of in vitro experiments demonstrated the ability of the SH3 domains of both Src kinases to bind the proline-rich domain of GPVI. Furthermore, depletion of the proline-rich domain in GPVI (Pro(-)-GPVI) prevented binding of Fyn and Lyn and markedly reduced phosphorylation of FcR gamma-chain in transiently transfected COS-7 cells, but did not affect the association of the gamma-chain with GPVI. Jurkat cells stably transfected with wild type GPVI show robust increases in tyrosine phosphorylation and intracellular Ca2+ in response to the snake venom convulxin that targets GPVI. Importantly, convulxin is not able to activate cells transfected with Pro(-)-GPVI, even though the association with the immunoreceptor tyrosine-based activation motif-containing chains is maintained. These findings demonstrate that the proline-rich domain of GPVI mediates the association with Fyn/Lyn via their SH3 domain and that this interaction initiates activation signals through GPVI.

    The Journal of biological chemistry 2002;277;24;21561-6

  • NMDA receptor function is regulated by the inhibitory scaffolding protein, RACK1.

    Yaka R, Thornton C, Vagts AJ, Phamluong K, Bonci A and Ron D

    Ernest Gallo Clinic and Research Center, University of California, San Francisco, CA 94110-3518, USA.

    Phosphorylation regulates the function of ligand-gated ion channels such as the N-methyl d-aspartate (NMDA) receptor. Here we report a mechanism for modulation of the phosphorylation state and function of the NMDA receptor via an inhibitory scaffolding protein, RACK1. We found that RACK1 binds both the NR2B subunit of the NMDA receptor and the nonreceptor protein tyrosine kinase, Fyn. RACK1 inhibits Fyn phosphorylation of NR2B and decreases NMDA receptor-mediated currents in CA1 hippocampal slices. Peptides that disrupt the interactions between RACK1, NR2B, and Fyn induce phosphorylation and potentiate NMDA receptor-mediated currents. Therefore, RACK1 is a regulator of NMDA recep 1f40 tor function and may play a role in synaptic plasticity, addiction, learning, and memory.

    Proceedings of the National Academy of Sciences of the United States of America 2002;99;8;5710-5

  • UCS15A, a novel small molecule, SH3 domain-mediated protein-protein interaction blocking drug.

    Oneyama C, Nakano H and Sharma SV

    Tokyo Research Laboratories, Kyowa Hakko Kogyo Co., Ltd 3-6-6 Asahi-cho, Machida-shi, Tokyo 194, Japan.

    Protein-protein interactions play critical regulatory roles in mediating signal transduction. Previous studies have identified an unconventional, small-molecule, Src signal transduction inhibitor, UCS15A. UCS15A differed from conventional Src-inhibitors in that it did not alter the levels or the tyrosine kinase activity of Src. Our studies suggested that UCS15A exerted its Src-inhibitory effects by a novel mechanism that involved the disruption of protein-protein interactions mediated by Src. In the present study we have examined the ability of UCS15A to disrupt the interaction of Src-SH3 with Sam68, both in vivo and in vitro. This ability of UCS15A was not restricted to Src-SH3 mediated protein-protein interactions, since the drug was capable of disrupting the in vivo interactions of Sam68 with other SH3 domain containing proteins such as Grb2 and PLCgamma. In addition, UCS15A was capable of disrupting other typical SH3-mediated protein-protein interactions such as Grb2-Sos1, cortactin-ZO1, as well as atypical SH3-mediated protein-protein interactions such as Grb2-Gab1. However, UCS15A was unable to disrupt the non-SH3-mediated protein-protein interactions of beta-catenin, with E-cadherin and alpha-catenin. In addition, UCS15A had no effect on the SH2-mediated interaction between Grb2 and activated Epidermal Growth Factor receptor. Thus, the ability of UCS15A, to disrupt protein-protein interactions appeared to be restricted to SH3-mediated protein-protein interactions. In this regard, UCS15A represents the first example of a non-peptide, small molecule agent capable of disrupting SH3-mediated protein-protein interactions. In vitro analyses suggested that UCS15A did not bind to the SH3 domain itself but rather may interact directly with the target proline-rich domains.

    Oncogene 2002;21;13;2037-50

  • Phosphorylation-dependent interactions between ADAM15 cytoplasmic domain and Src family protein-tyrosine kinases.

    Poghosyan Z, Robbins SM, Houslay MD, Webster A, Murphy G and Edwards DR

    School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom.

    The adamalysins (ADAMs) are transmembrane glycoproteins involved in cell adhesion and proteolytic ectodomain processing of cytokines and adhesion molecules. Many ADAM cytoplasmic domains are proline-rich and have potential phosphorylation sites. We show here that the cytoplasmic domain of ADAM15, metargidin, can interact specifically with Src family protein-tyrosine kinases (PTKs) and the adaptor protein Grb2 in hematopoietic cells (Jurkat, THP-1, U937, and K562 cell lines). Src homology 3 domains from several Src family PTKs including Lck, Fyn, Abl, and Src associate with ADAM15 in vitro. Dephosphorylation of cell extracts resulted in decreased association of ADAM15 with Src family PTK SH3 domains, indicating that phosphorylation influences ADAM15 interactions with its binding partners. This was confirmed in vitro for Hck, Lck, and Grb2, which showed enhanced association with tyrosine-phosphorylated glutathione S-transferase-ADAM15 cytoplasmic domain compared with unphosphorylated protein. In contrast, binding of MAD2 to ADAM15 was slightly reduced by phosphorylation of the ADAM. Immunoprecipitation of ADAM15 from Jurkat cells confirmed the association with Lck in vivo, and upon PMA stimulation, the phosphorylation level of ADAM15 was increased. Cotransfection of ADAM15 and Hck showed Hck-dependent phosphorylation of ADAM15 in vivo. Hck, and to a lesser extent Lck, phosphorylated the ADAM15 cytoplasmic domain in vitro in immune complex kinase assays. Binding of ADAM15 cytoplasmic domain to Hck and Lck was also shown by Far Western analysis. In contrast to Hck, Lck activity was not required for binding to ADAM15, as shown by treatment of cells with PP1. Deletion and point mutation analysis of the ADAM15 cytoplasmic domain confirmed the importance of the proline-rich motifs for Grb2 and Lck binding and indicated the regulatory nature of Tyr(715) and Tyr(735). These data demonstrate selective, phosphorylation-dependent interactions of ADAM15 with Src family PTKs and Grb2, which highlight the potential for integration of ADAM functions and cellular signaling.

    The Journal of biological chemistry 2002;277;7;4999-5007

  • Src family kinase-dependent phosphorylation of a 29-kDa caveolin-associated protein.

    Newcomb LF and Mastick CC

    Department of Biochemistry, University of Nevada, Reno, Nevada 89557, USA.

    PDGF receptors and Src family kinases are concentrated in caveolae, where signal transduction cascades involving these molecules are thought to be organized. The Src family tyrosine kinases are cotransducers of signals emanating from the activated PDGF receptor. However, the Src family kinase substrates that are involved in PDGF-induced signaling remain to be fully elucidated. We have identified a 29-kDa protein in caveolae that was phosphorylated in response to PDGF stimulation. This protein, pp29, was tightly bound to the caveolar coat protein caveolin-1. pp29 was among the most prominent phosphoproteins observed in cells overexpressing Fyn, suggesting that it may be a Fyn substrate. Consistent with this, pp29 was among a specific subset of proteins whose PDGF-stimulated phosphorylation was blocked by expression of kinase inactive Fyn. These data indicate that pp29 lies downstream of Fyn activation in a PDGF-stimulated signaling pathway, and that pp29 is an abundant site for nucleation of signal transduction cascades.

    Biochemical and biophysical research communications 2002;290;5;1447-53

  • Molecular dissection of the signaling and costimulatory functions of CD150 (SLAM): CD150/SAP binding and CD150-mediated costimulation.

    Howie D, Simarro M, Sayos J, Guirado M, Sancho J and Terhorst C

    Division of Immunology, RE-204, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave., Boston, MA 02215, USA. dhowie@caregroup.harvard.edu

    CD150 signaling lymphocytic activation molecule (SLAM), a T/B/dendritic cell surface glycoprotein, is a costimulatory receptor involved in T-cell activation and is also a receptor for measles virus. CD150-induced signal transduction is controlled by SAP/SH2D1A, the gene that is aberrant in X-linked lymphoproliferative disease and familial hemophagocytic lymphohistiocytosis. This report shows that CD150 colocalizes with the T-cell receptor (TCR) following CD3 triggering in human peripheral blood T cells and is rapidly and reversibly tyrosine phosphorylated on TCR cross-linking. The Src-like kinases Lck and Fyn phosphorylate tyrosine residues in the cytoplasmic tail of CD150. The results demonstrate that the SAP protein has 2 modes of binding to CD150. Binding to the motif Thr-Ile-Tyr281Ala-Gln-Val occurs in a phosphotyrosine-independent fashion and to the motif Thr-Val-Tyr327Ala-Ser-Val in a phosphotyrosine-dependent manner. Within both SAP binding motifs the threonine residue at position -2 to tyrosine is essential to stabilize the interaction irrespective of tyrosine phosphorylation, a feature unique to the SAP SH2 domain. A leucine residue, Leu278, further stabilizes nonphospho binding of SAP to Tyr281 of CD150. SAP blocking of the tyrosine phosphatase SHP-2 occurs primarily on Tyr281 of CD150 because SHP-2 requires both Tyr281 and Tyr327 for binding to CD150, and SAP binds to nonphosphorylated Tyr281. CD150 exhibits lateral mobility, segregating into intercellular contacts. The lateral mobility and homophilic clustering of CD150 between neighboring cells is not dependent on SAP/CD150 interaction.

    Blood 2002;99;3;957-65

  • Process outgrowth of oligodendrocytes is promoted by interaction of fyn kinase with the cytoskeletal protein tau.

    Klein C, Kramer EM, Cardine AM, Schraven B, Brandt R and Trotter J

    Departments of Neurobiology and Immunology, University of Heidelberg, 69120 Heidelberg, Germany.

    Fyn kinase plays an important role during myelination and has been shown to promote morphological differentiation of cultured oligodendrocytes. We analyzed the downstream targets of Fyn kinase in oligodendrocytes. Because process outgrowth and wrapping of axons involve cytoskeletal rearrangement, we focused on cytoskeletal proteins linked to Fyn. Here we demonstrate that Fyn binds to the cytoskeletal proteins Tau and alpha-Tubulin in oligodendrocytes. Tau interacts with the Fyn SH3 domain whereas alpha-Tubulin binds to the Fyn SH2 and SH3 domains. To study the function of the Fyn-Tau interaction in oligodendrocytes, we designed a Tau deletion mutant that would compete with endogenous Tau-Fyn binding in transfected cells. The mutant Tau protein binds to the Fyn SH3 domain but lacks the microtubuli interaction domain and thus cannot bind to microtubuli. In the presence of the mutant Tau protein, a reduction of the process number and process length in oligodendroglial cells was observed. This effect is likely to be caused by interference with the Fyn-Tau-microtubuli cascade rather than inactivation of the kinase, because Fyn bound to the mutant Tau retains activity. A similar inhibition of process outgrowth was observed when oliogodendroglial cells were cultured in the presence of Fumonisin B1, an inhibitor of sphingolipid synthesis that prevents the formation of rafts. Because ligation of the cell adhesion molecule F3 on oligodendrocytes leads to activation of Fyn kinase localized in rafts, these findings suggest that recruitment of Tau and Tubulin to activated Fyn kinase in rafts is an important step in the initiation of myelination.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2002;22;3;698-707

  • Multiple phosphorylation of alpha-synuclein by protein tyrosine kinase Syk prevents eosin-induced aggregation.

    Negro A, Brunati AM, Donella-Deana A, Massimino ML and Pinna LA

    Dipartimento di Chimica Biologica and Centro di Studio delle Biomembrane del C.N.R., University of Padova, Padova, Italy.

    The presence of aggregated alpha-synuclein molecules is a common denominator in a variety of neurodegenerative disorders. Here, we show that alpha-synuclein (alpha-syn) is an outstanding substrate for the protein tyrosine kinase p72syk (Syk), which phosphorylates three tyrosyl residues in its C-terminal domain (Y-125, Y-133, and Y-136), as revealed from experiments with mutants where these residues have been individually or multiply replaced by phenylalanine. In contrast, only Y-125 is phosphorylated by Lyn and c-Fgr. Eosin-induced multimerization is observed with wild-type alpha-syn, either phosphorylated or not by Lyn, and with all its Tyr to Phe mutants but not with the protein previously phosphorylated by Syk. Syk-mediated phosphorylation also counteracts alpha-syn assembly into filaments as judged from the disappearance of alpha-syn precipitated upon centrifugation at 100,000 x g. We also show that Syk and alpha-syn colocalize in the brain, and upon cotransfection in Chinese hamster ovary cells, alpha-syn becomes Tyr-phosphorylated by Syk. Moreover, Syk and alpha-syn interact with each other as judged from the mammalian two-hybrid system approach. These data suggest that Syk or tyrosine kinase(s) with similar specificity may play an antineurodegenerative role by phosphorylating a-syn, thereby preventing its aggregation.

    FASEB journal : official publication of the Federation of American Societies for Experimental Biology 2002;16;2;210-2

  • 'Srcasm: a novel Src activating and signaling molecule.

    Seykora JT, Mei L, Dotto GP and Stein PL

    Department of Dermatology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.

    The Src family tyrosine kinase, Fyn, can facilitate regulation of cell proliferation and differentiation. Mice with mutations in the fyn gene have defects in the brain, immune system, and epidermal differentiation. To identify molecules that may interact with Fyn in the epidermis, we performed a yeast two-hybrid interaction screen of a murine keratinocyte library. A novel adaptor-like molecule was isolated and termed Srcasm for Src activating and signaling molecule. Murine Srcasm is a 52.7-kDa protein that contains a VHS membrane association domain and a number of tyrosine motifs suggesting that it may be a substrate for Src family kinases and serve as an adaptor protein. Northern blot analysis of murine tissues demonstrates that Srcasm expression is highest in brain and kidney. In situ hybridization analysis reveals that srcasm mRNA is expressed in regions of the epidermis and hair follicle where keratinocyte differentiation occurs. In the brain, srcasm mRNA distribution correlates with that of fyn, with both being highly expressed in the hippocampal and cerebellar Purkinje neurons. Fyn can phosphorylate Srcasm, and association of these molecules relies on cooperative binding between the SH2 and SH3 domains of Fyn and corresponding canonical binding sites in Srcasm. Srcasm is capable of interacting with Grb2 and the regulatory subunit of phosphoinositide 3-kinase, p85, in a phosphorylation-dependent manner. The evidence suggests that Srcasm may help promote Src family kinase signaling in cells.

    Funded by: NIAMS NIH HHS: ARO7465, K08 AR047597

    The Journal of biological chemistry 2002;277;4;2812-22

  • NCAM regulates cell motility.

    Prag S, Lepekhin EA, Kolkova K, Hartmann-Petersen R, Kawa A, Walmod PS, Belman V, Gallagher HC, Berezin V, Bock E and Pedersen N

    Protein Laboratory, Institute of Molecular Pathology, University of Copenhagen, Denmark.

    Cell migration is required during development of the nervous system. The regulatory mechanisms for this process, however, are poorly elucidated. We show here that expression of or exposure to the neural cell adhesion molecule (NCAM) strongly affected the motile behaviour of glioma cells independently of homophilic NCAM interactions. Expression of the transmembrane 140 kDa isoform of NCAM (NCAM-140) caused a significant reduction in cellular motility, probably through interference with factors regulating cellular attachment, as NCAM-140-expressing cells exhibited a decreased attachment to a fibronectin substratum compared with NCAM-negative cells. Ectopic expression of the cytoplasmic part of NCAM-140 also inhibited cell motility, presumably via the non-receptor tyrosine kinase p59(fyn) with which NCAM-140 interacts. Furthermore, we showed that the extracellular part of NCAM acted as a paracrine inhibitor of NCAM-negative cell locomotion through a heterophilic interaction with a cell-surface receptor. As we showed that the two N-terminal immunoglobulin modules of NCAM, which are known to bind to heparin, were responsible for this inhibition, we presume that this receptor is a heparan sulfate proteoglycan. A model for the inhibitory effect of NCAM is proposed, which involves competition between NCAM and extracellular components for the binding to membrane-associated heparan sulfate proteoglycan.

    Journal of cell science 2002;115;Pt 2;283-92

  • Fyn tyrosine kinase is a downstream mediator of Rho/PRK2 function in keratinocyte cell-cell adhesion.

    Calautti E, Grossi M, Mammucari C, Aoyama Y, Pirro M, Ono Y, Li J and Dotto GP

    Cutaneous Biology Research Center, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129.

    The Rho GTPase and Fyn tyrosine kinase have been implicated previously in positive control of keratinocyte cell-cell adhesion. Here, we show that Rho and Fyn operate along the same signaling pathway. Endogenous Rho activity increases in differentiating keratinocytes and is required for both Fyn kinase activation and increased tyrosine phosphorylation of beta- and gamma-catenin, which is associated with the establishment of keratinocyte cell-cell adhesion. Conversely, expression of constitutive active Rho is sufficient to promote cell-cell adhesion through a tyrosine kinase- and Fyn-dependent mechanism, trigger Fyn kinase activation, and induce tyrosine phosphorylation of beta- and gamma-catenin and p120ctn. The positive effects of activated Rho on cell-cell adhesion are not induced by an activated Rho mutant with defective binding to the serine/threonine PRK2/PKN kinases. Endogenous PRK2 kinase activity increases with keratinocyte differentiation, and, like activated Rho, increased PRK2 activity promotes keratinocyte cell-cell adhesion and induces tyrosine phosphorylation of beta- and gamma-catenin and Fyn kinase activation. Thus, these findings reveal a novel role of Fyn as a downstream mediator of Rho in control of keratinocyte cell-cell adhesion and implicate the PRK2 kinase, a direct Rho effector, as a link between Rho and Fyn activation.

    Funded by: NCI NIH HHS: CA16038, CA73796, P01 CA016038, R01 CA073796; NIAMS NIH HHS: AR39190, R01 AR039190

    The Journal of cell biology 2002;156;1;137-48

  • Gab3, a new DOS/Gab family member, facilitates macrophage differentiation.

    Wolf I, Jenkins BJ, Liu Y, Seiffert M, Custodio JM, Young P and Rohrschneider LR

    Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA.

    Using the FDC-P1 cell line expressing the exogenous macrophage colony-stimulating factor (M-CSF) receptor, Fms, we have analyzed the role of a new mammalian DOS/Gab-related signaling protein, called Gab3, in macrophage cell development of the mouse. Gab3 contains an amino-terminal pleckstrin homology domain, multiple potential sites for tyrosine phosphorylation and SH2 domain binding, and two major polyproline motifs potentially interacting with SH3 domains. Among the growing family of Gab proteins, Gab3 exhibits a unique and overlapping pattern of expression in tissues of the mouse compared with Gab1 and Gab2. Gab3 is more restricted to the hematopoietic tissues such as spleen and thymus but is detectable at progressively lower levels within heart, kidney, uterus, and brain. Like Gab2, Gab3 is tyrosine phosphorylated after M-CSF receptor stimulation and associates transiently with the SH2 domain-containing proteins p85 and SHP2. Overexpression of exogenous Gab3 in FD-Fms cells dramatically accelerates macrophage differentiation upon M-CSF stimulation. Unlike Gab2, which shows a constant mRNA expression level after M-CSF stimulation, Gab3 expression is initially absent or low in abundance in FD cells expressing the wild-type Fms, but Gab3 mRNA levels are increased upon M-CSF stimulation. 1f40 Moreover, M-CSF stimulation of FD-FmsY807F cells (which grow but do not differentiate) fails to increase Gab3 expression. These results suggest that Gab3 is important for macrophage differentiation and that differentiation requires the early phosphorylation of Gab2 followed by induction and subsequent phosphorylation of Gab3.

    Funded by: NCI NIH HHS: CA40987, R01 CA040987

    Molecular and cellular biology 2002;22;1;231-44

  • Multiple interactions of the cytosolic polyproline region of the CD95 ligand: hints for the reverse signal transduction capacity of a death factor.

    Wenzel J, Sanzenbacher R, Ghadimi M, Lewitzky M, Zhou Q, Kaplan DR, Kabelitz D, Feller SM and Janssen O

    Institute for Immunology, Christian-Albrechts-University, Michaelisstrasse 5, 24105 Kiel, Germany.

    The CD95/Fas/Apo-1 ligand is expressed on activated lymphocytes, NK cells, platelets, certain immune-privileged cells and some tumor cells and induces apoptosis through the death receptor CD95/Fas/Apo-1. In murine T cells, membrane-bound CD95L (Fas ligand) also acts as a costimulatory receptor to coordinate activation and function in vivo. The molecular basis for this reverse signal transduction is yet unknown. In the present report, we identify individual interaction domains of enzymes and adapter molecules that selectively interact with full-length CD95L from transfectants and human T cells. These results may help to explain the costimulatory capacity of CD95L.

    FEBS letters 2001;509;2;255-62

  • Tyrosine phosphorylation of beta-dystroglycan at its WW domain binding motif, PPxY, recruits SH2 domain containing proteins.

    Sotgia F, Lee H, Bedford MT, Petrucci T, Sudol M and Lisanti MP

    Department of Molecular Pharmacology and The Albert Einstein Cancer Center, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA.

    beta-Dystroglycan is a ubiquitously expressed integral membrane protein that undergoes tyrosine phosphorylation in an adhesion-dependent manner. However, it remains unknown whether tyrosine-phosphorylated beta-dystroglycan interacts with SH2 domain containing proteins. Here, we show that the tyrosine phosphorylation of beta-dystroglycan is constitutively elevated in v-Src transformed cells. We next reconstituted this phosphorylation event in vivo by transiently coexpressing wild-type c-Src with a fusion protein containing full-length beta-dystroglycan. Our results demonstrate that Src-induced tyrosine phosphorylation of beta-dystroglycan is strictly dependent on the presence of a PPxY motif at its extreme C-terminus. In the nonphosphorylated state, this PPxY motif is normally recognized as a ligand by the WW domain; phosphorylation at this site blocks the binding of certain WW domain containing proteins. Using a GST fusion protein carrying the cytoplasmic tail of beta-dystroglycan, we identified five SH2 domain containing proteins that interact with beta-dystroglycan in a phosphorylation-dependent manner, including c-Src, Fyn, Csk, NCK, and SHC. We localized this binding activity to the PPxY motif by employing a panel of beta-dystroglycan-derived phosphopeptides. In addition, tyrosine phosphorylation of beta-dystroglycan in vivo resulted in the coimmunoprecipitation of the same SH2 domain containing proteins, and this binding event required the beta-dystroglycan C-terminal PPxY motif. We discuss the possibility that tyrosine phosphorylation of the PPxY motif within beta-dystroglycan may act as a regulatory switch to inhibit the binding of certain WW domain containing proteins, while recruiting SH2 domain containing proteins.

    Biochemistry 2001;40;48;14585-92

  • Interaction of the SH2 domain of Fyn with a cytoskeletal protein, beta-adducin.

    Shima T, Okumura N, Takao T, Satomi Y, Yagi T, Okada M and Nagai K

    Divisions of Protein Metabolism and Organic Chemistry, Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan.

    Fyn is a Src family tyrosine kinase expressed abundantly in neurons and believed to have specific functions in the brain. To understand the function of Fyn tyrosine kinase, we attempted to identify Fyn Src homology 2 (SH2) domain-binding proteins from a Nonidet P-40-insoluble fraction of the mouse brain. beta-Adducin, an actin filament-associated cytoskeletal protein, was isolated by two-dimensional gel electrophoresis and identified by tandem mass spectrometry. beta-Adducin was tyrosine phosphorylated by coexpression with wild type but not with a kinase-negative form of Fyn in COS-7 cells. Cell staining analysis showed that coexpression of beta-adducin with Fyn induced translocation of beta-adducin from the cytoplasm to the periphery of the cells where it was colocalized with actin filaments and Fyn. These findings suggest that tyrosine-phosphorylated beta-adducin associates with the SH2 domain of Fyn and colocalizes under plasma membranes.

    The Journal of biological chemistry 2001;276;45;42233-40

  • EGF-R signaling through Fyn kinase disrupts the function of integrin alpha6beta4 at hemidesmosomes: role in epithelial cell migration and carcinoma invasion.

    Mariotti A, Kedeshian PA, Dans M, Curatola AM, Gagnoux-Palacios L and Giancotti FG

    Cellular Biochemistry and Biophysics Program, Department of Surgery, Sloan-Kettering Institute for Cancer Research, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.

    We have examined the mechanism and functional significance of hemidesmosome disassembly during normal epithelial cell migration and squamous carcinoma invasion. Our findings indicate that a fraction of EGF receptor (EGF-R) combines with the hemidesmosomal integrin alpha6beta4 in both normal and neoplastic keratinocytes. Activation of the EGF-R causes tyrosine phosphorylation of the beta4 cytoplasmic domain and disruption of hemidesmosomes. The Src family kinase inhibitors PP1 and PP2 prevent tyrosine phosphorylation of beta4 and disassembly of hemidesmosomes without interfering with the activation of EGF-R. Coimmunoprecipitation experiments indicate that Fyn and, to a lesser extent, Yes combine with alpha6beta4. By contrast, Src and Lck do not associate with alpha6beta4 to a significant extent. A dominant negative form of Fyn, but not Src, prevents tyrosine phosphorylation of beta4 and disassembly of hemidesmosomes. These observations suggest that the EGF-R causes disassembly of hemidesmosomes by activating Fyn, which in turn phosphorylates the beta4 cytoplasmic domain. Neoplastic cells expressing dominant negative Fyn display increased hemidesmosomes and migrate poorly in vitro in response to EGF. Furthermore, dominant negative Fyn decreases the ability of squamous carcinoma cells to invade through Matrigel in vitro and to form lung metastases following intravenous injection in nude mice. These results suggest that disruption of hemidesmosomes mediated by Fyn is a prerequisite for normal keratinocyte migration and squamous carcinoma invasion.

    Funded by: NCI NIH HHS: P30 CA008748, P30 CA08748, R01 CA058976, R01 CA58976

    The Journal of cell biology 2001;155;3;447-58

  • Binding of Fyn to MAP-2c through an SH3 binding domain. Regulation of the interaction by ERK2.

    Zamora-Leon SP, Lee G, Davies P and Shafit-Zagardo B

    Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.

    Microtubule-associated protein 2 (MAP-2) isoforms are developmentally expressed in the nervous system and contain a number of functional domains. Adjacent to the first repeat of the microtubule-binding domain is an RTPPKSP motif for binding SH3 domains. To identify SH3-containing proteins that interact with MAP-2, transfections, filter overlay assays, glutathione S-transferase (GST)-mediated binding assays, co-immunoprecipitations and enzyme-linked immunosorbent assays were performed. Transfections of MAP-2a, MAP-2b, and MAP-2c constructs into COS7 cells, followed by incubation of the cell lysates with SH3-GST fusion proteins, determined that the strongest interaction was between MAP-2c and the non-receptor tyrosine kinase Fyn; however, MAP-2b and MAP-2c also bound to Grb2. Co-immunoprecipitation of Fyn and MAP-2c from human fetal homogenates confirmed the interaction in vivo. MAP-2 synthetic peptides spanning the RTPPKSP motif bound to Fyn, and the interaction was regulated by phosphorylation. Co-transfections with MAP-2c and the extracellular signal-regulated kinase 2 (ERK2) demonstrated that MAP-2c is threonine/serine-phosphorylated on its RTPPKSP motif and that threonine phosphorylation abolished the MAP-2c/Fyn binding. Kinase assays and co-transfection of MAP-2c and Fyn confirmed that Fyn tyrosine kinase phosphorylates MAP-2c. Thus, the activation of signaling pathways may regulate cytoskeletal dynamics by altering the state of phosphorylation of MAP-2 by both ERK2 and Fyn kinase.

    Funded by: NIMH NIH HHS: MH 38623; NINDS NIH HHS: NS 32100, NS 38102

    The Journal of biological chemistry 2001;276;43;39950-8

  • Phosphoryla 1df tion of human N-myristoyltransferase by N-myristoylated SRC family tyrosine kinase members.

    Rajala RV, Datla RS, Carlsen SA, Anderson DH, Qi Z, Wang JH and Sharma RK

    Department of Pathology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.

    N-Myristoyltransferase (NMT) is an essential eukaryotic enzyme that catalyzes the cotranslational and/or posttranslational transfer of myristate to the amino terminal glycine residue of a number of important proteins espe 1d59 cially the non-receptor tyrosine kinases whose activity is important for tumorigenesis. Human NMT was found to be phosphorylated by non-receptor tyrosine kinase family members of Lyn, Fyn and Lck and dephosphorylated by the Ca(2+)/calmodulin-dependent protein phosphatase, calcineurin. Deletion of 149 amino acids from the N-terminal end resulted in the absence of phosphorylation suggesting that the phosphorylation sites are located in the N-terminal end of NMT. Furthermore, a site-directed mutagenesis study indicated that substitution of tyrosine 100 with phenylalanine served NMT as a poor substrate for the Lyn kinase. A synthetic peptide corresponding to the amino-terminal region encompassing tyrosine 100 of NMT served as a good substrate for the Lyn and Fyn kinases. Our studies also indicated that NMT was found to interact with Lyn through its N-terminal end in a phosphorylation-dependent manner. This is the first study demonstrating the cross-talk between NMT and their myristoylated protein substrates in signaling pathways.

    Biochemical and biophysical research communications 2001;288;1;233-9

  • Plexin signaling via off-track and rho family GTPases.

    Whitford KL and Ghosh A

    Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.

    Two papers in this issue of Neuron examine new aspects of Semaphorin signaling via Plexin receptors. Winberg et al. present evidence that the transmembrane protein Off-track (OTK) interacts biochemically and genetically with Plexin A and is important for Sema 1a repulsive signaling. Hu et al. examine the coupling of Plexin B to Rac and RhoA and propose that Plexin B signaling involves inhibition of Rac function by direct sequestration and simultaneous activation of RhoA.

    Neuron 2001;32;1;1-3

  • Glycosylphosphatidyl inositol-anchored proteins and fyn kinase assemble in noncaveolar plasma membrane microdomains defined by reggie-1 and -2.

    Stuermer CA, Lang DM, Kirsch F, Wiechers M, Deininger SO and Plattner H

    Department of Biology, University of Konstanz, 78467 Konstanz, Germany. claudia.stuermer@uni.konstanz.de

    Using confocal laser scanning and double immunogold electron microscopy, we demonstrate that reggie-1 and -2 are colocalized in < or =0.1-microm plasma membrane microdomains of neurons and astrocytes. In astrocytes, reggie-1 and -2 do not occur in caveolae but clearly outside these structures. Microscopy and coimmunoprecipitation show that reggie-1 and -2 are associated with fyn kinase and with the glycosylphosphatidyl inositol-anchored proteins Thy-1 and F3 that, when activated by antibody cross-linking, selectively copatch with reggie. Jurkat cells, after cross-linking of Thy-1 or GM1 (with the use of cholera toxin), exhibit substantial colocalization of reggie-1 and -2 with Thy-1, GM1, the T-cell receptor complex and fyn. This, and the accumulation of reggie proteins in detergent-resistant membrane fractions containing F3, Thy-1, and fyn imparts to reggie-1 and -2 properties of raft-associated proteins. It also suggests that reggie-1 and -2 participate in the formation of signal transduction centers. In addition, we find reggie-1 and -2 in endolysosomes. In Jurkat cells, reggie-1 and -2 together with fyn and Thy-1 increase in endolysosomes concurrent with a decrease at the plasma membrane. Thus, reggie-1 and -2 define raft-related microdomain signaling centers in neurons and T cells, and the protein complex involved in signaling becomes subject to degradation.

    Molecular biology of the cell 2001;12;10;3031-45

  • Tyrosine phosphorylation of ionotropic glutamate receptors by Fyn or Src differentially modulates their susceptibility to calpain and enhances their binding to spectrin and PSD-95.

    Rong Y, Lu X, Bernard A, Khrestchatisky M and Baudry M

    Neuroscience Program, University of Southern California, Los Angeles 90089-2520, USA.

    Both tyrosine phosphorylation and calpain-mediated truncation of ionotropic glutamate receptors are important mechanisms for synaptic plasticity. Previous work from our laboratory has shown that calpain activation results in truncation of the C-terminal domains of several glutamate receptor subunits. To test whether and how tyrosine phosphorylation of glutamate ionotropic receptor subunits modulates calpain susceptibility, synaptic membranes were phosphorylated by Fyn or Src, two members of the Src family tyrosine kinases. Tyrosine phosphorylation of synaptic membranes by Src significantly reduced calpain-mediated truncation of both NR2A and NR2B subunits of NMDA receptors, but not of GluR1 subunits of AMPA receptors. In contrast, phosphorylation with Fyn significantly protected calpain-mediated truncation of GluR1 subunits of AMPA receptors, but enhanced calpain-mediated truncation of NR2A subunits of NMDA receptors. Similar results were observed with NR2A and NR2B C-terminal domain fusion proteins phosphorylated by Fyn or Src before incubation with calpain and calcium. In addition, phosphorylation of NR2A and NR2B C-terminal fusion proteins by Fyn or Src enhanced their binding to spectrin and PSD-95. Thus, tyrosine phosphorylation impairs or facilitates calpain-mediated truncation of glutamate receptor subunits, depending on which tyrosine kinase is activated. Such mechanisms could serve to regulate receptor integrity and location, in addition to modulating channel properties.

    Funded by: NIA NIH HHS: AG-14751

    Journal of neurochemistry 2001;79;2;382-90

  • Tyrosine phosphorylation of p190 RhoGAP by Fyn regulates oligodendrocyte differentiation.

    Wolf RM, Wilkes JJ, Chao MV and Resh MD

    Cell Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10021, USA.

    During development of the central nervous system, oligodendrocyte progenitor cells differentiate into mature myelinating cells. The molecular signals that promote this process, however, are not well defined. One molecule that has been implicated in oligodendrocyte differentiation is the Src family kinase Fyn. In order to probe the function of Fyn in this system, a yeast two hybrid screen was performed. Using Fyn as bait, p190 RhoGAP was isolated in the screen of an oligodendrocyte cDNA library. Coimmunoprecipitation and in vitro binding assays verified that p190 RhoGAP bound to the Fyn SH2 domain. Phosphorylation of p190 required active Fyn tyrosine kinase and was increased threefold upon differentiation of primary oligodendrocytes. Moreover, complex formation between p190 and p120 RasGAP occurred in differentiated oligodendrocytes. p190 RhoGAP activity is known to regulate the RhoGDP:RhoGTP ratio. Indeed, expression of dominant negative Rho in primary oligodendrocytes caused a hyperextension of processes. Conversely, constitutively activated Rho caused reduced process formation. These findings define a pathway in which Fyn activity regulates the phosphorylation of p190, leading to an increase in RhoGAP activity with a subsequent increase in RhoGDP, which in turn, regulates the morphological changes that accompany oligodendrocyte differentiation.

    Funded by: NIGMS NIH HHS: GM07739, GM57966; PHS HHS: N559904

    Journal of neurobiology 2001;49;1;62-78

  • Transient tyrosine phosphorylation of human ryanodine receptor upon T cell stimulation.

    Guse AH, Tsygankov AY, Weber K and Mayr GW

    Division of Cellular Signal Transduction, Institute for Medical Biochemistry and Molecular Biology, University of Hamburg, University Hospital Eppendorf, Martinistrasse 52, D-20246 Hamburg, Germany. guse@uke.uni-hamburg.de

    The ryanodine receptor of Jurkat T lymphocytes was phosphorylated on tyrosine residues upon stimulation of the cells via the T cell receptor/CD3 complex. The tyrosine phosphorylation was transient, reaching a maximum at 2 min, and rapidly declined thereafter. In co-immunoprecipitates of the ryanodine receptor, the tyrosine kinases p56(lck) and p59(fyn) were detected. However, only p59(fyn) associated with the ryanodine receptor in a stimulation-dependent fashion. Both tyrosine kinases, recombinantly expressed as glutathione S-transferase (GST) fusion proteins, phosphorylated the immunoprecipitated ryanodine receptor in vitro. In permeabilized Jurkat T cells, GST-p59(fyn), but not GST-p56(lck), GST-Grb2, or GST alone, significantly and concentration-dependently enhanced Ca(2+) release by cyclic ADP-ribose. The tyrosine kinase inhibitor PP2 specifically blocked the effect of GST-p59(fyn). This indicates that intracellular Ca(2+) release via ryanodine receptors may be modulated by tyrosine phosphorylation during T cell activation.

    The Journal of biological chemistry 2001;276;37;34722-7

  • Heterogeneous fatty acylation of Src family kinases with polyunsaturated fatty acids regulates raft localization and signal transduction.

    Liang X, Nazarian A, Erdjument-Bromage H, Bornmann W, Tempst P and Resh MD

    Cell Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.

    Fatty acylation of Src family kinases is essential for localization of the modified proteins to the plasma membrane and to plasma membrane rafts. It has been suggested that the presence of saturated fatty acyl chains on proteins is conducive for their insertion into liquid ordered lipid domains present in rafts. The ability of unsaturated dietary fatty acids to be attached to Src family kinases has not been investigated. Here we demonstrate that heterogeneous fatty acylation of Src family kinases occurs and that the nature of the attached fatty acid influences raft-mediated signal transduction. By using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, we show that in addition to 14:0 (myristate), 14:1 and 14:2 fatty acids can be attached to the N-terminal glycine of the Src family kinase Fyn when the growth media are supplemented with these dietary fatty acids. Moreover, we synthesized novel iodinated analogs of oleate and stearate, and we showed that heterogeneous S-acylation can occur on cysteine residues within Fyn as well as Galpha, GAP43, and Ras. Modification of Fyn with unsaturated or polyunsaturated fatty acids reduced its raft localization and resulted in decreased T cell signal transduction. These studies establish that heterogeneous fatty acylation is a widespread occurrence that serves to regulate signal transduction by membrane-bound proteins.

    Funded by: NCI NIH HHS: CA29502; NIGMS NIH HHS: GM57966

    The Journal of biological chemistry 2001;276;33;30987-94

  • Tyrosine phosphorylation of the N-methyl-D-aspartate receptor by exogenous and postsynaptic density-associated Src-family kinases.

    Cheung HH and Gurd JW

    Center for the Neurobiology of Stress, Division of Life Sciences, University of Toronto at Scarborough, Ontario, Canada.

    Phosphorylation of the NMDA receptor by Src-family tyrosine kinases has been implicated in the regulation of receptor function. We have investigated the tyrosine phosphorylation of NMDA receptor subunits NR2A and NR2B by exogenous Src and Fyn and compared this to phosphorylation by tyrosine kinases associated with the postsynaptic density (PSD). Phosphorylation of the receptor by exogenous Src and Fyn was dependent upon initial binding of the kinases to PSDs via their SH2-domains. Src and Fyn phosphorylated similar sites in NR2A and NR2B, tryptic peptide mapping identifying seven and five major tyrosine-phosphorylated peptides derived from NR2A and NR2B, respectively. All five tyrosine phosphorylation sites on NR2B were localized to the C-terminal, cytoplasmic domain. Phosphorylation of NR2B by endogenous PSD tyrosine kinases yielded only three tyrosine-phosphorylated tryptic peptides, two of which corresponded to Src phosphorylation sites, and one of which was novel. Phosphorylation-site specific antibodies identified NR2B Tyr1472 as a phosphorylation site for intrinsic PSD tyrosine kinases. Phosphorylation of this site was inhibited by the Src-family-specific inhibitor PP2. The results identify several potential phosphorylation sites for Src in the NMDA receptor, and indicate that not all of these sites are available for phosphorylation by kinases located within the structural framework of the PSD.

    Journal of neurochemistry 2001;78;3;524-34

  • Differential expression and subcellular distribution of the mouse metastasis-associated proteins Mta1 and Mta3.

    Simpson A, Uitto J, Rodeck U and Mahoney MG

    Department of Dermatology and Cutaneous Biology, Jefferson Medical College, Philadelphia, PA 19107, USA.

    The human metastasis-associated gene (MTA1) is overexpressed in cell lines and tissues representing metastatic tumors. Here we report cloning of the mouse Mta1 as well as a novel structurally related mouse gene, Mta3. The mouse Mta1 protein shares 94 and 59% homology to the human MTA1 and mouse Mta3 proteins, respectively. Northern blotting analysis using an Mta1 cDNA probe revealed a prevalent 3 kb hybridization signal in all mouse tissues except the skeletal muscle while a smaller approximately 1.0 kb mRNA product was also detected in the heart. Mta3 transcripts (approximately 2 kb) were detected in most tissues with an additional approximately 6.2 kb signal detected in the brain. In vitro transcription/translation of the full-length Mta1 and Mta3 cDNAs generated products of the expected molecular masses, i.e. 80 and 60 kDa, respectively. To assess subcellular localization, green fluorescence protein (GFP)-tagged expression constructs of Mta1 and Mta3 and various deletion constructs of GFP-Mta1 were transiently expressed in Balb/MK keratinocytes. GFP-Mta1 was found exclusively in the nucleus while GFP-Mta3 was present in both the nucleus and cytoplasm. Compared to Mta3, the carboxy terminal end of Mta1 contains an additional nuclear localization signal (NLS) and a proline-rich Src homology 3 (SH3) ligand. The results of transient expression experiments of various Mta1 fragments containing these domains in different combinations indicated that nuclear localization of Mta1 depended on the presence of at least one NLS and one SH3 binding site. These SH3 ligands appeared to be functional as they facilitated interaction with the adaptor protein, Grb2, and the Src-family tyrosine kinase, Fyn.

    Gene 2001;273;1;29-39

  • Src-class kinases act within the agrin/MuSK pathway to regulate acetylcholine receptor phosphorylation, cytoskeletal anchoring, and clustering.

    Mohamed AS, Rivas-Plata KA, Kraas JR, Saleh SM and Swope SL

    Department of Neuroscience, Georgetown University Medical Center, Washington DC 20007-2197, USA.

    Synaptogenesis at the neuromuscular junction requires agrin-induced stable localization of acetylcholine receptors (AChRs) at the endplate. The effects of agrin are transduced by the muscle-specific receptor tyrosine kinase (MuSK). This study provides evidence that Src-class protein tyrosine kinases mediate the effects of agrin-activated MuSK to regulate clustering and anchoring of AChRs in skeletal muscle. MuSK was complexed with both Src and Fyn in the C2 mouse muscle cell line. These associations were enhanced by agrin and by increasing protein tyrosine phosphorylation with pervanadate. Coupling between MuSK and the Src-class kinases in vivo appeared to be caused by a phosphotyrosine-SH2 domain interaction because binding of MuSK to the SH2 domains of Fyn and Src in vitro was specific, enhanced by phosphorylation, and dependent on MuSK autophosphorylation. In addition, Src and Fyn phosphorylated MuSK. AChR phosphorylation, stimulated by agrin or pervanadate, was inhibited by blocking Src-class kinases with PP1. Furthermore, agrin-induced clustering and cytoskeletal anchoring of AChRs was dependent on Src-family kinases. These data support the conclusion that Fyn and Src act downstream of MuSK to regulate the stable localization of AChRs at the neuromuscular endplate during agrin-induced synaptogenesis.

    Funded by: NINDS NIH HHS: NS35505

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2001;21;11;3806-18

  • The role of the Src homology 3-Src homology 2 interface in the regulation of Src kinases.

    Arold ST, Ulmer TS, Mulhern TD, Werner JM, Ladbury JE, Campbell ID and Noble ME

    Laboratory of Molecular Biophysics and Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.

    The regulatory fragment of Src kinases, comprising Src homology (SH) 3 and SH2 domains, is responsible for controlled repression of kinase activity. We have used a multidisciplinary approach involving crystallography, NMR, and isothermal titration calorimetry to study the regulatory fragment of Fyn (FynSH32) and its interaction with a physiological activator: a fragment of focal adhesion kinase that contains both phosphotyrosine and polyproline motifs. Although flexible, the preferred disposition of SH3 and SH2 domains in FynSH32 resembles the inactive forms of Hck and Src, differing significantly from LckSH32. This difference, which results from variation in the SH3-SH2 linker sequences, will affect the potential of the regulatory fragments to repress kinase activity. This surprising result implies that the mechanism of repression of Src family members may vary, explaining functional distinctions between Fyn and Lck. The interaction between FynSH32 and focal adhesion kinase is restricted to the canonical SH3 and SH2 binding sites and does not affect the dynamic independence of the two domains. Consequently, the interaction shows no enhancement by an avidity effect. Such an interaction may have evolved to gain specificity through an extended recognition site while maintaining rapid dissociation after signaling.

    The Journal of biological chemistry 2001;276;20;17199-205

  • alpha 7 nicotinic receptor transduces signals to phosphatidylinositol 3-kinase to block A beta-amyloid-induced neurotoxicity.

    Kihara T, Shimohama S, Sawada H, Honda K, Nakamizo T, Shibasaki H, Kume T and Akaike A

    Department of Neurology, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.

    Multiple lines of evidence, from molecular and cellular to epidemiological, have implicated nicotinic transmission in the pathogenesis of Alzheimer's disease (AD). Here we show the signal transduction mechanism involved in nicotinic receptor-mediated protection against beta-amyloid-enhanced glutamate neurotoxicity. Nicotine-induced protection was suppressed by an alpha7 nicotinic receptor antagonist (alpha-bungarotoxin), a phosphatidylinositol 3-kinase (PI3K) inhibitor (LY294002 and wortmannin), and a Src inhibitor (PP2). Levels of phosphorylated Akt, an effector of PI3K, and Bcl-2 were increased by nicotine. The alpha7 nicotinic receptor was physically associated with the PI3K p85 subunit and Fyn. These findings indicate that the alpha7 nicotinic receptor transduces signals to PI3K in a cascade, which ultimately contributes to a neuroprotective effect. This might form the basis of a new treatment for AD.

    The Journal of biological chemistry 2001;276;17;13541-6

  • Residues Y429 and Y463 of the human CD5 are targeted by protein tyrosine kinases.

    Vilà JM, Gimferrer I, Padilla O, Arman M, Places L, Simarro M, Vives J and Lozano F

    Servei d'Immunologia, Institut D'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Hospital Clínic, Barcelona, Spain.

    The human CD5 lymphocyte cell surface co-receptor modulates activation and differentiation responses mediated by the antigen-specific receptor of T and B cells. CD5 is phosphorylated following lymphocyte activation; however, the exact sites and kinases involved are yet to be determined. Jurkat T cell transfectants expressing tyrosine-mutated CD5 molecules have been used to show that residues Y429 and Y463 are targeted in vivo by protein tyrosine kinases following cell stimulation with anti-CD3 mAb or pervanadate. This is in agreement with data from direct in vitro kinase assays using purified recombinant Lck and Fyn protein tyrosine kinases. The analysis of Lck- and CD3-deficient Jurkat cells shows that tyrosine phosphorylation of CD5 requires Lck activity. We propose that T cell activation mediates CD5 tyrosine phosphorylation at residues Y429 and Y463 mainly through the activation of Lck.

    European journal of immunology 2001;31;4;1191-8

  • Stimulation of M3 muscarinic receptors induces phosphorylation of the Cdc42 effector activated Cdc42Hs-associated kinase-1 via a Fyn tyrosine kinase signaling pathway.

    Linseman DA, Heidenreich KA and Fisher SK

    Department of Pharmacology and Neuroscience Laboratory, Mental Health Research Institute, University of Michigan, Ann Arbor, Michigan 48104-1687, USA. Dan.Lines,am@UCHSC.edu

    The tyrosine kinase, activated Cdc42Hs-associated kinase-1 (ACK-1), is a specific effector of the Rho family GTPase Cdc42. GTP-bound Cdc42 has been shown to facilitate neurite outgrowth elicited by activation of muscarinic cholinergic receptors (mAChRs). Because tyrosine kinase activity is a requirement for neuritogenesis in several cell systems, we investigated whether endogenous mAChRs (principally of the M3 subtype) expressed in human SH-SY5Y neuroblastoma cells would signal to ACK-1. Incubation of cells with the cholinergic agonist oxotremorine-M (Oxo-M) induced an approximately 6-fold increase in the tyrosine phosphorylation of ACK-1 which was inhibited by atropine. ACK-1 phosphorylation was blocked by Clostridium difficile toxin B, an inhibitor of Rho family GTPases. In contrast, disruption of the actin cytoskeleton with cytochalasin D stimulated ACK-1 phosphorylation, and moreover, addition of Oxo-M to cells preincubated with this agent elicited a further increase in phosphorylation, indicating that an intact cytoskeleton is not required for mAChR signaling to ACK-1. Although stimulation of M3 mAChRs induces both an increase in intracellular Ca2+ and activation of protein kinase C (PKC), neither of these second messenger pathways was required for receptor-stimulated ACK-1 phosphorylation. Instead, inhibition of PKC resulted in a 2-fold increase in Oxo-M-stimulated ACK-1 phosphorylation, whereas acute activation of PKC with phorbol ester decreased ACK-1 phosphorylation. The agonist-induced tyrosine phosphorylation of ACK-1 was blocked by inhibitors of Src family kinases, and ACK-1 was coprecipitated with Fyn (but not Src) in an agonist-dependent manner. Finally, scrape loading cells with glutathione S-transferase fusion proteins of either the Fyn-SH2 or Fyn-SH3 domain significantly attenuated mAChR-stimulated ACK-1 tyrosine phosphorylation. The data are the first to show phosphorylation of ACK-1 after stimulation of a receptor coupled to neurite outgrowth and indicate that a Rho family GTPase (i.e. Cdc42) and Fyn are essential upstream elements of this signaling pathway.

    Funded by: NIGMS NIH HHS: GM07767; NIMH NIH HHS: MH12193; NINDS NIH HHS: NS23831

    The Journal of biological chemistry 2001;276;8;5622-8

  • Activated Fyn phosphorylates alpha-synuclein at tyrosine residue 125.

    Nakamura T, Yamashita H, Takahashi T and Nakamura S

    Third Department of Internal Medicine, Hiroshima University School of Medicine, 1-2-3 Kasumi, Minamiku, Hiroshima, 734-8551, Japan.

    alpha-Synuclein is a presynaptic protein of unknown function that has been implicated in the pathogenesis of several neurodegenerative diseases, including Parkinson's and Alzheimer's diseases. To gain insight into the functions of alpha-synuclein, we sought protein kinases that phosphorylate alpha-synuclein in the central nervous system. In contrast to Lyn, PYK2, FAK, MAPK/ERK1, SAPK/JNK, and Cdk5, only Fyn could phosphorylate alpha-synuclein. In addition, A30P and A53T mutations did not affect the phosphorylation of alpha-synuclein by Fyn. Mutation analysis revealed that activated Fyn phosphorylates specifically tyrosine residue 125 of alpha-synuclein. The distribution of alpha-synuclein and Fyn expression was similar in various parts of the brain and was colocalized in subcellular structures. Since Fyn regulates various signal transduction pathways in the central nervous system and plays an essential role in the neuronal cell differentiation, survival, and plasticity, results of this paper indicate that phosphorylation of alpha-synuclein might be involved in one of the Fyn-mediated signaling pathways in neuronal cells.

    Biochemical and biophysical research communications 2001;280;4;1085-92

  • RING finger mutations that abolish c-Cbl-directed polyubiquitination and downregulation of the EGF receptor are insufficient for cell transformation.

    Thien CB, Walker F and Langdon WY

    Department of Pathology, University of Western Australia, Western Australia 6009, Crawley, Australia.

    The c-Cbl protooncogene can function as a negative regulator of receptor protein tyrosine kinases (RPTKs) by targeting activated receptors for polyubiquitination and downregulation. This function requires its tyrosine kinase binding (TKB) domain for targeting RPTKs and RING finger domain to recruit E2 ubiquitin-conjugating enzymes. It has therefore been proposed that oncogenic Cbl proteins act in a dominant-negative manner to block this c-Cbl activity. In testing this hypothesis, we found that although mutations spanning the RING finger abolish c-Cbl-directed polyubiquitination and downregulation of RPTKs, they do not induce transformation. In contrast, it is mutations within a highly conserved alpha-helical structure linking the SH2 and RING finger domains that render Cbl proteins oncogenic. Thus, Cbl transformation involves effects additional to polyubiquitination of RPTKs that are independent of the RING finger and its ability to recruit E2-conjugating enzymes.

    Molecular cell 2001;7;2;355-65

  • SH2 domain-mediated interaction of inhibitory protein tyrosine kinase Csk with protein tyrosine phosphatase-HSCF.

    Wang B, Lemay S, Tsai S and Veillette A

    Laboratory of Molecular Oncology, IRCM, Montréal, Québec, Canada H2W 1R7.

    The protein tyrosine kinase (PTK) Csk is a potent negative regulator of several signal transduction processes, as a consequence of its exquisite ability to inactivate Src-related PTKs. This function requires not only the kinase domain of Csk, but also its Src homology 3 (SH3) and SH2 regions. We showed previously that the Csk SH3 domain mediates highly specific associations with two members of the PEP family of nonreceptor protein tyrosine phosphatases (PTPs), PEP and PTP-PEST. In comparison, the Csk SH2 domain interacts with several tyrosine phosphorylated molecules, presumed to allow targetting of Csk to sites of Src family kinase activation. Herein, we attempted to understand better the regulation of Csk by identifying ligands for its SH2 domain. Using a modified yeast two-hybrid screen, we uncovered the fact that Csk associates with PTP-HSCF, the third member of the PEP family of PTPs. This association was documented not only in yeast cells but also in a heterologous mammalian cell system and in cytokine-dependent hemopoietic cells. Surprisingly, the Csk-PTP-HSCF interaction was found to be mediated by the Csk SH2 domain and two putative sites of tyrosine phosphorylation in the noncatalytic portion of PTP-HSCF. Transfection experiments indicated that Csk and PTP-HSCF synergized to inhibit signal transduction by Src family kinases and that this cooperativity was dependent on the domains mediating their association. Finally, we obtained evidence that PTP-HSCF inactivated Src-related PTKs by selectively dephosphorylating the positive regulatory tyrosine in their kinase domain. Taken together, these results demonstrate that part of the function of the Csk SH2 domain is to mediate an inducible association with a PTP, thereby engineering a more efficient inhibitory mechanism for Src-related PTKs. Coupled with previously published observations, these data also establish that Csk forms complexes with all three known members of the PEP family.

    Molecular and cellular biology 2001;21;4;1077-88

  • Characterization of Fyn-mediated tyrosine phosphorylation sites on GluR epsilon 2 (NR2B) subunit of the N-methyl-D-aspartate receptor.

    Nakazawa T, Komai S, Tezuka T, Hisatsune C, Umemori H, Semba K, Mishina M, Manabe T and Yamamoto T

    Department of Oncology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan.

    The N-methyl-d-aspartate (NMDA) receptors play critical roles in synaptic plasticity, neuronal development, and excitotoxicity. Tyrosine phosphorylation of NMDA receptors by Src-family tyrosine kinases such as Fyn is implicated in synaptic plasticity. To precisely address the roles of NMDA receptor tyrosine phosphorylation, we identified Fyn-mediated phosphorylation sites on the GluR epsilon 2 (NR2B) subunit of NMDA receptors. Seven out of 25 tyrosine residues in the C-terminal cytoplasmic region of GluR epsilon 2 were phosphorylated by Fyn in vitro. Of these 7 residues, Tyr-1252, Tyr-1336, and Tyr-1472 in GluR epsilon 2 were phosphorylated in human embryonic kidney fibroblasts when co-expressed with active Fyn, and Tyr-1472 was the major phosphorylation site in this system. We then generated rabbit polyclonal antibodies specific to Tyr-1472-phosphorylated GluR epsilon 2 and showed that Tyr-1472 of GluR epsilon 2 was indeed phosphorylated in murine brain using the antibodies. Importantly, Tyr-1472 phosphorylation was greatly reduced in fyn mutant mice. Moreover, Tyr-1472 phosphorylation became evident when hippocampal long term potentiation started to be observed, and its magnitude became larger in murine brain. Finally, Tyr-1472 phosphorylation was significantly enhanced after induction of long term potentiation in the hippocampal CA1 region. These data suggest that Tyr-1472 phosphorylation of GluR epsilon 2 is important for synaptic plasticity.

    The Journal of biological chemistry 2001;276;1;693-9

  • Requirements for activation and RAFT localization of the T-lymphocyte kinase Rlk/Txk.

    Chamorro M, Czar MJ, Debnath J, Cheng G, Lenardo MJ, Varmus HE and Schwartzberg PL

    National Cancer Institute, National Institutes of Health, Bethesda, MD, USA. chamorrm@mskcc.org

    Background: The Tec family kinases are implicated in signaling from lymphocyte antigen receptors and are activated following phosphorylation by Src kinases. For most Tec kinases, this activation requires an interaction between their pleckstrin homology (PH) domains and the products of phosphoinositide 3-Kinase, which localizes Tec kinases to membrane RAFTs. Rlk/Txk is a Tec related kinase expressed in T cells that lacks a pleckstrin homology domain, having instead a palmitoylated cysteine-string motif. To evaluate Rlk's function in T cell receptor signaling cascades, we examined the requirements for Rlk localization and activation by Src family kinases.

    Results: We demonstrate that Rlk is also associated with RAFTs, despite its lack of a pleckstrin homology domain. Rlk RAFT association requires the cysteine-string motif and is independent of PI3 Kinase activity. We further demonstrate that Rlk can be phosphorylated and activated by Src kinases, leading to a decrease in its half-life. A specific tyrosine in the activation loop of Rlk, Y420, is required for phosphorylation and activation, as well as for decreased stability, but is not required for lipid RAFT association. Mutation of this tyrosine also prevents increased tyrosine phosphorylation of Rlk after stimulation of the T cell receptor, suggesting that Rlk is phosphorylated by Src family kinases in response to T cell receptor engagement.

    Conclusions: Like the other related Tec kinases, Rlk is associated with lipid RAFTs and can be phosphorylated and activated by Src family kinases, supporting a role for Rlk in signaling downstream of Src kinases in T cell activation.

    BMC immunology 2001;2;3

  • Mutation and association analysis of the Fyn kinase gene with alcoholism and schizophrenia.

    Ishiguro H, Saito T, Shibuya H, Toru M and Arinami T

    Department of Medical Genetics, Institute of Basic Medical Sciences, University of Tsukuba, Ibaraki, Japan.

    Lack of Fyn tyrosine kinase increases alcohol sensitivity. Fyn phosphorylates a component of the NMDA receptor, which may be involved in schizophrenia. The Fyn gene is located on human chromosome 6q21, to which linkage of schizophrenia has been suggested. We hypothesized that the Fyn gene is a candidate for predisposition to alcoholism and schizophrenia, and we performed a mutation study of the 5'-flanking region, all coding exons, and exon-intron junctions of the Fyn gene. The SSCP mutation analysis was performed in 48 unrelated alcoholics and 16 unrelated schizophrenics. Three polymorphisms, -93A/G in the 5'-flanking region, IVS10+37T/C in intron 10, and Ex12+894T/G in the 3'-untranslated region, were identified. A rare variant of Ex12+1162TG in the 3'-untranslated region was also detected. Neither missense nor nonsense mutations were found. Case-control studies using a larger sample of unrelated patients and controls did not reveal significant associations between these 1f40 polymorphisms and alcoholism or schizophrenia. In addition, genotyping a microsatellite marker, D6S302, located in intron 10 of the Fyn gene, did not show a significant association between the marker and alcoholism or schizophrenia. Results of the present study did not provide evidence for the involvement of the genomic Fyn gene mutations in alcoholism or schizophrenia. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:716-720, 2000.

    American journal of medical genetics 2000;96;6;716-20

  • cAMP-dependent protein kinase phosphorylation of EVL, a Mena/VASP relative, regulates its interaction with actin and SH3 domains.

    Lambrechts A, Kwiatkowski AV, Lanier LM, Bear JE, Vandekerckhove J, Ampe C and Gertler FB

    Flanders Interuniversity Institute for Biotechnology, Department of Medical Protein Chemistry, Faculty of Medicine, Ghent University, Ledeganckstraat 35, 9000 Gent, Belgium.

    Proteins of the Ena/VASP family are implicated in processes that require dynamic actin remodeling such as axon guidance and platelet activation. In this work, we explored some of the pathways that likely regulate actin dynamics in part via EVL (Ena/VASP-like protein). Two isoforms, EVL and EVL-I, were highly expressed in hematopoietic cells of thymus and spleen. In CD3-activated T-cells, EVL was found in F-actin-rich patches and at the distal tips of the microspikes that formed on the activated side of the T-cells. Like the other family members, EVL localized to focal adhesions and the leading edge of lamellipodia when expressed in fibroblasts. EVL was a substrate for the cAMP-dependent protein kinase, and this phosphorylation regulated several of the interactions between EVL and its ligands. Unlike VASP, EVL nucleated actin polymerization under physiological conditions, whereas phosphorylation of both EVL and VASP decreased their nucleating activity. EVL bound directly to the Abl, Lyn, and nSrc SH3 domains; the FE65 WW domain; and profilin, likely via its proline-rich core. Binding of Abl and nSrc SH3 domains, but not profilin or other SH3 domains, was abolished by cAMP-dependent protein kinase phosphorylation of EVL. We show strong cooperative binding of two profilin dimers on the polyproline sequence of EVL. Additionally, profilin competed with the SH3 domains for binding to partially overlapping binding sites. These data suggest that the function of EVL could be modulated in a complex manner by its interactions with multiple ligands and through phosphorylation by cyclic nucleotide dependent kinases.

    Funded by: NIGMS NIH HHS: GM58801

    The Journal of biological chemistry 2000;275;46;36143-51

  • Intracellular signaling mechanisms leading to synergistic effects of endothelin-1 and stem cell factor on proliferation of cultured human melanocytes. Cross-talk via trans-activation of the tyrosine kinase c-kit receptor.

    Imokawa G, Kobayasi T and Miyagishi M

    Kao Biological Science Laboratories, Haga, Tochigi 321-3497, Japan. 073733@kastanet.kao.co.jp

    We previously reported that activation of mitogen-activated protein kinase (MAPK) is involved in the mitogenic stimulation of normal human melanocytes (NHMC) by endothelin-1 (ET-1). In the present study, we determined signaling mechanisms upstream of MAPK activation that are involved in ET-1 stimulation and their synergism with stem cell factor (SCF). Pretreatment of cultured NHMC with ET(B) receptor antagonists, pertussis toxin, a specific phospholipase C inhibitor (), or a protein kinase C inhibitor (calphostine) blocked a transient tyrosine phosphorylation of MAPK induced by ET-1, whereas the addition of a calcium chelator (BAPTA) failed to inhibit that tyrosine phosphorylation of MAPK. Treatment with ET-1 and SCF together synergistically increased DNA synthesis, which was accompanied by synergism for MAPK phosphorylation. The time course of inositol 1,4,5-trisphosphate formation revealed that there is no difference in the level of inositol 1,4,5-trisphosphate stimulated by ET-1 + SCF or by ET-1 alone. Evaluations of the serine phosphorylation of MEK and Raf-1 activity showed a synergistic effect in SCF + ET-1-treated NHMC. Stimulation with SCF + ET-1 induced a more rapid and stronger tyrosyl phosphorylation of proteins corresponding to p52 and p66 Shc than did stimulation with SCF only, and this was accompanied by a stronger association of tyrosine-phosphorylated Shc with Grb2. Interestingly, a more rapid and marked tyrosine phosphorylation of c-kit was also detected in NHMC-treated with SCF + ET-1 than NHMC treated with SCF only. These data indicate that the synergistic cross-talk between SCF and ET-1 signaling is initiated through the pathway of tyrosine phosphorylation of c-kit, which results in the enhanced formation of the Shc-Grb(2) complex which leads in turn to the synergistic activation of the Ras/Raf-1/MEK/MAP kinase loop.

    The Journal of biological chemistry 2000;275;43;33321-8

  • Brain migration disorder and T-cell activation deficiency associated with abnormal signaling through TCR/CD3 complex and hyperactivity of Fyn tyrosine kinase.

    Del Giudice E, Gaetaniello L, Matrecano E, Cosentini E, Ursini MV, Racioppi L, Arrigo G and Pignata C

    Department of Pediatrics, Federico II University, Naples, Italy.

    In this study we report on a patient affected by a brain migration disorder and a T-cell activation deficiency presumably inherited as an autosomal recessive trait. The immunological evaluation revealed that the mitogen stimulation failed to induce a proper up-regulation of membrane expression of T-cell activation markers, and cell proliferation. This functional impairment was associated with abnormalities of the signal transduction process that follows T-cell receptor stimulation. A constitutive hyperphosphorylation of the Fyn tyrosine kinase was documented. This is the first report on a T-cell signaling abnormality associated with a developmental brain disorder. Whether the alteration of Fyn, which plays a role in both neurological and immunological systems, is responsible for either disorder remains to be elucidated.

    Funded by: Telethon: E.0934

    Neuropediatrics 2000;31;5;265-8

  • T-cell receptor antagonists induce Vav phosphorylation by selective activation of Fyn kinase.

    Huang J, Tilly D, Altman A, Sugie K and Grey HM

    La Jolla Institute for Allergy and Immunology, Division of Immunochemistry, and Division of Cell Biology, 10355 Science Center Drive, San Diego, CA 92121, USA. jianyong@lial.org

    T cell receptor (TCR) antagonists inhibit antigen-induced T cell activation and by themselves fail to induce phenotypic changes associated with T cell activation. However, we have recently shown that TCR antagonists are inducers of antigen-presenting cell (APC)-T cell conjugates. The signaling pathway associated with this cytoskeleton-dependent event appears to involve tyrosine phosphorylation and activation of Vav. In this study, we investigated the role played by the protein tyrosine kinases Fyn, Lck, and ZAP-70 in antagonist-induced signaling pathway. Antagonist stimulation increased tyrosine phosphorylation and kinase activity of Fyn severalfold, whereas little or no increase in Lck and ZAP-70 activity was observed. Second, TCR stimulation of Lck(-), Fyn(hi) Jurkat cells induced strong tyrosine phosphorylation of Vav. In contrast, minimal increase in tyrosine phosphorylation of Vav was observed in Lck(hi), Fyn(lo) Jurkat cells. Finally, study of T cells from a Fyn-deficient TCR transgenic mouse also showed that Fyn was required for tyrosine phosphorylation and activation of Vav induced by both antagonist and agonist peptides. The deficiency in Vav phosphorylation in Fyn-deficient T cells was associated with a defect in the formation of APC-T cell conjugates when T cells were stimulated with either agonist or antagonist peptide. We conclude from these results that Vav is a selective substrate for Fyn, especially under conditions of low-affinity TCR-mediated signaling, and that this signaling pathway involving Fyn, Vav, and Rac-1 is required for the cytoskeletal reorganization that leads to T cell-APC conjugates and the formation of the immunologic synapse.

    Proceedings of the National Academy of Sciences of the United States of America 2000;97;20;10923-9

  • Collagen, convulxin, and thrombin stimulate aggregation-independent tyrosine phosphorylation of CD31 in platelets. Evidence for the involvement of Src family kinases.

    Cicmil M, Thomas JM, Sage T, Barry FA, Leduc M, Bon C and Gibbins JM

    School of Animal and Microbial Sciences, University of Reading, Whiteknights, Reading, Berkshire RG6 6AJ, United Kingdom.

    Platelet endothelial cell adhesion molecule-1 (CD31) is a 130-kDa glycoprotein receptor present on the surface of platelets, neutrophils, monocytes, certain T-lymphocytes, and vascular endothelial cells. CD31 is involved in adhesion and signal transduction and is implicated in the regulation of a number of cellular processes. These include transendothelial migration of leukocytes, integrin regulation, and T-cell function, although its function in platelets remains unclear. In this study, we demonstrate the ability of the platelet agonists collagen, convulxin, and thrombin to induce tyrosine phosphorylation of CD31. Furthermore, we show that this event is independent of platelet aggregation and secretion and is accompanied by an increase in surface expression of CD31. A kinase capable of phosphorylating CD31 was detected in CD31 immunoprecipitates, and its activity was increased following activation of platelets. CD31 tyrosine phosphorylation was reduced or abolished by the Src family kinase inhibitor PP2, suggesting a role for these enzymes. In accordance with this, each of the Src family members expressed in platelets, namely Fyn, Lyn, Src, Yes, and Hck, was shown to co-immunoprecipitate with CD31. The involvement of Src family kinases in this process was confirmed through the study of mouse platelets deficient in Fyn.

    The Journal of biological chemistry 2000;275;35;27339-47

  • The functional significance of Shc in insulin signaling as a substrate of the insulin receptor.

    Sasaoka T and Kobayashi M

    Department of Clinical Pharmacology, Toyama Medical & Pharmaceutical University, Japan.

    Shc is composed of 46-, 52-, 66-kDa isoforms which arise from alternative splicing of the primary Shc transcript. Upon insulin stimulation, the activated insulin receptor interacts with Shc. The NPXY motif around 960-Tyr residue of the insulin receptor binds to the N-terminal PTB domain of Shc. Subsequently, the 52-kDa, and, to a lesser extent, the 46-kDa Shc isoforms are tyrosine phosphorylated. Although Tyr-239/240 and Tyr-317 residues are the possible candidates of Shc phosphorylation sites, insulin predominantly phosphorylates the Shc Tyr-317 residue. Phosphorylated Shc binds to Grb2 which forms a complex with Sos guanine nucleotide exchange factor for p21ras. Both tyrosine-phosphorylated Shc and IRS can bind to Grb2, but Shc . Grb2 . Sos is the predominant coupling pathway from the activated insulin receptor to p21ras. Along this line, microinjection of anti-Shc antibody inhibited insulin-induced mitogenesis, and the guanine nucleotide exchange activity for p21ras is tightly associated with Shc, but not with IRS. On the other hand, insulin only transiently activates p21ras for the strict hormonal regulation. For this regulation, longer time of insulin treatment deactivates p21ras by dissociation of Sos from the Shc . Grb2 . Sos complex while Shc is still complexed with Grb2. Thus, Shc plays a critical role in insulin-induced mitogenesis through regulation of p21ras activity. As regards the impact of Shc on the metabolic aspects, Shc is shown to compete with IRS as the substrate of the insulin receptor. Thus, IRS mediated downstream signaling leading to glycogen synthesis was decreased by overexpression of Shc. Taken together, Shc appears to play an important role in insulin induced mitogenesis, whereas Shc may not be required for regulation of the metabolic aspects of insulin.

    Endocrine journal 2000;47;4;373-81

  • Alpha(2) adrenoceptors regulate proliferation of human intestinal epithelial cells.

    Schaak S, Cussac D, Cayla C, Devedjian JC, Guyot R, Paris H and Denis C

    Institut National de la Santé et de la Recherche Médicale, Unité INSERM388, Toulouse, France.

    Previous studies on rodents have suggested that catecholamines stimulate proliferation of the intestinal epithelium through activation of alpha(2) adrenoceptors located on crypt cells. The occurrence of this effect awaits demonstration in humans and the molecular mechanisms involved have not yet been elucidated. Here, we examined the effect of alpha(2) agonists on a clone of Caco2 cells expressing the human alpha(2A) adrenoceptor.

    Methods: Cells were transfected with a bicistronic plasmid containing the alpha2C10 and neomycin phosphotransferase genes. G418 resistant clones were assayed for receptor expression using radioligand binding. Receptor functionality was assessed by testing its ability to couple Gi proteins and to inhibit cAMP production. Mitogen activated protein kinase (MAPK) phosphorylation was followed by western blot, and cell proliferation was estimated by measuring protein and DNA content.

    Results: Permanent transfection of Caco2 cells allowed us to obtain a clone (Caco2-3B) expressing alpha(2A) adrenoceptors at a density similar to that found in normal human intestinal epithelium. Caco2-3B retained morphological features and brush border enzyme expression characteristic of enterocytic differentiation. The receptor was coupled to Gi2/Gi3 proteins and its stimulation caused marked diminution of forskolin induced cAMP production. Treatment of Caco2-3B with UK14304 (alpha(2) agonist) induced a rapid increase in the phosphorylation st 17d5 ate of MAPK, extracellular regulated protein kinase 1 (Erk1), and 2 (Erk2). This event was totally abolished in pertussis toxin treated cells and in the presence of kinase inhibitors (genistein or PD98059). It was unaffected by protein kinase C downregulation but correlated with a transient increase in Shc tyrosine phosphorylation. Finally, sustained exposure of Caco2-3B to UK14304 resulted in modest but significant acceleration of cell proliferation. None of these effects was observed in the parental cell line Caco2.

    Conclusion: The results obtained in the present study support a regulatory role for alpha(2) adrenoceptors in intestinal cell proliferation.

    Gut 2000;47;2;242-50

  • Protein-tyrosine kinase Pyk2 is involved in interleukin-2 production by Jurkat T cells via its tyrosine 402.

    Katagiri T, Takahashi T, Sasaki T, Nakamura S and Hattori S

    Division of Biochemistry and Cellular Biology, National Institute of Neuroscience, Kodaira, Tokyo 187-8502, Japan. katagiri@ncnp.go.jp

    We established Jurkat transfectants that overexpress Pyk2 or its mutants, K457A (lysine 457 was mutated to alanine), Pyk2-Y402F (tyrosine 402 to phenylalanine), and Pyk2-Y881F to investigate the role of Pyk2 in T cell activation. Pyk2 as well as kinase-inactive Pyk2-K457A, was phosphorylated at tyrosine residues 402, 580, and 881 upon T cell antigen receptor cross-linking, indicating that these residues are phosphorylated by other tyrosine kinase(s). However, no tyrosine phosphorylation of Pyk2-Y402F was detected while more than 60% of the tyrosine phosphorylation was observed in Pyk2-Y881F. Pyk2-Y402F inhibited the activation of endogenous Pyk2. The degree of activation of both c-Jun NH(2)-terminal kinase and p38 mitogen-activated protein kinase but not extracellular signal-regulated protein kinase after concurrent ligation of T cell antigen receptor and CD28 was reduced by more than 50% in the clones expressing Pyk2-Y402F. Consistent with this inhibition, IL-2 production was significantly diminished in the Pyk2-Y402F-expressing clones. Furthermore, we found that Pyk2, when overexpressed, associates with Zap70 and Vav. Taken together, these findings suggest that Pyk2 is involved in the activation of T cells through its tyrosine 402.

    The Journal of biological chemistry 2000;275;26;19645-52

  • Identification of Grb10 as a direct substrate for members of the Src tyrosine kinase family.

    Langlais P, Dong LQ, Hu D and Liu F

    Department of Pharmacology and Biochemistry, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, TX 78229, USA.

    Treatment of cells with insulin and protein tyrosine phosphatase inhibitors such as vanadate and pervanadate resulted in the tyrosine phosphorylation of Grb10, a Src homology 2 (SH2) and pleckstrin homology domain-containing adaptor protein which binds to a number of receptor tyrosine kinases including the insulin receptor (IR). Although Grb10 binds directly to the kinase domain of the IR, our data show that Grb10 is not a direct substrate for the IR tyrosine kinase. Consistent with this finding, Grb10 tyrosine phosphorylation in cells was inhibited by herbimycin A, a relatively specific inhibitor for members of the Src tyrosine kinase family, and by the expression of dominant negative Src or Fyn. In addition, Grb10 tyrosine phosphorylation was stimulated by expression of constitutively active Src or Fyn in cells and by incubation with purified Src or Fyn in vitro. The insulin stimulated or Src/Fyn-mediated tyrosine phosphorylation in vivo was significantly reduced when Grb10 tyrosine 67 was changed to glycine. This mutant form of Grb10 bound with higher affinity to the IR in cells than that of the wild-type protein, suggesting that tyrosine phosphorylation of Grb10 may normally negatively regulate its binding to the IR. Our data show that Grb10 is a new substrate for members of the Src tyrosine kinase family and that the tyrosine phosphorylation of the protein may play a potential role in cell signaling processes mediated by these kinases. Oncogene (2000).

    Funded by: NIDDK NIH HHS: DK52933

    Oncogene 2000;19;25;2895-903

  • The m3 muscarinic acetylcholine receptor is coupled to mitogen-activated protein kinase via protein kinase C and epidermal growth factor receptor kinase.

    Slack BE

    Boston University School of Medicine, Department of Pathology and Laboratory Medicine, 85 East Newton Street, Room M1007, Boston, MA 02118, USA. bslack@bu.edu

    The acetylcholine analogue carbachol rapidly activated mitogen-activated protein kinase (MAPK), and caused tyrosine phosphorylation of the adapter protein p52 Shc and the epidermalgrowth factor (EGF) receptor, in human embryonic kidney cells stably expressing m3 muscarinic receptors. The protein kinase C (PKC) inhibitor GF109203X caused a significant partial inhibition of m3 receptor-mediated activation of MAPK. The PKC-independent MAPK activity elicited by carbachol in the presence of GF109203X was reproducibly abolished by AG1478, an inhibitor of EGF-receptor tyrosine kinase activity, and by the Src tyrosine kinase inhibitor PP1. In a subset of these experiments, GF109203X concomitantly increased carbachol-induced tyrosine phosphorylation of p52 Shc and the EGF receptor. In co-stimulation experiments, carbachol and EGF activated MAPK in a non-additive fashion; moreover, EGF-induced association of Shc with the phosphorylated EGF receptor was inhibited by carbachol. This effect of carbachol was blocked by GF109203X. The results indicate that MAPK activation by m3 receptor stimulation is regulated by two pathways; one dependent on PKC, and the other mediated via the EGF receptor and Src. Moreover, the EGF-receptor-dependent pathway may be subject to negative-feedback regulation via m3 receptor-coupled activation of PKC.

    Funded by: NIA NIH HHS: AG09525; NINDS NIH HHS: NS30791

    The Biochemical journal 2000;348 Pt 2;381-7

  • Molecular cloning of the mouse APS as a member of the Lnk family adaptor proteins.

    Iseki M, Takaki S and Takatsu K

    Department of Immunology, Institute of Medical Science, University of Tokyo, Japan.

    Engagement of cell-surface receptors leads to activation of protein tyrosine kinases, which in turn phosphorylate various downstream enzymes and adaptor proteins. Lnk is an adaptor protein that appears to be involved in signal transduction in lymphocytes, and forms an adaptor protein family with SH2-B. We tried to identify another member of the adaptor protein family and isolated the mouse APS (adaptor molecule containing PH and SH2 domains). APS contains a proline-rich region, PH and SH2 domains, and a putative tyrosine phosphorylation site at the C-terminal, and the overall structure resembles those of Lnk and SH2-B. APS is expressed in brain, kidney, muscle, and mature B cells in spleen. Mouse APS gene consists of 8 coding exons and is deduced to map to chromosome 5. APS is tyrosine phosphorylated at the C-terminal phosphorylation site conserved among the Lnk family adaptor proteins by stimulation of IL-5 or IL-3 as well as by crosslinking of B cell receptor complex. These results suggest that APS is a member of the Lnk family adaptor protein and likely plays a role in signaling in B cells.

    Biochemical and biophysical research communications 2000;272;1;45-54

  • Association of beta 1 integrin with focal adhesion kinase and paxillin in differentiating Schwann cells.

    Chen LM, Bailey D and Fernandez-Valle C

    Department of Molecular Biology and Microbiology, University of Central Florida, Orlando, Florida 32816-2360, USA.

    Schwann cells (SCs) differentiate into a myelinating cell when simultaneously adhering to an axon destined for myelination and basal lamina. We are interested in defining the signaling pathway activated by basal lamina. Using SC/sensory neuron (N) cocultures, we identified beta1 integrin and F-actin as components of a pathway leading to myelin gene expression and myelination (Fernandez-Valle et al., 1994, 1997). Here, we show that focal adhesion kinase (FAK) and paxillin are constitutively expressed by SCs contacting axons in the absence of basal lamina. Tyrosine phosphorylation of FAK and paxillin increases as SCs form basal lamina and differentiate. FAK and paxillin specifically coimmunoprecipitate with beta1 integrin in differentiating SC/N cocultures but not SC-only cultures. Paxillin coimmunoprecipitates with FAK and fyn kinase in differentiating SC/N cocultures. A subset of tyrosine-phosphorylated beta1 integrin, FAK, and paxillin molecules reside in the insoluble, F-actin-rich fraction of differentiating cocultures. Cytochalasin D, an actin depolymerizing agent, decreases tyrosine phosphorylation of FAK and paxillin and their association with beta1 integrin and causes a dose-dependent increase in the abundance of insoluble FAK and paxillin complexes. Collectively, our work indicates that beta1 integrin, FAK, paxillin, and fyn kinase form an actin-associated complex in SCs adhering to basal lamina in the presence of axons. This complex may be important for initiating the process of SC differentiation into a myelinating cell.

    Funded by: NINDS NIH HHS: NSRO1-34499

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2000;20;10;3776-84

  • Hck enhances the adherence of lipopolysaccharide-stimulated macrophages via Cbl and phosphatidylinositol 3-kinase.

    Scholz G, Cartledge K and Dunn AR

    Molecular Biology Laboratory, Ludwig Institute for Cancer Research, P. O. Box 2008, Royal Melbourne Hospital, Victoria 3050, Australia. Glen.Scholz@ludwig.edu.au

    Src family tyrosine kinases have previously been proposed to mediate some of the biological effects of lipopolysaccharide on macrophages. Accordingly, we have sought to identify substrates of Src family kinases in lipopolysaccharide-stimulated macrophages. Stimulation of Bac1.2F5 macrophage cells with lipopolysaccharide was found to induce gradual and persistent tyrosine phosphorylation of Cbl in an Src family kinase-dependent manner. Immunoprecipitation experiments revealed that Cbl associates with Hck in Bac1.2F5 cells, while expression of an activated form of Hck in Bac1.2F5 cells induces tyrosine phosphorylation of Cbl in the absence of lipopolysaccharide stimulation. The Src homology 3 domain of Hck can directly bind Cbl, and this interaction is important for phosphorylation of Cbl. Association of the p85 subunit of phosphatidylinositol (PI) 3-kinase with Cbl is enhanced following lipopolysaccharide stimulation of Bac1.2F5 cells, and transient expression experiments indicate that phosphorylation of Cbl by Hck can facilitate the association of p85 with Cbl. Lipopolysaccharide treatment also stimulates the partial translocation of Hck to the cytoskeleton of Bac1.2F5 cells. Notably, lipopolysaccharide enhances the adherence of Bac1.2F5 cells, an effect that is dependent on the activity of Src family kinases and PI 3-kinase. Thus, we postulate that Hck enhances the adherence of lipopolysaccharide-stimulated macrophages, at least in part, via Cbl and PI 3-kinase.

    The Journal of biological chemistry 2000;275;19;14615-23

  • Phosphoprotein associated with glycosphingolipid-enriched microdomains (PAG), a novel ubiquitously expressed transmembrane adaptor protein, binds the protein tyrosine kinase csk and is involved in regulation of T cell activation.

    Brdicka T, Pavlistová D, Leo, Bruyns E, Korínek V, Angelisová P, Scherer J, Shevchenko A, Hilgert I, Cerný J, Drbal K, Kuramitsu Y, Kornacker B, Horejsí V and Schraven B

    Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 14220 Prague, Czech Republic.

    According to a recently proposed hypothesis, initiation of signal transduction via immunoreceptors depends on interactions of the engaged immunoreceptor with glycosphingolipid-enriched membrane microdomains (GEMs). In this study, we describe a novel GEM-associated transmembrane adaptor protein, termed phosphoprotein associated with GEMs (PAG). PAG comprises a short extracellular domain of 16 amino acids and a 397-amino acid cytoplasmic tail containing ten tyrosine residues that are likely phosphorylated by Src family kinases. In lymphoid cell lines and in resting peripheral blood alpha/beta T cells, PAG is expressed as a constitutively tyrosine-phosphorylated protein and binds the major negative regulator of Src kinases, the tyrosine kinase Csk. After activation of peripheral blood alpha/beta T cells, PAG becomes rapidly dephosphorylated and dissociates from Csk. Expression of PAG in COS cells results in recruitment of endogenous Csk, altered Src kinase activity, and impaired phosphorylation of Src-specific substrates. Moreover, overexpression of PAG in Jurkat cells downregulates T cell receptor-mediated activation of the transcription factor nuclear factor of activated T cells. These findings collectively suggest that in the absence of external stimuli, the PAG-Csk complex transmits negative regulatory signals and thus may help to keep resting T cells in a quiescent state.

    The Journal of experimental medicine 2000;191;9;1591-604

  • Crk-associated substrate p130(Cas) interacts with nephrocystin and both proteins localize to cell-cell contacts of polarized epithelial cells.

    Donaldson JC, Dempsey PJ, Reddy S, Bouton AH, Coffey RJ and Hanks SK

    Department of Cell Biology, Vanderbilt University School of Medicine, 1161 21st Avenue South, Nashville, Tennessee 37232, USA.

    Crk-associated substrate (p130(Cas), Cas) is a docking protein first recognized as having elevated phosphotyrosine content in mammalian cells transformed by v-Src and v-Crk oncoproteins. Subsequent studies have implicated Cas in the control of normal cell behavior through its roles in integrin-mediated signal transduction and organization of the actin cytoskeleton at sites of cell adhesion. In this study, we sought to gain new insight into normal Cas function by identifying previously unrecognized interacting proteins. A yeast two-hybrid screen using the C-terminal region of Cas as a bait identified the Src homology 3 (SH3) domain of the mouse "nephrocystin" protein-orthologous to a human protein whose loss of function leads to the cystic kidney disease familial juvenile nephronophthisis. The putative full-length mouse and partial canine nephrocystin sequences were deduced from cDNA clones. Additional studies using epitope-tagged mouse nephrocystin indicated that nephrocystin and Cas can interact in mammalian cells and revealed that both proteins prominently localize at or near sites of cell-cell contact in polarized Madin-Darby canine kidney epithelial cells. Our findings provide novel insight into the normal cellular activities regulated by both Cas and nephrocystin, and raise the possibility that these proteins have a related function in polarized epithelial cells.

    Funded by: NCI NIH HHS: CA46413, CA68485; NIGMS NIH HHS: GM49882; ...

    Experimental cell research 2000;256;1;168-78

  • A novel pro-Arg motif recognized by WW domains.

    Bedford MT, Sarbassova D, Xu J, Leder P and Yaffe MB

    Department of Genetics, Harvard Medical School, Howard Hughes Medical Institute, Boston, Massachusetts 02115, USA.

    WW domains mediate protein-protein interactions through binding to short proline-rich sequences. Two distinct sequence motifs, PPXY and PPLP, are recognized by different classes of WW domains, and another class binds to phospho-Ser-Pro sequences. We now describe a novel Pro-Arg sequence motif recognized by a different class of WW domains using data from oriented peptide library screening, expression cloning, and in vitro binding experiments. The prototype member of this group is the WW domain of formin-binding protein 30 (FBP30), a p53-regulated molecule whose WW domains bind to Pro-Arg-rich cellular proteins. This new Pro-Arg sequence motif re-classifies the organization of WW domains based on ligand specificity, and the Pro-Arg class now includes the WW domains of FBP21 and FE65. A structural model is presented which rationalizes the distinct motifs selected by the WW domains of YAP, Pin1, and FBP30. The Pro-Arg motif identified for WW domains often overlaps with SH3 domain motifs within protein sequences, suggesting that the same extended proline-rich sequence could form discrete SH3 or WW domain complexes to transduce distinct cellular signals.

    Funded by: NHLBI NIH HHS: HL03601; NIGMS NIH HHS: GM56203

    The Journal of biological chemistry 2000;275;14;10359-69

  • Dok-3, a novel adapter molecule involved in the negative regulation of immunoreceptor signaling.

    Lemay S, Davidson D, Latour S and Veillette A

    McGill Cancer Centre, McGill University, Montréal, Québec, Canada H3G 1Y6.

    Adapters are typically viewed as molecules coordinating the recruitment of positive effectors of cell signaling. Herein, we report the identification of Dok-3, a novel adapter molecule belonging to the Dok family. Our studies show that Dok-3 is highly expressed in several hemopoietic cell types, including B cells and macrophages. It undergoes rapid tyrosine phosphorylation in response to immunoreceptor-mediated cellular activation, seemingly as a result of the action of Src family kinases. This phosphorylation induces the binding of Dok-3 to at least two inhibitory molecules, the 5' inositol phosphatase SHIP and the protein tyrosine kinase Csk. We also demonstrate that augmented expression of wild-type Dok-3 in a B-cell line results in an inhibition of immunoreceptor-mediated nuclear factor of activated T-cells (NFAT) activation and cytokine release, while introduction of a Dok-3 mutant with impaired ability to associate with SHIP and Csk enhances B-cell responsiveness. Taken together, these results indicate that Dok-3 is an adapter involved in the recruitment of inhibitory molecules and that it may play a significant role in the negative regulation of immunoreceptor signaling in hemopoietic cells such as B cells and macrophages.

    Molecular and cellular biology 2000;20;8;2743-54

  • Identification of a novel protein complex containing annexin VI, Fyn, Pyk2, and the p120(GAP) C2 domain.

    Chow A, AJ and Gawler DJ

    School of Biomedical Sciences, University of Leeds, Woodhouse Lane, Leeds, UK.

    p120(GAP) (RasGAP) has been proposed to function as both an inhibitor and effector of Ras. Previously we have shown that RasGAP contains a C2 domain which mediates both Ca(2+)-dependent membrane association and protein-protein interactions. Specifically, three proteins have been isolated in a complex with the C2 domain of RasGAP; these are the Ca(2+)-dependent lipid binding protein annexin VI (p70) and two previously unidentified proteins, p55 and p120. Here we provide evidence that p55 is the Src family kinase Fyn and p120 is the focal adhesion kinase family member Pyk2. In addition, in vitro binding assays indicate that Fyn, but not Pyk2 binds directly to annexin VI. Finally, co-immunoprecipitation studies in Rat-1 fibroblasts confirm that Fyn, Pyk2, annexin VI and RasGAP can form a protein complex in mammalian cells.

    FEBS letters 2000;469;1;88-92

  • Affinity of Src family kinase SH3 domains for HIV Nef in vitro does not predict kinase activation by Nef in vivo.

    Briggs SD, Lerner EC and Smithgall TE

    Eppley Institute for Research in Cancer and Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA.

    Nef is an HIV accessory protein required for high-titer viral replication and AIDS progression. Previous studies have shown that the SH3 domains of Hck and Lyn bind to Nef via proline-rich sequences in vitro, identifying these Src-related kinases as potential targets for Nef in vivo. Association of Nef with Hck causes displacement of the intramolecular interaction between the SH3 domain and the SH2-kinase linker, leading to kinase activation both in vitro and in vivo. In this study, we investigated whether interaction with Nef induces activation of other Src family kinases (Lyn, Fyn, Src, and Lck) following coexpression with Nef in Rat-2 fibroblasts. Coexpression with Nef induced Hck kinase activation and fibroblast transformation, consistent with previous results. In contrast, coexpression of Nef with Lyn was without effect, despite equivalent binding of Nef to full-length Lyn and Hck. Furthermore, Nef was found to suppress the kinase and transforming activities of Fyn, the SH3 domain of which exhibits low affinity for Nef. Coexpression with Nef did not alter c-Src or Lck tyrosine kinase or transforming activity in this system. Differential modulation of Src family members by Nef may produce unique downstream signals depending on the profile of Src kinases expressed in a given cell type.

    Funded by: NCI NIH HHS: CA81398; NHLBI NIH HHS: HL10097

    Biochemistry 2000;39;3;489-95

  • Biochemical interactions integrating Itk with the T cell receptor-initiated signaling cascade.

    Bunnell SC, Diehn M, Yaffe MB, Findell PR, Cantley LC and Berg LJ

    Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.

    Itk, a Tec family tyrosine kinase, acts downstream of Lck and phosphatidylinositol 3'-kinase to facilitate T cell receptor (TCR)-dependent calcium influxes and increases in extracellular-regulated kinase activity. Here we demonstrate interactions between Itk and crucial components of TCR-dependent signaling pathways. First, the inositide-binding pocket of the Itk pleckstrin homology domain directs the constitutive association of Itk with buoyant membranes that are the primary site of TCR activation and are enriched in both Lck and LAT. This association is required for the transphosphorylation of Itk. Second, the Itk proline-rich region binds to Grb2 and LAT. Third, the Itk Src homology (SH3) 3 and SH2 domains interact cooperatively with Syk-phosphorylated SLP-76. Notably, SLP-76 contains a predicted binding motif for the Itk SH2 domain and binds to full-length Itk in vitro. Finally, we show that kinase-inactive Itk can antagonize the SLP-76-dependent activation of NF-AT. The inhibition of NF-AT activation depends on the Itk pleckstrin homology domain, proline-rich region, and SH2 domain. Together, these observations suggest that multivalent interactions recruit Itk to LAT-nucleated signaling complexes and facilitate the activation of LAT-associated phospholipase Cgamma1 by Itk.

    Funded by: NHLBI NIH HHS: HL03601; NIAID NIH HHS: AI32494; NIGMS NIH HHS: GM56203

    The Journal of biological chemistry 2000;275;3;2219-30

  • Selective attenuation of metabolic branch of insulin receptor down-signaling by high glucose in a hepatoma cell line, HepG2 cells.

    Nakajima K, Yamauchi K, Shigematsu S, Ikeo S, Komatsu M, Aizawa T and Hashizume K

    Department of Aging Medicine and Geriatrics, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.

    The effects of a high concentration of glucose on the insulin receptor-down signaling were investigated in human hepatoma (HepG2) cells in vitro to delineate the molecular mechanism of insulin resistance under glucose toxicity. Treatment of the cells with high concentrations of glucose (15-33 mm) caused phosphorylation of serine residues of the insulin receptor substrate 1 (IRS-1), leading to reduced electrophoretic mobility of it. The phosphorylation of IRS-1 with high glucose treatment was blocked only by protein kinase C (PKC) inhibitors. The high glucose treatment attenuated insulin-induced association of IRS-1 and phosphatidylinositol 3-kinase and insulin-stimulated phosphorylation of Akt. A metabolic effect of insulin, stimulation of glycogen synthesis, was also inhibited by the treatment. In contrast, insulin-induced association of Shc and Grb2 was not inhibited. Treatment of the cells with high glucose promoted the translocation of PKCepsilon and PKCdelta from the cytosol to the plasma membrane but not that of other PKC isoforms. Finally, PKCepsilon and PKCdelta directly phosphorylated IRS-1 under cell-free conditions. We conclude that a high concentration of glucose causes phosphorylation of IRS-1, leading to selective attenuation of metabolic signaling of insulin. PKCepsilon and PKCdelta are involved in the down-regulation of insulin signaling, and they may lie in a pathway regulating the phosphorylation of IRS-1.

    The Journal of biological chemistry 2000;275;27;20880-6

  • Regulated association between the tyrosine kinase Emt/Itk/Tsk and phospholipase-C gamma 1 in human T lymphocytes.

    Perez-Villar JJ and Kanner SB

    Immunology, Inflammation, and Pulmonary Drug Discovery, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ 08543, USA. perezvillar@bms.com

    The Emt/Itk/Tsk tyrosine kinase is involved in intracellular signaling events induced by several lymphocyte surface receptors. Modulation of TCR/CD3-induced phospholipase-C gamma 1 (PLC gamma 1) activity by the tyrosine kinase Emt/Itk/Tsk has been demonstrated based on studies of Itk-deficient murine T lymphocytes. Here we report a TCR/CD3-regulated association between Emt and PLC gamma 1 in both normal and leukemic T cells. In addition, this association was enhanced following independent ligation of the CD2, CD4, or CD28 costimulatory molecules, but not of CD5 or CD6 surface receptors, correlating to the induced tyrosine phosphorylation of Emt. Before Ab-induced T cell activation, we found that the Emt-SH3 domain was crucial for the constitutive Emt/PLC gamma 1 association; however, upon TCR/CD3 engagement, the Emt-SH2 domain was more efficient in mediating the enhanced Emt/PLC gamma 1 interaction. Furthermore, the PLC gamma 1-SH3 domain, but not the two PLC gamma 1-SH2 domains, contributed to formation of the protein complex. Thus, we describe a regulated interaction between Emt and PLC gamma 1, and based on our studies with individual Emt and PLC gamma 1 SH2/SH3 domains, we propose a mechanism for this association.

    Journal of immunology (Baltimore, Md. : 1950) 1999;163;12;6435-41

  • Cutting edge: SLP-76 cooperativity with FYB/FYN-T in the Up-regulation of TCR-driven IL-2 transcription requires SLP-76 binding to FYB at Tyr595 and Tyr651.

    Geng L, Raab M and Rudd CE

    Division of Tumor Immunology, Department of Cancer Immunology and AIDS, Harvard Medical School, Boston, MA 02115, USA.

    SLP-76 (Src homology (SH) 2-domain-containing leukocyte protein of 76 kDa) and FYB/SLAP (FYN-T-binding protein/SLP-76-associated protein) are two hemopoietic cell-specific adaptor proteins downstream of TCR-activated protein tyrosine kinases. SLP-76 has been implicated as an essential component in T cell signaling. FYB is selectively phosphorylated by FYN-T, providing a template for the recruitment of FYN-T and SLP-76 SH2 domains. Coexpression of FYN-T, FYB, and SLP-76 can synergistically up-regulate IL-2 production in T cells upon TCR ligation. In this report, we show that two tyrosines, Tyr595 and Tyr651, of FYB are major sites of phosphorylation by FYN-T and mediate binding to SLP-76 in Jurkat T cells. Furthermore, the synergistic up-regulation of IL-2 promoter activity in the FYN-T-FYB-SLP-76 pathway is contingent upon the interaction between FYB and SLP-76, but not the interaction between FYB and FYN-T. These observations define a pathway by which SLP-76 interacts with downstream components in the up-regulation of T cell cytokine production.

    Journal of immunology (Baltimore, Md. : 1950) 1999;163;11;5753-7

  • A catalytically active Jak2 is required for the angiotensin II-dependent activation of Fyn.

    Sayeski PP, Ali MS, Safavi A, Lyles M, Kim SO, Frank SJ and Bernstein KE

    Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.

    Recent work with interleukins has shown a convergence of tyrosine phosphorylation signal transduction cascades at the level of the Janus and Src families of tyrosine kinases. Here we demonstrate that activation of the seven-transmembrane AT(1) receptor by angiotensin II induces a physical association between Jak2 and Fyn, in vivo. This association requires the catalytic activity of Jak2 but not Fyn. Deletion studies indicate that the region of Jak2 that binds Fyn is located between amino acids 1 and 240. Studies of the Fyn SH2 and SH3 domains demonstrate that the SH2 domain plays the primary role in Jak2/Fyn association. Not surprisingly, this domain shows a marked preference for tyrosine-phosphorylated Jak2. Surface plasmon resonance estimated the dissociation equilibrium constant (K(d)) of this association to be 2.36 nM. Last, in vivo studies in vascular smooth muscle cells show that, in response to angiotensin II, Jak2 activation is required for Fyn activation and induction of the c-fos gene. The significance of these data is that Jak2, in addition to serving as a critical angiotensin II activated signal transduction kinase, also functions as a docking protein and participates in the activation of Fyn by providing phosphotyrosine residues that bind the SH2 domain of Fyn.

    Funded by: NIDDK NIH HHS: DK39777, DK44280, DK45215; ...

    The Journal of biological chemistry 1999;274;46;33131-42

  • The conserved core of human immunodeficiency virus type 1 Nef is essential for association with Lck and for enhanced viral replication in T-lymphocytes.

    Cheng H, Hoxie JP and Parks WP

    Department of Microbiology and Pediatrics, New York University School of Medicine, New York, New York 10016, USA.

    The Nef protein of the primate lentiviruses, including human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV), is a myristylated protein associated with increased viral replication and enhanced pathogenicity. Both the potentiation of T-lymphocyte activation and the enhanced serine-phosphorylation of HIV-1 capsid by Nef correlate with increased viral replication. We report the functional interactions of the Nef proteins with Src kinases. The Nef proteins from HIV-1 and SIV bind to Lck as well as Hck, Lyn, and Fyn. The SH3 and SH2 domains of Lck are sufficient for coprecipitation with non-tyrosine-phosphorylated Nef proteins. The conserved core region of HIV-1 Nef is essential for the interaction with Lck and is also important for enhanced HIV-1 replication in T-lymphocytes. In addition, we show that SIV and HIV-1 Nef proteins are differentially tyrosine-phosphorylated. The kinase-active Lck tyrosine-phosphorylates SIVmac239 Nef but does not phosphorylate HIV-1 Nef. These data suggest that the association of Nef and Lck is central to the enhanced viral replication of HIV-1 and SIV in T-lymphocytes.

    Virology 1999;264;1;5-15

  • The interaction and colocalization of Sam68 with the splicing-associated factor YT521-B in nuclear dots is regulated by the Src family kinase 879 p59(fyn).

    Hartmann AM, Nayler O, Schwaiger FW, Obermeier A and Stamm S

    Max-Planck-Institut of Neurobiology, Max-Planck-Institut of Biochemistry, D-82152 Martinsried, Germany.

    Alternative pre-mRNA splicing patterns can change an extracellular stimulus, but the signaling pathways leading to these changes are still poorly characterized. Here, we describe a tyrosine-phosphorylated nuclear protein, YT521-B, and show that it interacts with the nuclear transcriptosomal component scaffold attachment factor B, and the 68-kDa Src substrate associated during mitosis, Sam68. Northern blot analysis demonstrated ubiquitous expression, but detailed RNA in situ analysis revealed cell type specificity in the brain. YT521-B protein is localized in the nucleoplasm and concentrated in 5-20 large nuclear dots. Deletion analysis demonstrated that the formation of these dots depends on the presence of the amino-terminal glutamic acid-rich domain and the carboxyl-terminal glutamic acid/arginine-rich region. We show that the latter comprises an important protein-protein interaction domain. The Src family kinase p59(fyn)-mediated tyrosine phosphorylation of Sam68 negatively regulates its association with YT521-B, and overexpression of p59(fyn) dissolves nuclear dots containing YT521-B. In vivo splicing assays demonstrated that YT521-B modulates alternative splice site selection in a concentration-dependent manner. Together, our data indicate that YT521-B and Sam68 may be part of a signal transduction pathway that influences splice site selection.

    Molecular biology of the cell 1999;10;11;3909-26

  • Physical and functional association of LFA-1 with DNAM-1 adhesion molecule.

    Shibuya K, Lanier LL, Phillips JH, Ochs HD, Shimizu K, Nakayama E, Nakauchi H and Shibuya A

    58a Department of Immunology, Institute of Basic Medical Sciences, Center for TARA, University of Tsukuba, Japan.

    Whereas ligation of the DNAM-1 adhesion molecule triggers cytotoxicity mediated by normal NK and T cells, this function was defective in NK cell clones from leukocyte adhesion deficiency syndrome. However, genetic reconstitution of cell surface expression of LFA-1 restored the ability of DNAM-1 to initiate anti-DNAM-1 mAb-induced cytotoxicity, indicating a functional relationship between DNAM-1 and LFA-1. Further studies demonstrated that LFA-1 physically associates with DNAM-1 in NK cells and anti-CD3 mAb stimulated T cells, for which serine phosphorylation of DNAM-1 plays a critical role. In addition, cross-linking of LFA-1 induces tyrosine phosphorylation of DNAM-1, for which the Fyn protein tyrosine kinase is responsible. These results indicate that DNAM-1 is involved in the LFA-1-mediated intracellular signals.

    Immunity 1999;11;5;615-23

  • The unique N-terminal domain of the cAMP phosphodiesterase PDE4D4 allows for interaction with specific SH3 domains.

    Beard MB, O'Connell JC, Bolger GB and Houslay MD

    Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, University of Glasgow, UK.

    Of the five PDE4D isoenzymes, only the PDE4D4 cAMP specific phosphodiesterase was able to bind to SH3 domains. Only PDE4D4 and PDE4A5, but not any other PDE4A, B, C and D isoforms expressed in rat brain, bound to src, lyn and fyn kinase SH3 domains. Purified PDE4D4 could bind to purified lyn SH3. PDE4D4 and PDE4A5 both exhibited selectivity for binding the SH3 domains of certain proteins. PDE4D4 did not bind to WW domains. We suggest that an important function of the unique N-terminal region of PDE4D4 may be to allow for association with certain SH3 domain-containing proteins.

    Funded by: Wellcome Trust

    FEBS letters 1999;460;1;173-7

  • Molecular cloning and characterization of a novel cbl-family gene, cbl-c.

    Kim M, Tezuka T, Suziki Y, Sugano S, Hirai M and Yamamoto T

    Department of Oncology, The Institute of Medical Science, The University of Tokyo, Japan.

    We have cloned a novel gene, cbl-c, of mammalian cbl-family. The cbl-c gene is predicted to encode a protein of 52 kDa that has a phosphotyrosine-binding domain, a RING finger and a proline-rich region. Cbl-c shows 50% homology to the amino-terminal sequences of Cbl and Cbl-b, but a sequence corresponding to the carboxy-terminal half of Cbl and Cbl-b is largely missing in Cbl-c. The expression of cbl-c mRNA is distinct from that of cbl and cbl-b mRNAs, being high in the colon and small intestine, but undetectable in brain and lymphoid tissues. The cbl-c gene is mapped in 19q13.2-13.3. Finally, the 52 kDa Cbl-c protein binds to the EGF receptor and Fyn tyrosine kinase. We conclude that Cbl-c is a novel Cbl-family adaptor protein that would regulate intracellular signaling mediated by various tyrosine kinases.

    Gene 1999;239;1;145-54

  • Phosphorylation at Tyr-838 in the kinase domain of EphA8 modulates Fyn binding to the Tyr-615 site by enhancing tyrosine kinase activity.

    Choi S and Park S

    Institute of Environment and Life Science, Hallym University, 1 Okcheon-dong, Chuncheon, Kangwon-do, 200-702, Korea.

    Eph-related receptors and their ephrin ligands are highly conserved protein families which play important roles in targeting axons and migrating cells. In this study we have examined the functional roles of two major autophosphorylation sites, Tyr-615 and Tyr-838, in the EphA8 receptor. Two-dimensional phosphopeptide mapping analysis demonstrated that Tyr-615 and Tyr-838 constitute major autophosphorylation sites in EphA8. Tyr-615 was phosphorylated to the highest stoichiometry, suggesting that phosphorylation at this site may have a physiologically important role. Upon conservative mutation of Tyr-838 located in the tyrosine kinase domain, the catalytic activity of EphA8 was strikingly reduced both in vitro and in vivo, whereas a mutation at Tyr-615 in the juxtamembrane domain did not impair the tyrosine kinase activity. In vitro binding experiments revealed that phosphorylation at Tyr-615 in EphA8 mediates the preferential binding to Fyn-SH2 domain rather than Src and Ras GTPase-activating protein (Ras GAP)-SH2 domains. Additionally, a high level of EphA8 was detected in Fyn immunoprecipitates in intact cells, indicating that EphA8 and Fyn can physically associate in vivo. In contrast, the association of full-length Fyn to EphA8 containing mutation at either Tyr-615 or Tyr-838 was greatly reduced. These data indicate that phosphorylation of Tyr-615 is critical for determining the association with Fyn whereas the integrity of Tyr-838 phosphorylation is required for efficient phosphorylation at Tyr-615 as well as other major sites. Finally, it was observed that cell attachment responses are attenuated by overexpression of wild type EphA8 receptor but to much less extent by EphA8 mutants lacking phosphorylation at either Tyr-615 or Tyr-838. Furthermore, transient expression of kinase-inactive Fyn in EphA8-overexpressing cells blocked cell attachment responses attenuated by the EphA8 signaling. We therefore propose that Fyn kinase is one of the major downstream targets for the EphA8 signaling pathway leading to a modification of cell adhesion, and that autophosphorylation at Tyr-838 is critical for positively regulating the EphA8 signaling event.

    Oncogene 1999;18;39;5413-22

  • SHC and SHIP phosphorylation and interaction in response to activation of the FLT3 receptor.

    Marchetto S, Fournier E, Beslu N, Aurran-Schleinitz T, Dubreuil P, Borg JP, Birnbaum D and Rosnet O

    Laboratoire d'Oncologie Moléculaire, INSERM U119, Marseille, France.

    The FLT3 receptor tyrosine kinase and its ligand, FL, regulate the development of hematopoietic stem cells and early B lymphoid progenitors. FL has a strong capacity to boost production of dendritic and natural killer cells in vivo, thereby providing a new and promising tool for anti-cancer immunotherapy. Intracellular FLT3 signaling involves tyrosine phosphorylation of several cytoplasmic proteins including SHC. We have found that upon FLT3 activation SHC phosphorylation occurs at tyrosine 239/240 and 313. SHC possesses two phosphotyrosine-binding domains: an amino-terminal phosphotyrosine binding (PTB) and a carboxy-terminal Src Homology 2 (SH2) domain. Neither is required for SHC phosphorylation, but the PTB domain is necessary and sufficient for SHC binding to the SH2 containing inositol phosphatase (SHIP). Overexpression of SHC increases the level of SHIP phosphorylation on tyrosines in response to FLT3 activation, suggesting that SHC availability is a limiting step for SHIP phosphorylation. This effect is observed only if the SHC PTB domain is functional. Interestingly, SHC overexpression in FLT3-activatable Ba/F3 cells limits FLT3-dependent cell growth and this effect requires tyrosine 313. Taken together, the present data show that SHC can antagonize cell proliferation induced by FLT3 stimulation and regulate phosphorylation of the SHIP negative regulator. In addition, our study provides the structural bases for SHC phosphorylation and formation of the SHC/SHIP complex.

    Leukemia 1999;13;9;1374-82

  • The effect of transient global ischemia on the interaction of Src and Fyn with the N-methyl-D-aspartate receptor and postsynaptic densities: possible involvement of Src homology 2 domains.

    Takagi N, Cheung HH, Bissoon N, Teves L, Wallace MC and Gurd JW

    Division of Life Sciences, University of Toronto at Scarborough, West Hill, Ontario, Canada.

    Transient ischemia increases tyrosine phosphorylation of N-methyl-D-aspartate (NMDA) receptor subunits NR2A and NR2B in the rat hippocampus. The authors investigated the effects of this increase on the ability of the receptor subunits to bind to the Src homology 2 (SH2) domains of Src and Fyn expressed as glutathione-S-transferase-SH2 fusion proteins. The NR2A and NR2B bound to each of the SH2 domains and binding was increased approximately twofold after ischemia and reperfusion. Binding was prevented by prior incubation of hippocampal homogenates with a protein tyrosine phosphatase or by a competing peptide for the Src SH2 domain. Ischemia induced a marked increase in the tyrosine phosphorylation of several proteins in the postsynaptic density (PSD), including NR2A and NR2B, but had no effect on the amounts of individual NMDA receptor subunits in the PSD. The level of Src and Fyn in PSDs, but not in other subcellular fractions, was increased after ischemia. The ischemia-induced increase in the interaction of NR2A and NR2B with the SH2 domains of Src and Fyn suggests a possible mechanism for the recruitment of signaling proteins to the PSD and may contribute to altered signal transduction in the postischemic hippocampus.

    Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism 1999;19;8;880-8

  • Interaction between Wiskott-Aldrich Syndrome protein (WASP) and the Fyn protein-tyrosine kinase.

    Banin S, Gout I and Brickell P

    Leukaemia Research Fund Centre for Childhood Leukaemia, Molecular Haematology Unit, Institute of Child Health, London, UK.

    Wiskott-Aldrich Syndrome (WAS) is a severe X-linked disorder characterised by immune deficiency, thrombocytopenia and eczema, resulting from abnormalities in a range of haematopoietic cell types. The protein that is defective in WAS, named WASP, appears to be involved in regulating changes in the cytoskeletal organisation of haematopoietic cells in response to external stimuli. In support of this idea, WASP has been found to be physically associated in haematopoietic cells in vivo with a number of SH3 domain-containing proteins involved in signal transduction, including the cytoplasmic protein-tyrosine kinase Fyn. Here, we have used a baculovirus expression system to explore the biochemical consequences of the interaction between WASP and Fyn. We find that the kinase activity of Fyn is stimulated as a result of binding to WASP, and that a cellular protein, which may be WASP itself, becomes phosphorylated on tyrosine as a result of the binding of WASP to Fyn.

    Molecular biology reports 1999;26;3;173-7

  • Cleavage and relocation of the tyrosine kinase P59FYN during Fas-mediated apoptosis in T lymphocytes.

    Ricci JE, Maulon L, Luciano F, Guerin S, Livolsi A, Mari B, Breittmayer JP, Peyron JF and Auberger P

    CJF 96.05 Activation des Cellules Hematopoietiques Faculté de Médecine, Nice, France.

    Ligation of Fas with its natural ligand or with anti-Fas antibodies induces an apoptotic program in Fas sensitive cells. We report here the identification of the tyrosine kinase p59Fyn as a substrate for CPP32-like proteinases and more particularly caspase 3 during Fas-mediated apoptosis in Jurkat T cells. Inhibition of CPP32-like proteinases by Ac-Asp-Glu-Val-Asp-aldehyde but not by Ac-Tyr-Val-Ala-Asp-aldehyde prevents CPP32, PARP and p59Fyn cleavage indicating that CPP32 or CPP32-like proteinases are responsible for the cleavage of p59Fyn. Cleavage occurs in the N-terminal domain of p59Fyn between Asp19 and Gly20 and is accompanied by relocation of an active p57Fyn kinase to cytoplasm of Fas-stimulated Jurkat cells as judged by both biochemical and confocal microscopy experiments. Thus, p59Fyn relocation and activity may play an important role during Fas-mediated cell death in human T lymphocytes.

    Oncogene 1999;18;27;3963-9

  • Direct interaction in T-cells between thetaPKC and the tyrosine kinase p59fyn.

    Ron D, Napolitano EW, Voronova A, Vasquez NJ, Roberts DN, Calio BL, Caothien RH, Pettiford SM, Wellik S, Mandac JB and Kauvar LM

    Telik, Inc., South San Francisco, California 94080, USA.

    The protein kinase C (PKC) family has been clearly implicated in T-cell activation as have several nonreceptor protein-tyrosine kinases associated with the T-cell receptor, including p59fyn. This report demonstrates that thetaPKC and p59fyn specifically interact in vitro, in the yeast two-hybrid system, and in T-cells. Further indications of direct interaction are that p59fyn potentiates thetaPKC catalytic activity and that thetaPKC is a substrate for tyrosine phosphorylation by p59fyn. This interaction may account for the localization of thetaPKC following T-cell activation, pharmacological disruption of which results in specific cell-signaling defects. The demonstration of a physical interaction between a PKC and a protein-tyrosine kinase expands the class of PKC-anchoring proteins (receptors for activated C kinases (RACKs)) and demonstrates a direct connection between these two major T-cell-signaling pathways.

    The Journal of biological chemistry 1999;274;27;19003-10

  • CMS: an adapter molecule involved in cytoskeletal rearrangements.

    Kirsch KH, Georgescu MM, Ishimaru S and Hanafusa H

    Laboratory of Molecular Oncology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA. kirschk@rockvax.rockfeller.edu

    Cas ligand with multiple Src homology (SH) 3 domains (CMS) is an ubiquitously expressed signal transduction molecule that interacts with the focal adhesion protein p130(Cas). CMS contains three SH3 in its NH2 terminus and proline-rich sequences in its center region. The latter sequences mediate the binding to the SH3 domains of p130(Cas), Src-family kinases, p85 subunit of phosphatidylinositol 3-kinase, and Grb2. The COOH-terminal region contains putative actin binding sites and a coiled-coil domain that mediates homodimerization of CMS. CMS is a cytoplasmic protein that colocalizes with F-actin and p130(Cas) to membrane ruffles and leading edges of cells. Ectopic expression of CMS in COS-7 cells resulted in alteration in arrangement of the actin cytoskeleton. We observed a diffuse distribution of actin in small dots and less actin fiber formation. Altogether, these features suggest that CMS functions as a scaffolding molecule with a specialized role in regulation of the actin cytoskeleton.

    Funded by: NCI NIH HHS: CA44356

    Proceedings of the National Academy of Sciences of the United States of America 1999;96;11;6211-6

  • Altered expression of tyrosine kinases of the Src and Syk families in human T-cell leukemia virus type 1-infected T-cell lines.

    Weil R, Levraud JP, Bessia C, Hazan U, Kourilsky P and Israël A

    Unité de Biologie Moléculaire de l'Expression Génique, URA 1773 Centre National de la Recherche Scientifique, 75724 Paris Cedex 15, France. rweil@pasteur.fr

    During the late phase of adult T-cell leukemia/lymphoma, a severe lymphoproliferative disorder caused by human T-cell leukemia virus type 1 (HTLV-1), leukemic cells no longer produce interleukin-2. Several studies have reported the lack of the Src-like protein tyrosine kinase Lck and overexpression of Lyn and Fyn in these cells. In this report we demonstrate that, in addition to the downregulation of TCR, CD45, and Lck (which are key components of T-cell activation), HTLV-1-infected cell lines demonstrate a large increase of FynB, a Fyn isoform usually poorly expressed in T cells. Furthermore, similar to anergic T cells, Fyn is hyperactive in one of these HTLV-1-infected T-cell lines, probably as a consequence of Csk downregulation. A second family of two proteins, Zap-70 and Syk, relay the signal of T-cell activation. We demonstrate that in contrast to uninfected T cells, Zap-70 is absent in HTLV-1-infected T cells, whereas Syk is overexpressed. In searching for the mechanism responsible for FynB overexpression and Zap-70 downregulation, we have investigated the ability of the Tax and Rex proteins to modulate Zap-70 expression and the alternative splicing mechanism which gives rise to either FynB or FynT. By using Jurkat T cells stably transfected with the tax and rex genes or inducibly expressing the tax gene, we found that the expression of Rex was necessary to increase fynB expression, suggesting that Rex controls fyn gene splicing. Conversely, with the same Jurkat clones, we found that the expression of Tax but not Rex could downregulate Zap-70 expression. These results suggest that the effect of Tax and Rex must cooperate to deregulate the pathway of T-cell activation in HTLV-1-infected T cells.

    Journal of virology 1999;73;5;3709-17

  • Fyn and Lck tyrosine kinases regulate tyrosine phosphorylation of p105CasL, a member of the p130Cas docking protein family, in T-cell receptor-mediated signalling.

    Kanda H, Mimura T, Hamasaki K, Yamamoto K, Yazaki Y, Hirai H and Nojima Y

    The Third Department of Internal Medicine, University of Tokyo, Japan.

    We have previously shown that engagement of the T-cell receptor (TCR)/CD3 complex with anti-CD3 antibody induces tyrosine phosphorylation of p105CasL (CasL), a member of the p130Cas docking protein family. In the present work, we attempted to determine which protein tyrosine kinases (PTKs) regulate TCR-mediated phosphorylation of CasL. We show here that an association between CasL and two types of Src family PTKs, Fyn and Lck, is induced by anti-CD3 cross-linking of human H9 T cells. In contrast, ZAP-70, another PTK that also plays a critical role in the TCR signalling, failed to bind CasL, even after anti-CD3 stimulation. In vitro kinase assays revealed that Fyn and Lck, but not ZAP-70, were capable of phosphorylating CasL. Moreover, we found that CasL was constitutively hyperphosphorylated in vivo in splenocytes of MRL-MP-lpr/lpr mice, in which overproduction and excessive activation of Fyn and Lck have previously been shown to occur. Constitutive in vivo binding of CasL to both kinases was also demonstrated in lpr splenocytes. These results strongly suggest that CasL is a substrate for Fyn and Lck PTKs in TCR signal transduction.

    Immunology 1999;97;1;56-61

  • Fyn kinase-directed activation of SH2 domain-containing protein-tyrosine phosphatase SHP-2 by Gi protein-coupled receptors in Madin-Darby canine kidney cells.

    Tang H, Zhao ZJ, Huang XY, Landon EJ and Inagami T

    Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.

    SHP-2, an SH2 domain-containing protein-tyrosine phosphatase, plays an important role in receptor tyrosine kinase-regulated cell proliferation and differentiation. Little is known about the activation mechanisms and the participation of SHP-2 in the activity of G protein-coupled receptors lacking intrinsic tyrosine kinase activity. We show that the activity of SHP-2 (but not SHP-1) is specifically stimulated by the selective alpha2A-adrenergic receptor agonist UK14304 and by lysophosphatidic acid (LPA) in Madin-Darby canine kidney (MDCK) cells. UK14304 and LPA promote the tyrosine phosphorylation of SHP-2 and its association with Grb2. The agonist-induced direct interaction of Grb2 with SHP-2 is mediated by the SH2 domain of Grb2 and the tyrosine phosphorylation of SHP-2. Rapid activation of Src family kinase by UK14304 preceded the SHP-2 activation. Among the Src family members (Src, Fyn, Lck, Yes, and Lyn) present in MDCK cells, Fyn was the only one specifically associated with SHP-2, and the physical interaction between them, which requires the Src family kinase activity, was increased in response to the agonists. Pertussis toxin, PP1 (a selective Src family kinase inhibitor), or overexpression of a catalytically inactive mutant of Fyn blocked the UK14304- or LPA-stimulated activity of SHP-2, SHP-2 tyrosine phosphorylation, and SHP-2 association with Grb2. Therefore, we have demonstrated for the first time that the activation of SHP-2 by these Gi protein-coupled receptors requires Fyn kinase and that there is a specific physical interaction of Fyn kinase with SHP-2 in MDCK cells.

    Funded by: NHLBI NIH HHS: HL-57393, HL-58205

    The Journal of biological chemistry 1999;274;18;12401-7

  • SHP2-interacting transmembrane adaptor protein (SIT), a novel disulfide-linked dimer regulating human T cell activation.

    Marie-Cardine A, Kirchgessner H, Bruyns E, Shevchenko A, Mann M, Autschbach F, Ratnofsky S, Meuer S and Schraven B

    Immunomodulation Laboratory of the Institute for Immunology, University of Heidelberg, 69120 Heidelberg, Germany.

    T lymphocytes express several low molecular weight transmembrane adaptor proteins that recruit src homology (SH)2 domain-containing intracellular molecules to the cell membrane via tyrosine-based signaling motifs. We describe here a novel molecule of this group termed SIT (SHP2 interacting transmembrane adaptor protein). SIT is a disulfide-linked homodimeric glycoprotein that is expressed in lymphocytes. After tyrosine phosphorylation by src and possibly syk protein tyrosine kinases SIT recruits the SH2 domain-containing tyrosine phosphatase SHP2 via an immunoreceptor tyrosine-based inhibition motif. Overexpression of SIT in Jurkat cells downmodulates T cell receptor- and phytohemagglutinin-mediated activation of the nuclear factor of activated T cells (NF-AT) by interfering with signaling processes that are probably located upstream of activation of phospholipase C. 1490 However, binding of SHP2 to SIT is not required for inhibition of NF-AT induction, suggesting that SIT not only regulates NF-AT activity but also controls NF-AT unrelated pathways of T cell activation involving SHP2.

    The Journal of experimental medicine 1999;189;8;1181-94

  • The proto-oncogene p120(Cbl) is a downstream substrate of the Hck protein-tyrosine kinase.

    Howlett CJ, Bisson SA, Resek ME, Tigley AW and Robbins SM

    Department of Oncology, University of Calgary, Calgary, Alberta, Canada.

    Hematopoietic cell kinase (Hck) is a member of the Src-family of protein tyrosine kinases. We have found that upon enzymatic activation of Hck by the heavy metal mercuric chloride, there was a rapid increase in the levels of tyrosine phosphorylation of several proteins including the proto-oncogene p120(Cbl). Fibroblasts that are transformed with an activated allele of Hck exhibit constitutive Cbl phosphorylation. Upon Fcgamma receptor activation, a more physiologically relevant extracellular signal, Cbl is tyrosine phosphorylated and the Src-family selective inhibitor, PP1, can prevent this phosphorylation on Cbl. Hck phosphorylates Cbl in vitro and the interaction between Cbl and Hck is direct, requiring Hck's unique, SH3 and SH2 domains for optimal binding. Using a novel estrogen-regulated chimera of Hck we have shown a hormone-dependent association between Hck and Cbl in murine fibroblasts. This work suggests that Cbl serves as a key mediator of Hck induced signalling in hematopoietic cells.

    Biochemical and biophysical research communications 1999;257;1;129-38

  • Wiskott-Aldrich syndrome protein, WASP.

    O'Sullivan E, Kinnon C and Brickell P

    Paul O'Gorman Leukaemia Research Fund Centre for Childhood Leukaemia, Molecular Haematology Unit, Institute of Child Health, London, UK.

    Wiskott-Aldrich Syndrome protein (WASP) is the product of the gene mutated in children with Wiskott-Aldrich Syndrome (WAS). It is a predominantly cytoplasmic protein, expressed only in haematopoietic cells. It binds in vivo to the adaptor proteins Nck and Grb2, to the cytoplasmic protein-tyrosine kinase Fyn and to the small Rho-like GTPase Cdc42, which is required for formation of filopodia in fibroblasts and macrophages. WASP also interacts, directly or indirectly, with the actin cytoskeleton. Together with studies of a closely related, ubiquitously expressed protein named N-WASP, these findings suggest that WASP is a component of signalling pathways that control reorganisation of the actin cytoskeleton in haematopoietic cells in response to external stimuli. In support of this idea, haematopoietic cells from WAS patients show defects in cytoskeletal organisation that compromise their ability to polarise and to migrate in response to physiological stimuli. These defects could account for many of the clinical features of WAS. WAS is now a candidate for gene therapy based on the delivery of a wild-type WASP gene to autologous haematopoietic stem cells. In addition, recent studies of cell defects in WAS patients suggest that it may prove possible, in time, to rescue WAS cells using more conventional drug therapies.

    The international journal of biochemistry & cell biology 1999;31;3-4;383-7

  • Socs1 binds to multiple signalling proteins and suppresses steel factor-dependent proliferation.

    De Sepulveda P, Okkenhaug K, Rose JL, Hawley RG, Dubreuil P and Rottapel R

    Ontario Cancer Institute, Princess Margaret Hospital, 610 University Avenue, Toronto M5G 2M9.

    We have identified Socs1 as a downstream component of the Kit receptor tyrosine kinase signalling pathway. We show that the expression of Socs1 mRNA is rapidly increased in primary bone marrow-derived mast cells following exposure to Steel factor, and Socs1 inducibly binds to the Kit receptor tyrosine kinase via its Src homology 2 (SH2) domain. Previous studies have shown that Socs1 suppresses cytokine-mediated differentiation in M1 cells inhibiting Janus family kinases. In contrast, constitutive expression of Socs1 suppresses the mitogenic potential of Kit while maintaining Steel factor-dependent cell survival signals. Unlike Janus kinases, Socs1 does not inhibit the catalytic activity of the Kit tyrosine kinase. In order to define the mechanism by which Socs1-mediated suppression of Kit-dependent mitogenesis occurs, we demonstrate that Socs1 binds to the signalling proteins Grb-2 and the Rho-family guanine nucleotide exchange factors Vav. We show that Grb2 binds Socs1 via its SH3 domains to putative diproline determinants located in the N-terminus of Socs1, and Socs1 binds to the N-terminal regulatory region of Vav. These data suggest that Socs1 is an inducible switch which modulates proliferative signals in favour of cell survival signals and functions as an adaptor protein in receptor tyrosine kinase signalling pathways.

    The EMBO journal 1999;18;4;904-15

  • Regulation of cytotoxic T lymphocyte-associated molecule-4 by Src kinases.

    Chuang E, Lee KM, Robbins MD, Duerr JM, Alegre ML, Hambor JE, Neveu MJ, Bluestone JA and Thompson CB

    Gwen Knapp Center for Lupus and Immunology Research, Department of Medicine, University of Chicago, Chicago, IL 60637, USA.

    Cytotoxic T lymphocyte-associated molecule-4 (CTLA-4) is a cell surface receptor expressed on activated T cells that can inhibit T cell responses induced by activation of the TCR and CD28. Studies with phosphorylated peptides based on the CTLA-4 intracellular domain have suggested that tyrosine phosphorylation of CTLA-4 may regulate its interactions with cytoplasmic proteins that could determine its intracellular trafficking and/or signal transduction. However, the kinase(s) that phosphorylate CTLA-4 remain uncharacterized. In this report, we show that CTLA-4 can associate with the Src kinases Fyn and Lck and that transfection of Fyn or Lck, but not the unrelated kinase ZAP70, can induce tyrosine phosphorylation of CTLA-4 on residues Y201 and Y218. A similar pattern of tyrosine phosphorylation was found in pervanadate-treated Jurkat T cells stably expressing CTLA-4. Phosphorylation of CTLA-4 Y201 in Jurkat cells correlated with cell surface accumulation of CTLA-4. CTLA-4 phosphorylation induced the association of CTLA-4 with the tyrosine phosphatase SHP-2, but not with phosphatidylinositol 3-kinase. In contrast, Lck-induced phosphorylation of CD28 resulted in the recruitment of phosphatidylinositol 3-kinase, but not SHP-2. These findings suggest that phosphorylation of CD28 and CTLA-4 by Lck activates distinct intracellular signaling pathways. The association of CTLA-4 with Src kinases and with SHP-2 results in the formation of a CTLA-4 complex with the potential to regulate T cell activation.

    Funded by: NCI NIH HHS: K08CA78591; NIDDK NIH HHS: P01DK49799

    Journal of immunology (Baltimore, Md. : 1950) 1999;162;3;1270-7

  • Fyn associates with Cbl and phosphorylates tyrosine 731 in Cbl, a binding site for phosphatidylinositol 3-kinase.

    Hunter S, Burton EA, Wu SC and Anderson SM

    Department of Pathology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.

    We have investigated the interaction between Cbl and the Src-related tyrosine kinase Fyn. Fyn was observed to be constitutively associated with Cbl in lysates of several different cell types including the interleukin-3-dependent murine myeloid cell line 32Dcl3, and the prolactin-dependent rat thymoma cell line Nb2. Binding studies indicated that Cbl could bind to glutathione S-transferase (GST) fusion proteins encoding the unique, Src homology domain 3 (SH3), and SH2 domains of Fyn, Hck, or Lyn. Fusion proteins encoding either the SH3 or SH2 domains of Fyn bound to Cbl as effectively as the fusion protein encoding the unique, SH3, and SH2 domains of Fyn. The Fyn SH2 domain bound to both tyrosine-phosphorylated and nonphosphorylated Cbl, implying that this interaction might be phosphotyrosine-independent. Binding of the Fyn SH2 domain to Cbl was not disrupted by the addition of phosphotyrosine, phosphoserine, or phosphothreonine. A GST fusion protein encoding the proline-rich region of Cbl bound to Fyn present in a total cell lysate. Far Western blot analysis also indicated that the SH3 domain of Fyn bound preferentially to the proline-rich region of Cbl. The addition of [gamma-32P]ATP to either anti-Cbl immunoprecipitates or anti-Fyn immunoprecipitates resulted in the phosphorylation of both Cbl and Fyn as demonstrated by immunoprecipitation of the phosphorylated proteins with specific antisera. Fyn directly phosphorylated a GST fusion protein containing the C-terminal region of Cbl (GST-CBL-LZIP). In contrast, immunoprecipitated JAK2 was not able to phosphorylate this same region of Cbl. The GST-CBL-LZIP fusion protein contains a binding site for the SH2 domain of the p85 subunit of phosphatidylinositol 3-kinase, which mapped to Tyr731, which is present in the sequence YEAM. Mutation of Tyr731 in GST-CBL-LZIP eliminated binding of the p85 subunit of phosphatidylinositol 3-kinase and substantially reduced the phosphorylation of this fusion protein by Fyn, despite the presence of four other tyrosine residues in this fusion protein. These data are consistent with the hypothesis that Cbl represents a substrate for Src-like kinases that are activated in response to the engagement of cell surface receptors, and that Src-like kinases are responsible for the phosphorylation of a tyrosine residue in Cbl that may regulate activation of phosphatidylinositol 3-kinase.

    Funded by: NCI NIH HHS: CA45241; NIDDK NIH HHS: DK48845, DK48878; ...

    The Journal of biological chemistry 1999;274;4;2097-106

  • PSD-95 promotes Fyn-mediated tyrosine phosphorylation of the N-methyl-D-aspartate receptor subunit NR2A.

    Tezuka T, Umemori H, Akiyama T, Nakanishi S and Yamamoto T

    Department of Oncology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.

    Fyn, a member of the Src-family protein-tyrosine kinase (PTK), is implicated in learning and memory that involves N-methyl-D-aspartate (NMDA) receptor function. In this study, we examined how Fyn participates in synaptic plasticity by analyzing the physical and functional interaction between Fyn and NMDA receptors. Results showed that tyrosine phosphorylation of NR2A, one of the NMDA receptor subunits, was reduced in fyn-mutant mice. NR2A was tyrosine-phosphorylated in 293T cells when coexpressed with Fyn. Therefore, NR2A would be a substrate for Fyn in vivo. Results also showed that PSD-95, which directly binds to and coclusters with NMDA receptors, promotes Fyn-mediated tyrosine phosphorylation of NR2A. Different regions of PSD-95 associated with NR2A and Fyn, respectively, and so PSD-95 could mediate complex formation of Fyn with NR2A. PSD-95 also associated with other Src-family PTKs, Src, Yes, and Lyn. These results suggest that PSD-95 is critical for regulation of NMDA receptor activity by Fyn and other Src-family PTKs, serving as a molecular scaffold for anchoring these PTKs to NR2A.

    Proceedings of the National Academy of Sciences of the United States of America 1999;96;2;435-40

  • High-resolution structures of three new trypsin-squash-inhibitor complexes: a detailed comparison with other trypsins and their complexes.

    Helland R, Berglund GI, Otlewski J, Apostoluk W, Andersen OA, Willassen NP and Smalås AO

    Department of Chemistry, University of Tromso, N-9037 Tromso, Norway.

    An anionic trypsin from Atlantic salmon and bovine trypsin have been complexed with the squash-seed inhibitors, CMTI-I (Cucurbita maxima trypsin inhibitor I, P1 Arg) and CPTI-II (Cucurbita pepo trypsin inhibitor II, P1 Lys). The crystal structures of three such complexes have been determined to 1.5-1.8 A resolution and refined to crystallographic R factors ranging from 17.6 to 19.3%. The two anionic salmon-trypsin complexes (ST-CPTI and ST-CMTI) and the bovine-trypsin complex (BT-CPTI) have been compared to other trypsin-inhibitor complexes by means of general structure and primary and secondary binding features. In all three new structures, the primary binding residue of the inhibitor binds to trypsin in the classical manner, but with small differences in the primary and secondary binding patterns. Lysine in CPTI-II binds deeper in the specificity pocket of bovine trypsin than lysine in other known lysine-bovine-trypsin complexes, and anionic salmon trypsin lacks some of the secondary binding interactions found in the complexes formed between squash inhibitors and bovine trypsin. The ST-CMTI complex was formed from the reactive-site-cleaved form of the inhibitor. However, well defined electron density was observed for the P1-P1' peptide bond, together with a hydrogen-bonding pattern virtually identical to those of all serine-protease-protein-inhibitor complexes, indicating a resynthesis of the scissile bond.

    Acta crystallographica. Section D, Biological crystallography 1999;55;Pt 1;139-48

  • Growth hormone stimulates the formation of a multiprotein signaling complex involving p130(Cas) and CrkII. Resultant activation of c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK).

    Zhu T, Goh EL, LeRoith D and Lobie PE

    Institute of Molecular and Cell Biology and Defence Medical Research Institute, National University of Singapore, 30 Medical Drive, Singapore 117609, Republic of Singapore.

    We have demonstrated previously that growth hormone (GH) activates focal adhesion kinase (FAK), and this activation results in the tyrosine phosphorylation of two FAK substrates, namely paxillin and tensin. We now show here in Chinese hamster ovary cells stably transfected with rat GH receptor cDNA that human (h)GH induces the formation of a large multiprotein signaling complex centered around another FAK-associated protein, p130(Cas) and the adaptor protein CrkII. hGH stimulates the tyrosine phosphorylation of both p130(Cas) and CrkII, their association, and the association of multiple other tyrosine-phosphorylated proteins to the complex. Both the c-Src and c-Fyn tyrosine kinases are tyrosine phosphorylated and activated by cellular hGH stimulation and form part of the multiprotein signaling complex as does tensin, paxillin, IRS-1, the p85 subunit of phosphatidylinositol 3-kinase, C3G, SHC, Grb-2, and Sos-1. c-Cbl and Nck are also tyrosine-phosphorylated by cellular stimulation with hGH and associate with the p130(Cas)-CrkII complex. c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) is activated in response to hGH in accordance with the formation of the abovementioned signaling complex, and hGH stimulated JNK/SAPK activity is increased in CrkII overexpressing NIH3T3 cells compared with vector transfected NIH3T3 cells. The formation of such a large multiprotein signaling complex by GH, with the resultant activation of multiple downstream effector molecules, may be central to many of the pleiotropic effects of GH.

    The Journal of biological chemistry 1998;273;50;33864-75

  • ASAP1, a phospholipid-dependent arf GTPase-activating protein that associates with and is phosphorylated by Src.

    Brown MT, Andrade J, Radhakrishna H, Donaldson JG, Cooper JA and Randazzo PA

    Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.

    Membrane trafficking is regulated in part by small GTP-binding proteins of the ADP-ribosylation factor (Arf) family. Arf function depends on the controlled exchange and hydrolysis of GTP. We have purified and cloned two variants of a 130-kDa phosphatidylinositol 4, 5-biphosphate (PIP2)-dependent Arf1 GTPase-activating protein (GAP), which we call ASAP1a and ASAP1b. Both contain a pleckstrin homology (PH) domain, a zinc finger similar to that found in another Arf GAP, three ankyrin (ANK) repeats, a proline-rich region with alternative splicing and SH3 binding motifs, eight repeats of the sequence E/DLPPKP, and an SH3 domain. Together, the PH, zinc finger, and ANK repeat regions possess PIP2-dependent GAP activity on Arf1 and Arf5, less activity on Arf6, and no detectable activity on Arl2 in vitro. The cDNA for ASAP1 was independently identified in a screen for proteins that interact with the SH3 domain of the tyrosine kinase Src. ASAP1 associates in vitro with the SH3 domains of Src family members and with the Crk adapter protein. ASAP1 coprecipitates with Src from cell lysates and is phosphorylated on tyrosine residues in cells expressing activated Src. Both coimmunoprecipitation and tyrosine phosphorylation depend on the same proline-rich class II Src SH3 binding site required for in vitro association. By directly interacting with both Arfs and tyrosine kinases involved in regulating cell growth and cytoskeletal organization, ASAP1 could coordinate membrane remodeling events with these processes.

    Funded by: NCI NIH HHS: CA41072, CA62598, F32 CA062598, R01 CA041072, R37 CA041072

    Molecular and cellular biology 1998;18;12;7038-51

  • Fyn and ZAP-70 are required for Vav phosphorylation in T cells stimulated by antigen-presenting cells.

    Michel F, Grimaud L, Tuosto L and Acuto O

    Molecular Immunology Unit, Department of Immunology, Institut Pasteur, 25 Rue du Docteur Roux, 75724 Paris Cedex 15, France.

    In T cells, triggering of the T cell antigen receptor or of the co-stimulatory receptor CD28 can direct tyrosine phosphorylation of the signaling protein Vav. We investigated the role played by the protein tyrosine kinases Fyn, Lck, and ZAP-70 in these processes in a T cell hybridoma after physiological stimulation of the T cell receptor (TCR) and CD28. A dominant-negative mutant approach based on overexpression of catalytically inactive alleles of these kinases showed that CD28-induced Vav phosphorylation preferentially requires Fyn, whereas ZAP-70 had no role. Consistently, Vav was strongly phosphorylated in Lck-deficient JCAM-1 cells after CD28 ligation. In contrast, ZAP-70 appeared to control TCR-directed Vav phosphorylation. However, overexpression of ZAP-70 carrying a mutated Tyr315, contained within a motif previously suggested to be a Vav Src homology 2 domain binding site, had little or no effect. Immunoprecipitation assays showed that phosphorylated Vav associated with Fyn after CD28 triggering and that this interaction, likely to involve binding of Fyn Src homology 2 domain to Vav, was more strongly detectable after concomitant CD28 and TCR stimulation. These data suggest that Fyn plays a major role in controlling Vav phosphorylation upon T cell activation and that the mechanism implicating ZAP-70 in this process may be more complex than previously anticipated.

    The Journal of biological chemistry 1998;273;48;31932-8

  • RA70 is a src kinase-associated protein expressed ubiquitously.

    Kouroku Y, Soyama A, Fujita E, Urase K, Tsukahara T and Momoi T

    Division of Development and Differentiation, National Institute of Neuroscience, NCNP, Kodaira, Tokyo, 187-8502, Japan.

    RA70, which is expressed during neuronal differentiation of P19 EC, is highly homologous to human src kinase-associated phosphoprotein (SKAP55). Here we isolated human full-length RA70 cDNA. Unlike SKAP55, which is specifically expressed in thymus and T cells, RA70 was expressed ubiquitously in various tissues including lung, skeletal muscle, and spleen, and in various cell lines including human monocytic leukemia (U937) cells, but RA70 was undetectable in thymus and T cell lymphoma (Jurkat) cells. RA70 as well as SKAP55 proved to be a protein with molecular weight 55 kDa associated with SH2 domain of Fyn. Interaction between RA70 and src family kinases, Fyn, Hck and Lyn, was detected during monocytes/macrophage-differentiation of U937 cells. Thus, like SKAP55, RA70 is an adaptor protein of the src family kinases. RA70 may play an essential role in the src signaling pathway in various cells.

    Biochemical and biophysical research communications 1998;252;3;738-42

  • Angiotensin II-induced tyrosine phosphorylation of signal transducers and activators of transcription 1 is regulated by Janus-activated kinase 2 and Fyn kinases and mitogen-activated protein kinase phosphatase 1.

    Venema RC, Venema VJ, Eaton DC and Marrero MB

    Vascular Biology Center, Medical College of Georgia, Augusta, Georgia 30912, USA.

    Angiotensin II (Ang II) AT1 receptors on vascular smooth muscle cells (VSMCs) are coupled to the Janus-activated kinase (JAK)/signal transducers and activators of transcription (STAT) pathway. We have shown previously that Ang II stimulation of VSMCs results in the tyrosine phosphorylation of JAK2 and STAT1 and the translocation of STAT1 to the nucleus. In the present study, we demonstrate using specific enzyme inhibitors and antisense oligonucleotides that both JAK2 and p59 Fyn tyrosine kinases are required for the Ang II-induced tyrosine phosphorylation and nuclear translocation of STAT1 in VSMCs. Neither tyrosine kinase, however, appears to function upstream from the other in a phosphorylation cascade. Rather, p59 Fyn functions as an Ang II-activated docking protein for both JAK2 and STAT1, a docking interaction that may facilitate JAK2-mediated STAT1 tyrosine phosphorylation. In this study, we have also identified the nuclear dual-specificity phosphatase mitogen-activated protein kinase phosphatase 1 as the enzyme responsible for STAT1 tyrosine dephosphorylation in VSMCs.

    Funded by: NHLBI NIH HHS: HL57201, HL58129; NIDDK NIH HHS: P01-DK50268

    The Journal of biological chemistry 1998;273;46;30795-800

  • Kit signaling through PI 3-kinase and Src kinase pathways: an essential role for Rac1 and JNK activation in mast cell proliferation.

    Timokhina I, Kissel H, Stella G and Besmer P

    Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, Cornell University Graduate School of Medical Sciences, New York, NY 10021, USA.

    The receptor tyrosine kinase Kit plays critical roles in hematopoiesis, gametogenesis and melanogenesis. In mast cells, Kit receptor activation mediates several cellular responses including cell proliferation and suppression of apoptosis induced by growth factor deprivation and gamma-irradiation. Kit receptor functions are mediated by kinase activation, receptor autophosphorylation and association with various signaling molecules. We have investigated the role of phosphatidylinositol 3'-kinase (PI 3-kinase) and Src kinases in Kit-mediated cell proliferation and suppression of apoptosis induced both by factor deprivation and irradiation in bone marrow-derived mast cells (BMMC). Analysis of Kit-/- BMMC expressing mutant Kit receptors and the use of pharmacological inhibitors revealed that both signaling pathways contribute to these Kit-mediated responses and that elimination of both pathways abolishes them. We demonstrate that the PI 3-kinase and Src kinase signaling pathways converge to activate Rac1 and JNK. Analysis of BMMC expressing wild-type and dominant-negative mutant forms of Rac1 and JNK revealed that the Rac1/JNK pathway is critical for Kit ligand (KL)-induced proliferation of mast cells but not for suppression of apoptosis. In addition, KL was shown to inhibit sustained activation of JNK induced by gamma-irradiation and concomitant irradiation-induced apoptosis.

    Funded by: NCI NIH HHS: R37 CA32926; NHLBI NIH HHS: HL/DK55748

    The EMBO journal 1998;17;21;6250-62

  • Adaptor function for the Syk kinases-interacting protein 3BP2 in IL-2 gene activation.

    Deckert M, Tartare-Deckert S, Hernandez J, Rottapel R and Altman A

    Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA.

    Syk-family tyrosine kinases are essential for lymphocyte development and activation. Using a yeast two-hybrid screen to identify Syk kinases-interacting proteins (SKIPs), we isolated 3BP2, an Abl SH3-interacting protein of unknown function. 3BP2 was selectively expressed in hematopoietic/lymphoid tissues and bound via its SH2 domain activated Syk-family kinases in mammalian cells, including in antigen receptor-stimulated T cells. In addition to Zap-70, the 3BP2 SH2 domain associated in vitro with LAT, Grb2, PLCgamma1, and Cbl from activated T cell lysates. Transient 3BP2 overexpression induced transcriptional activation of the IL-2 promoter and its NFAT or AP-1 elements. This activity was dependent on the SH2 and pleckstrin-homology domains of 3BP2, and required functional Syk kinases, Ras, and calcineurin. Thus, 3BP2 is an important adaptor that may couple activated Zap-70/Syk to a LAT-containing signaling complex involved in TCR-mediated gene transcription.

    Funded by: NCI NIH HHS: CA35299; NIGMS NIH HHS: GM50819

    Immunity 1998;9;5;595-605

  • Tau interacts with src-family non-receptor tyrosine kinases.

    Lee G, Newman ST, Gard DL, Band H and Panchamoorthy G

    Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA. gloria-lee@uiowa.edu

    Tau and other microtubule-associated proteins promote the assembly and stabilization of neuronal microtubules. While each microtubule-associated protein has distinct properties, their in vivo roles remain largely unknown. Tau is important in neurite outgrowth and axonal development. Recently, we showed that the amino-terminal region of tau, which is not involved in microtubule interactions, is important in NGF induced neurite outgrowth in PC12 cells. Here we report that a proline rich sequence in the amino terminus of tau interacts with the SH3 domains of fyn and src non-receptor tyrosine kinases. Tau and fyn were co-immunoprecipitated from human neuroblastoma cells and co-localization of tau and fyn was visualized in co-transfected NIH3T3 cells. Co-transfection of tau and fyn also resulted in an alteration in NIH3T3 cell morphology, consistent with an in vivo interaction. Fyn-dependent tyrosine phosphorylation of tau occurred in transfected cells and tyrosine phosphorylated tau was identified in human neuroblastoma cells as well. Our data suggest that tau is involved in signal transduction pathways. An interaction between tau and fyn may serve as a mechanism by which extracellular signals influence the spatial distribution of microtubules. The tyrosine phosphorylation of tau by fyn may also have a role in neuropathogenesis, as fyn is upregulated in Alzheimer's disease.

    Funded by: NINDS NIH HHS: NS32100M

    Journal of cell science 1998;111 ( Pt 21);3167-77

  • Son of sevenless binds to the SH3 domain of src-type tyrosine kinase.

    Park C, Choi Y and Yun Y

    Signal Transduction Laboratory, Mogam Biotechnology Research Institute, Younginsi, Korea.

    To identify molecules which bind to the SH3 domains of p56lck, we screened a mouse T-cell lymphoma cDNA library using the yeast two-hybrid system. As a result, we obtained several positive clones including the Son of Sevenless gene which encodes a mammalian homolog of Drosophila Ras GDP/GTP exchange factor. In a subsequent analysis with the yeast two-hybrid system, Sos associated only with the constitutively active form of p56lck (F505) but not with wild type p56lck (Y505), indicating the requirement for an active conformation of p56lck for binding to Sos. Subsequently, we have demonstrated in vitro that the SH3 domain of p56lck as well as the proline-rich sequences of Sos are responsible for this association. In addition, the proline-rich domain of Sos also bound to the SH3 domains of other src-type tyrosine kinases, src and fyn, but not to that of PLC-gamma. More importantly, the p56lck SH3-Sos interaction was enhanced by serum stimulation, suggesting the possibility that the direct interaction between p56lck SH3 and Sos may contribute to the regulation of the Ras pathway.

    Molecules and cells 1998;8;5;518-23

  • RT loop flexibility enhances the specificity of Src family SH3 domains for HIV-1 Nef.

    Arold S, O'Brien R, Franken P, Strub MP, Hoh F, Dumas C and Ladbury JE

    Centre de Biochimie Structurale, UMR C9955 CNRS, U414 INSERM, Université Montpellier 1, France.

    Understanding the issue of specificity imposed in the interactions of SH3 domains has largely been addressed in studies investigating the interaction of proline-rich amino acid sequences derived from potential ligands for these domains. Although the interaction with this motif forms an essential platform in the binding of SH3 domains, in many cases little specificity is observed and the difference in affinity for so-called specific and nonspecific proline-rich sequences is not great. Furthermore, the binding interface between an SH3 domain and a protein ligand appears to encompass more interactions than are represented by that involving the proline-rich motif. Here we investigate the issue of specificity from the opposite point of view; namely, how does a ligand recognize different SH3 domains? We present the crystal structure of the unbound SH3 domain from hemopoietic cell kinase (Hck) which is a member of the Src family of tyrosine kinases. This structure reveals that, unlike the structures of other Src kinase SH3 domains, the RT loop region is highly mobile and lacks a network of hydrogen bonds that is elsewhere apparent. The RT loop has been shown to form a major part of the binding interface between SH3 domains and HIV-1 Nef. Thermodynamic data, derived from isothermal titration calorimetry, for the binding of Hck SH3 to HIV-1 Nef show that the binding of Hck (KD = 1.5 microM) is approximately an order of magnitude tighter than those of other Src family kinases that were investigated (Fyn, Lck, and Src). This increase in affi 112f nity is attributed to, among other effects, the inherent flexibility in the RT loop which does not require breaking the network of hydrogen bonds to adopt the conformation required for binding.

    Funded by: Wellcome Trust

    Biochemistry 1998;37;42;14683-91

  • Activation of human endothelial cells via S-endo-1 antigen (CD146) stimulates the tyrosine phosphorylation of focal adhesion kinase p125(FAK).

    Anfosso F, Bardin N, Francès V, Vivier E, Camoin-Jau L, Sampol J and Dignat-George F

    Laboratoire d'Hématologie-Immunologie, Unité de Formation et de Recherche Pharmacie, 13385 Marseille, France.

    S-Endo-1 antigen (CD146), a transmembrane receptor also known as MUC18/MCAM, is a member of the immunoglobulin superfamily and belongs to a group of cell adhesion molecules. CD146 is highly expressed on the whole vascular tree. We demonstrate here that engagement of CD146 on human endothelial cells isolated from cord blood results in tyrosine phosphorylation of a large panel of cellular proteins, although no tyrosine phosphorylation of CD146 was detected. In particular, CD146 cross-linking induces the tyrosine phosphorylation of the protein tyrosine kinase p125(FAK) as well as p125(FAK) association with paxillin, both events being inhibited by cytochalasin D. No direct association of CD146 with p125(FAK) was observed. Consistent with these data, CD146 associates with p59(fyn), a Src family kinase known to phosphorylate p125(FAK). The identification of a signaling pathway initiated by CD146 engagement and which includes p59(fyn), p125(FAK), and paxillin indicates that CD146 participates in outside-in signaling in endothelial cells.

    The Journal of biological chemistry 1998;273;41;26852-6

  • Molecular interaction between the Fyn-associated protein SKAP55 and the SLP-76-associated phosphoprotein SLAP-130.

    Marie-Cardine A, Hendricks-Taylor LR, Boerth NJ, Zhao H, Schraven B and Koretzky GA

    Ruprecht-Karls University of Heidelberg, Institute for Immunology, 69120 Heidelberg, Germany.

    It has previously been reported that in resting T-lymphocytes the protein tyrosine kinase p59 constitutively co-precipitates with four phosphoproteins of 43, 55, 85, and 120 kDa, respectively. We have recently cloned the 55-kDa protein that was termed Src kinase-associated phosphoprotein of 55 kDa (SKAP55). Here we demonstrate that the recently characterized SH2-domain-containing leukocyte protein 76-associated phosphoprotein of 130 kDa (SLAP-130) is one of the components of the Fyn complex and that it also co-precipitates with SKAP55 in human T-cells. We establish that SKAP55 and SLAP-130 associate with each other when both molecules are co-expressed in COS cells. By co-transfection of truncated mutants of SKAP55 and SLAP-130 as well as by using the two-hybrid selection system, we further demonstrate that the association between SLAP-130 and SKAP55 is direct and involves the Src homology 3 domain of SKAP55 and the proline-rich sequence of SLAP-130.

    Funded by: NIAID NIH HHS: 2T32 AI07260; NIGMS NIH HHS: R01 GM53256

    The Journal of biological chemistry 1998;273;40;25789-95

  • Dot far-western blot analysis of relative binding affinities of the Src homology 3 domains of Efs and its related proteins.

    Ohba T, Ishino M, Aoto H and Sasaki T

    Cancer Research Institute, Sapporo Medical University School of Medicine, South-1, West-17, Sapporo, Chuo-Ku, 060-8556, Japan.

    The Src homology 3 (SH3) domains are a modular structure of about 60 amino acid residues found in many proteins important in signal transduction. Each SH3 domain has a binding specificity to sequences containing a PXXP motif in ligand proteins. We found that a focal adhesion kinase (FAK)-related protein, cell adhesion kinase beta (CAKbeta), was bound in vitro by the SH3 domain of embryonal Fyn-associated substrate (Efs), a docking protein structurally related to p130Cas (Cas) and HEF1. Here, we employed a dot far-Western blotting technique to evaluate the affinity and specificity of the binding by the SH3 domains of Efs and its related proteins. The SH3 domains and their ligands were prepared as glutathione S-transferase fusion proteins, and one of the binding components was immobilized on membranes while the other was labeled with 32P to use as a probe. The amount of the bound probe was determined by autoradiography using an imaging plate and a bioimaging analyzer. A competitive binding assay showed that Efs, compared with Cas and HEF1, had a SH3 domain with a lower relative affinity to CAKbeta and FAK and with a preference to interact with FAK rather than CAKbeta. Our assay based on dot far-Western blotting is a simple and sensitive method to evaluate fine differences in the binding affinity of SH3-mediated interactions.

    Analytical biochemistry 1998;262;2;185-92

  • A requirement for caveolin-1 and associated kinase Fyn in integrin signaling and anchorage-dependent cell growth.

    Wary KK, Mariotti A, Zurzolo C and Giancotti FG

    Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.

    Caveolin-1 functions as a membrane adaptor to link the integrin alpha subunit to the tyrosine kinase Fyn. Upon integrin ligation, Fyn is activated and binds, via its SH3 domain, to Shc. Shc is subsequently phosphorylated at tyrosine 317 and recruits Grb2. This sequence of events is necessary to couple integrins to the Ras-ERK pathway and promote cell cycle progression. These findings reveal an unexpected function of caveolin-1 and Fyn in integrin signaling and anchorage-dependent cell growth.

    Funded by: NCI NIH HHS: CA58976, P30 CA08748

    Cell 1998;94;5;625-34

  • Src family tyrosine kinases associate with and phosphorylate CTLA-4 (CD152).

    Miyatake S, Nakaseko C, Umemori H, Yamamoto T and Saito T

    Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Tokyo, Minato-ku, 108-8639, Japan. sho@ims.u-tokyo.ac.jp

    CTLA-4 (CD152) transduces inhibitory signals for T cell activation. Phosphorylation and dephosphorylation of tyrosine residue (Y)-165 in the cytoplasmic region of CTLA-4 play an important role in the signal transduction and in the cell surface. While signaling molecules such as SHP-2 and the p85 subunit of PI3 kinase associate with this tyrosine residue through SH2 domains upon phosphorylation, the adapter complex AP-2 interacts with the same tyrosine when dephosphorylated, leading to clathrin-mediated endocytosis of CTLA-4. We searched for the tyrosine kinase responsible for the phosphorylation of CTLA-4. Src family tyrosine kinases Fyn, Lyn, and Lck associate with CTLA-4 and phosphorylate both Y-165 and Y-182 that are mainly responsible for interaction with Fyn through its SH2 domain. SHP-2 associates with CTLA-4, in a Fyn-dependent manner. Our observations show that src family tyrosine kinases associate with and phosphorylate CTLA-4 and thereby have an important role in the signal transduction and the endocytosis of CTLA-4.

    Biochemical and biophysical research communications 1998;249;2;444-8

  • T cell receptor (TCR) interacting molecule (TRIM), a novel disulfide-linked dimer associated with the TCR-CD3-zeta complex, recruits intracellular signaling proteins to the plasma membrane.

    Bruyns E, Marie-Cardine A, Kirchgessner H, Sagolla K, Shevchenko A, Mann M, Autschbach F, Bensussan A, Meuer S and Schraven B

    Institute for Immunology, University of Heidelberg, 69120 Heidelberg, Germany.

    The molecular mechanisms regulating recruitment of intracellular signaling proteins like growth factor receptor-bound protein 2 (Grb2), phospholipase Cgamma1, or phosphatidylinositol 3-kinase (PI3-kinase) to the plasma membrane after stimulation of the T cell receptor (TCR)- CD3-zeta complex are not very well understood. We describe here purification, tandem mass spectrometry sequencing, molecular cloning, 1f40 and biochemical characterization of a novel transmembrane adaptor protein which associates and comodulates with the TCR-CD3-zeta complex in human T lymphocytes and T cell lines. This protein was termed T cell receptor interacting molecule (TRIM). TRIM is a disulfide-linked homodimer which is comprised of a short extracellular domain of 8 amino acids, a 19-amino acid transmembrane region, and a 159-amino acid cytoplasmic tail. In its intracellular domain, TRIM contains several tyrosine-based signaling motifs that could be involved in SH2 domain-mediated protein-protein interactions. Indeed, after T cell activation, TRIM becomes rapidly phosphorylated on tyrosine residues and then associates with the 85-kD regulatory subunit of PI3-kinase via an YxxM motif. Thus, TRIM represents a TCR-associated transmembrane adaptor protein which is likely involved in targeting of intracellular signaling proteins to the plasma membrane after triggering of the TCR.

    The Journal of experimental medicine 1998;188;3;561-75

  • Roles of Lck, Syk and ZAP-70 tyrosine kinases in TCR-mediated phosphorylation of the adapter protein Shc.

    Walk SF, March ME and Ravichandran KS

    Beirne Carter Center for Immunology Research, Department of Microbiology, University of Virginia, Charlottesville 22908, USA.

    The adapter protein Shc has been implicated in mitogenic signaling via growth factor receptors, antigen receptors and cytokine receptors. Recent studies have suggested that tyrosine phosphorylation of Shc may play a key role in T lymphocyte proliferation via interaction of phosphorylated Shc with downstream molecules involved in activation of Ras and Myc proteins. However, the sites on Shc that are tyrosine phosphorylated in response to TCR engagement and the ability of different T cell tyrosine kinases to phosphorylate Shc have not been defined. In this report, we show that during TCR signaling, the tyrosines Y239, Y240 and Y317 of Shc are the primary sites of tyrosine phosphorylation. Mutation of all three tyrosines completely abolished tyrosine phosphorylation of Shc following TCR stimulation. Our data also suggest that multiple T cell tyrosine kinases contribute to tyrosine phosphorylation on Shc. In T cells, CD4/Lck-dependent tyrosine phosphorylation on Shc was markedly diminished when Y317 was mutated, suggesting a preference of Lck for the Y317 site. The syk-family kinases (Syk and ZAP-70) were able to phosphorylate the Y239 and Y240 sites, and less efficiently the Y317 site. Moreover, co-expression of Syk or ZAP-70 with Lck resulted in enhanced phosphorylation of Shc on all three sites, suggesting a synergy between the syk-family and scr-family kinases. Of the two potential Grb2 binding sites (Y239 and Y317), Y239 appears to play a greater role in recruiting Sos through Grb2. These studies have implications for Ras activation and mitogenic signaling during T cell activation.

    European journal of immunology 1998;28;8;2265-75

  • Association of p59(fyn) with the T lymphocyte costimulatory receptor CD2. Binding of the Fyn Src homology (SH) 3 domain is regulated by the Fyn SH2 domain.

    Lin H, Hutchcroft JE, Andoniou CE, Kamoun M, Band H and Bierer BE

    Department of Pediatric Oncology, Dana-Farber Cancer Institute, Brigham and Woman's Hospital, Boston, Massachusetts 02115, USA.

    Human CD2 is a 50-55-kDa cell surface receptor specifically expressed on the surface of T lymphocytes and NK cells. Stimulation of human peripheral blood T cells with mitogenic pairs of anti-CD2 monoclonal antibodies (mAbs) is sufficient to induce interleukin-2 production and T cell proliferation in the absence of an antigen-specific signal through the T cell receptor. CD2 has been shown previously to associate physically with the Src family protein-tyrosine kinases p56(lck) and p59(fyn). We now report that stimulation of T cells with mitogenic pairs of anti-CD2 mAbs enhanced the association of the Fyn polypeptide with the CD2 complex, whereas stimulation with single anti-CD2 mAb had minimal effect. Using glutathione S-transferase (GST) fusion proteins, we found that CD2 bound to the Src homology (SH) 3 domain of Fyn. Interestingly, the CD2-Fyn association was negatively regulated by the Fyn SH2 domain; CD2 bound poorly to GST fusion proteins expressing both the SH2 and SH3 domains of Fyn. However, the inhibitory effect of the Fyn SH2 domain on binding of the Fyn SH3 domain to CD2 was relieved by peptides containing a phosphorylated YEEI sequence that bound directly to the Fyn SH2 domain. In addition, we found that the ability of the Fyn SH2 domain to precipitate tyrosine-phosphorylated proteins, including the CD3zeta chain, was enhanced after T cell stimulation with mitogenic pairs of CD2 mAbs. Finally, overexpression of a mutated Fyn molecule, in which the ability of the Fyn SH2 domain to bind phosphotyrosine-containing proteins was abrogated, inhibited CD2-induced transcriptional activation of the nuclear factor of activated T cells (NFAT), suggesting a functional involvement of the Fyn SH2 domain in CD2-induced T cell signaling. We thus propose that stimulation through the CD2 receptor leads to the tyrosine phosphorylation of intracellular proteins, including CD3zeta itself, which in turn bind to the Fyn-SH2 domain, allowing the direct association of the Fyn SH3 domain with CD2 and the initiation of downstream signaling events.

    The Journal of biological chemistry 1998;273;31;19914-21

  • Tyrosine-614, the major autophosphorylation site of the receptor tyrosine kinase HEK2, functions as multi-docking site for SH2-domain mediated interactions.

    Hock B, Böhme B, Karn T, Feller S, Rübsamen-Waigmann H and Strebhardt K

    Chemotherapeutisches Forschungsinstitut, Georg-Speyer-Haus, Frankfurt, Germany.

    HEK2 belongs to the family of EPH-related receptor tyrosine kinases (RTK) which are involved in axonal pathfinding and the formation of the embryonic body plan. The knowledge about intracellular pathways of signal transduction mediated by EPH-related receptors is still limited. Many of the known key players of cellular signalling contain Src homology 2 (SH2) domains, which recognize phosphotyrosine motifs in RTKs. Thus, we examined the interactions of various SH2-containing molecules like PLC-gamma1, rasGAP, p85 subunit of PI3-kinase, Src, Fyn, Crk, Nck, Grb2 and Shc with HEK2 using in vitro binding assays, immunoprecipitations and yeast Two-Hybrid assays. We found that rasGAP, Crk and Fyn bind in a SH2-dependent manner to autophosphorylated HEK2. rasGAP, which contains two SH2- and one SH3-domain, was shown to associate with its N-terminal SH2-domain to HEK2. Furthermore, we demonstrated that a single amino acid substitution (Y614F) clearly reduces the phosphotyrosine content of HEK2 and abrogates its ability to bind rasGAP, Crk and Fyn indicating that this residue functions as major phosphorylation and multi-docking site. The conservation of this predicted binding site among various EPH-related RTKs provides evidence that Fyn, Crk and rasGAP are key players in signal transduction of at least a subset of these receptors.

    Oncogene 1998;17;2;255-60

  • Association of the Src family tyrosine kinase Fyn with TrkB.

    Iwasaki Y, Gay B, Wada K and Koizumi S

    Novartis Pharma K.K., Research Department, Takarazuka Research Institute, Japan.

    Fyn tyrosine kinase, a member of the Src family, was recently reported to be present in neurons and glia cells. We investigated whether Fyn is involved in the Trk-dependent signal transduction pathways of neurotrophin. The Fyn-Src homology domain 2 (SH2) was observed to associate in vitro with the intracellular domain of TrkB (ICD-TrkB). This association was dependent on the autophosphorylation of ICD-TrkB. The Fyn-SH2 domains bound to phosphorylated ICD-TrkB (pICD-TrkB) with an affinity similar to the binding of phospholipase Cgamma (PLCgamma)-SH2 domains to its autophosphorylation site in TrkB. The Src-SH2 domains showed substantially lower affinity with pICD-TrkB, suggesting that the association between Fyn-SH2 and pICD-TrkB is not due to nonspecific interactions of SH2 domains with phosphorylated tyrosine residues. This is further supported by the observation that Fyn-SH2 was able to trap phosphorylated TrkB in cell lysate prepared from primary rat cortical neurons stimulated with brain-derived neurotrophic factor (BDNF). In contrast, endogenous Fyn was coprecipitated with TrkB from cortical neurons without BDNF stimulation. This basal association showed a threefold increase on BDNF stimulation, probably due to the SH2/phosphotyrosine interaction that was observed in the cell-free system. All these data suggest the involvement of Fyn in the neurotrophin signal transduction pathways downstream of TrkB.

    Journal of neurochemistry 1998;71;1;106-11

  • T cell activation through the CD43 molecule leads to Vav tyrosine phosphorylation and mitogen-activated protein kinase pathway activation.

    Pedraza-Alva G, Mérida LB, Burakoff SJ and Rosenstein Y

    Instituto de Biotecnología/UNAM, APDO. Postal 510-3 Cuernavaca, Morelos, 62250, México.

    CD43, the most abundant membrane protein of T lymphocytes, is able to initiate signals that lead to Ca2+ mobilization and interleukin-2 production, yet the molecular events involved in signal transduction pathway of the CD43 molecule are only beginning to be understood. We have shown recently that cross-linking CD43 on the cell surface of human T lymphocytes with the anti-CD43 monoclonal antibody L10 leads to CD43-Fyn kinase interactions and to Fyn phosphorylation on tyrosine residues. This interaction seems to be mediated by the SH3 domain of Fyn and a proline-rich sequence located in the cytoplasmic domain of CD43. Here we show that CD43-specific activation of human T lymphocytes induced tyrosine phosphorylation of the adaptor protein Shc and of the guanine exchange factor Vav, as well as the formation of a macromolecular complex that comprises Shc, GRB2, and Vav. CD43 ligation resulted in enhanced formation of Vav.SLP-76 complexes and in the activation and nuclear translocation of ERK2. Cross-linking of the CD43 molecule in 3T3-CD43(+) cells induced luciferase activity from a construct under the control of the Fos serum responsive element. Altogether, these data suggest that the mitogen-activated protein kinase pathway is involved in CD43-dependent interleukin-2 gene expression.

    The Journal of biological chemistry 1998;273;23;14218-24

  • CD44 selectively associates with active Src family protein tyrosine kinases Lck and Fyn in glycosphingolipid-rich plasma membrane domains of human peripheral blood lymphocytes.

    Ilangumaran S, Briol A and Hoessli DC

    Department of Pathology, Centre Médical Universitaire, Geneva, Switzerland.

    CD44 is the major cell surface receptor for the extracellular matrix glycosaminoglycan hyaluronan and is implicated in a variety of biological events that include embryonic morphogenesis, lymphocyte recirculation, inflammation, and tumor metastasis. CD44 delivers activation signals to T lymphocytes, B lymphocytes, natural killer cells, polymorphonuclear leukocytes, and macrophages by stimulating protein tyrosine phosphorylation and calcium influx. The mechanism of signal transduction via CD44 remains undefined, although CD44 was shown to physically associate with intracellular protein tyrosine kinase Lck in T lymphocytes. In the present report, we show that a significant proportion of CD44 in human peripheral blood T lymphocytes and endothelial cells is associated with low-density plasma membrane fractions that represent specialized plasma membrane domains enriched in glycosphingolipids and glycosylphosphatidylinositol (GPI)-anchored proteins. CD44 and the GPI-anchored CD59 do not appear to directly interact in the low-density membrane fractions. In human peripheral blood T lymphocytes, 20% to 30% of the Src family protein tyrosine kinases, Lck and Fyn, are recovered from these fractions. CD44-associated protein kinase activity was selectively recovered from the low-density membrane fractions, corresponding to glycosphingolipid-rich plasma membrane microdomains. Reprecipitation of the in vitro phosphorylated proteins showed that CD44 associates not only with Lck but also with Fyn kinase in these membrane domains. Our results suggest that cellular stimulation via CD44 may proceed through the signaling machinery of glycosphingolipid-enriched plasma membrane microdomains and, hence, depend on the functional integrity of such domains.

    Blood 1998;91;10;3901-8

  • Signal-dependent translation of a regulatory protein, Bcl-3, in activated human platelets.

    Weyrich AS, Dixon DA, Pabla R, Elstad MR, McIntyre TM, Prescott SM and Zimmerman GA

    Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA. andrew_weyrich@gatormail.cvrti.utah.edu

    Circulating human platelets lack nuclei, cannot synthesize mRNA, and are considered incapable of regulated protein synthesis. We found that thrombin-activated, but not resting, platelets synthesize Bcl-3, a member of the IkappaB-alpha family of regulatory proteins. The time- and concentration-dependent generation of Bcl-3 in platelets signaled by thrombin was blocked by translational inhibitors, by rapamycin, and by inhibitors of phosphatidylinositol-3-kinase, indicating that it occurs via a specialized translational control pathway that involves phosphorylation of the inhibitory protein 4E-BP1. After its synthesis in activated platelets Bcl-3 binds to the SH3 domain of Fyn (p59(fyn)), a Src-related tyrosine kinase. This, along with its expression in anucleate cells, suggests that Bcl-3 has previously unrecognized functions aside from modulation of transcription. We also demonstrate that platelets synthesize and secrete numerous proteins besides Bcl-3 after they adhere to fibrinogen, which mediates adhesion and outside-in signaling of these cells by engagement of alphaIIb/beta3 integrin. Taken together, these data demonstrate that regulated synthesis of proteins is a signal-dependent activation response of human platelets.

    Funded by: NHLBI NIH HHS: HL44525, HL56713, R01 HL044525, R37 HL044525

    Proceedings of the National Academy of Sciences of the United States of America 1998;95;10;5556-61

  • Complex formation between EphB2 and Src requires phosphorylation of tyrosine 611 in the EphB2 juxtamembrane region.

    Zisch AH, Kalo MS, Chong LD and Pasquale EB

    The Burnham Institute, La Jolla, California 92037, USA.

    The cellular components of the neuronal signaling pathways of Eph receptor tyrosine kinases are only beginning to be elucidated. Here we show that in vivo tyrosine phosphorylation sites of the Eph receptors EphA3, EphA4, and EphB2 in embryonic retina serve as binding sites for the Src-homology 2 (SH2) domain of Src kinase. Furthermore, tyrosine-phosphorylated EphB2 was detected in Src immunoprecipitates from transfected Cos cells, indicating that EphB2 and Src can physically associate. Interestingly, a form of Src with reduced electrophoretic mobility and increased tyrosine phosphorylation was detected in Cos cells expressing tyrosine-phosphorylated EphB2, suggesting a functional interaction between EphB2 and Src. Yeast two-hybrid analysis in conjunction with site-directed mutagenesis demonstrated that phosphorylated tyrosine 611 in the juxtamembrane region of EphB2 is crucial for the interaction with the SH2 domain of Src. In contrast, binding of the carboxy-terminal SH2 domain of phospholipase Cgamma was not abolished upon mutation of tyrosine 611 in EphB2. Phosphopeptide mapping of autophosphorylated full-length EphB2, and wild-type and tyrosine to phenylalanine mutants of the EphB2 cytoplasmic domain fused to LexA, showed tyrosine 611 in the sequence motif YEDP as a major site of autophosphorylation in EphB2. Our mutational analysis also indicated that tyrosines 605 and 611 are important for EphB2 kinase activity. We propose Src kinase as a downstream effector that mediates the neuron's response to Eph receptor activation.

    Funded by: NEI NIH HHS: EY105576; NICHD NIH HHS: HD25938

    Oncogene 1998;16;20;2657-70

  • Cortactin-Src kinase signaling pathway is involved in N-syndecan-dependent neurite outgrowth.

    Kinnunen T, Kaksonen M, Saarinen J, Kalkkinen N, Peng HB and Rauvala H

    Laboratory of Molecular Neurobiology, Institute of Biotechnology, University of Helsinki, P. O. Box 56, 00014 Helsinki, Finland.

    N-syndecan (syndecan-3) was previously isolated as a cell surface receptor for heparin-binding growth-associated molecule (HB-GAM) and suggested to mediate the neurite growth-promoting signal from cell matrix-bound HB-GAM to the cytoskeleton of neurites. However, it is unclear whether N-syndecan would possess independent signaling capacity in neurite growth or in related cell differentiation phenomena. In the present study, we have transfected N18 neuroblastoma cells with a rat N-syndecan cDNA and show that N-syndecan transfection clearly enhances HB-GAM-dependent neurite growth and that the transfected N-syndecan distributes to the growth cones and the filopodia of the neurites. The N-syndecan-dependent neurite outgrowth is inhibited by the tyrosine kinase inhibitors herbimycin A and PP1. Biochemical studies show that a kinase activity, together with its substrate(s), binds specifically to the cytosolic moiety of N-syndecan immobilized to an affinity column. Western blotting reveals both c-Src and Fyn in the active fractions. In addition, cortactin, tubulin, and a 30-kDa protein are identified in the kinase-active fractions that bind to the cytosolic moiety of N-syndecan. Ligation of N-syndecan in the transfected cells by HB-GAM increases phosphorylation of c-Src and cortactin. We suggest that N-syndecan binds a protein complex containing Src family tyrosine kinases and their substrates and that N-syndecan acts as a neurite outgrowth receptor via the Src kinase-cortactin pathway.

    The Journal of biological chemistry 1998;273;17;10702-8

  • Coordinated regulation of the tyrosine phosphorylation of Cbl by Fyn and Syk tyrosine kinases.

    Deckert M, Elly C, Altman A and Liu YC

    Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA.

    Cross-linking of the T cell antigen receptor (TCR)-CD3 complex induces rapid tyrosine phosphorylation and activation of Src (Lck and Fyn) and Syk (Syk and Zap-70) family protein tyrosine kinases (PTKs) which, in turn, phosphorylate multiple intracellular substrates. Cbl is a prominent PTK substrate suggesting a pivotal role for it in early signal transduction events. However, the regulation of Cbl function and tyrosine phosphorylation in T cells by upstream PTKs remains poorly understood. In the present study, we used genetic and biochemical approaches to demonstrate that Cbl directly interacts with Syk and Fyn via its N-terminal and C-terminal regions, respectively. Tyr-316 of Syk was required for the interaction with Cbl as well as for the maximal tyrosine phosphorylation of Cbl. However, both wild-type Syk and Y316F-mutated Syk phosphorylated equally well the C-terminal fragment of Cbl in vivo, suggesting the existence of an alternative, N terminus-independent mechanism for the Syk-induced tyrosine phosphorylation of Cbl. This mechanism appears to involve Fyn, since, in addition to its association with the C-terminal region of Cbl, Fyn also associated with Syk and enhanced the Syk-induced tyrosine phosphorylation of Cbl. These findings implicate Fyn as an adaptor protein that facilitates the interaction between Syk and Cbl, and suggest that Src and Syk family PTKs coordinately regulate the tyrosine phosphorylation of Cbl.

    Funded by: NCI NIH HHS: CA35299; NIGMS NIH HHS: GM50819

    The Journal of biological chemistry 1998;273;15;8867-74

  • Physical and functional interactions between receptor-like protein-tyrosine phosphatase alpha and p59fyn.

    Bhandari V, Lim KL and Pallen CJ

    Cell Regulation Laboratory, Institute of Molecular and Cell Biology, National University of Singapore, 30 Medical Drive, Singapore 117609, Republic of Singapore.

    We have examined the in vivo activity of receptor-like protein-tyrosine phosphatase alpha (PTPalpha) toward p59(fyn), a widely expressed Src family kinase. In a coexpression system, PTPalpha effected a dose-dependent tyrosine dephosphorylation and activation of p59(fyn), where maximal dephosphorylation correlated with a 5-fold increase in kinase activity. PTPalpha expression resulted in increased accessibility of the p59(fyn) SH2 domain, consistent with a PTPalpha-mediated dephosphorylation of the regulatory C-terminal tyrosine residue of p59(fyn). No p59(fyn) dephosphorylation was observed with an enzymatically inactive mutant form of PTPalpha or with another receptor-like PTP, CD45. Many enzyme-linked receptors are complexed with their substrates, and we examined whether PTPalpha and p59(fyn) underwent association. Reciprocal immunoprecipitations and assays detected p59(fyn) and an appropriate kinase activity in PTPalpha immunoprecipitates and PTPalpha and PTP activity in p59(fyn) immunoprecipitates. No association between CD45 and p59(fyn) was detected in similar experiments. The PTPalpha-mediated activation of p59(fyn) is not prerequisite for association since wild-type and inactive mutant PTPalpha bound equally well to p59(fyn). Endogenous PTPalpha and p59(fyn) were also found in association in mouse brain. Together, these results demonstrate a physical and functional interaction of PTPalpha and p59(fyn) that may be of importance in PTPalpha-initiated signaling events.

    The Journal of biological chemistry 1998;273;15;8691-8

  • Asymmetrical phosphorylation and function of immunoreceptor tyrosine-based activation motif tyrosines in B cell antigen receptor signal transduction.

    Pao LI, Famiglietti SJ and Cambier JC

    Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO 80206, USA.

    CD79a and CD79b function as transducers of B cell antigen receptor signals via a cytoplasmic sequence, termed the immunoreceptor tyrosine-based activation motif (ITAM). ITAMs contain two conserved tyrosines that may become phosphorylated upon receptor aggregation and bind distinct effectors by virtue of the distinct preference of phosphotyrosyl-containing sequences for SH2 domains. To explore the function of CD79a and CD79b ITAM tyrosines, we created membrane molecules composed of MHC class II I-Ak extracellular and transmembrane domains, and CD79a or CD79b cytoplasmic domains in which one or both of the ITAM tyrosines were mutated to phenylalanine. Functional analysis revealed that both ITAM tyrosines are required for ligand-induced Syk phosphorylation. However CD79a-ITAM and CD79b-ITAM tyrosine phosphorylations were asymmetrical, with >80% of phosphorylation occurring on the N-terminal tyrosine (Y-E-G-L). Thus, these findings suggest that following receptor ligation, only a minor proportion of phosphorylated ITAMs are doubly phosphorylated and thus can engage Syk. Only the N-terminal ITAM tyrosine of CD79a was required for ligand-mediated phosphorylation of the receptor and a subset of downstream substrates, including p62, p110, and Shc, and for Ca2+ mobilization. However, responses mediated through CD79b exhibited a greater dependence on the presence of both tyrosines. Neither tyrosine in CD79a or CD79b appeared absolutely essential for Src family kinase phosphorylation. These results indicate that phosphorylations of the tyro df7 sines in CD79a and CD79b occur with very different stoichiometry, and the respective tyrosyl residues have distinct functions.

    Journal of immunology (Baltimore, Md. : 1950) 1998;160;7;3305-14

  • Identification of sirm, a novel insulin-regulated SH3 binding protein that associates with Grb-2 and FYN.

    Salvatore P, Hanash CR, Kido Y, Imai Y and Accili D

    Developmental Endocrinology Branch, NICHHD, National Institutes of Health, Bethesda, Maryland 20892, USA.

    We have previously developed a mouse model of insulin-resistant diabetes by targeted inactivation of the insulin receptor gene. During studies of gene expression in livers of insulin receptor-deficient mice, we identified a novel cDNA, which we have termed sirm (Son of Insulin Receptor Mutant mice). sirm is largely, albeit not exclusively, expressed in insulin-responsive tissues. Insulin is a potent modulator of sirm expression, and sirm mRNA levels correlate with tissue sensitivity to insulin. The product of the sirm gene is a serine/threonine-rich protein with several proline-rich motifs and an NPNY motif, conforming to the consensus sequence recognized by the phosphotyrosine binding domains of insulin receptor substrate and Shc proteins. However, Sirm bears no extended homologies with other known proteins. Based on the sequences of the proline-rich domains, we sought to determine whether Sirm binds to the SH3 domains of FYN and Grb-2. We demonstrate here that Sirm binds to FYN and Grb-2 in 3T3-L1 adipocytes and that insulin treatment results in the dissociation of the Sirm.FYN and Sirm.Grb-2 complexes. We also show that Sirm is a substrate for the kinase activity of FYN in vitro. Based on the patterns of expression of sirm, its regulation by insulin, and the interactions with molecules in the insulin signaling pathway, we surmise that Sirm plays a role in modulating tissue sensitivity to insulin.

    The Journal of biological chemistry 1998;273;12;6989-97

  • Activation of P2Y2 receptors by UTP and ATP stimulates mitogen-activated kinase activity through a pathway that involves related adhesion focal tyrosine kinase and protein kinase C.

    Soltoff SP, Avraham H, Avraham S and Cantley LC

    Division of Signal Transduction,Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA. ssoltoff@bidmc.harvard.edu

    We examined downstream signaling events that followed the exposure of PC12 cells to extracellular ATP and UTP, and we compared the effects of these P2 receptor agonists with those of growth factors and other stimuli. Based on early findings, we focused particular attention on the mitogen-activated protein (MAP) kinase pathway. ATP and/or UTP produced increases in tyrosine phosphorylation of multiple proteins, including p42 MAP (ERK2) kinase, related adhesion focal tyrosine kinase (RAFTK) (PYK2, CAKbeta), focal adhesion kinase (FAK), Shc, and protein kinase Cdelta (PKCdelta). MAP (ERK2) kinase activity (quantified by substrate phosphorylation) was increased by UTP, ATP, phorbol 12-myristate 13-acetate, ionomycin, and growth factors. UTP and ATP were equipotent (EC50 approximately 25 microM) in stimulating MAP kinase activity, suggesting that these effects were mediated via the Gi-linked P2Y2 (P2U) receptor. Consistent with this, the UTP- and ATP-promoted activation of MAP kinase was diminished in pertussis toxin-treated cells. Treatment of cells with pertussis toxin also reduced both the UTP-dependent increases in intracellular calcium ion concentration ([Ca2+]i) and the tyrosine phosphorylation of RAFTK. Similarly, when [Ca2+]i elevation was prevented using BAPTA and EGTA, the activation of MAP kinase by UTP and ionomycin was blocked, and the tyrosine phosphorylation of RAFTK was reduced. The UTP-promoted increase in MAP kinase activity was partially reduced in cells in which PKC was down-regulated, suggesting that both PKC-dependent and PKC-independent pathways were involved. PKCdelta, which increases MAP kinase activity in some systems, became tyrosine-phosphorylated within 15 s of exposure of cells to ATP or UTP; but epidermal growth factor, nerve growth factor, and insulin had little effect. UTP also promoted the association of Shc with Grb2. These results suggest that the P2Y2 receptor-initiated activation of MAP kinase was dependent on the elevation of [Ca2+]i, involved the recruitment of Shc and Grb2, and was mediated by RAFTK and PKC.

    Funded by: NHLBI NIH HHS: HL55445; NIDCR NIH HHS: DE10877 1f40

    The Journal of biological chemistry 1998;273;5;2653-60

  • The Jak/Stat pathway and urokinase receptor signaling in human aortic vascular smooth muscle cells.

    Dumler I, Weis A, Mayboroda OA, Maasch C, Jerke U, Haller H and Gulba DC

    Franz Volhard Clinic and Max-Delbrück Center for Molecular Medicine, Virchow Klinikum, Humboldt University of Berlin, 13125 Berlin, Germany. dumler@fvk-berlin.de

    The binding of urokinase plasminogen activator (uPA) to its specific receptor (uPAR) facilitates migration of vascular smooth muscle cells (VSMC). However, the signaling cascade utilized by the urokinase receptor is only incompletely understood. We investigated intracellular uPA/uPAR signaling in human aortic VSMC from the cell membrane to the nucleus. uPA binding to VSMC induced a rapid and pronounced increase in tyrosine phosphorylation of several proteins with molecular masses of 53-60, 85-90, and 130-140 kDa. By using co-immunoprecipitation techniques and in vitro kinase assays, the uPAR-associated proteins were identified as Janus (Jak) and Src non-receptor protein-tyrosine kinases (PTK) Jak1, Tyk2, and p59(fyn), p53/56(lyn), p53/59(hck), and p55(fgr). Furthermore, uPA induced a time-dependent reversible translocation of the Stat1 (signal transducer and activator of transcription) protein to the VSMC nuclei, as shown by confocal microscopy studies. Using an electrophoretic mobility shift assay, we then demonstrated that Stat1 is rapidly activated in response to stimulation with uPA and specifically binds to the DNA regulatory elements GAS (interferon-gamma activation site) and ISRE (interferon-stimulated response element). Mobility supershift experiments confirmed DNA-protein complexes containing Stat1 protein. Migration experiments with double immunofluorescence staining revealed polarization of uPAR, and colocalization with Jak1 and Tyk2 to the leading edge of the migrating cells. Under the same conditions, Jak2, Jak3, and the Src-PTKs remained randomly distributed over the entire body of the cells. Our studies therefore suggest that, in VSMC, the uPAR-signaling complex utilizes at least two different mechanisms, a direct signaling pathway utilizing the Jak/Stat cascade and a second signal transduction mechanism via Src-like protein-tyrosine kinases. uPA-induced signaling via Jak/Stat is most likely involved in the regulation of cell migration, while the functional purpose of the uPA-associated Src-PTK activation remains to be elucidated.

    The Journal of biological chemistry 1998;273;1;315-21

  • PDGF-induced phosphorylation of Tyr28 in the N-terminus of Fyn affects Fyn activation.

    Hansen K, Alonso G, Courtneidge SA, Rönnstrand L and Heldin CH

    Ludwig Institute for Cancer Research, Biomedical Center, Uppsala, Sweden.

    Binding of platelet-derived growth factor (PDGF) to its receptors leads to the activation of members of the Src family of protein tyrosine kinases. We show here that Fyn, a member of the Src family, is phosphorylated on Tyr28 in the unique N-terminal part of the molecule after interaction with the intracellular domain of the PDGF beta-receptor. Activated Fyn furthermore undergoes autophosphorylation on Tyr30, Tyr39 and Tyr420. When Fyn mutants with Tyr28, Tyr30 or Tyr39 replaced with phenylalanine residues were transfected into NIH3T3 cells a decreased activation after PDGF stimulation was seen, suggesting a functional importance of the N-terminal tyrosine phosphorylation of Fyn.

    Biochemical and biophysical research communications 1997;241;2;355-62

  • Alpha 4 beta 1 integrin-mediated tyrosine phosphorylation in human T cells: characterization of Crk- and Fyn-associated substrates (pp105, pp115, and human enhancer of filamentation-1) and integrin-dependent activation of p59fyn1.

    Hunter AJ and Shimizu Y

    Department of Laboratory Medicine and Pathology, Center for Immunology, University of Minnesota Medical School, Minneapolis 55455, USA.

    Integrin adhesion receptors transduce signals that transmit information from the extracellular environment to the cell interior. Although integrins lack intrinsic tyrosine kinase activity, stimulation of the alpha 4 beta 1 integrin on human H9 T cells results in rapid tyrosine phosphorylation of proteins in the 105 to 115 kDa range. In this study, we report that alpha 4 integrin stimulation of H9 T cells results in tyrosine phosphorylation of three distinct proteins: pp105, pp115, and human enhancer of filamentation 1 (HEF1), all of which associate with the adapter protein c-Crk. However, pp115 can be distinguished from pp105 and HEF1 by its ability to associate with the SH2 domain of the tyrosine kinase p59fyn. Both pp105 and pp115 are antigenically distinct from HEF1, p130Cas, pp125FAK, Pyk2, p120cbl, and the p110 subunit of phosphatidylinositol 3-kinase. The functional significance of pp115 association with p59fyn is suggested by the ability of alpha 4 integrin stimulation to activate Fyn tyrosine kinase activity. These studies show that alpha 4 integrin stimulation of T cells results in the tyrosine phosphorylation of several distinct substrates. The association of these substrates with intracellular signaling intermediates, such as Crk and Fyn, may play a critical role in integrin-mediated regulation of T cell function.

    Funded by: NIAID NIH HHS: AI07313, AI38474

    Journal of immunology (Baltimore, Md. : 1950) 1997;159;10;4806-14

  • Tyrosine phosphorylation of Crk-associated substrates by focal adhesion kinase. A putative mechanism for the integrin-mediated tyrosine phosphorylation of Crk-associated substrates.

    Tachibana K, Urano T, Fujita H, Ohashi Y, Kamiguchi K, Iwata S, Hirai H and Morimoto C

    Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA. tachiban@mbcrr.harvard.edu

    Integrin-ligand binding induces the tyrosine phosphorylation of various proteins including focal adhesion kinase (pp125(FAK)) and Crk-associated substrate (Cas). FAK is activated and autophosphorylated by the ligation of integrins, although the substrate of FAK has not been revealed. We show here that p130(Cas) and Cas-L are FAK substrates. FAK directly phosphorylates Cas proteins primarily at the YDYVHL sequence that is conserved among all Cas proteins. Furthermore, the phosphorylated YDYVHL sequence is a binding site for Src family protein-tyrosine kinases, and the recruited Src family kinase phosphorylates the other tyrosine residues within Cas. The Cas-L YDYVHL sequence is phosphorylated upon integrin-ligand binding, and this integrin-mediated tyrosine phosphorylation is inhibited by the cotransfection of the FAK COOH-terminal domain that does not contain a kinase domain. These findings strongly suggest that FAK initiates integrin-mediated tyrosine phosphorylation of Cas proteins; then, Src family tyrosine kinases, which are recruited to phosphorylated Cas and FAK, further phosphorylate Cas proteins.

    Funded by: NIAID NIH HHS: AI-29530; NIAMS NIH HHS: AR-33713

    The Journal of biological chemistry 1997;272;46;29083-90

  • Signals transduced through the CD4 molecule interfere with TCR/CD3-mediated ras activation leading to T cell anergy/apoptosis.

    Tamma SM, Chirmule N, McCloskey TW, Oyaizu N, Kalyanaraman VS and Pahwa S

    Department of Pediatrics, North Shore University Hospital-New York University School of Medicine, Manhasset, New York 11030, USA.

    It has been previously demonstrated that the occupancy of CD4 molecules by the HIV-1 envelope glycoprotein gp120 results in marked inhibition of T cell receptor-CD3 complex (TCR/CD3) activation-induced IL-2 secretion. To elucidate the mechanism of inhibitory effects of gp160 on T cell signaling, we have investigated the intracellular biochemical events and biological output in response to anti-CD3 mAb activation of purified peripheral blood CD4+ T cells from healthy donors with and without prior exposure to HIV-1 gp160. Pretreatment with gp160 resulted in marked inhibition of tyrosine phosphorylation of p59(fyn), PLC-gamma1, ras activation, and TNF-alpha secretion in anti-CD3 mAb activated CD4+ T cells, and a subset of CD4+ cells underwent activation-induced cell death. The data presented here provide insight into the mechanism by which the interaction of HIV-1 envelope glycoproteins with CD4 molecules may alter TCR/CD3-activation-induced signal transduction resulting in anergy and apoptosis with consequent functional deficiency of CD4+ T cells.

    Funded by: NIAID NIH HHS: AI28281; NIDA NIH HHS: DA 05161

    Clinical immunology and immunopathology 1997;85;2;195-201

  • A novel ligand for an SH3 domain of the adaptor protein Nck bears an SH2 domain and nuclear signaling motifs.

    Matuoka K, Miki H, Takahashi K and Takenawa T

    Department of Biosignal Research, Tokyo Metropolitan Institute of Gerontology, Japan.

    Nck is a small protein composed of Src homology regions (SH) 2 and 3, paralleling the adaptors c-Crk and Grb2/Ash, but its function remains enigmatic. To clarify Nck signaling, a human brain cDNA library was searched for targets of the SH3 moiety of Nck. A novel molecule detected therefrom (referred to as Nck-, Ash- and phospholipase Cgamma-binding protein 4) contained proline-rich sequences and, through the function of one of them, interacted with the middle SH3 domain of Nck. A NAP4 fusion peptide exhibited an affinity for Nck, Ash and phospholipase Cgamma in whole cell lysates. NAP4 also had an SH2 domain, which could bind to activated EGF receptor. These intermolecular interactions imply the intricacy of Nck-mediated signaling around the receptor protein-tyrosine kinases. In addition, NAP4 bore a putative nuclear localization signal and a Q-run/P-run composite, both characteristic of nuclear proteins, and might therefore relate to the presence of Nck in the cellular nucleus.

    Biochemical and biophysical research communications 1997;239;2;488-92

  • The crystal structure of HIV-1 Nef protein bound to the Fyn kinase SH3 domain suggests a role for this complex in altered T cell receptor signaling.

    Arold S, Franken P, Strub MP, Hoh F, Benichou S, Benarous R and Dumas C

    Centre de Biochimie Structurale, UMR C9955 CNRS, U414 INSERM, Université Montpellier I, Faculté de Pharmacie, France.

    Background: Human immunodeficiency virus (HIV) Nef protein accelerates virulent progression of acquired immunodeficiency syndrome (AIDS) by its interaction with specific cellular proteins involved in signal transduction and host cell activation. Nef has been shown to bind specifically to a subset of the Src family of kinases. The structures of free Nef and Nef bound to Src homology region 3 (SH3) domain are important for the elucidation of how the affinity and specificity for the Src kinase family SH3 domains are achieved, and also for the development of potential drugs and vaccines against AIDS.

    Results: We have determined the crystal structures of the conserved core of HIV-1 Nef protein alone and in complex with the wild-type SH3 domain of the p59fyn protein tyrosine kinase (Fyn), at 3.0 A resolution. Comparison of the bound and unbound Nef structures revealed that a proline-rich motif (Pro-x-x-Pro), which is implicated in SH3 binding, is partially disordered in the absence of the binding partner; this motif only fully adopts a left-handed polyproline type II helix conformation upon complex formation with the Fyn SH3 domain. In addition, the structures show how an arginine residue (Arg77) of Nef interacts with Asp 100 of the so-called RT loop within the Fyn SH3 domain, and triggers a hydrogen-bond rearrangement which allows the loop to adapt to complement the Nef surface. The Arg96 residue of the Fyn SH3 domain is specifically accommodated in the same hydrophobic pocket of Nef as the isoleucine residue of a previously described Fyn SH3 (Arg96-->lle) mutant that binds to Nef with higher affinity than the wild type.

    Conclusions: The three-dimensional structures support evidence that the Nef-Fyn complex forms in vivo and may have a crucial role in the T cell perturbating action of Nef by altering T cell receptor signaling. The structures of bound and unbound Nef reveal that the multivalency of SH3 binding may be achieved by a ligand induced flexibility in the RT loop. The structures suggest possible targets for the design of inhibitors which specifically block Nef-SH3 interactions.

    Structure (London, England : 1993) 1997;5;10;1361-72

  • The SH2 domain from the tyrosine kinase Fyn in complex with a phosphotyrosyl peptide reveals insights into domain stability and binding specificity.

    Mulhern TD, Shaw GL, Morton CJ, Day AJ and Campbell ID

    Oxford Centre for Molecular Sciences, UK.

    Background: SH2 domains are found in a variety of signal transduction proteins; they bind phosphotyrosine-containing sequences, allowing them to both recognize target molecules and regulate intramolecular kinase activity. Fyn is a member of the Src family of tyrosine kinases that are involved in signal transduction by association with a number of membrane receptors. The kinase activity of these signalling proteins is modulated by switching the binding mode of their SH2 and SH3 domains from intramolecular to intermolecular. The molecular basis of the signalling roles observed for different Src family members is still not well understood; although structures have been determined for the SH2 domains of other Src family molecules, this is the first structure of the Fyn SH2 domain.

    Results: The structure of the Fyn SH2 domain in complex with a phosphotyrosyl peptide (EPQpYEEIPIYL) was determined by high resolution NMR spectroscopy. The overall structure of the complex is analogous to that of other SH2-peptide complexes. Noteworthy aspects of the structure are: the BG loop, which contacts the bound peptide, contains a type-I' turn; a capping-box-like interaction is present at the N-terminal end of helix alpha A; cis-trans isomerization of the Val beta G1-Pro beta G2 peptide bond causes conformational heterogeneity of residues near the N and C termini of the domain.

    Conclusions: Comparison of the Fyn SH2 domain structure with other structures of SH2 domains highlights several interesting features. Conservation of helix capping interactions among various SH2 domains is suggestive of a role in protein stabilisation. The presence of a type-I' turn in the BG loop, which is dependent on the presence of a glycine residue at position BG3, is indicative of a binding pocket, characteristic of the Src family, SykC and Abl, rather than a binding groove found in PLC-gamma 1C, p85 alpha N and Shc, for example.

    Funded by: Wellcome Trust

    Structure (London, England : 1993) 1997;5;10;1313-23

  • Co-localization of Fyn with CD3 complex, CD45 or CD28 depends on different mechanisms.

    zur Hausen JD, Burn P and Amrein KE

    Roche Research Center, Hoffmann-La Roche Inc., Nutley, USA.

    The Src family protein tyrosine kinase Fyn (p59fyn) plays an important role in thymocyte development and T cell receptor (TCR) signal transduction. Fyn has been shown to associate with the TCR-CD3 complex, the protein tyrosine phosphatase CD45 and several co-receptors such as CD28 which are crucial for initiating T cell activation and proliferation. The molecular basis of how Fyn is associated with these transmembrane proteins is largely unknown. To investigate the Fyn association with the TCR-CD3 complex, CD45 and CD28 at the molecular level, various Fyn/beta-galactosidase fusion proteins were constructed and expressed in Jurkat cells. Co-localization experiments applying antibody-induced co-capping and double immunofluorescence staining techniques were used to study the association of these fusion proteins with the TCR-CD3 complex, CD45 and CD28. Our results revealed that co-localization of Fyn with the TCR-CD3 complex requires the unique N terminus whereas co-localization with CD45 depends on the unique N terminus, the Src homology (SH)3- and a functional SH2 domain. CD28 co-localizes with Fyn molecules that contain the N terminus and a functional SH2 domain. These results suggest that Fyn association with the TCR-CD3 complex, CD45 and CD28 is mediated by different molecular mechanisms.

    European journal of immunology 1997;27;10;2643-9

  • A novel association of Fc receptor gamma-chain with glycoprotein VI and their co-expression as a collagen receptor in human platelets.

    Tsuji M, Ezumi Y, Arai M and Takayama H

    Department of Hematology and Oncology, Clinical Sciences for Pathological Organs, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawaramachi, Sakyo-ku, Kyoto 606-01, Japan.

    The mechanism by which occupancy of collagen receptors is coupled to platelet activation has been uncertain. Our group previously demonstrated that glycoprotein (GP) VI, an uncharacterized platelet membrane protein, is specifically required for collagen-platelet interaction leading to activation of protein-tyrosine kinase Syk. Since collagen stimulation of platelets has recently been found to induce tyrosine phosphorylation of Fc receptor (FcR) gamma-chain, a signal-generating subunit of FcR, we further investigated the relationships between FcR gamma-chain and GPVI in human platelets. Our present study revealed the following. FcR gamma-chain was physically and stably associated with GPVI in human platelets; both FcR gamma-chain and GPVI were proportionally absent in GPVI-deficient platelets; GPVI cross-linking or collagen stimulation of platelets resulted in tyrosine phosphorylation of GPVI-associated FcR gamma-chain accompanied by Syk association and activation. These findings strongly suggest that the associated complex of GPVI and FcR gamma-chain is a collagen receptor featuring the signaling through immune receptors.

    The Journal of biological chemistry 1997;272;38;23528-31

  • CD4 cross-linking (CD4XL) induces RAS activation and tumor necrosis factor-alpha secretion in CD4+ T cells.

    Tamma SM, Chirmule N, Yagura H, Oyaizu N, Kalyanaraman V and Pahwa S

    Department of Pediatrics, North Shore University Hospital, New York University School of Medicine, Manhasset, NY 11030, USA.

    CD4 molecules are the primary receptors for human immunodeficiency virus (HIV) and bind the envelope glycoprotein gp120 of HIV with high-affinity. We have previously shown that cross-linking of CD4 molecules (CD4XL) in normal peripheral blood mononuclear cells (PBMC) results in secretion of cytokines tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), but not of interleukin-2 (IL-2) or IL-4. To investigate the intracellular signaling events associated with CD4-gp120 interaction, we incubated CD4+ T cells from peripheral blood of HIV-negative healthy donors with HIV envelope protein gp160 alone or performed CD4XL with gp160 and anti-gp160 antibody. This procedure resulted in tyrosine phosphorylation of intracellular substrates p59fyn, zap 70, and p95vav and also led to ras activation, as assessed by conversion of rasGDP to rasGTP. The role of ras in CD4 signaling was further investigated using CD4+ Jurkat cells transfected with a dominant negative ras mutant. CD4+ T cells expressing dn-ras secreted significantly reduced levels of TNF-alpha in response to CD4XL. These studies indicate that interaction of HIV gp160 with CD4 molecules activates the ras pathway in T cells, which may result in the cells becoming unresponsive to subsequent stimulation.

    Funded by: NIAID NIH HHS: AI 128281; NIDA NIH HHS: DA 05161

    Blood 1997;90;4;1588-93

  • Cloning of a novel T-cell protein FYB that binds FYN and SH2-domain-containing leukocyte protein 76 and modulates interleukin 2 production.

    da Silva AJ, Li Z, de Vera C, Canto E, Findell P and Rudd CE

    Division of Tumor Immunology, Dana-Farber Cancer Institute, Harvard Medical School, Boston MA 02115, USA.

    T cell receptor zeta (TcRzeta)/CD3 ligation initiates a signaling cascade that involves src kinases p56(lck) and zeta-associated protein 70, leading to the phosphorylation of substrates such as TcRzeta, Vav, SH2-domain-containing leukocyte protein 76 (SLP-76), cbl, and p120/130. FYN binding protein (FYB or p120/130) associates with p59(fyn), the TcRzeta/CD3 complex, and becomes tyrosine-phosphorylated in response to receptor ligation. In this study, we report the cDNA cloning of human and murine FYB and show that it is restricted in expression to T cells and myeloid cells and possesses an overall unique hydrophilic sequence with several tyrosine-based motifs, proline-based type I and type II SH3 domain binding motifs, several putative lysine/glutamic acid-rich nuclear localization motifs, and a SH3-like domain. In addition to binding the src kinase p59(fyn), FYB binds specifically to the hematopoietic signaling protein SLP-76, an interaction mediated by the SLP-76 SH2 domain. In keeping with this, expression of FYB augmented interleukin 2 secretion from a T cell hybridoma, DC27.10, in response to TcRzeta/CD3 ligation. FYB is therefore a novel hematopoietic protein that acts as a component of the FYN and SLP-76 signaling cascades in T cells.

    Proceedings of the National Academy of Sciences of the United States of America 1997;94;14;7493-8

  • Binding of src-like kinases to the beta-subunit of the interleukin-3 receptor.

    Burton EA, Hunter S, Wu SC and Anderson SM

    University of Colorado Health Sciences Center, Department of Pathology, Denver, Colorado 80262, USA.

    We have previously shown that stimulation of 32D cl3 cells with interleukin (IL)-3 results in the activation of three src-like tyrosine kinases, fyn, hck, and lyn. The beta subunit of the IL-3 receptor co-immunoprecipitated with hck in lysates of both unstimulated and IL-3-stimulated cells; however, the beta subunit did not precipitate with either fyn or lyn. The association of these three kinases with the beta subunit of the IL-3 receptor was further investigated using bacterial fusion proteins encoding the unique, SH3, and SH2 domains of these three kinases. Fusion proteins of both hck and fyn bound to a 150-kDa tyrosine-phosphorylated protein present in lysates of IL-3-stimulated cells. This protein was identified as the beta subunit of the IL-3 receptor by immunoblotting with an anti-beta antibody. Glutathione S-transferase (GST) fusion proteins containing the SH2 domain of hck bound to the beta subunit although the amount of beta subunit that bound to the SH2 domain alone was only 30% of that which bound to the fusion protein containing the unique, SH3, and SH2 domains. This indicates that the SH2 domain is one of the motifs involved in binding hck to the beta subunit. A GST fusion protein encoding a 236-amino acid region of the cytoplasmic tail of the beta subunit, which contained four tyrosine residues, bound to hck and fyn. Binding to both proteins was dramatically increased when the GST-beta fusion protein was tyrosine-phosphorylated. Far Western blot analysis was used to demonstrate the binding of the unique, SH3, and SH2 domains of hck to this 236-amino acid region of the beta subunit; tyrosine phosphorylation of this protein increased the binding of both the unique region and the SH2 domain probes. These data indicate that binding of hck to the beta subunit is mediated by both phosphotyrosine-dependent and -independent mechanisms.

    The Journal of biological chemistry 1997;272;26;16189-95

  • Molecular cloning of SKAP55, a novel protein that associates with the protein tyrosine kinase p59fyn in human T-lymphocytes.

    Marie-Cardine A, Bruyns E, Eckerskorn C, Kirchgessner H, Meuer SC and Schraven B

    Ruprecht-Karls University Heidelberg, Institute of Immunology, 69120 Heidelberg, Germany. m71@ix.urz.uni-heidelberg/de

    In human T-lymphocytes the Src family protein tyrosine kinase p59(fyn) associates with three phosphoproteins of 43, 55, and 85 kDa (pp43, pp55, and pp85). Employing a GST-Fyn-Src homology 2 (SH2) domain fusion protein pp55 was purified from lysates of Jurkat T-cells. Molecular cloning of the pp55 cDNA reveals that the pp55 gene codes for a so far nondescribed polypeptide of 359 amino acids that comprises a pleckstrin homology domain, a C-terminal SH3 domain, as well as several potential tyrosine phosphorylation sites, among which one fulfills the criteria to bind Src-like SH2 domains with high affinity. Consistent with this observation, pp55 selectively binds to isolated SH2 domains of Lck, Lyn, Src, and Fyn but not to the SH2 domains of ZAP70, Syk, Shc, SLP-76, Grb2, phosphatidylinositol 3-kinase, and c-abl in vitro. Based on these properties the protein was termed SKAP55 (src kinase-associated phosphoprotein of 55 kDa). Northern blot analysis shows that SKAP55 mRNA is preferentially expressed in lymphatic tissues. SKAP55 is detected in resting human T-lymphocytes as a constitutively tyrosine phosphorylated protein that selectively interacts with p59(fyn). These data suggest that SKAP55 represents a novel adaptor protein likely involved in Fyn-mediated signaling in human T-lymphocytes.

    The Journal of biological chemistry 1997;272;26;16077-80

  • Regulation of integrin-mediated p130(Cas) tyrosine phosphorylation in human B cells. A role for p59(Fyn) and SHP2.

    Manié SN, Astier A, Haghayeghi N, Canty T, Druker BJ, Hirai H and Freedman AS

    Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115, USA.

    Engagement of beta1 integrins in terminally differentiated human B cell lines, such as ARH-77, leads to prominent tyrosine phosphorylation of the p130 Crk-associated substrate (Cas). Cas regulates the assembly of several SH2 and SH3 domain-containing proteins into signaling complexes, which are potentially involved in the propagation of downstream signals. We demonstrate here that immunoprecipitated Cas from beta1 integrin-stimulated ARH-77 cells was associated with tyrosine kinase and phosphatase activities and that integrin ligation led to the recruitment of at least p59(Fyn) tyrosine kinase and SHP2 tyrosine phosphatase in Cas immune complexes. Cotransfection studies in COS-7 cells further indicated that Fyn/Cas physical interaction and Fyn-mediated Cas phosphorylation required amino acids 638-889 in the C-terminal region of Cas. This sequence contains both c-Src SH2 and SH3 domain-binding motifs. In vitro binding studies using glutathione S-transferase fusion proteins derived from the SH2 or SH3 domains of Fyn suggested that both Fyn domains can participate in Fyn/Cas interaction. These data implicate Fyn and SHP2 as potential modulators of Cas signaling complexes in B cells.

    Funded by: NCI NIH HHS: CA55207, CA66996

    The Journal of biological chemistry 1997;272;25;15636-41

  • Interaction of p59fyn with interferon-activated Jak kinases.

    Uddin S, Sher DA, Alsayed Y, Pons S, Colamonici OR, Fish EN, White MF and Platanias LC

    Department of Medicine, University of Illinois at Chicago and West Side Veterans Affairs Hospital, 60607, USA.

    During IFN alpha stimulation, p59(fyn) associates with the Type I IFNR-associated Tyk-2 kinase in several human hematopoietic cell lines in vivo. This interaction is direct, and is mediated by the SH2 domain in p59(fyn), as shown by binding studies using glutathione-S-transferase fusion proteins and far western blots. Furthermore, in response to IFN alpha-treatment of cells, the SH2 domain of Fyn interacts with the Tyk-2-associated c-cbl proto-oncogene product. In a similar manner, during IFN gamma stimulation, p59(fyn) associates via its SH2 domain with the activated form of the IFN gamma-dependent Jak-2 kinase. These data suggest that p59(fyn) is a common element in IFN alpha and IFN gamma signaling, and is selectively engaged by the Type I or II IFN receptors via specific interactions with distinct Jak kinases.

    Funded by: NCI NIH HHS: CA73381; NIDDK NIH HHS: DK38712, DK43808

    Biochemical and biophysical research communications 1997;235;1;83-8

  • Identification of novel human WW domain-containing proteins by cloning of ligand targets.

    Pirozzi G, McConnell SJ, Uveges AJ, Carter JM, Sparks AB, Kay BK and Fowlkes DM

    Cytogen Corporation, Princeton, New Jersey 08540-5309, USA. gpirozzi@mru3.cytogen.com

    A recently described protein module consisting of 35-40 semiconserved residues, termed the WW domain, has been identified in a number of diverse proteins including dystrophin and Yes-associated protein (YAP). Two putative ligands of YAP, termed WBP-1 and WBP-2, have been found previously to contain several short peptide regions consisting of PPPPY residues (PY motif) that mediate binding to the WW domain of YAP. Although the function(s) of the WW domain remain to be elucidated, these observations strongly support a role for the WW domain in protein-protein interactions. Here we report the isolation of three novel human cDNAs encoding a total of nine WW domains, using a newly developed approach termed COLT (cloning of ligand targets), in which the rapid cloning of modular protein domains is accomplished by screening cDNA expression libraries with specific peptide ligands. Two of the new genes identified appear to be members of a family of proteins, including Rsp5 and Nedd-4, which have ubiquitin-protein ligase activity. In addition, we demonstrate that peptides corresponding to PY and PY-like motifs present in several known signaling or regulatory proteins, including RasGAP, AP-2, p53BP-2 (p53-binding protein-2), interleukin-6 receptor-alpha, chloride channel CLCN5, and epithelial sodium channel ENaC, can selectively bind to certain of these novel WW domains.

    The Journal of biological chemistry 1997;272;23;14611-6

  • Molecular cloning of Fyn-associated molecules in the mouse central nervous system.

    Kai N, Mishina M and Yagi T

    Laboratory of Neurobiology and Behavioral Genetics, National Institute for Physiological Sciences, Myodaiji, Okazaki, Japan. yagi@nips.ac.jp

    Fyn tyrosine kinase is expressed extensively in the central nervous system (CNS) of mammals, and its genetic disruption in mouse displays several behavioral abnormalities with morphological and electrophysiological defects in the brain. To understand the signaling pathways in which Fyn is involved in the CNS, we screened molecules that directly associate with Fyn in neonatal mouse brain by using a two-hybrid yeast system. We isolated five cDNA clones with strong and reproducible Fyn-binding activity. Sequence analyses revealed that three of them are previously reported molecules, SON, tctex-1, and hnRNP K, and that two clones encode novel sequences. The hnRNP K has been shown to associate with Fyn, so our yeast system is appropriate to isolate Fyn-binding molecules. Northern hybridization analyses indicated that all isolated clones are expressed in the mouse brain and that the mRNA levels of the two molecules (tctex-1 and clone 82) change during development in the brain. A full-length cDNA of clone 82 was obtained and its deduced amino acid sequence was homologous to the RNA-binding proteins. Isolation of many Fyn-binding molecules suggest that, in the mouse CNS, Fyn mediates multiple signaling pathways by binding to multiple molecules and that some of these pathways play critical roles in determining a certain type of behavior.

    Journal of neuroscience research 1997;48;5;407-24

  • Tyrosine phosphorylation of Pyk2 is selectively regulated by Fyn during TCR signaling.

    Qian D, Lev S, van Oers NS, Dikic I, Schlessinger J and Weiss A

    Department of Medicine, University of California, San Francisco 94143, USA.

    The Src family protein tyrosine kinases (PTKs), Lck and Fyn, are coexpressed in T cells and perform crucial functions involved in the initiation of T cell antigen receptor (TCR) signal transduction. However, the mechanisms by which Lck and Fyn regulate TCR signaling are still not completely understood. One important question is whether Lck and Fyn have specific targets or only provide functional redundancy during TCR signaling. We have previously shown that Lck plays a major role in the tyrosine phosphorylation of the TCR-zeta chain and the ZAP-70 PTK. In an effort to identify the targets that are specifically regulated by Fyn, we have studied the tyrosine phosphorylation of Pyk2, a recently discovered new member of the focal adhesion kinase family PTK. We demonstrated that Pyk2 was rapidly tyrosine phosphorylated following TCR stimulation. TCR-induced tyrosine phosphorylation of Pyk2 was selectively dependent on Fyn but not Lck. Moreover, in heterologous COS-7 cells, coexpression of Pyk2 with Fyn but not Lck resulted in substantial increases in Pyk2 tyrosine phosphorylation. The selective regulation of Pyk2 tyrosine phosphorylation by Fyn in vivo correlated with the preferential phosphorylation of Pyk2 by Fyn in vitro. Our results demonstrate that Pyk2 is a specific target regulated by Fyn during TCR signaling.

    The Journal of experimental medicine 1997;185;7;1253-9

  • Tyrosine phosphorylation sites at amino acids 239 and 240 of Shc are involved in epidermal growth factor-induced mitogenic signaling that is distinct from Ras/mitogen-activated protein kinase activation.

    Gotoh N, Toyoda M and Shibuya M

    Department of Genetics, Institute of Medical Science, University of Tokyo, Japan.

    Epidermal growth factor (EGF) induces tyrosine phosphorylation of the Shc adapter protein, which plays an important role in EGF-stimulated mitogenesis. Shc stimulates Ras/mitogen-activated protein kinase (MAPK) through forming a complex with Grb2 at the phosphorylated tyrosine (Y) residue 317. In this study, we identified novel phosphorylation sites of Shc, at Y239 and Y240. To define the Shc pathway further, we used NIH 3T3 cells expressing the previously characterized mutant EGF receptor (EGF-R) which lacks all known autophosphorylation sites but retains EGF-stimulated mitogenesis with selective phosphorylation of Shc. We constructed wild-type (WT) or mutant Shc cDNAs in which Y317 or/and Y239 and Y240 are replaced with phenylalanine (F) and introduced them into NIH 3T3 cells expressing WT or mutant EGF-R. In the WT EGF-R-expressing cells, the Y239/240/317F Shc, but not Y317F or Y239/240F Shc, decreased EGF-stimulated cell growth. In the mutant EGF-R-expressing cells, Y317F Shc or Y239/240F Shc decreased EGF-stimulated cell growth significantly, though Y317F was a little more potent than Y239/240F. Although cells expressing the Y317F Shc hardly activated MAPK in response to EGF, cells expressing the Y239/240F Shc fully activated MAPK. In contrast, Y239/240F Shc, but not Y317F Shc, reduced the EGF-induced c-myc message. These results suggest that Shc activates two distinct signaling pathways, Y317 to Ras/MAPK and Y239 and Y240 to another pathway including Myc, and that both are involved in EGF-induced mitogenic signaling.

    Molecular and cellular biology 1997;17;4;1824-31

  • NCAM140 interacts with the focal adhesion kinase p125(fak) and the SRC-related tyrosine kinase p59(fyn).

    Beggs HE, Baragona SC, Hemperly JJ and Maness PF

    Department of Biochemistry, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599-7260, USA.

    Axonal growth cones respond to adhesion molecules and extracellular matrix components by rapid morphological changes and growth rate modification. Neurite outgrowth mediated by the neural cell adhesion molecule (NCAM) requires the src family tyrosine kinase p59(fyn) in nerve growth cones, but the molecular basis for this interaction has not been defined. The NCAM140 isoform, which is found in migrating growth cones, selectively co-immunoprecipitated with p59(fyn) from nonionic detergent (Brij 96) extracts of early postnatal mouse cerebellum and transfected rat B35 neuroblastoma and COS-7 cells. p59(fyn) did not associate significantly with the NCAM180 isoform, which is found at sites of stable neural cell contacts, or with the glycophosphatidylinositol-linked NCAM120 isoform. pp60(c-)src, a tyrosine kinase that promotes neurite growth on the neuronal cell adhesion molecule L1, did not interact with any NCAM isoform. Whereas p59(fyn) was constitutively associated with NCAM140, the focal adhesion kinase p125(fak), a nonreceptor tyrosine kinase known to mediate integrin-dependent signaling, became recruited to the NCAM140-p59(fyn) complex when cells were reacted with antibodies against the extracellular region of NCAM. Treatment of cells with a soluble NCAM fusion protein or with NCAM antibodies caused a rapid and transient increase in tyrosine phosphorylation of p125(fak) and p59(fyn). These results suggest that NCAM140 binding interactions at the cell surface induce the assembly of a molecular complex of NCAM140, p125(fak), and p59(fyn) and activate the catalytic function of these tyrosine kinases, initiating a signaling cascade that may modulate growth cone migration.

    Funded by: NINDS NIH HHS: NS26620

    The Journal of biological chemistry 1997;272;13;8310-9

  • RAFTK, a novel member of the focal adhesion kinase family, is phosphorylated and associates with signaling molecules upon activation of mature T lymphocytes.

    Ganju RK, Hatch WC, Avraham H, Ona MA, Druker B, Avraham S and Groopman JE

    Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.

    The related adhesion focal tyrosine kinase (RAFTK), a recently discovered member of the focal adhesion kinase family, has previously been reported to participate in signal transduction in neuronal cells, megakaryocytes, and B lymphocytes. We have found that RAFTK is constitutively expressed in human T cells and is rapidly phosphorylated upon the activation of the T cell receptor (TCR). This activation also results in an increase in the autophosphorylation and kinase activity of RAFTK. After its stimulation, there was an increase in the association of the src cytoplasmic tyrosine kinase Fyn and the adapter protein Grb2. This association was mediated through the SH2 domains of Fyn and Grb2. RAFTK also co-immunoprecipitates with the SH2 domain of Lck and with the cytoskeletal protein paxillin through its COOH-terminal proline-rich domain. The tyrosine phosphorylation of RAFTK after T cell receptor-mediated stimulation was reduced by the pretreatment of cells with cytochalasin D, suggesting the role of the cytoskeleton in this process. These observations indicate that RAFTK participates in T cell receptor signaling and may act to link signals from the cell surface to the cytoskeleton and thereby affect the host immune response.

    Funded by: NHLBI NIH HHS: HL 43510-07, HL 53745-02, HL 55187-01, R01 HL053745

    The Journal of experimental medicine 1997;185;6;1055-63

  • Rapid plasma membrane anchoring of newly synthesized p59fyn: selective requirement for NH2-terminal myristoylation and palmitoylation at cysteine-3.

    van't Hof W and Resh MD

    Cell Biology and Genetics Program, Sloan-Kettering Institute for Cancer Research, New York, NY 10021, USA.

    The trafficking of Src family proteins after biosynthesis is poorly defined. Here we studied the role of dual fatty acylation with myristate and palmitate in biosynthetic transport of p59fyn. Metabolic labeling of transfected COS or NIH 3T3 cells with [35S]methionine followed by analysis of cytosolic and total membrane fractions showed that Fyn became membrane bound within 5 min after biosynthesis. Newly synthesized Src, however, accumulated in the membranes between 20-60 min. Northern blotting detected Fyn mRNA specifically in soluble polyribosomes and soluble Fyn protein was only detected shortly (1-2 min) after radiolabeling. Use of chimeric Fyn and Src constructs showed that rapid membrane targeting was mediated by the myristoylated NH2-terminal sequence of Fyn and that a cysteine at position 3, but not 6, was essential. Examination of G alpha(o)-, G alpha(s)-, or GAP43-Fyn fusion constructs indicated that rapid membrane anchoring is exclusively conferred by the combination of N-myristoylation plus palmitoylation of cysteine-3. Density gradient analysis colocalized newly synthesized Fyn with plasma membranes. Interestingly, a 10-20-min lag phase was observed between plasma membrane binding and the acquisition of non-ionic detergent insolubility. We propose a model in which synthesis and myristoylation of Fyn occurs on soluble ribosomes, followed by rapid palmitoylation and plasma membrane anchoring, and a slower partitioning into detergent-insoluble membrane subdomains. These results serve to define a novel trafficking pathway for Src family proteins that are regulated by dual fatty acylation.

    The Journal of cell biology 1997;136;5;1023-35

  • Interaction between Sam68 and Src family tyrosine kinases, Fyn and Lck, in T cell receptor signaling.

    Fusaki N, Iwamatsu A, Iwashima M and Fujisawa Ji

    Department of Microbiology, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi-shi, Osaka 570, Japan.

    The Src family protein-tyrosine kinase, Fyn, is associated with the T cell receptor (TCR) and plays an important role in TCR-mediated signaling. We found that a human T cell leukemia virus type 1-infected T cell line, Hayai, overexpressed Fyn. To identify the molecules downstream of Fyn, we analyzed the tyrosine phosphorylation of cellular proteins in the cells. In Hayai, a 68-kDa protein was constitutively tyrosine-phosphorylated. The 68-kDa protein was coimmunoprecipitated with various signaling proteins such as phospholipase C gamma1, the phosphatidylinositol 3-kinase p85 subunit, Grb2, SHP-1, Cbl, and Jak3, implying that the protein might function as an adapter. Purification and microsequencing of this protein revealed that it was the RNA-binding protein, Sam68 (Src associated in mitosis, 68 kDa). Sam68 was associated with the Src homology 2 and 3 domains of Fyn and also those of another Src family kinase, Lck. CD3 cross-linking induced tyrosine phosphorylation of Sam68 in uninfected T cells. These data suggest that Sam68 participates in the signal transduction pathway downstream of TCR-coupled Src family kinases Fyn and Lck in lymphocytes, that is not only in the mitotic pathway downstream of c-Src in fibroblasts.

    The Journal of biological chemistry 1997;272;10;6214-9

  • Identification of a novel contactin-associated transmembrane receptor with multiple domains implicated in protein-protein interactions.

    Peles E, Nativ M, Lustig M, Grumet M, Schilling J, Martinez R, Plowman GD and Schlessinger J

    Sugen, Inc., Redwood City, CA 94063, USA.

    Receptor protein tyrosine phosphatase beta (RPTPbeta) expressed on the surface of glial cells binds to the glycosylphosphatidylinositol (GPI)-anchored recognition molecule contactin on neuronal cells leading to neurite outgrowth. We describe the cloning of a novel contactin-associated transmembrane receptor (p190/Caspr) containing a mosaic of domains implicated in protein-protein interactions. The extracellular domain of Caspr contains a neurophilin/coagulation factor homology domain, a region related to fibrinogen beta/gamma, epidermal growth factor-like repeats, neurexin motifs as well as unique PGY repeats found in a molluscan adhesive protein. The cytoplasmic domain of Caspr contains a proline-rich sequence capable of binding to a subclass of SH3 domains of signaling molecules. Caspr and contactin exist as a complex in rat brain and are bound to each other by means of lateral (cis) interactions in the plasma membrane. We propose that Caspr may function as a signaling component of contactin, enabling recruitment and activation of intracellular signaling pathways in neurons. The binding of RPTPbeta to the contactin-Caspr complex could provide a mechanism for cell-cell communication between glial cells and neurons during development.

    Funded by: NINDS NIH HHS: NS21629

    The EMBO journal 1997;16;5;978-88

  • Lck regulates Vav activation of members of the Rho family of GTPases.

    Han J, Das B, Wei W, Van Aelst L, Mosteller RD, Khosravi-Far R, Westwick JK, Der CJ and Broek D

    Department of Biochemistry and Molecular Biology, Norris Comprehensive Cancer Center, School of Medicine, University of Southern California, Los Angeles 90033, USA.

    Vav is a member of a family of oncogene proteins that share an approximately 250-amino-acid motif called a Dbl homology domain. Paradoxically, Dbl itself and other proteins containing a Dbl domain catalyze GTP-GDP exchange for Rho family proteins, whereas Vav has been reported to catalyze GTP-GDP exchange for Ras proteins. We present Saccharomyces cerevisiae genetic data, in vitro biochemical data, and animal cell biological data indicating that Vav is a guanine nucleotide exchange factor for Rho-related proteins, but in similar genetic and biochemical experiments we fail to find evidence that Vav is a guanine nucleotide exchange factor for Ras. Further, we present data indicating that the Lck kinase activates the guanine nucleotide exchange factor and transforming activity of Vav.

    Molecular and cellular biology 1997;17;3;1346-53

  • Regulation of the low molecular weight phosphotyrosine phosphatase by phosphorylation at tyrosines 131 and 132.

    Tailor P, Gilman J, Williams S, Couture C and Mustelin T

    Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA.

    Activation of resting T lymphocytes is initiated by rapid but transient tyrosine phosphorylation of a number of cellular proteins. Several protein tyrosine kinases and protein tyrosine phosphatases are known to be important for this response. Here we report that normal T lymphocytes express the B isoform of low molecular weight protein tyrosine phosphatase B (LMPTP-B). The cDNA was cloned from Jurkat T cells, and an antiserum was raised against it. LMPTP immunoprecipitated from resting Jurkat T cells was found to be tyrosine phosphorylated. On stimulation of the cells through their T cell antigen receptor, the phosphotyrosine content of LMPTP-B declined rapidly. In co-transfected COS cells, Lck and Fyn caused phosphorylation of LMPTP, whereas Csk, Zap, and Jak2 did not. Most of the phosphate was located at Tyr-131, and some was also located at Tyr-132. Incubation of wild-type LMPTP with Lck and adenosine 5'-O-(thiotriphosphate) caused a 2-fold increase in the activity of LMPTP. Site-directed mutagenesis showed that Tyr-131 is important for the catalytic activity of LMPTP, and that thiophosphorylation of Tyr-131, and to a lesser degree Tyr-132, is responsible for the activation.

    Funded by: NIAID NIH HHS: AI35603; NIGMS NIH HHS: GM48960

    The Journal of biological chemistry 1997;272;9;5371-4

  • A collagen-like peptide stimulates tyrosine phosphorylation of syk and phospholipase C gamma2 in platelets independent of the integrin alpha2beta1.

    Asselin J, Gibbins JM, Achison M, Lee YH, Morton LF, Farndale RW, Barnes MJ and Watson SP

    Department of Pharmacology, University of Oxford, UK.

    Activation of platelets by collagen is mediated through a tyrosine kinase-dependent pathway that is associated with phosphorylation of the Fc receptor gamma chain, the tyrosine kinase syk, and phospholipase C gamma2 (PLC gamma2). We recently described a collagen-related triple-helical peptide (CRP) with the sequence GCP*(GPP*)GCP*G (single letter amino acid code: P* = hydroxyproline; Morton et al, Biochem J306:337, 1995). The cross-linked peptide is a potent stimulus of platelet activation but, unlike collagen, does not support alpha2beta1-mediated, Mg2+-dependent adhesion, suggesting that its action is independent of the integrin alpha2beta1. This finding suggests the existence of a platelet receptor other than alpha2beta1 that underlies activation. In the present study, we show that CRP stimulates tyrosine phosphorylation of the same pattern of proteins in platelets as collagen, including syk and PLC gamma2. Protein tyrosine phosphorylation induced by CRP is not altered in the absence of Mg2+ or the presence of monoclonal antibodies (MoAbs) to the integrin alpha2beta1 (MoAb 6F1 and MoAb 13), conditions that prevent the interaction of collagen with the integrin. In contrast, phosphorylation of syk and PLC gamma2 by collagen is partially reduced by MoAb 6F1 and MoAb 13 or by removal of Mg2+. This may reflect a direct role of alpha2beta1 in collagen-induced signaling events or an indirect role in which the integrin facilitates the binding of collagen to its signaling receptor. The results show an alpha2beta1-independent pathway of platelet activation by CRP that involves phosphorylation of syk and PLC gamma2. This pathway appears to contribute to platelet activation by collagen.

    Funded by: Wellcome Trust

    Blood 1997;89;4;1235-42

  • Regulation of Vav-SLP-76 binding by ZAP-70 and its relevance to TCR zeta/CD3 induction of interleukin-2.

    Raab M, da Silva AJ, Findell PR and Rudd CE

    Division of Tumor Immunology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 0 1010 2115, USA.

    T cell activation stimulates p56(lck), p59(fyn), ZAP-70, Vav-SLP-76 binding, and IL-2 transcription. Major questions concern the tyrosine-kinase and relevant site(s) needed for Vav-SLP-76 complex formation and its role in IL-2 production. Here, we show that of the three kinases, only ZAP-70 phosphorylates SLP-76 at specific sites that allow Vav SH2 domain binding. Therefore, while p56(lck) regulates proximal events, ZAP-70 acts downstream on targets such as SLP-76. We also show by in vitro and in vivo analysis that two SLP-76 pYESP motifs (Y113 and Y128) mediate binding, the first being more efficient. A third pYEPP motif (Y145) failed to bind. Finally, TCR zeta CD3 ligation of T cell hybridoma DC27.10 induces IL-2 production without detectable Vav-SLP-76 binding. Therefore, despite effects of Vav-SLP-76 on IL-2 expression, Vav-SLP-76 binding per se is not essential for IL-2 production in all T cells.

    Funded by: NCI NIH HHS: CA5 1887-06

    Immunity 1997;6;2;155-64

  • The role of a lymphoid-restricted, Grb2-like SH3-SH2-SH3 protein in T cell receptor signaling.

    Trüb T, Frantz JD, Miyazaki M, Band H and Shoelson SE

    Research Division, Joslin Diabetes Center, Boston, Massachusetts 02215, USA.

    We have characterized an SH3-SH2-SH3 linker protein that is prominently expressed in lymphoid tissues. This protein has 58% sequence identity to Grb2. An identical protein called Grap has been found in hematopoietic cells. In Jurkat cells, T cell receptor activation leads to the association of Grap with phosphoproteins p36/38 and, to a lesser degree, Shc. This interaction is mediated by the Grap SH2 domain, which has similar binding specificity to the Grb2 SH2 domain. Grap also associates via its SH3 domains with Sos, the Ras guanine nucleotide exchange factor; with dynamin, a GTPase involved in membrane protein trafficking; and with Sam68, a nuclear RNA-binding protein that serves as a substrate of Src kinases during mitosis. T cell activation effects an increase in Grap association with p36/38, Shc, Sos, and dynamin. Sam68 binding is constitutive. Phospholipase C-gamma1 and Fyn are also found in activated Grap signaling complexes, although these interactions may not be direct. We conclude that Grap is a prominent component of lymphocyte receptor signaling. Based on the known functions of bound effector molecules, Grap-mediated responses to antigen challenge may include endocytosis of the T cell receptor, cellular proliferation, and regulated entry into the cell cycle.

    Funded by: NIAMS NIH HHS: AR36308; NIDDK NIH HHS: DK36836, DK45943; ...

    The Journal of biological chemistry 1997;272;2;894-902

  • HIV glycoprotein gp120 inhibits TCR-CD3-mediated activation of fyn and lck.

    Morio T, Chatila T and Geha RS

    Division of Immunology, Children's Hospital, Boston, MA 02115, USA.

    HIV major glycoprotein gp120 interacts with CD4 molecules and perturbs signaling through the TCR-CD3 complex. We examined the effects of gp120 on TCR-CD3-induced phosphorylation and activation of the src-type protein tyrosine kinases (PTK), fyn and lck. gp120 caused minimal changes in lck phosphorylation or lck enzymatic activity, but preincubation of Jurkat cells with gp120 for 20 min strongly inhibited TCR-CD3-mediated phosphorylation and activation of lck and fyn, as well as phosphorylation of CD3 zeta. Inhibition of TCR-CD3 signaling in T cells preincubated with gp120 was paralleled by inhibition of T cell proliferation to the antigen tetanus toxoid. Neither surface CD4 expression nor CD4-lck association was affected by gp120. Furthermore, gp120 inhibited lck phosphorylation induced by cross-linking of TCR-CD3 and CD4 suggesting that the inhibition of lck phosphorylation could not be simply accounted for by sequestration of CD4 molecules. gp120 selectively enhanced the phosphorylation of the lck peptide containing the autoinhibitory tyrosine residue Tyr505 relative to the lck peptide containing the positive regulatory residue Tyr394, suggesting that a qualitative alteration in lck may underlie the inhibition of TCR-CD3 signaling by gp120.

    Funded by: NIAID NIH HHS: AI-29906

    International immunology 1997;9;1;53-64

  • Lineage- and differentiation stage-specific expression of LSM-1 (LPAP), a possible substrate for CD45, in human hematopoietic cells.

    Shimizu Y, Sugiyama H, Fujii Y, Sasaki K, Inoue K, Ogawa H, Tamaki H, Miyake S, Oji Y, Soma T, Yamagami T, Hirata M, Ikeda K, Monden T and Kishimoto T

    Department of Medicine III, Osaka University Medical School, Japan.

    CD45, a transmembrane tyrosine phosphatase, is found on almost all nucleated hematopoietic cells and plays a crucial role in lymphocyte activation and differentiation. We recently achieved isolation of the human LSM-1 (hLSM-1) gene, whose product is a possible substrate for CD45, and we raised antibodies against the hLSM-1 protein. hLSM-1 expression in hematopoietic cells was examined with Northern and Western blot, fluorescence-activated cell sorter, and immunocytochemical analyses. It was found that in the lymphoid lineage, T and B lymphocytes as well as NK cells expressed LSM-1, whereas terminally differentiated plasma cells did not. As for the myeloid lineage, immature myeloid cells expressed LSM-1, whereas terminally differentiated granulocytes and monocytes did not. In the erythroid lineage, normal erythroblasts expressed very low levels of LSM-1, while erythroid cell lines (K562 and HEL) did not. Megakaryocytes did not express LSM-1. Both CD34+/CD33- and CD34+/CD33+ hematopoietic progenitor cells weakly expressed LSM-1. These results showed that LSM-1 is expressed in a lineage- and differentiation stage-specific fashion.

    American journal of hematology 1997;54;1;1-11

  • Structural and thermodynamic characterization of the interaction of the SH3 domain from Fyn with the proline-rich binding site on the p85 subunit of PI3-kinase.

    Renzoni DA, Pugh DJ, Siligardi G, Das P, Morton CJ, Rossi C, Waterfield MD, Campbell ID and Ladbury JE

    Oxford Centre for Molecular Science, University o 8d7 f Oxford, U.K.

    The interaction of the Fyn SH3 domain with the p85 subunit of PI3-kinase is investigated using structural detail and thermodynamic data. The solution structure complex of the SH3 domain with a proline-rich peptide mimic of the binding site on the p85 subunit is described. This indicates that the peptide binds as a poly(L-proline) type II helix. Circular dichroism spectroscopic studies reveal that in the unbound state the peptide exhibits no structure. Thermodynamic data for the binding of this peptide to the SH3 domain suggest that the weak binding (approximately 31 microM) of this interaction is, in part, due to the entropically unfavorable effect of helix formation (delta S0 = -78 J.mol-1.K-1). Binding of the SH3 domain to the intact p85 subunit (minus its own SH3 domain) is tighter, and the entropic and enthalpic contributions are very different from those given by the peptide interaction (delta S0 = +252 J.mol-1.K-1; delta H0 = +44 kJ.mol-1). From these dramatically different thermodynamic measurements we are able to conclude that the interaction of the proline-rich peptide does not effectively mimic the interaction of the intact p85 subunit with the SH3 domain and suggest that other interactions could be important.

    Funded by: Wellcome Trust

    Biochemistry 1996;35;49;15646-53

  • The protein-tyrosine kinase Lck associates with and is phosphorylated by Cdc2.

    Pathan NI, Geahlen RL and Harrison ML

    Department of Biology, Purdue University, West Lafayette, Indiana 47907, USA.

    The protein-tyrosine kinase Lck is essential for signaling through the T-cell antigen receptor. Treatment of T-cells with a variety of extracellular stimuli increases the phosphorylation of Lck on serine residues. This results in shifts in the apparent molecular weight of Lck to forms that exhibit reduced electrophoretic mobility on SDS-polyacrylamide gels. We found that as a result of arresting cells in mitosis, forms of Lck were generated that migrated with slower mobilities on SDS-polyacrylamide gels. This suggested that a serine/threonine kinase, active at mitosis, was phosphorylating Lck. Using antibodies to Lck and to the cyclin-dependent serine kinase, Cdc2, as well as the cyclin-dependent kinase affinity resin, Suc1-agarose, we detected a stable interaction between Lck and Cdc2. The interaction was mediated through the Src homology 3 domain of Lck and was selective, as only the active form of Cdc2 was found to associate with Lck. Moreover, Cdc2 was able to phosphorylate Lck in vitro and shift its electrophoretic mobility to a more slowly migrating form. An association between active Cdc2 and the Src-related kinases Lyn and Fyn was also demonstrated, although Cdc2 was not found associated with the tyrosine kinases, Csk and Syk. These results demonstrate that at mitosis, Cdc2 associates with and phosphorylates Lck.

    Funded by: NIGMS NIH HHS: GM48099

    The Journal of biological chemistry 1996;271;44;27517-23

  • Identification of Itk/Tsk Src homology 3 domain ligands.

    Bunnell SC, Henry PA, Kolluri R, Kirchhausen T, Rickles RJ and Berg LJ

    Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.

    The tyrosine kinase Itk/Tsk is a T cell specific analog of Btk, the tyrosine kinase defective in the human immunodeficiency X-linked agammaglobulinemia and in xid mice. T lymphocytes from Itk-deficient mice are refractory to mitogenic stimuli delivered through the T cell receptor (TCR). To gain insights into the biochemical role of Itk, the binding properties of the Itk SH3 domain were examined. An optimal Itk SH3 binding motif was derived by screening biased phage display libraries; peptides based on this motif bound with high affinity and selectivity to the Itk SH3 domain. Initial studies with T cell lysates indicated that the Itk SH3 domain bound Cbl, Fyn, and other tyrosine phosphoproteins from TCR-stimulated Jurkat cells. Under conditions of increased detergent stringency Sam 68, Wiskott-Aldrich Syndrome protein, and hnRNP-K, but not Cbl and Fyn, were bound to the Itk SH3 domain. By examining the ability of different SH3 domains to interact with deletion variants of Sam 68 and WASP, we demonstrated that the Itk-SH3 domain and the SH3 domains of Src family kinases bind to overlapping but distinct sets of proline-rich regions in Sam 68 and WASP.

    Funded by: NIAID NIH HHS: AI37584

    The Journal of biological chemistry 1996;271;41;25646-56

  • The Ca2+-dependent lipid binding domain of P120GAP mediates protein-protein interactions with Ca2+-dependent membrane-binding proteins. Evidence for a direct interaction between annexin VI and P120GAP.

    Davis AJ, Butt JT, Walker JH, Moss SE and Gawler DJ

    Department of Pharmacology, University of Leeds, Leeds LS2 9JT, United Kingdom.

    The CaLB domain is a 43-amino acid sequence motif found in a number of functionally diverse signaling proteins including three Ras-specific GTPase activating proteins (GAPs). In the Ras GTPase activating protein, P120(GAP), this domain has the ability to confer membrane association in response to intracellular Ca2+ elevation. Here we have isolated three proteins, p55, p70, and p120, which interact with the P120(GAP) CaLB domain in vitro. We identify p70 as the Ca2+-dependent phospholipid-binding protein annexin VI. Using co-immunoprecipitation studies, we have shown that the interaction between P120(GAP) and annexin VI is also detectable in rat fibroblasts, suggesting that this interaction may have a physiological role in vivo. Thus, the CaLB domain in P120(GAP) appears to have the ability to direct specific protein-protein interactions with Ca2+-dependent membrane-associated proteins. In addition, annexin VI is known to have tumor suppressor activity. Therefore, it is possible that the interaction of annexin VI with P120(GAP) may be important in the subsequent modulation of p21(ras) activity.

    The Journal of biological chemistry 1996;271;40;24333-6

  • HIV infection in vitro enhances the activity of src-family protein tyrosine kinases.

    Phipps DJ, Read SE, Piovesan JP, Mills GB and Branch DR

    Department of Oncology Research, Toronto Hospital, Canada.

    Objective: We examined the effect of HIV infection on src-family protein tyrosine kinase (PTK) activity to determine if alterations in src-family PTK activity could contribute to the HIV-related chronic immune system activation observed in patients infected with HIV.

    Methods: Jurkat, a CD4+ human T lymphocyte cell line was infected with HIV IIIB. Kinase activity was determined by in vitro immune complex kinase assays using antibodies specific for the src-family PTKs, p56lck, p59fyn and p60c-src expressed in T lymphocytes. PTK protein and total phosphotyrosine levels were assessed by Western blotting. The role of the gp120-CD4-Lck interaction in HIV-related PTK activation was determined using gp 120-treated Jurkat cells and HIV-infection of JCaM 1.6 cells, a Jurkat-derived cell line that lacks p56lck.

    Results: Cells infected with HIV for 24 h exhibited increased levels of total tyrosine phosphorylation and enhanced src-family PTK activity without altered levels of expression of src-family kinases. The activity of Lck and Fyn was enhanced within 30 min of infection. HIV-related src-family PTK activation was not a function of the gp120-CD4-Lck interaction and occurred in the presence of 10 mmol/l zidovudine indicating that reverse transcriptase and activation of the HIV genome is not required.

    Conclusions: HIV-related activation of src-family PTK is a response of the cell to early stages of the virus life cycle, possibly either membrane fusion or viral uncoating. These results indicate that endogenous src-family PTKs may play a role in HIV-related immune activation and dysfunction. Moreover, activation of src-family PTK may be a mechanism used by the virus to facilitate some aspect of its own life cycle.

    AIDS (London, England) 1996;10;11;1191-8

  • In vivo and in vitro specificity of protein tyrosine kinases for immunoglobulin G receptor (FcgammaRII) phosphorylation.

    Bewarder N, Weinrich V, Budde P, Hartmann D, Flaswinkel H, Reth M and Frey J

    Biochemie II, Fakultät für Chemie, Universität Bielefeld, Germany.

    Human B cells express four immunoglobulin G receptors, FcgammaRIIa, FcgammaRIIb1, FcgammaRIIb2, and FcgammaRIIc. Coligation of either FcgammaRII isoform with the B-cell antigen receptor (BCR) results in the abrogation of B-cell activation, but only the FcgammaRIIa/c and FcgammaIIb1 isoforms become phosphorylated. To identify the FcgammaRII-phosphorylating protein tyrosine kinase (PTK), we used the combination of an in vitro and an in vivo approach. In an in vitro assay using recombinant cytoplasmic tails of the different FcgammaRII isoforms as well as tyrosine exchange mutants, we show that each of the BCR-associated PTKs (Lyn, Blk, Fyn, and Syk) shows different phosphorylation patterns with regard to the different FcgammaR isoforms and point mutants. While each PTK phosphorylated FcgammaRIIa/c, FcgammaRIIb1 was phosphorylated by Lyn and Blk whereas FcgammaRIIb2 became phosphorylated only by Blk. Mutants lacking both tyrosine residues of the immune receptor tyrosine-based activation motif (ITAM) of FcgammaRIIa/c were not phosphorylated by Blk and Fyn, while Lyn-mediated phosphorylation was dependent on the presence of the C-terminal tyrosine of the ITAM. Results obtained in assays using an FcgammaR- B-cell line transfected with wild-type or mutated FcgammaRIIa demonstrated that exchange of the C-terminal tyrosine of the ITAM of FcgammaRIIa/c was sufficient to abolish FcgammaRIIa/c phosphorylation in B cells. Additionally, we could show that Lyn and Fyn bind to FcgammaRIIa/c, with the ITAM being necessary for association. Comparison of the phosphorylation pattern of each PTK observed in vitro with the phosphorylation pattern observed in vivo suggests that Lyn is the most likely candidate for FcgammaRIIa/c and FcgammaRIIb1 phosphorylation in vivo.

    Molecular and cellular biology 1996;16;9;4735-43

  • Differential association of protein tyrosine kinases with the T cell receptor is linked to the induction of anergy and its prevention by B7 family-mediated costimulation.

    Boussiotis VA, Barber DL, Lee BJ, Gribben JG, Freeman GJ and Nadler LM

    Division of Hematologic Malignancies, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA.

    When stimulated through their antigen receptor, without costimulation, T cells enter a state of antigen-specific unresponsiveness, termed anergy. B7-mediated costimulation, signaling via CD28, is sufficient to prevent the induction of anergy. Here we show that ligation of T cell receptor (TCR) by alloantigen alone, which results in anergy, activates tyrosine phosphorylation of TCR zeta and its association with fyn. In contrast, TCR ligation in the presence of B7 costimulation, which results in productive immunity, activates tyrosine phosphorylation of TCR zeta and CD3 chains, which associate with activated lck and zeta-associated protein (ZAP) 70. Under these conditions, CD28 associates with activated lck and TCR zeta. These data suggest that the induction of anergy is an active signaling process characterized by the association of TCR zeta and fyn. In addition, CD28-mediated costimulation may prevent the induction of anergy by facilitating the effective association of TCR zeta and CD3 epsilon with the critical protein tyrosine kinase lck, and the subsequent recruitment of ZAP-70. Strategies to inhibit or activate TCR-associated, specific protein tyrosine kinase-mediated pathways may provide a basis for drug development with potential applications in the fields of transplantation, autoimmunity, and tumor immunity.

    Funded by: NCI NIH HHS: CA-40216; NIAID NIH HHS: AI-35225; PHS HHS: AL-54785

    The Journal of experimental medicine 1996;184;2;365-76

  • Wiskott-Aldrich syndrome protein (WASp) is a binding partner for c-Src family protein-tyrosine kinases.

    Banin S, Truong O, Katz DR, Waterfield MD, Brickell PM and Gout I

    Leukaemia Research Fund Centre for Childhood Leukaemia, Molecular Haematology Unit, Institute of Child Health, 30 Guilford Street, LondonWC1N 1EH, UK.

    Background: Receptor-mediated signal transduction requires the assembly of multimeric complexes of signalling proteins, and a number of conserved protein domains, such as the SH2, SH3 and PH domains, are involved in mediating protein-protein interactions in such complexes. The identification of binding partners for these domains has added considerably to our understanding of signal-transduction pathways, and the purpose of this work was to identify SH3-binding proteins in haematopoietic cells.

    Results: We performed affinity-chromatography experiments with a panel of GST-SH3 fusion proteins (composed of glutathione-S-transferase appended to various SH3 domains) to search for SH3-binding proteins in a human megakaryocytic cell line. Protein microsequencing identified one of the SH3-binding proteins as WASp, the protein that is defective in Wiskott-Aldrich syndrome (WAS) and isolated X-linked thrombocytopenia. WASp bound preferentially in vitro to SH3 domains from c-Src family kinases, and analysis of proteins expressed in insect cells using a baculovirus vector demonstrated a specific interaction between WASp and the Fyn protein-tyrosine kinase. Finally, in vivo experiments showed that WASp and Fyn physically associate in human haematopoietic cells.

    Conclusions: Haematopoietic cells from individuals with WAS exhibit defects in cell morphology and signal transduction, including reduced proliferation and tyrosine phosphorylation in response to stimulatory factors. Members of the c Src family of protein-tyrosine kinases, including Fyn, are involved in a range of signalling pathways - such as those regulating cytoskeletal structure - in both haematopoietic and non-haematopoietic cells. Our data suggest that binding of Fyn to WASp may be a critical event in such signalling pathways in haematopoietic cells.

    Current biology : CB 1996;6;8;981-8

  • Solution structure and peptide binding of the SH3 domain from human Fyn.

    Morton CJ, Pugh DJ, Brown EL, Kahmann JD, Renzoni DA and Campbell ID

    Oxford Centre for Molecular Sciences, UK.

    Background: The Src family of tyrosine kinases is involved in the propagation of intracellular signals from many transmembrane receptors. Each member of the family contains two domains that regulate interactions with other molecules, one of which is the Src homology 3 (SH3) domain. Although structures have previously been determined for SH3 domains, and ideas about peptide-binding modes have been proposed, their physiological role is still unclear.

    Results: We have determined the solution structure of the SH3 domain from the Src family tyrosine kinase Fyn in two forms: unbound and complexed with a peptide corresponding to a putative ligand sequence from phosphatidylinositol 3' kinase. Fyn SH3 shows the typical SH3 topology of two perpendicular three-stranded beta sheets and a single turn of 3(10) helix. The interaction of SH3 with three potential ligand peptides was investigated, demonstrating that they all bind to the same site on the molecule. A previous model for ligand binding to SH3 domains predicts binding in one of two orientations (class I or II), each characterized by a consensus sequence. The ligand with the closest match to the class I consensus sequence bound with highest affinity and in the predicted orientation.

    Conclusions: The Fyn SH3 domain has a well-defined structure in solution. The relative binding affinities of the three ligand peptides and their orientation within the Fyn SH3 complex were consistent with recently proposed models for the binding of 'consensus' polyproline sequences. Although the affinities of consensus and non-consensus peptides are different, the degree of difference is not very large, suggesting that SH3 domains bind to polyproline peptides in a promiscuous manner.

    Structure (London, England : 1993) 1996;4;6;705-14

  • Crystal structure of the conserved core of HIV-1 Nef complexed with a Src family SH3 domain.

    Lee CH, Saksela K, Mirza UA, Chait BT and Kuriyan J

    The Rockefeller University, New York, New York 10021, USA.

    The crystal structure of the conserved core of HIV-1 Nef has been determined in complex with the SH3 domain of a mutant Fyn tyrosine kinase (a single amino acid substitution, Arg-96 to isoleucine), to which Nef binds tightly. The conserved PxxP sequence motif of Nef, known to be important for optimal viral replication, is part of a polyproline type II helix that engages the SH3 domain in a manner resembling closely the interaction of isolated peptides with SH3 domains. The Nef-SH3 structure also reveals how high affinity and specificity in the SH3 interaction is achieved by the presentation of the PxxP motif within the context of the folded structure of Nef.

    Cell 1996;85;6;931-42

  • Multiple features of the p59fyn src homology 4 domain define a motif for immune-receptor tyrosine-based activation motif (ITAM) binding and for plasma membrane localization.

    Timson Gauen LK, Linder ME and Shaw AS

    Center for Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

    The src family tyrosine kinase p59fyn binds to a signaling motif contained in subunits of the TCR known as the immune-receptor tyrosine-based activation motif (ITAM). This is a specific property of p59fyn because two related src family kinases, p60src and p56lck, do not bind to ITAMs. In this study, we identify the residues of p59fyn that are required for binding to ITAMs. We previously demonstrated that the first 10 residues of p59fyn direct its association with the ITAM. Because this region of src family kinases also directs their fatty acylation and membrane association (Resh, M.D. 1993, Biochim. Biophys. Acta 1155:307-322; Resh, M.D. 1994. Cell. 76:411-413), we determined whether fatty acylation and membrane association of p59fyn correlates with its ability to bind ITAMs. Four residues (Gly2, Cys3, Lys7, and Lys9) were required for efficient binding of p59fyn to the TCR. Interestingly, the same four residues are present in p56lyn, the other src family tyrosine kinase known to bind to the ITAM, suggesting that this set of residues constitutes an ITAM recognition motif. These residues were also required for efficient fatty acylation (myristoylation at Gly2 and palmitoylation at Cys3), and plasma membrane targeting of p59fyn. Thus, the signals that direct p59fyn fatty acylation and plasma membrane targeting also direct its specific ability to bind to TCR proteins.

    Funded by: NIAID NIH HHS: AI34094; NIGMS NIH HHS: GM51466

    The Journal of cell biology 1996;133;5;1007-15

  • The Fyn tyrosine kinase binds Irs-1 and forms a distinct signaling complex during insulin stimulation.

    Sun XJ, Pons S, Asano T, Myers MG, Glasheen E and White MF

    Research Division, Joslin Diabetes Center, Boston, Massachusetts 02215, USA.

    Irs-proteins link the receptors for insulin/IGF-1, growth hormones, and several interleukins and interferons to signaling proteins that contain Src homology-2 (SH2). To identify new Irs-1-binding proteins, we screened a mouse embryo expression library with recombinant [32P]Irs-1, which revealed a specific association between p59fyn and Irs-1. The SH2 domain in p59fyn bound to phosphorylated Tyr895 and Tyr1172, which are located in YXX(L/I) motifs. Mutation of p59fyn at the COOH-terminal tyrosine phosphorylation site (Tyr531) enhanced its binding to Irs-1 during insulin stimulation. Binding experiments with various SH2 protein revealed that Grb-2 was largely excluded from Irs-1 complexes containing p59fyn, whereas Grb-2 and p85 occurred in the same Irs-1 complex. By comparison with the insulin receptor, p59fyn kinase phosphorylated a unique cohort of tyrosine residues in Irs-1. These results outline a role for p59fyn or other related Src-kinases during insulin and cytokine signaling.

    Funded by: NIDDK NIH HHS: DK 43808, DK38712

    The Journal of biological chemistry 1996;271;18;10583-7

  • A physical interaction between the cell death protein Fas and the tyrosine kinase p59fynT.

    Atkinson EA, Ostergaard H, Kane K, Pinkoski MJ, Caputo A, Olszowy MW and Bleackley RC

    Department of Biochemistry, University of Alberta, Edmonton, Canada.

    The Fas antigen (Apo1/CD95) is a transmembrane protein belonging to the nerve growth factor receptor family. It is expressed on a variety of cells, including activated T lymphocytes. Ligation of Fas with its natural ligand or with anti-Fas antibodies often results in the apoptotic death of the cell, making Fas an important mediator of down-regulating immune responses. The signal transduction pathways utilized by Fas are currently unknown, although tyrosine kinase activity has recently been strongly implicated. Here, we report that the tyrosine kinase p59fyn physically associates with Fas in Fas-sensitive cells. In addition, we show that activated T lymphocytes from fyn knockout mice exhibit elevated lifespans and reduced apoptosis in vitro compared to their normal counterparts. Furthermore, activated T lymphocytes from the fyn-deficient mice are less sensitive to killing by both anti-Fas antibody and Fas-ligand cytotoxic T cells. These results suggest that p59fyn plays an important role in Fas signal transduction.

    The Journal of biological chemistry 1996;271;11;5968-71

  • Activation of the epidermal growth factor receptor signal transduction pathway stimulates tyrosine phosphorylation of protein kinase C delta.

    Denning MF, Dlugosz AA, Threadgill DW, Magnuson T and Yuspa SH

    Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland 20892-4255, USA.

    The expression of an oncogenic rasHa gene in epidermal keratinocytes stimulates the tyrosine phosphorylation of protein kinase C delta and inhibits its enzymatic activity (Denning, M. F., Dlugosz, A. A., Howett, M. K., and Yuspa, S. H. (1993) J. Biol. Chem. 268, 26079-26081). Keratinocytes expressing an activated rasHa gene secrete transforming growth factor alpha (TGFalpha) and have an altered response to differentiation signals involving protein kinase C (PKC). Because the neoplastic phenotype of v-rasHa expressing keratinocytes can be partially mimicked in vitro by chronic treatment with TGF alpha and the G protein activator aluminum fluoride (AlF4-), we determined if TGF alpha or AlF4- could induce tyrosine phosphorylation of PKCdelta. Treatment of primary keratinocyte cultures for 4 days with TGFalpha induced tyrosine phosphorylation of PKCdelta, whereas AlF4- only slightly stimulated PKCdelta tyrosine phosphorylation. The PKCdelta that was tyrosine-phosphorylated in response to TGFalpha had reduced activity compared with the nontyrosine-phosphorylated PKCdelta. Treatment of keratinocytes expressing a normal epidermal growth factor receptor (EGFR) with TGFalpha or epidermal growth factor for 5 min induced PKCdelta tyrosine phosphorylation. This acute epidermal growth factor treatment did not induce tyrosine phosphorylation of PKCdelta in keratinocytes isolated from waved-2 mice that have a defective epidermal growth factor receptor. In addition, the level of PKCdelta tyrosine phosphorylation in v-rasHa-transduced keratinocytes from EGFR null mice was substantially lower than in v-rasHa transduced wild type cells, suggesting that activation of the EGFR is important for PKC delta tyrosine phosphorylation in ras transformation. However, purified EGFR did not phosphorylate recombinant PKC delta in vitro, whereas members of the Src family (c-Src, c-Fyn) and membrane preparations from keratinocytes did. Furthermore, clearing c-Src or c-Fyn from keratinocyte membrane lysates decreased PKCdelta tyrosine phosphorylation, and c-Src and c-Fyn isolated from keratinocytes treated with TGFalpha had increased kinase activity. Acute or chronic treatment with TGFalpha did not induce significant PKCdelta translocation in contrast to the phorbol ester 12-O-tetradecanoylphorbol-13-acetate, which induced both translocation and tyrosine phosphorylation of PKCdelta. This suggests that TGFalpha-induced tyrosine phosphorylation of PKC delta results from the activation of a tyrosine kinase rather than physical association of PKCdelta with a membrane-anchored tyrosine kinase. Taken together, these results indicate that PKCdelta activity is inhibited by tyrosine phosphorylation in response to EGFR-mediated signaling and activation of a member of the Src kinase family may be the proximal tyrosine kinase acting on PKCdelta in keratinocytes.

    The Journal of biological chemistry 1996;271;10;5325-31

  • p120cbl is a major substrate of tyrosine phosphorylation upon B cell antigen receptor stimulation and interacts in vivo with Fyn and Syk tyrosine kinases, Grb2 and Shc adaptors, and the p85 subunit of phosphatidylinositol 3-kinase.

    Panchamoorthy G, Fukazawa T, Miyake S, Soltoff S, Druker B, Shoelson S, Cantley L and Band H

    Lymphocyte Biology Section, Division of Rheumatology and Immunology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.

    We and others have demonstrated that the c-cbl proto-oncogene product is one of the earliest targets of tyrosine phosphorylation upon T cell receptor stimulation. Given the similarities in the B and T lymphocyte antigen receptors, and the induction of pre-B leukemias in mice by the v-cbl oncogene, we examined the potential involvement of Cbl in B cell receptor signaling. We demonstrate prominent and early tyrosine phosphorylation of Cbl upon stimulation of human B cell lines through surface IgM. Cbl was associated in vivo with Fyn and, to a lesser extent, other Src family kinases. B cell activation also induced a prominent association of Cbl with Syk tyrosine kinase. A substantial fraction of Cbl was constitutively associated with Grb2 and this interaction was mediated by Grb2 SH3 domains. Tyrosine-phosphorylated Shc, which prominently associated with Grb2, was detected in association with Cbl in activated B cells. Thus, Grb2 and Shc adaptors, which associate with immunoreceptor tyrosine based activation motifs, may link Cbl to the B cell receptor. B cell activation also induced a prominent association between Cbl and the p85 subunit of phosphatidylinositol (PI) 3-kinase resulting in the association of a substantial fraction of PI 3-kinase activity with Cbl. Thus, Cbl is likely to play an important role to couple the B cell receptor to the PI 3-kinase pathway. Our results strongly suggest a role for p120cbl in signaling downstream of the B cell receptor and support the idea that Cbl participates in a general signal transduction function downstream of the immune cell surface receptors.

    Funded by: NIAMS NIH HHS: AR36308; NIGMS NIH HHS: GM36624, R01 GM041890

    The Journal of biological chemistry 1996;271;6;3187-94

  • HIV envelope-directed signaling aberrancies and cell death of CD4+ T cells in the absence of TCR co-stimulation.

    Tian H, Lempicki R, King L, Donoghue E, Samelson LE and Cohen DI

    Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institute of Health, Bethesda, MD 20892, USA.

    HIV-1 infection in CD4(+) T cells initiates a viral cytopathic effect (CPE) that is dependent on the activation of intracellular protein tyrosine kinases (PTK). PTK in T cells are also activated during the course of TCR or CD4 receptor engagement and the manner of receptor engagement may generate signals leading either to cell proliferation, tolerance induction (anergy) or programmed cell death (PCD). We have identified PTK triggered during the interaction of cells stably expressing surface HIV envelope (gp 120/gp41; HIVenv) and CD4(+)T cells, which leads to extensive and rapid individual cell death. We have found that killing is accompanied by tyrosine phosphorylation and activation of the CD4-associated p56(ICK) kinase, and by activation of a second member of the scr family of PTK, p59(fyn) kinase, normally associated with T cell stimulation through the TCR. Interestingly, in contrast with normal T cell signaling, the zeta subunit of the TCR fails to become tyrosine-phosphorylated during signaling accompanying HIV-directed cell killing. Downstream activation of the ZAP-70 PTK also does not occur. Unlike T cell apoptosis triggered by soluble HIVenv glycoproteins, which requires co-stimulation of CD4 and the antigen-specific TCR, T cell killing by membrane-associated HIVenv does not require TCR co-stimulation, because aberrant signaling and cell death are triggered by CD4(+) but TCR- cell lines. These results are the first report where dual activation of the Lck and Fyn PTK does not result in normal downstream signaling through the ZAP PTK, We suggest by analogy to SCID resulting from ZAP-70 mutations, that the dissociation of upstream PTK activation from ZAP-70 signaling contributes to T cell depletion by HIV and to the development of AIDS.

    International immunology 1996;8;1;65-74

  • Human T lymphocyte activation induces tyrosine phosphorylation of alpha-tubulin and its association with the SH2 domain of the p59fyn protein tyrosine kinase.

    Marie-Cardine A, Kirchgessner H, Eckerskorn C, Meuer SC and Schraven B

    Department of Applied Immunology, German Cancer Research Center, Heidelberg, Germany.

    A glutathione-S-transferase-src-homology domain 2 (GST-SH2) fusion protein was employed to identify molecules interacting with the protein tyrosine kinase p59fyn. Among several proteins which bound to the fyn SH2 domain in lysates of human Jurkat T lymphocytes, alpha- and beta-tubulin were identified by N-terminal sequencing. Further analysis established that alpha-tubulin exists as a tyrosine-phosphorylated protein in Jurkat cells, where it interacts with p59fyn, but not with p56lck. By contrast, in untransformed resting human T lymphocytes alpha-tubulin is not detectable as a tyrosine phosphorylated protein. However, following T cell activation, it becomes rapidly phosphorylated on tyrosine residues and subsequently associates with the SH2 domain of fyn. Interestingly, constitutively tyrosine-phosphorylated alpha-tubulin that is able to interact with the fyn-SH2 domain is expressed in peripheral blood T lymphoblasts isolated from leukemic patients in the absence of external stimulation.

    European journal of immunology 1995;25;12;3290-7

  • The F3 neuronal glycosylphosphatidylinositol-linked molecule is localized to glycolipid-enriched membrane subdomains and interacts with L1 and fyn kinase in cerebellum.

    Olive S, Dubois C, Schachner M and Rougon G

    Laboratoire de Génétique et Physiologie du Développement, UMR 9943 CNRS-Université Aix-Marseille II, Paris, France.

    The F3 molecule is a member of the immunoglobulin superfamily anchored to plasma membranes by a glycosylphosphatidylinositol group. In adult mouse cerebellum, F3 is predominantly expressed on a subset of axons, the parallel fibers, and at their synapses. In vitro studies established that it is a plurifunctional molecule that, depending on the cellular context and the ligand with which it interacts, either mediates repulsive interactions or promotes neurite outgrowth. In the present study, we report the isolation of two fractions of F3-containing microdomains from adult cerebellum on the basis of their resistance to solubilization by Triton X-100 at 4 degrees C. Both fractions were composed of vesicles, ranging from 100 to 200 nm in diameter. Lipid composition analysis indicated that the lighter fraction was enriched in cerebrosides and sulfatides. F3 sensitivity to phosphatidylinositol phospholipase C differed between the two fractions, possibly reflecting structural differences in the lipid anchor of the F3 molecule. Both fractions were highly enriched in other glycosylphosphatidylinositol-anchored proteins such as NCAM 120 and Thy-1. It is interesting that these vesicles were devoid of the transmembrane forms (NCAM 180 and NCAM 140), which were recovered in Triton X-100-soluble fractions, but contained the L1 transmembrane adhesion molecule that is coexpressed with F3 on parallel fibers and the fyn tyrosine kinase. Immunoprecipitation experiments indicated that F3, but not NCAM 120 or Thy-1, was physically associated in a complex with both L1 and fyn tyrosine kinase. This strongly suggests that the interaction between L1 and F3, already described to occur with isolated molecules, is present in neural tissue. More important is that our study provides information on the molecular machinery likely to be involved in F3 signaling.

    Journal of neurochemistry 1995;65;5;2307-17

  • A single amino acid in the SH3 domain of Hck determines its high affinity and specificity in binding to HIV-1 Nef protein.

    Lee CH, Leung B, Lemmon MA, Zheng J, Cowburn D, Kuriyan J and Saksela K

    Laboratory of Molecular Biophysics, Rockefeller University, New York, NY 10021, USA.

    We have examined the differential binding of Hck and Fyn to HIV-1 Nef to elucidate the structural basis of SH3 binding affinity and specificity. Full-length Nef bound to Hck SH3 with the highest affinity reported for an SH3-mediated interaction (KD 250 nM). In contrast to Hck, affinity of the highly homologous Fyn SH3 for Nef was too weak (KD > 20 microM) to be accurately determined. We show that this distinct specificity lies in a variable loop, the 'RT loop', positioned close to conserved SH3 residues implicated in the binding of proline-rich (PxxP) motifs. A mutant Fyn SH3 with a single amino acid substitution (R96I) in its RT loop had an affinity (KD 380 nM) for Nef comparable with that of Hck SH3. Based on additional mutagenesis studies we propose that the selective recognition of Nef by Hck SH3 is determined by hydrophobic interactions involving an isoleucine residue in its RT loop. Although Nef contains a PxxP motif which is necessary for the interaction with Hck SH3, high affinity binding was only observed for intact Nef protein. The binding of a peptide containing the Nef PxxP motif showed > 300-fold weaker affinity for Hck SH3 than full-length Nef.

    Funded by: NIGMS NIH HHS: GM47021

    The EMBO journal 1995;14;20;5006-15

  • Interaction of peptides derived from the Fas ligand with the Fyn-SH3 domain.

    Hane M, Lowin B, Peitsch M, Becker K and Tschopp J

    Institute of Biochemistry, University of Lausanne, Epalinges, Switzerland.

    Interaction of the widely expressed Fas with its membrane-bound ligand (FasL) leads to rapid cell death via apoptosis. To avoid pathological tissue damage, the activity of FasL requires tight regulation. Here, we report that the Src homology 3 (SH3) domain of Fyn binds to the proline-rich cytoplasmic region of FasL. Binding of the SH3 domain occurs between amino acid residues 44-71 which contains several potential SH3 interaction sites. This binding is specific, as SH3 domains of Lck, Grb2 and ras-GAP bind only weakly or not at all. We suggest that FasL activity may be modulated by SH3 domains of the src-like Fyn kinase.

    FEBS letters 1995;373;3;265-8

  • The role of tyrosine phosphorylation in the interaction of cellular tyrosine kinases with the T cell receptor zeta chain tyrosine-based activation motif.

    Osman N, Lucas S and Cantrell D

    Lymphocyte Activation Laboratory, Imperial Cancer Research Fund, London, GB.

    Immunoglobulin receptor family tyrosine-based activation motifs (ITAM) define a conserved signaling sequence, EX2YX2L/IX7YX2L/I, that mediates coupling of the T cell antigen receptor (TCR) to protein tyrosine kinases (PTK). In the present study, we explored the role of phosphorylation of the two ITAM tyrosine residues in the interactions of the motif with the PTK ZAP-70 and p59fyn. The data show that the phosphorylation of a single tyrosine within the motif enables binding of p59fyn, whereas phosphorylation of both tyrosines within the motif is required for maximal binding of the PTK ZAP-70. Quantitative binding experiments show that nanomolar concentrations of the doubly phosphorylated zeta 1-ITAM are sufficient for ZAP-70 recruitment, whereas micromolar levels of singly phosphorylated ITAM are necessary for p59fyn binding. ZAP-70 binds with low efficiency to a singly phosphorylated ITAM, but shows preferential binding to the C-terminal phosphotyrosine in the ITAM, whereas p59fyn binds selectively to the N-terminal phosphotyrosine. The present data thus show that there is the potential for a singly phosphorylated ITAM to couple to cellular PTK. Moreover, the data suggest a mechanism for heterogeneity in signal transduction responses by the TCR, since ITAM could differentially couple the TCR to downstream signaling events depending on their phosphorylation state.

    European journal of immunology 1995;25;10;2863-9

  • Specific binding of Fyn and phosphatidylinositol 3-kinase to the B cell surface glycoprotein CD19 through their src homology 2 domains.

    Chalupny NJ, Aruffo A, Esselstyn JM, Chan PY, Bajorath J, Blake J, Gilliland LK, Ledbetter JA and Tepper MA

    Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, USA.

    CD19 is a B cell surface protein capable of forming non-covalent molecular complexes with a number of other B cell surface proteins including the CD21/CD81/Leu-13 complex as well as with surface immunoglobulin. CD19 tyrosine phosphorylation increases after B cell activation, and is proposed to play a role in signal transduction through its cytoplasmic domain, which contains nine tyrosine residues. Several second messenger proteins have been shown to immunoprecipitate with CD19, including p59 Fyn (Fyn), p59 Lyn (Lyn) and phosphatidylinositol-3 kinase (PI-3 kinase). These associations are predicted to occur via the src-homology 2 (SH2) domains of the second messenger proteins. Two of the cytoplasmic tyrosines in the CD19 cytoplasmic region contain the consensus binding sequence for the PI-3 kinase SH2 domain (YPO4-X-X-M). However, the reported consensus binding sequence for the Fyn and Lyn SH2 domains (YPO4-X-X-I/L) is not found in CD19. We investigated the capacity of CD19 cytoplasmic tyrosines to bind both Fyn and PI-3 kinase SH2-domain fusion proteins. In activated B cells, both Fyn and PI-3 kinase SH2-domain fusion proteins precipitate CD19. Using synthetic tyrosine-phosphorylated peptides comprising each of the CD19 cytoplasmic tyrosines and surrounding amino acids, we investigated the ability of the Fyn SH2 and PI-3 kinase SH2 fusion proteins to bind to the different CD19 cytoplasmic phosphotyrosine peptides. ELISA revealed that the two CD19 cytoplasmic tyrosine residues contained within the Y-X-X-M sequences (Y484 and Y515) bound preferentially to the PI-3 kinase SH2-domain fusion proteins. Two different tyrosines (Y405 and Y445) bound preferentially to the Fyn SH2-domain fusion protein via a novel sequence, Y-E-N-D/E, different from that previously reported for the Fyn SH2 domain. In precipitation studies, peptide Y484 was able to compete with tyrosine phosphorylated CD19 specifically for binding to the PI-3 kinase SH2 domain fusion proteins, while peptides Y405 and Y445 were able to compete specifically for binding to the Fyn SH2 domain fusion proteins. These results indicate that CD19 may be capable of binding both Fyn and PI-3 kinase concurrently, suggesting a mechanism for CD19 signal transduction, in which binding of PI-3 kinase to the Fyn SH3 domain results in activation of PI-3 kinase.

    European journal of immunology 1995;25;10;2978-84

  • Wiskott-Aldrich syndrome protein physically associates with Nck through Src homology 3 domains.

    Rivero-Lezcano OM, Marcilla A, Sameshima JH and Robbins KC

    Laboratory of Cellular Development and Oncology, National Institute of Dental Research, Bethesda, Maryland 20892-4330, USA.

    In the second of a series of experiments designed to identify p47nck-Src homology 3 (SH3)-binding molecules, we report the cloning of SAKAP II (Src A box Nck-associated protein II) from an HL60 cDNA expression library. This molecule has been identified as a cDNA encoding the protein product of WASP, which is mutated in Wiskott-Aldrich syndrome patients. Studies in vivo and in vitro demonstrated a highly specific interaction between the SH3 domains of p47nck and Wiskott-Aldrich syndrome protein. Furthermore, anti-Wiskott-Aldrich syndrome protein antibodies recognized a protein of 66 kDa by Western blot (immunoblot) analysis. In vitro translation studies identified the 66-kDa protein as the protein product of WASP, and subcellular fractionation experiments showed that p66WASP is mainly present in the cytosol fraction, although significant amounts are also present in membrane and nuclear fractions. The main p47nck region implicated in the association with p66WASP was found to be the carboxy-terminal SH3 domain.

    Molecular and cellular biology 1995;15;10;5725-31

  • Association of 75/80-kDa phosphoproteins and the tyrosine kinases Lyn, Fyn, and Lck with the B cell molecule CD20. Evidence against involvement of the cytoplasmic regions of CD20.

    Deans JP, Kalt L, Ledbetter JA, Schieven GL, Bolen JB and Johnson P

    Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada.

    CD20, a non-glycosylated cell-surface protein expressed exclusively on B lymphocytes, is one of a family of 4-pass transmembrane molecules that also includes the beta chain of the high affinity receptor for IgE. The precise function of CD20 is unknown, although in vitro effects of CD20-specific antibodies on resting B cells indicate that it is able to transduce an extracellular signal affecting the G0/G1 cell cycle transition. Previous studies have demonstrated that CD20-initiated intracellular signals involve tyrosine kinase activation and that CD20 is tightly associated with both serine and tyrosine kinases. Here, analysis of CD20-associated molecules has revealed that CD20 is associated with the Src family tyrosine kinases p56/53lyn, p56lck, and p59fyn and with 75/80-kDa proteins phosphorylated in vivo on tyrosine residues. Mutagenesis of CD20 was performed to define regions of CD20 involved in intermolecular interactions. Mutants were analyzed in the human T lymphoblastoid cell line Molt-4, in which ectopically expressed wild-type CD20 associated with p59fyn, p56lck, and 75/80-kDa phosphoproteins. Deletion of major portions of the cytoplasmic regions of CD20 did not abolish its association with either p75/80 or tyrosine kinases. The interaction between CD20 and the Src-related kinases is therefore likely to be independent of CD20 cytoplasmic domains and may occur indirectly. The interaction may be mediated by the p75/80 phosphoproteins, which were found to be tightly associated with the Src family kinases isolated from the CD20 complex.

    The Journal of biological chemistry 1995;270;38;22632-8

  • The SH3 domain-binding T cell tyrosyl phosphoprotein p120. Demonstration of its identity with the c-cbl protooncogene product and in vivo complexes with Fyn, Grb2, and phosphatidylinositol 3-kinase.

    Fukazawa T, Reedquist KA, Trub T, Soltoff S, Panchamoorthy G, Druker B, Cantley L, Shoelson SE and Band H

    Department of Rheumatology and Immunology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.

    Previously, we have identified p120 as a Fyn/Lck SH3 and SH2 domain-binding protein that is tyrosine phosphorylated rapidly after T cell receptor triggering. Here, we used direct protein purification, amino acid sequence analysis, reactivity with antibodies, and two-dimensional gel analyses to identify p120 as the human c-cbl protooncogene product. We demonstrate in vivo complexes of p120cbl with Fyn tyrosine kinase, the adaptor protein Grb2, and the p85 subunit of phosphatidylinositol (PI) 3-kinase. The association of p120cbl with Fyn and the p85 subunit of PI 3-kinase (together with PI 3-kinase activity) was markedly increased by T cell activation, consistent with in vitro binding of p120cbl to their SH2 as well as SH3 domains. In contrast, a large fraction of p120cbl was associated with Grb2 prior to activation, and this association did not change upon T cell activation. In vitro, p120cbl interacted with Grb2 exclusively through its SH3 domains. These results demonstrate a novel Grb2-p120cbl signaling complex in T cells, distinct from the previously analyzed Grb2-Sos complex. The association of p120cbl with ubiquitous signaling proteins strongly suggests a general signal transducing function for this enigmatic protooncogene with established leukemogenic potential but unknown physiological function.

    Funded by: NIAID NIH HHS: R29-AI28508; NIAMS NIH HHS: AR36308; NIGMS NIH HHS: R01 GM041890

    The Journal of biological chemistry 1995;270;32;19141-50

  • Binding of ZAP-70 to phosphorylated T-cell receptor zeta and eta enhances its autophosphorylation and generates specific binding sites for SH2 domain-containing proteins.

    Neumeister EN, Zhu Y, Richard S, Terhorst C, Chan AC and Shaw AS

    Center for Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

    ZAP-70 is a protein tyrosine kinase thought to play a critical role in T-cell receptor (TCR) signal transduction. During T-cell activation, ZAP-70 binds to a conserved signalling motif known as the immune receptor tyrosine activating motif (ITAM) and becomes tyrosine phosphorylated. To determine whether binding of ZAP-70 to the phosphorylated ITAM was able to activate its kinase activity, we measured the kinase activity of ZAP-70 both when it was bound and when it was unbound to phosphorylated TCR subunits. The ability of ZAP-70 to phosphorylate itself, but not exogenous substrates, was enhanced when it was bound to the tyrosine-phosphorylated TCR zeta and eta chains or to a construct that contained duplicated epsilon ITAMs. No enhanced ZAP-70 autophosphorylation was noted when it was bound to tyrosine-phosphorylated CD3 gamma or epsilon. In addition, autophosphorylation of ZAP-70 when bound to zeta or eta resulted in the generation of multiple distinct ZAP-70 phosphorylated tyrosine residues which had the capacity to bind the SH2 domains of fyn, lck, GAP, and abl. As the effect was noted only when ZAP-70 was bound to TCR subunits containing multiple ITAMs, we propose that one of the roles of the tandem ITAMs is to facilitate the autophosphorylation of ZAP-70. Tyrosine-phosphorylated ZAP-70 then mediates downstream signalling by recruiting SH2 domain-containing signalling proteins.

    Molecular and cellular biology 1995;15;6;3171-8

  • Differential requirement for protein tyrosine kinase Fyn in the functional activation of antigen-specific T lymphocyte clones through the TCR or Thy-1.

    Lancki DW, Qian D, Fields P, Gajewski T and Fitch FW

    Department of Pathology, University of Chicago, IL 60637, USA.

    The protein tyrosine kinase Fyn has been shown to be involved in signal transduction through the TCR and the glycosyl-phosphatidylinositol-linked surface molecule Thy-1 expressed on T cells. In this study, we examine the requirement for Fyn expression in signaling through the TCR or Thy-1 using a panel of Ag-specific T cell clones derived from fyn-/- mutant mice. These clones do not express normal Fyn protein, as measured by immune-complex kinase reaction using anti-Fyn Ab. Stimulation through the TCR, either by APC bearing relevant Ag or by immobilized anti-CD3 mAb, resulted in comparable levels of proliferation, lymphokine production, and cytolysis by clones from both wild-type and fyn-/- mice. In contrast, stimulation through Thy-1, using soluble (or cross-linked) anti-Thy-1 mAb, was deficient, as measured by these responses. Thus, Fyn 1229 expression is selectively required for functional activation through Thy-1 in these T cell clones.

    Funded by: NCI NIH HHS: CA-19266, CA-44372; NIAID NIH HHS: AI-29531; ...

    Journal of immunology (Baltimore, Md. : 1950) 1995;154;9;4363-70

  • Autophosphorylation activity and association with Src family kinase of Sky receptor tyrosine kinase.

    Toshima J, Ohashi K, Iwashita S and Mizuno K

    Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.

    "Sky" is a putative receptor tyrosine kinase predominantly expressed in the brain. Sky, like Axl/Ufo/Ark and c-Eyk, has an extracellular domain composed of two immunoglobulin-like domains and two fibronectin type III domains. Immunoblot analysis using an antibody raised against a C-terminal peptide of Sky identified a 98-kDa Sky protein in COS cells transfected with sky cDNA (COS/sky cells). A 98-kDa protein in the immunoprecipitates with anti-Sky antibody was autophosphorylated on tyrosine, by in vitro kinase reaction. When the lysates of COS/sky cells were immunoprecipitated with anti-Sky antibody and immunoblotted with an anti-phosphotyrosine antibody, a 60-kDa phosphotyrosine-containing protein, in addition to the tyrosine-phosphorylated Sky, was detected. Using the anti-Src antibody, which is reactive to Src, Fyn and Yes, we obtained evidence for an association between the Src family tyrosine kinase and the tyrosine-phosphorylated Sky receptor. These results suggest that the Src family kinase may play an important role in signal transduction of the Sky receptor.

    Biochemical and biophysical research communications 1995;209;2;656-63

  • Human p59fyn(T) regulates OKT3-induced calcium influx by a mechanism distinct from PIP2 hydrolysis in Jurkat T cells.

    Rigley K, Slocombe P, Proudfoot K, Wahid S, Mandair K and Bebbington C

    Cantab Pharmaceuticals Research Limited, Cambridge, UK.

    The earliest biochemical event after cross-linking of TCR is the tyrosine phosphorylation of a variety of substrates. At least three nonreceptor tyrosine kinases have been implicated in this signaling cascade: p59fyn(T), p56lck, and ZAP-70. Recently, PLC gamma 1 has been shown to be tyrosine phosphorylated in T cells after receptor activation. This increase in tyrosine phosphorylation correlates with the increased activity of the enzyme. The substrate for PLC gamma 1, phosphatidylinositol 4,5-bisphosphate (PIP2), is hydrolyzed to the protein kinase C activator diacylglycerol and inositol 1,4,5-triphosphate (IP3), which promotes calcium release from the endoplasmic reticulum. These results lend support to the notion that calcium mobilization after TCR cross-linking is mediated by increased levels of IP3. In this study we have cloned and transfected a human p59fyn(T) cDNA in the anti-sense configuration into the human T cell line, Jurkat, resulting in decreased expression of the protein. We find that cell lines expressing significantly reduced levels of p59fyn(T) exhibit significantly lower calcium influx following OKT3 activation. However, the level of IP3 production was unchanged and IP1 and IP2 levels were elevated. These data indicate that p59fyn(T) can regulate calcium influx by a mechanism distinct from PIP2 hydrolysis.

    Journal of immunology (Baltimore, Md. : 1950) 1995;154;3;1136-45

  • Proline-rich (PxxP) motifs in HIV-1 Nef bind to SH3 domains of a subset of Src kinases and are required for the enhanced growth of Nef+ viruses but not for down-regulation of CD4.

    Saksela K, Cheng G and Baltimore D

    Rockefeller University, New York, NY 10021.

    Human immunodeficiency virus (HIV) and simian immunodeficiency virus Nef proteins contain a conserved motif with the minimal consensus (PxxP) site for Src homology region 3 (SH3)-mediated protein-protein interactions. Nef PxxP motifs show specific binding to biotinylated SH3 domains of Hck and Lyn, but not to those of other tested Src family kinases or less related proteins. A unique cooperative role of a distant proline is also observed. Endogenous Hck of monocytic U937 cells can be specifically precipitated by matrix-bound HIV-1 Nef, but not by mutant protein lacking PxxP. Intact Nef PxxP motifs are dispensable for Nef-induced CD4 down-regulation, but are required for the higher in vitro replicative potential of Nef+ viruses. Thus, CD4 down-regulation and promotion of viral growth are two distinct functions of Nef, and the latter is mediated via SH3 binding.

    Funded by: NIAID NIH HHS: AI22346

    The EMBO journal 1995;14;3;484-91

  • Identification of tyrosine 620 as the major phosphorylation site of myelin-associated glycoprotein and its implication in interacting with signaling molecules.

    Jaramillo ML, Afar DE, Almazan G and Bell JC

    Department of Biochemistry, University of Ottawa, Ontario, Canada.

    Myelin-associated glycoprotein (MAG) is a myelin-specific cell adhesion molecule of the immunoglobulin supergene family and is tyrosine-phosphorylated in the developing brain. To define the role of MAG in signal transduction, the tyrosine phosphorylation sites were analyzed. The major tyrosine phosphorylation residue was identified as Tyr-620, which was found to interact specifically with the SH2 domains of phospholipase C (PLC gamma). This domain may represent a novel protein binding motif that can be regulated by tyrosine phosphorylation. MAG also specifically bound the Fyn tyrosine kinase, suggesting that MAG serves as a docking protein that allows the interaction between different signaling molecules.

    The Journal of biological chemistry 1994;269;44;27240-5

  • Different signal transduction properties of KDR and Flt1, two receptors for vascular endothelial growth factor.

    Waltenberger J, Claesson-Welsh L, Siegbahn A, Shibuya M and Heldin CH

    Ludwig Institute for Cancer Research, Uppsala Branch, Sweden.

    Vascular endothelial growth factor (VEGF) is a homodimeric peptide growth factor which binds to two structurally related tyrosine kinase receptors denoted Flt1 and KDR. In order to compare the signal transduction via these two receptors, the human Flt1 and KDR proteins were stably expressed in porcine aortic endothelial cells. Binding analyses using 125I-VEGF revealed Kd values of 16 pM for Flt1 and 760 pM for KDR. Cultured human umbilical vein endothelial (HUVE) cells were found to express two distinct populations of binding sites with affinities similar to those for Flt1 and KDR, respectively. The KDR expressing cells showed striking changes in cell morphology, actin reorganization and membrane ruffling, chemotaxis and mitogenicity upon VEGF stimulation, whereas Flt1 expressing cells lacked such responses. KDR was found to undergo ligand-induced autophosphorylation in intact cells, and both Flt1 and KDR were phosphorylated in vitro in response to VEGF, however, KDR much more efficiently than Flt1. Neither the receptor-associated activity of phosphatidylinositol 3'-kinase nor tyrosine phosphorylation of phospholipase C-gamma were affected by stimulation of Flt1 or KDR expressing cells, and phosphorylation of GTPase activating protein was only slightly increased. Members of the Src family such as Fyn and Yes showed an increased level of phosphorylation upon VEGF stimulation of cells expressing Flt1 but not in cells expressing KDR. The maximal responses in KDR expressing porcine aortic endothelial cells were obtained at higher VEGF concentrations as compared to HUVE cells, i.e. in the presence of Flt1. This difference could possibly be explained by the formation of heterodimeric complexes between KDR and Flt1, or other molecules, in HUVE cells.

    The Journal of biological chemistry 1994;269;43;26988-95

  • Src-related protein tyrosine kinases are physically associated with the surface antigen CD36 in human dermal microvascular endothelial cells.

    Bull HA, Brickell PM and Dowd PM

    Department of Medicine University College London Medical School, Rayne Institute, UK.

    Src-related cytoplasmic PTKs are physically and functionally associated with cell surface receptors and are involved in signal transduction. In this paper we report the identification of src-related proteins p59fyn, pp60c-src and p62yes in human microvascular endothelial cells cultured from normal human skin and their physical association with the thrombospondin receptor CD36. Such an association represents a potential signalling pathway by which thrombospondin may regulate angiogenesis.

    FEBS letters 1994;351;1;41-4

  • Binding of Bruton's tyrosine kinase to Fyn, Lyn, or Hck through a Src homology 3 domain-mediated interaction.

    Cheng G, Ye ZS and Baltimore D

    Rockefeller University, New York, NY 10021.

    Bruton's tyrosine kinase (Btk) is a recently described B-cell-specific tyrosine kinase. Mutations in this gene lead to human X chromosome-linked agammaglobulinemia and murine X-linked immunodeficiency. Although genetic evidence strongly suggests that Btk plays a crucial role in B-lymphocyte differentiation and activation, its precise mechanism of action remains unknown, primarily because the proteins that it interacts with have not yet been identified. Here, we show that Btk interacts with Src homology 3 domains of Fyn, Lyn, and Hck, protein-tyrosine kinases that get activated upon stimulation of B- and T-cell receptors. These interactions are mediated by two 10-aa motifs in Btk. An analogous site with the same specificity is also present in Itk, the T-cell-specific homologue of Btk. Our data extend the range of interactions mediated by Src homology 3 domains and provide an indication of a link between Btk and established signaling pathways in B lymphocytes.

    Funded by: NIAID NIH HHS: AI22346

    Proceedings of the National Academy of Sciences of the United States of America 1994;91;17;8152-5

  • High-resolution crystal structures of tyrosine kinase SH3 domains complexed with proline-rich peptides.

    Musacchio A, Saraste M and Wilmanns M

    European Molecular Biology Laboratory, Heidelberg, Germany.

    Src-homology 3 (SH3) domains bind to proline-rich motifs in target proteins. We have determined high-resolution crystal structures of the complexes between the SH3 domains of Abl and Fyn tyrosine kinases, and two ten-residue proline-rich peptides derived from the SH3-binding proteins 3BP-1 and 3BP-2. The X-ray data show that the basic mode of binding of both proline-rich peptides is the same. Peptides are bound over their entire length and interact with three major sites on the SH3 molecules by both hydrogen-bonding and van der Waals contacts. Residues 4-10 of the peptide adopt the conformation of a left-handed polyproline helix type II. Binding of the proline at position 2 requires a kink at the non-proline position 3.

    Nature structural biology 1994;1;8;546-51

  • Activation of src family kinases in human pre-B cells by IL-7.

    Seckinger P and Fougereau M

    Immunology Center of Marseille-Luminy, France.

    IL-7 was identified originally as a specific pre-B cell growth factor. We have investigated its signal transduction mechanism by using the human pre-B cell line Nalm-6, and have found that it stimulates tyrosine phosphorylation of various proteins: pp27, pp43, pp54, pp64, pp78, pp90, pp105, and pp120. Antiphosphotyrosine immunoprecipitates from IL-7-stimulated Nalm-6 showed two major proteins of M(r) = 60,000 and 55,000, capable of autophosphorylation. Autophosphorylation was maximal 10 min after the cells were challenged with the cytokine. Antiphosphotyrosine immunoprecipitates from IL-7-stimulated cells also increased tyrosine phosphorylation of the exogenously added substrate histone H2B. Furthermore, by using a polyclonal anti-IL-7 receptor (IL-7R) Ab in Western blotting analysis, we observed that antiphosphotyrosine immunoprecipitates were associated with the IL-7R in a transient manner. These data indicate that the IL-7R associates with tyrosine-phosphorylated proteins as its amino acid sequence is devoid of a putative site of tyrosine phosphorylation. These results were confirmed as several 32P-labeled proteins were visualized after immunoprecipitation by using anti-IL-7R Ab. Anti-IL-7R immunoprecipitates from IL-7-stimulated cells revealed a unique band of M(r) = 60,000 associated with the receptor able to autophosphorylate in the presence of ATP and Mn2+. Hence, we identified p59fyn and p53/56lyn to be stimulated by IL-7. In contrast to p53/56lyn, p59fyn was found to be associated constitutively with the cloned IL-7R. These data emphasize the role of the src family in hematopoiesis.

    Journal of immunology (Baltimore, Md. : 1950) 1994;153;1;97-109

  • Raf-1 interacts with Fyn and Src in a non-phosphotyrosine-dependent manner.

    Cleghon V and Morrison DK

    Molecular Mechanisms of Carcinogenesis Laboratory, ABL-Basic Research Program National Cancer Institute-Frederick Cancer Research and Development Center, Maryland 21702.

    To identify novel proteins capable of associating with the Raf-1 serine/threonine kinase, we investigated whether Raf-1 could interact with the Src homology 2 (SH2) domains of various signal-transducing molecules. In this report, we demonstrate that Raf-1 associated with the SH2 domain of Fyn (a member of the Src tyrosine kinase family) but not with the SH2 domains of phospholipase C-gamma 1, the p85 alpha subunit of phosphatidylinositol 3-kinase, and SH2-containing protein tyrosine phosphatase 2. Unlike most SH2 domain interactions that require tyrosine-phosphorylated residues, the Raf-1/Fyn SH2 domain association was dependent on the serine phosphorylation of Raf-1. Our results also demonstrate that Raf-1 interacted with the SH2 domain of Src and that this interaction was destabilized by mutation of Arg175 found within the conserved SH2 domain FLVRES sequence. In addition, we show that inclusion of additional Src sequences containing the SH3 domain increased the association of Raf-1 with the Src SH2 domain. Finally, using the baculovirus/Sf9 cell system, we show that coexpression of Raf-1 with full-length Fyn/Src resulted in the coimmunoprecipitation of Raf-1 with Fyn/Src, the tyrosine phosphorylation of Raf-1, and the stimulation of Raf-1 kinase activity. These results suggest that Raf-1 may form a functional complex with Fyn/Src mediated in part by SH2 domains and the serine phosphorylation of Raf-1.

    Funded by: NCI NIH HHS: N01-CO-74101

    The Journal of biological chemistry 1994;269;26;17749-55

  • Identification of Src, Fyn, and Lyn SH3-binding proteins: implications for a function of SH3 domains.

    Weng Z, Thomas SM, Rickles RJ, Taylor JA, Brauer AW, Seidel-Dugan C, Michael WM, Dreyfuss G and Brugge JS

    ARIAD Pharmaceuticals, Cambridge, Massachusetts 02139.

    Src homology 3 (SH3) domains mediate protein-protein interactions necessary for the coupling of cellular proteins involved in intracellular signal transduction. We previously established solution-binding conditions that allow affinity isolation of Src SH3-binding proteins from cellular extracts (Z. Weng, J. A. Taylor, C. E. Turner, J. S. Brugge, and C. Seidel-Dugan, J. Biol. Chem. 268:14956-14963, 1993). In this report, we identified three of these proteins: Shc, a signaling protein that couples membrane tyrosine kinases with Ras; p62, a protein which can bind to p21rasGAP; and heterogeneous nuclear ribonucleoprotein K, a pre-mRNA-binding protein. All of these proteins contain proline-rich peptide motifs that could serve as SH3 domain ligands, and the binding of these proteins to the Src SH3 domain was inhibited with a proline-rich Src SH3 peptide ligand. These three proteins, as well as most of the other Src SH3 ligands, also bound to the SH3 domains of the closely related protein tyrosine kinases Fyn and Lyn. However, Src- and Lyn-specific SH3-binding proteins were also detected, suggesting subtle differences in the binding specificity of the SH3 domains from these related proteins. Several Src SH3-binding proteins were phosphorylated in Src-transformed cells. The phosphorylation of these proteins was not detected in cells transformed by a mutant variant of Src lacking the SH3 domain, while there was little change in tyrosine phosphorylation of other Src-induced phosphoproteins. In addition, the coprecipitation of v-Src with two tyrosyl-phosphorylated proteins with M(r)s of 62,000 and 130,000 was inhibited by incubation with a Src SH3 peptide ligand, suggesting that the binding of these substrate proteins is dependent on interactions with the SH3 domain. These results strongly suggest a role for the Src SH3 domain in the recruitment of substrates to this protein tyrosine kinase, either through direct interaction with the SH3 domain or indirectly through interactions with proteins that bind to the SH3 domain.

    Funded by: NCI NIH HHS: CA27951

    Molecular and cellular biology 1994;14;7;4509-21

  • Identification of two SH3-binding motifs in the regulatory subunit of phosphatidylinositol 3-kinase.

    Kapeller R, Prasad KV, Janssen O, Hou W, Schaffhausen BS, Rudd CE and Cantley LC

    Department of Physiology, Tufts University Medical School, Boston, Massachusetts 02111.

    Src homology 3 (SH3) domains have been recently shown to bind to proline-rich sequences contained in 3BP1, 3BP2, and SOS. In a recent study we demonstrated that phosphatidylinositol 3-kinase (PI 3-kinase) associates with the Fyn SH3 domain. Here we show that p85, the regulatory subunit of PI 3-kinase, binds directly to the SH3 domains of Abl, Lck, Fyn, and p85 itself. An examination of p85 amino acid sequence revealed two proline-rich sequences in its N-terminal region similar to those present in 3BP1, 3BP2, and SOS. To test whether these sequences mediate the association of p85 with SH3 domains two peptides with amino acid composition corresponding to the p85 alpha proline-rich sequences were synthesized and used in competition assays. Both peptides worked equally well in inhibiting the binding of PI 3-kinase activity and p85 alpha to Fyn SH3 domain, whereas a control peptide had no effect. These results indicate that, as in 3BP1 and SOS, the proline-rich sequences in p85 mediate its interaction with SH3 domains. These results also suggest that the SH3 domain of p85 may "self-associate" with the proline-rich motifs of the same subunit as part of the PI 3-kinase regulatory mechanism.

    Funded by: NIGMS NIH HHS: GM 36624, GM 41890, R01 GM041890

    The Journal of biological chemistry 1994;269;3;1927-33

  • Functional and physical interaction of protein-tyrosine kinases Fyn and Csk in the T-cell signaling system.

    Takeuchi M, Kuramochi S, Fusaki N, Nada S, Kawamura-Tsuzuku J, Matsuda S, Semba K, Toyoshima K, Okada M and Yamamoto T

    Institute of Medical Science, University of Tokyo, Japan.

    The Src-like protein-tyrosine kinase Fyn is associated with T-cell antigen receptor. Transient expression of actively mutated Fyn, having Phe-528 instead of Tyr-528 or Thr-338 instead of Ile-338, in Jurkat T-cells stimulated the serum response element (SRE), 12-O-tetradecanoyl-phorbol-13-acetate response element, cyclic AMP response element, and c-fos promoter. The stimulation of SRE was particularly prominent not only with active Fyn but also with normal (wild-type) Fyn. SRE was also stimulated by both normal and active Lck. Furthermore, normal and active Fyn stimulated transcription from the IL-2 gene promoter when transfected cells were stimulated by concanavalin A plus 12-O-tetradecanoylphorbol-13-acetate. Under the same conditions, Lck did not stimulate IL-2 promoter unless it was activated by mutation. Interestingly, a mutant Fyn, which has deletions within the SH2 region and so is able to transform chicken embryo fibroblasts, did not stimulate either the c-fos or IL-2 promoter, suggesting the importance of this region in T-cell signaling. Csk, which phos 1f40 phorylates tyrosine residues in the negative regulatory sites of Src family kinases, down-regulated Fyn- and Lck-mediated stimulation of the serum response element and Fyn-mediated enhancement of IL-2 promoter activity. These data suggest that Fyn and Lck, whose activities are regulated by Csk, are involved in different phases of T-cell activation.

    The Journal of biological chemistry 1993;268;36;27413-9

  • A role for Fyn tyrosine kinase in the suckling behaviour of neonatal mice.

    Yagi T, Aizawa S, Tokunaga T, Shigetani Y, Takeda N and Ikawa Y

    Laboratory of Molecular Oncology, Tsukuba Life Science Center, Institute of Physical and Chemical Research (RIKEN), Ibaraki, Japan.

    Non-receptor-type tyrosine kinases of the Src family, such as Src, Yes and Fyn, are strongly expressed in the brain and have been suggested to have an important function in the central nervous system. We generated Fyn-deficient mice by inserting the beta-galactosidase gene (lacZ) into the fyn gene. The homozygous Fyn-mutant neonates from homozygous Fyn-deficient parents died because of a suckling problem. Neonates were, however, able to suckle milk normally when the homozygous mother's mammary glands had been activated by suckling of a heterozygous or wild-type pup. In these homozygous pups, the modified glomerular complex of the olfactory bulb, which had been suggested to play a role in perceiving pheromones, was abnormal in shape and reduced in size, and the hippocampal cell-layer was undulated. These results suggest that Fyn may be involved in the initial step of instinctive suckling behaviour in neonates.

    Nature 1993;366;6457;742-5

  • T cell receptor zeta/CD3-p59fyn(T)-associated p120/130 binds to the SH2 domain of p59fyn(T).

    da Silva AJ, Janssen O and Rudd CE

    Division of Tumor Immunology, Dana-Farber Cancer Institute, Boston, Massachusetts.

    Intracellular signaling from the T cell receptor (TCR)zeta/CD3 complex is likely to be mediated by associated protein tyrosine kinases such as p59fyn(T), ZAP-70, and the CD4:p56lck and CD8:p56lck coreceptors. The nature of the signaling cascade initiated by these kinases, their specificities, and downstream targets remain to be elucidated. The TCR-zeta/CD3:p59fyn(T) complex has previously been noted to coprecipitate a 120/130-kD doublet (p120/130). This intracellular protein of unknown identity associates directly with p59fyn(T) within the receptor complex. In this study, we have shown that this interaction with p120/130 is specifically mediated by the SH2 domain (not the fyn-SH3 domain) of p59fyn(T). Further, based on the results of in vitro kinase assays, p120/130 appears to be preferentially associated with p59fyn(T) in T cells, and not with p56lck. Antibody reprecipitation studies identified p120/130 as a previously described 130-kD substrate of pp60v-src whose function and structure is unknown. TCR-zeta/CD3 induced activation of T cells augmented the tyrosine phosphorylation of p120/130 in vivo as detected by antibody and GST:fyn-SH2 fusion proteins. p120/130 represents the first identified p59fyn(T):SH2 binding substrate in T cells, and as such is likely to play a key role in the early events of T cell activation.

    Funded by: PHS HHS: R01 12069

    The Journal of experimental medicine 1993;178;6;2107-13

  • The association of the protein tyrosine kinases p56lck and p60fyn with the glycosyl phosphatidylinositol-anchored proteins Thy-1 and CD48 in rat thymocytes is dependent on the state of cellular activation.

    Garnett D, Barclay AN, Carmo AM and Beyers AD

    MRC Cellular Immunology Unit, Sir William Dunn School of Pathology, University of Oxford, GB.

    Cell surface glycoproteins anchored to the plasma membrane via glycosylphosphatidylinositol (GPI) structures, and hence having no cytoplasmic domains, can nevertheless transmit activation signals in lymphocytes. By immunoprecipitation from detergent lysates and in vitro immune complex kinase reactions the GPI-anchored molecules Thy-1 and CD48 are shown to be associated with multimolecular complexes of phosphoproteins including the protein tyrosine kinases p56lck and p60fyn in both rat and mouse thymocytes. Moreover, the kinase activity associated with Thy-1 on rat thymocytes is shown to be dependent on the activation state of the cells, with stimulation by the lectin, concanavalin A, producing a marked decrease in Thy-1-associated kinase activity. In such activated cells, there is an increased association of kinase activity with CD48, but this may be explained in terms of increased surface expression of CD48 and of increased total kinase activity. Additional phosphoproteins of 85, 36 and 32 kDa were consistently seen as components of the complexes.

    Funded by: Wellcome Trust

    European journal of immunology 1993;23;10;2540-4

  • Mapping of sites on the Src family protein tyrosine kinases p55blk, p59fyn, and p56lyn which interact with the effector molecules phospholipase C-gamma 2, microtubule-associated protein kinase, GTPase-activating protein, and phosphatidylinositol 3-kinase.

    Pleiman CM, Clark MR, Gauen LK, Winitz S, Coggeshall KM, Johnson GL, Shaw AS and Cambier JC

    Depar 1f40 tment of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206.

    Engagement of the B-cell antigen receptor complex induces immediate activation of receptor-associated Src family tyrosine kinases including p55blk, p59fyn, p53/56lyn, and perhaps p56lck, and this response is accompanied by tyrosine phosphorylation of distinct cellular substrates. These kinases act directly or indirectly to phosphorylate and/or activate effector proteins including p42 (microtubule-associated protein kinase) (MAPK), phospholipases C-gamma 1 (PLC gamma 1) and C-gamma 2 (PLC gamma 2), phosphatidylinositol 3-kinase (PI 3-K), and p21ras-GTPase-activating protein (GAP). Although coimmunoprecipitation results indicate that the Src family protein tyrosine kinases interact physically with some of these effector molecules, the molecular basis of this interaction has not been established. Here, we show that three distinct sites mediate the interaction of these kinases with effectors. The amino-terminal 27 residues of the unique domain of p56lyn mediate association with PLC gamma 2, MAPK, and GAP. Binding to PI 3-K is mediated through the Src homology 3 (SH3) domains of the Src family kinases. Relatively small proportions of cellular PI 3-K, PLC gamma 2, MAPK, and GAP, presumably those which are tyrosine phosphorylated, bind to the SH2 domains of these kinases. Comparative analysis of binding activities of Blk, Lyn, and Fyn shows that these kinases differ in their abilities to associate with MAPK and PI 3-K, suggesting that they may preferentially bind and subsequently phosphorylate distinct sets of downstream effector molecules in vivo. Fast protein liquid chromatography Mono Q column-fractionated MAPK maintains the ability to bind bacterially expressed Lyn, suggesting that the two kinases may interact directly.

    Funded by: NIAID NIH HHS: AI20519, AI21768, AI29903

    Molecular and cellular biology 1993;13;9;5877-87

  • Src-homology 3 domain of protein kinase p59fyn mediates binding to phosphatidylinositol 3-kinase in T cells.

    No authors listed

    Division of Tumor Immunology, Dana-Farber Cancer Institute, Boston, MA 02115.

    The Src-related tyrosine kinase p59fyn(T) plays an important role in the generation of intracellular signals from the T-cell antigen receptor TCR zeta/CD3 complex. A key question concerns the nature and the binding sites of downstream components that interact with this Src-related kinase. p59fyn(T) contains Src-homology 2 and 3 domains (SH2 and SH3) with a capacity to bind to intracellular proteins. One potential downstream target is phosphatidylinositol 3-kinase (PI 3-kinase). In this study, we demonstrate that anti-CD3 and anti-Fyn immunoprecipitates possess PI 3-kinase activity as assessed by TLC and HPLC. Both free and receptor-bound p59fyn(T) were found to bind to the lipid kinase. Further, our results indicate that Src-related kinases have developed a novel mechanism to interact with PI 3-kinase. Precipitation using GST fusion proteins containing Fyn SH2, SH3, and SH2/SH3 domains revealed that PI 3-kinase bound principally to the SH3 domain of Fyn. Fyn SH3 bound directly to the p85 subunit of PI 3-kinase as expressed in a baculoviral system. Anti-CD3 crosslinking induced an increase in the detection of Fyn SH3-associated PI 3-kinase activity. Thus PI 3-kinase is a target of SH3 domains and is likely to play a major role in the signals derived from the TCR zeta/CD3-p59fyn complex.

    Funded by: NCI NIH HHS: CA51887-02; NIGMS NIH HHS: GM36624, GM41890, R01 GM041890

    Proceedings of the National Academy of Sciences of the United States of America 1993;90;15;7366-70

  • Crystal structure of the SH3 domain in human Fyn; comparison of the three-dimensional structures of SH3 domains in tyrosine kinases and spectrin.

    Noble ME, Musacchio A, Saraste M, Courtneidge SA and Wierenga RK

    EMBL, Heidelberg, Germany.

    The Src-homology 3 (SH3) region is a protein domain consisting of approximately 60 residues. It occurs in a large number of eukaryotic proteins involved in signal transduction, cell polarization and membrane--cytoskeleton interactions. The function is unknown, but it is probably involved in specific protein--protein interactions. Here we report the crystal structure of the SH3 domain of Fyn (a Src family tyrosine kinase) at 1.9 A resolution. The crystals have two SH3 molecules per asymmetric unit. These two Fyn SH3 domains are not related by a local twofold axis. The crystal structures of spectrin and Fyn SH3 domains as well as the solution structure of the Src SH3 domain show that these all have the same basic fold. A protein domain which has the same topology as SH3 is present in the prokaryotic regulatory enzyme BirA. The comparison between the crystal structures of Fyn and spectrin SH3 domains shows that a conserved surface patch, consisting mainly of aromatic residues, is flanked by two hairpin-like loops (residues 94-104 and 114-118 in Fyn). These loops are different in tyrosine kinase and spectrin SH3 domains. They could modulate the binding properties of the aromatic surface.

    The EMBO journal 1993;12;7;2617-24

  • Human Sos1: a guanine nucleotide exchange factor for Ras that binds to GRB2.

    Chardin P, Camonis JH, Gale NW, van Aelst L, Schlessinger J, Wigler MH and Bar-Sagi D

    Institut de Pharmacologie Moleculaire et Cellulaire, CNRS, Valbonne, France.

    A human complementary DNA was isolated that encodes a widely expressed protein, hSos1, that is closely related to Sos, the product of the Drosophila son of sevenless gene. The hSos1 protein contains a region of significant sequence similarity to CDC25, a guanine nucleotide exchange factor for Ras from yeast. A fragment of hSos1 encoding the CDC25-related domain complemented loss of CDC25 function in yeast. This hSos1 domain specifically stimulated guanine nucleotide exchange on mammalian Ras proteins in vitro. Mammalian cells overexpressing full-length hSos1 had increased guanine nucleotide exchange activity. Thus hSos1 is a guanine nucleotide exchange factor for Ras. The hSos1 interacted with growth factor receptor-bound protein 2 (GRB2) in vivo and in vitro. This interaction was mediated by the carboxyl-terminal domain of hSos1 and the Src homology 3 (SH3) domains of GRB2. These results suggest that the coupling of receptor tyrosine kinases to Ras signaling is mediated by a molecular complex consisting of GRB2 and hSos1.

    Funded by: NCI NIH HHS: CA46370, CA55360

    Science (New York, N.Y.) 1993;260;5112;1338-43

  • Functional coupling of the src-family protein tyrosine kinases p59fyn and p53/56lyn with the interleukin 2 receptor: implications for redundancy and pleiotropism in cytokine signal transduction.

    Kobayashi N, Kono T, Hatakeyama M, Minami Y, Miyazaki T, Perlmutter RM and Taniguchi T

    Institute for Molecular and Cellular Biology, Osaka University, Japan.

    The binding of interleukin 2 (IL-2) to the IL-2 receptor (IL-2R) induces a rapid increase in tyrosine phosphorylation of cellular proteins. In a previous study, we have shown that p56lck (lck), a src-family protein tyrosine kinase (src-PTK), physically and functionally associates with the IL-2R beta chain (IL-2R beta). To further investigate a role of src-PTKs in IL-2 signaling, we analyzed a mouse pro-B-cell line, in which lck is not expressed detectably. We observed that in this cell line, IL-2 induces activation of at least two src-PTKs, p59fyn (fyn) and p53/56lyn (lyn). Interestingly, stimulation of this cell line with IL-3 also induces activation of src-PTKs. The activation of fyn or lyn seems to be selective for stimulation with IL-2 or IL-3 since stimulation with IL-6 fails to activate them. Furthermore, we provide evidence for the physical association of fyn with IL-2R beta. Taken together with previous results, our current study suggests that different src-PTKs, each of which is expressed in a cell-type-specific manner, can participate in the IL-2 signal transduction.

    Proceedings of the National Academy of Sciences of the United States of America 1993;90;9;4201-5

  • In vitro tyrosine phosphorylation of PLC-gamma 1 and PLC-gamma 2 by src-family protein tyrosine kinases.

    Liao F, Shin HS and Rhee SG

    Department of Molecular Biology and Genetics, Johns Hopkins University, School of Medicine, Baltimore, MD 21205.

    The phosphorylation of purified phospholipase C-gamma 1 (PLC-gamma 1) and PLC-gamma 2 by src-family-protein tyrosine kinases (PTKs) P56lck, p53/56lyn, p59hck, p59fyn, and p60src was studied in vitro. All five PTKs phosphorylated PLC-gamma 1 and PLC-gamma 2, suggesting that both PLC-gamma isozymes can be phosphorylated in cells by any of the src-family PTKs in response to the activation of cell surface receptors. Comparison of the in vitro phosphorylation rates revealed no distinct specificity between PLC-gamma 1 and PLC-gamma 2, or between the five PTKs.

    Biochemical and biophysical research communications 1993;191;3;1028-33

  • Activation of Src family kinases by colony stimulating factor-1, and their association with its receptor.

    Courtneidge SA, Dhand R, Pilat D, Twamley GM, Waterfield MD and Roussel MF

    Differentiation Programme, European Molecular Biology Laboratory, Heidelberg, Germany.

    The receptor for the macrophage colony stimulating factor-1 (CSF-1R) is a transmembrane glycoprotein with intrinsic tyrosine kinase activity. CSF-1 stimulation promotes the growth of cells of the macrophage lineage and of fibroblasts engineered to express CSF-1R. We show that CSF-1 stimulation resulted in activation of three Src family kinases, Src, Fyn and Yes. Concomitant with their activation, all three Src family kinases were found to associate with the ligand-activated CSF-1 receptor. These interactions were also demonstrated in SF9 insect cells co-infected with viruses encoding the CSF-1 receptor and Fyn, and the isolated SH2 domain of Fyn was capable of binding the CSF-1R in vitro. Analysis of mutant CSF-1Rs revealed that the 'kinase insert' (KI) domain of CSF-1R was not required for interactions with Src family kinases, but that mutation of one of the receptor autophosphorylation sites, Tyr809, reduced both their binding and enzymatic activation. Because fibroblasts expressing this receptor mutant are unable to form colonies in semi-solid medium or to grow in chemically defined medium in the presence of CSF-1, the Src family kinases may play a physiological role in the mitogenic response to CSF-1.

    Funded by: NCI NIH HHS: CA-56819

    The EMBO journal 1993;12;3;943-50

  • Impaired long-term potentiation, spatial learning, and hippocampal development in fyn mutant mice.

    Grant SG, O'Dell TJ, Karl KA, Stein PL, Soriano P and Kandel ER

    Center for Neurobiology and Behavior, Howard Hughes Medical Institute, College of Physicians and Surgeons, Columbia University, New York, NY 10032.

    Mice with mutations in four nonreceptor tyrosine kinase genes, fyn, src, yes, and abl, were used to study the role of these kinases in long-term potentiation (LTP) and in the relation of LTP to spatial learning and memory. All four kinases were expressed in the hippocampus. Mutations in src, yes, and abl did not interfere with either the induction or the maintenance of LTP. However, in fyn mutants, LTP was blunted even though synaptic transmission and two short-term forms of synaptic plasticity, paired-pulse facilitation and post-tetanic potentiation, were normal. In parallel with the blunting of LTP, fyn mutants showed impaired spatial learning, consistent with a functional link between LTP and learning. Although fyn is expressed at mature synapses, its lack of expression during development resulted in an increased number of granule cells in the dentate gyrus and of pyramidal cells in the CA3 region. Thus, a common tyrosine kinase pathway may regulate the growth of neurons in the developing hippocampus and the strength of synaptic plasticity in the mature hippocampus.

    Funded by: NIA NIH HHS: AG08702; NICHD NIH HHS: HD24875; NIMH NIH HHS: MH45923; ...

    Science (New York, N.Y.) 1992;258;5090;1903-10

  • Expression and characterization of the p85 subunit of the phosphatidylinositol 3-kinase complex and a related p85 beta protein by using the baculovirus expression system.

    Gout I, Dhand R, Panayotou G, Fry MJ, Hiles I, Otsu M and Waterfield MD

    Receptor Studies Group, Ludwig Institute for Cancer Research (Middlesex Branch), London, U.K.

    PtdIns 3-kinase associates with certain activated protein-tyrosine kinase receptors and with the pp60c-src/polyoma middle-T complex, suggesting that the enzyme is involved in growth regulation. The purified PtdIns 3-kinase appears to have two subunits, of 85 kDa and 110 kDa. Structural analysis at protein and cDNA levels revealed two forms of the 85 kDa subunit, one which associates with PtdIns 3-kinase activity termed p85 alpha, and a protein of unknown function, p85 beta. Both 85 kDa proteins contain src-homology regions 2 and 3 (SH2 and SH3), but lack enzymic activity, suggesting that they may be regulatory subunits of PtdIns 3-kinase. To probe their structure and function further, p85 alpha and p85 beta have been expressed and purified in large amounts from insect cells by using baculovirus vectors. Specific antisera detect p85 alpha, but not p85 beta, associated with PtdIns 3-kinase activity in various cell types. Co-expression studies in insect cells have shown that p85 alpha and p85 beta are substrates for the protein-tyrosine kinases of epidermal growth factor, colony-stimulating factor 1 and c-erbB2 receptors and the src family kinase p59c-fyn. Both p85 alpha and p85 beta form tight complexes with these protein-tyrosine kinases as measured by immunoprecipitation and kinase assays in vitro. The specificity of binding of free p85 is less restricted than that of p85 in the active PtdIns 3-kinase complex with the 110 kDa protein. The relevance of these results to growth-factor-induced PtdIns 3-kinase activation is discussed.

    The Biochemical journal 1992;288 ( Pt 2);395-405

  • Signal transduction through decay-accelerating factor. Interaction of glycosyl-phosphatidylinositol anchor and protein tyrosine kinases p56lck and p59fyn 1.

    Shenoy-Scaria AM, Kwong J, Fujita T, Olszowy MW, Shaw AS and Lublin DM

    Department of Pathology, Washington University School of Medicine, St. Louis, MO 63110.

    Decay-accelerating factor (DAF or CD55) is a 70-kDa glycosyl-phosphatidylinositol (GPI)-anchored protein that protects cells from complement-mediated lysis by either preventing the formation of or dissociating C3 convertases. Cross-linking of DAF on human peripheral T cells by polyclonal antibodies has previously been reported to lead to lymphocyte proliferation. Two mAb, both mapping to the third short consensus repeat region of DAF, were able to trigger proliferation of human peripheral T cells. To determine the role of the GPI anchor in cell activation, we transfected EL-4 murine thymoma cells with cDNA encoding either DAF or a transmembrane form of DAF (DAF-TM). The DAF-transfected cells were able to transduce late activation events as evidenced by IL-2 production, whereas DAF-TM transfected cells were unable to do so. The GPI-anchored DAF was able to transduce early activation events leading to the tyrosine phosphorylation of a 40-kDa protein and several proteins in the 85-95 kDa range--an event absent in DAF-TM-transfected cells. Furthermore, anti-DAF immunoprecipitates of DAF-transfected cells contain tyrosine kinase activity leading to the phosphorylation of 40-, 56-60-, and 85-kDa proteins, whereas anti-DAF immunoprecipitates of DAF-TM-transfected cells did not have an associated kinase activity. Both p56lck and p59fyn were associated with DAF in DAF-transfected EL-4 cells. In HeLa cells transfected with fyn, DAF associated with p59fyn. This complex of DAF with src family protein tyrosine kinases requires the GPI anchor and suggests a pathway for signaling through GPI-anchored membrane proteins.

    Funded by: NIGMS NIH HHS: GM41297

    Journal of immunology (Baltimore, Md. : 1950) 1992;149;11;3535-41

  • Engagement of the TcR/CD3 complex stimulates p59fyn(T) activity: detection of associated proteins at 72 and 120-130 kD.

    da Silva AJ, Yamamoto M, Zalvan CH and Rudd CE

    Division of Tumor Immunology, Dana-Farber Cancer Institute, Boston, MA 02115.

    Engagement of the T cell antigen-receptor complex (TcR/CD3) induces the rapid tyrosine phosphorylation of a spectrum of substrates whose modification is crucial to the activation process. Although CD4-associated p56lck and TcR/CD3-associated p59fyn(T) could account for this cascade, TcR/CD3 driven stimulation of p59fyn(T) activity has not been demonstrated. In this study, we confirm in Brij 96 based buffers that p59fyn(T) can be co-purified in association with the TcR/CD3 complex, and further demonstrate that antibody-induced cross-linking of TcR/CD3 on the cell surface results in a dramatic increase in the detection of receptor associated kinase activity. This results in an increased phosphorylation and detection of TcR/CD3-p59fyn(T) associated zeta (16-21 kD), p72 (72 kD) and p120/130 (120-130 kD) chains. A distinction between increased recruitment and/or activity of p59fyn(T) was not possible due to the fact that receptor associated p59fyn(T) could not be detected by immunoblotting. However, an alternative approach using membrane vesicles demonstrated an anti-CD3 mediated induced increase (2-5-fold) in the phosphorylation of the fyn kinase. Augmented catalytic activity was accompanied by p59fyn(T) labelling at the autophosphorylation site Tyr420, consistent with stimulated fyn catalytic activity, as well as the phosphorylation of polypeptides at 18-20 (TcR zeta), 31, 90 and 130 kD. Stimulation of fyn activity implicates this kinase as a mediator of the tyrosine phosphorylation events originating from the TcR/CD3 complex.

    Funded by: NCI NIH HHS: CA51887-02

    Molecular immunology 1992;29;12;1417-25

  • The glycophosphatidylinositol-anchored Thy-1 molecule interacts with the p60fyn protein tyrosine kinase in T cells.

    Thomas PM and Samelson LE

    Cell Biology and Metabolism Branch, National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892.

    Stimulation of murine T cells by engagement of the multi-component T cell antigen receptor or by cross-linking the Thy-1 molecule leads to a similar response characterized by lymphocyte activation and lymphokine production. The early biochemical events induced by engaging these molecules also are similar and begin with activation of a tyrosine kinase pathway and tyrosine phosphorylation of a comparable set of substrates. Previous work demonstrates that the protein tyrosine kinase p60fyn is associated with the antigen receptor and therefore it may participate in the tyrosine phosphorylations that are observed with antigen receptor signaling. In this study we demonstrate that the Thy-1 molecule is also associated with p60fyn in a murine T cell hybridoma and in murine thymocytes. The interaction is independent of antigen receptor expression. Thy-1 is a member of the class of molecules anchored to the plasma membrane by a glycophosphatidylinositol (GPI) group. The association of Thy-1 with p60fyn is dependent on the GPI linkage, since cleavage of the GPI anchor disrupts the interaction. The association of Thy-1 and p60fyn suggests a means by which Thy-1 cross-linking leads to tyrosine phosphorylation and T cell activation.

    The Journal of biological chemistry 1992;267;17;12317-22

  • Induction of Fc epsilon RII/CD23 on PHA-activated human peripheral blood T lymphocytes and the association of Fyn tyrosine kinase with Fc epsilon RII/CD23.

    Maekawa N, Kawabe T, Sugie K, Kawakami T, Iwata S, Uchida A and Yodoi J

    Department of Biological Responses, Kyoto University Medical School, Japan.

    Research in immunology 1992;143;4;422-5

  • p21rasGAP association with Fyn, Lyn, and Yes in thrombin-activated platelets.

    Cichowski K, McCormick F and Brugge JS

    Howard Hughes Medical Institute, Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia 19104-6148.

    Activation of platelets by thrombin and other physiological agonists leads to a dramatic increase in tyrosine phosphorylation of multiple cellular proteins (Ferrell, J. E., and Martin, G. S. (1988) Mol. Cell. Biol. 8, 3606-3610; Golden, A., and Brugge, J. S. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 901-905; Nakamura, S., and Yamamura, H. (1989) J. Biol. Chem. 264, 7089-7091). To date, none of the tyrosine kinases that are involved in platelet activation, nor the substrates that are phosphorylated in response to agonists, have been identified. A "kinase trapping" strategy, designed to take advantage of the stability of known tyrosine kinase-substrate interactions, was employed to address both issues. p21rasGAP antibodies were used to examine the phosphorylated state of GAP in agonist-treated platelets and to isolate potential GAP-kinase complexes. We show that GAP and two proteins of 59 and 68 kDa are phosphorylated on tyrosine after thrombin stimulation and that three Src-related protein tyrosine kinases, Fyn, Lyn and Yes, are associated with GAP in complexes, detectable only after agonist stimulation. The thrombin-dependent detection of these kinases in GAP immunoprecipitates suggests that thrombin may either induce the formation of these complexes or activate kinases that are associated with GAP prior to, or following, agonist stimulation. This approach of "trapping" kinases bound to their substrates will be useful in identifying non-receptor tyrosine kinases involved in signaling pathways. Furthermore, although GAP phosphorylation has been previously implicated in growth factor signaling pathways, this is the first example of its involvement downstream from a G-protein-coupled receptor.

    Funded by: NCI NIH HHS: CA47572

    The Journal of biological chemistry 1992;267;8;5025-8

  • Protein tyrosine kinase p59fyn is associated with the T cell receptor-CD3 complex in functional human lymphocytes.

    Gassmann M, Guttinger M, Amrein KE and Burn P

    Department of Biology, Pharmaceutical Research New Technologies, F. Hoffmann-La Roche Ltd., Basel, Switzerland.

    The binding of antigen to the multicomponent T cell antigen receptor (TcR)-CD3 complex leads to the activation of several signal transduction pathways which result in T lymphocyte proliferation and lymphokine secretion by molecular mechanisms and catalytic molecules as yet poorly defined. One of the earliest events that follows the triggering of the antigen-specific TcR-CD3 complex is a rapid tyrosine phosphorylation of several intracellular substrates, suggesting stimulation of at least one protein tyrosine kinase (PTK). Since none of the seven TcR-CD3 subunits exhibits a recognizable kinase domain, it seems likely that the receptor complex is associated with an intracellular PTK. p59fyn and the T lymphocyte-specific p56lck are two intracellular, non-receptor, cell membrane-associated PTK of the src family expressed in T lymphocytes. Here, we show by double immunofluorescence microscopy a specific co-distribution of p59fyn, but not p56lck, with antibody-induced TcR or CD3 caps in intact human T lymphocytes. These findings provide direct evidence for a significant association of p59fyn with the TcR-CD3 complex under physiologically relevant conditions in functional T lymphocytes. They suggest that p59fyn is a crucial component of the TcR signal transduction machinery and that one of the earliest consequences of antigen recognition by the TcR is p59fyn-mediated phosphorylation of intracellular substrates on tyrosine residues.

    European journal of immunology 1992;22;1;283-6

  • Maekawa N, Kawabe T, Sugie K, Kawakami T, Maeda Y, Uchida A and Yodoi J

    Department of Biological Responses, Kyoto University Medical School, Japan.

    Despite the evidence for the expression of Fc epsilon RII/CD23, a glycoprotein that is a low-affinity Fc receptor for IgE, obtained on T cell lines and some pathological T cells, that of Fc epsilon RII/CD23 on normal human T cells is still unclear. We studied the emergence of T cells bearing Fc epsilon RII/CD23 in short-term culture of normal human peripheral blood mononuclear cells stimulated with 15 microliters/ml phytohemagglutinin (PHA). Using two-dimension flow cytometry, more than 10% of Fc epsilon RII/CD23(+) cells were shown to co-express CD3 antigen. Both CD4(+) and CD8(+) T cells expressed Fc epsilon RII/CD23. The expression of mRNA for Fc epsilon RII/CD23 on PHA and IL-4 stimulated PBMC was demonstrated by northern blotting and in-situ hybridization. The mechanism of signal transduction through Fc epsilon RII/CD23 was dissected by transfection of cDNA coding for Fc epsilon RII to the human natural killer-like cell line YT, activation of which was easily detected by the induction of interleukin-2 receptor/p55 (Tac). Cross-linking of Fc epsilon RII/CD23 with H107 anti-Fc epsilon RII monoclonal antibody enhanced IL-2R/p55 expression on YT cells transfected with Fc epsilon RII cDNA (YTSER). A possible involvement of protein-tyrosine kinase in the Fc epsilon RII-mediated signal transduction was studied using YTSER. Fc epsilon RII was physically associated with an src-family tyrosine kinase p59fyn and not with p56lck, which was also found in YT cells. Recently it was reported that p59fyn was associated with T-cell antigen receptor. Our results collectively suggest the multiple function of p59fyn which may be implicated in the Fc epsilon RII-mediated activation signal in YT cells.

    International journal of tissue reactions 1992;14;3;121-30

  • Fyn tyrosine kinase associated with Fc epsilon RII/CD23: possible multiple roles in lymphocyte activation.

    Sugie K, Kawakami T, Maeda Y, Kawabe T, Uchida A and Yodoi J

    Department of Biological Responses, Kyoto University Medical School, Japan.

    Expression of low-affinity Fc receptor for IgE (Fc epsilon RII), which is identical to the lymphocyte differentiation antigen CD23, is associated with activation of lymphoid cells. The mechanism of signal transduction through Fc epsilon RII/CD23 was dissected by transfection of cDNA coding for Fc epsilon RII to the YT human natural killer-like cell line, activation of which was easily detected by the induction of interleukin 2 receptor/p55(Tac). Cross-linking of Fc epsilon RII/CD23 with H107 anti-Fc epsilon RII monoclonal antibody markedly enhanced interleukin 2 receptor/p55 expression on the YT cells transfected with Fc epsilon RII cDNA (YTSER cells). Similar induction of interleukin 2 receptor/p55 by the cross-linking of Fc epsilon RII was observed on an Epstein-Barr virus-transformed B-cell line, 3B6, and fresh leukemic cells isolated from a patient with B-cell chronic lymphoblastic leukemia. Thus Fc epsilon RII/CD23 provides activation signals not only in YTSER cells but also in activated B cells. A possible involvement of protein-tyrosine kinase in the Fc epsilon RII-mediated signal transduction was studied. Fc epsilon RII was physically associated with a src family tyrosine kinase p59fyn and not with p56lck, which was also found in YT cells. Recently it was reported that p59fyn was associated with T-cell antigen receptor. Our results collectively suggest the multiple functions of p59fyn that may be implicated in Fc epsilon RII-mediated activation signal in YT cells.

    Proceedings of the National Academy of Sciences of the United States of America 1991;88;20;9132-5

  • Membrane glycoprotein IV (CD36) is physically associated with the Fyn, Lyn, and Yes protein-tyrosine kinases in human platelets.

    Huang MM, Bolen JB, Barnwell JW, Shattil SJ and Brugge JS

    Howard Hughes Medical Institute, University of Pennsylvania, School of Medicine, Philadelphia 19104.

    Activation of platelets with thrombin and other agonists causes a rapid increase in the phosphorylation of multiple proteins on tyrosine. To identify candidate protein-tyrosine kinases (PTKs; EC 2.7.1.112) that may be responsible for these phosphorylation events, we analyzed the expression of seven Src-family PTKs and examined the association of these kinases with known platelet membrane glycoproteins. Five Src-related PTKs were detected in platelets: pp60SRC, pp60FYN, pp62YES, pp61HCK, and two LYN products of Mr 54,000 and 58,000. The Fgr and Lck PTKs were not detected. Although strict comparative quantification of protein levels was not possible, pp60SRC was detected at higher levels than any of the other kinases. In addition, glycoprotein IV (GPIV, CD36), one of the major platelet membrane glycoproteins, was associated in a complex with the Fyn, Yes, and Lyn proteins in platelet lysates. Similar complexes were also found in two GPIV-expressing cell lines, C32 melanoma cells and HEL cells. Since PTKs appear to be involved in stimulus-response coupling at the plasma membrane, these results suggest that ligand interaction with GPIV may activate signaling pathways that are triggered by tyrosine phosphorylation.

    Funded by: NCI NIH HHS: CA27951

    Proceedings of the National Academy of Sciences of the United States of America 1991;88;17;7844-8

  • Structural elements that regulate pp59c-fyn catalytic activity, transforming potential, and ability to associate with polyomavirus middle-T antigen.

    Cheng SH, Espino PC, Marshall J, Harvey R, Merrill J and Smith AE

    Laboratory of Cellular Regulation, Genzyme Corporation, Framingham, Massachusetts 01701.

    Except for its unique amino-terminal region (residues 1 through 83), which possibly dictates substrate recognition, pp59c-fyn bears a high degree of homology with other members of the src family of tyrosine kinases. Here we show that the carboxy terminus of pp59c-fyn is necessary for stable middle-T-antigen association, that pp59c-fyn is normally phosphorylated on both serine and tyrosine residues, and that Tyr-531 and Tyr-420 are phosphorylation sites in vivo and in vitro, respectively. Analysis of a spontaneously generated mutant encoding a truncated form of pp59c-fyn and of variants specifically mutated at the Tyr-531 and Tyr-420 phosphorylation sites indicates that pp59c-fyn has regulatory elements analogous to those that have already been identified for other src-like tyrosine kinases. However, further examination of the pp59c-fyn variants suggests the likelihood of additional means by which its activities might be regulated. Although alteration of Tyr-531 to phenylalanine (531F) in pp59c-fyn results in a protein which is more active enzymatically that the wild type, the enhancement is much less than that for the analogous variant of pp60c-src. Furthermore, contrary to results of similar experiments on other src-like proto-oncogene products, 531F did not induce transformation of NIH 3T3 cells. Studies involving pp59c-fyn-pp60c-src chimeras in which the unique amino-terminal sequences (residues 1 through 83) of the two kinases were precisely interchanged implied that the inability of 531F to induce transformation is probably not caused by the absence of substrates for pp59c-fyn in NIH 3T3 cells but rather by the insufficient enhancement of pp59c-fyn kinase activity. It is therefore probable that the kinase and transforming activities of pp59c-fyn are repressed by additional regulatory elements possibly located in the amino-terminal half of the molecule.

    Funded by: NCI NIH HHS: CA 43186, CA 50661

    Journal of virology 1991;65;1;170-9

  • In vivo phosphorylation and membrane association of the fyn proto-oncogene product in IM-9 human lymphoblasts.

    Peters DJ, McGrew BR, Perron DC, Liptak LM and Laudano AP

    Department of Biochemistry, University of New Hampshire, Durham 03824.

    The protein product of the src-related proto-oncogene, fyn, was isolated from IM-9 cells with antibodies specific for the amino-terminal 22 residues of the fyn protein. Peptide mapping demonstrated that the fyn protein was distinct from the closely related c-src and c-fgr proteins. The fyn protein from IM-9 cells incorporated [3H]myristate in vivo and was found to be membrane associated. Phosphoamino acid analysis demonstrated that the fyn protein from IM-9 cells was phosphorylated in vivo predominantly on tyrosine and threonine with only a small amount of phosphoserine detected. the major chymotryptic phosphopeptide of the fyn protein was phosphorylated exclusively on tyrosine. This peptide was specifically precipitated by antibodies directed against a peptide modeled on the closely related carboxy termini of the c-src and fyn proteins. These results provide direct evidence for phosphorylation of tyrosine-531 in the carboxy-terminal chymotryptic peptide of the fyn protein. Phosphorylation of the corresponding site in the closely related c-src protein (tyrosine-527) represses src kinase activity and transforming ability. Loss of the phosphorylation site at tyrosine-531 may similarly contribute to the transforming abilities of carboxy-terminal deletion mutants of the fyn protein.

    Oncogene 1990;5;9;1313-9

  • Association between the PDGF receptor and members of the src family of tyrosine kinases.

    Kypta RM, Goldberg Y, Ulug ET and Courtneidge SA

    Differentiation Programme, European Molecular Biology Laboratory, Heidelberg, Federal Republic of Germany.

    We have examined the interaction between the platelet-derived growth factor (PDGF) receptor and three src family tyrosine kinases, pp60c-src, p59fyn, and pp62c-yes. The kinase activities of all three enzymes were elevated after PDGF stimulation of quiescent fibroblasts, coincident with association of the src family kinases with the PDGF receptor and other proteins. The presence of a protein of 81-85 kd in these complexes correlated with the detection of phosphatidylinositol (PI) kinase activity (previously described to associate with both the PDGF receptor and pp60c-src-middle T antigen). These results suggest that the physiological response to PDGF involves interaction of the receptor not only with serine/threonine and lipid kinases and a phospholipase, but also with other tyrosine kinases.

    Cell 1990;62;3;481-92

  • Chromosomal localization of the human fyn gene.

    Popescu NC, Kawakami T, Matsui T and Robbins KC

    Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, Maryland 20892.

    Oncogene 1987;1;4;449-51

  • Isolation and oncogenic potential of a novel human src-like gene.

    Kawakami T, Pennington CY and Robbins KC

    We have isolated cDNA molecules representing the complete coding sequence of a new human gene which is a member of the src family of oncogenes. Nucleotide sequence analysis revealed that this gene, termed slk, encoded a 537-residue protein which was 86% identical to the chicken proto-oncogene product, p60c-src, over a stretch of 191 amino acids at its carboxy terminus. In contrast, only 6% amino acid homology was observed within the amino-terminal 82 amino acid residues of these two proteins. It was possible to activate slk as a transforming gene by substituting approximately two-thirds of the slk coding sequence for an analogous region of the v-fgr onc gene present in Gardner-Rasheed feline sarcoma virus. The resulting hybrid protein molecule expressed in transformed cells demonstrated protein kinase activity with specificity for tyrosine residues.

    Molecular and cellular biology 1986;6;12;4195-201

  • yes-related protooncogene, syn, belongs to the protein-tyrosine kinase family.

    Semba K, Nishizawa M, Miyajima N, Yoshida MC, Sukegawa J, Yamanashi Y, Sasaki M, Yamamoto T and Toyoshima K

    An src/yes-related novel gene named syn (SYN in human gene nomenclature) has been identified in the human genome on chromosome 6 and characterized by molecular cloning. Nucleotide sequence analysis of cDNA clones showed that the c-syn gene could encode a protein-tyrosine kinase that is very similar in primary structure to the v-yes and human c-src proteins. A 2.8-kilobase transcript of the c-syn gene, which differs in size from those of the c-yes, c-src, and c-fgr genes, was observed in various cell types. These results show that syn is a new member of the tyrosine kinase oncogene family.

    Proceedings of the National Academy of Sciences of the United States of America 1986;83;15;5459-63

  • Classical conditioning of blood pressure in Macaca mulatta with cardiac rate controlled.

    Turkkan JS and Schoenfeld WN

    The Pavlovian journal of biological science 1979;14;1;10-9

  • The behavior of holo- and apo-forms of bovine superoxide dismutase at low pH.

    Fee JA and Phillips WD

    1. Holo-superoxide dismutase from bovine erythrocytes has been shown to undergo a reversible structural modification in the pH 3-5 range. 2. The spectral alterations observed on changing from neutrality to pH 2 were: a slight attenuation of the 680 nm absorbance; the loss of the 450 nm shoulder, apparent in the optical spectrum of the native protein; and a new band appeared at 330 nm. The circular dichroism at 600 nm was essentially lost while a weak negative band appeared at approx. 380 nm and a positive band at 310 nm. 3. The EPR spectrum was also modified on changing from the native to the low pH form: A parallel increased from approximately 130 to approximately 150 G, g parallel remained unchanged at approximately 2.27, and gm decreased from approximately 2.09 to approximately 2.08. The apparent linewidth remained essentially constant. 4. High resolution (220 MHz) PMR spectra of holo- and apoproteins revealed that the metals influence the three-dimensional structure of the protein. 5. PMR studies indicated that at pH 3 the apoprotein existed almost entirely in a random coil form and that it assumed a compact well-ordered structure on returning to neutral pH. The holoprotein maintained a compact, apparently dimeric, structure even at pH 3.

    Biochimica et biophysica acta 1975;412;1;26-38

Gene lists (6)

Gene List Source Species Name Description Gene count
L00000009 G2C Homo sapiens Human PSD Human orthologues of mouse PSD adapted from Collins et al (2006) 1080
L00000016 G2C Homo sapiens Human PSP Human orthologues of mouse PSP adapted from Collins et al (2006) 1121
L00000059 G2C Homo sapiens BAYES-COLLINS-HUMAN-PSD-CONSENSUS Human cortex PSD consensus 748
L00000061 G2C Homo sapiens BAYES-COLLINS-MOUSE-PSD-CONSENSUS Mouse cortex PSD consensus (ortho) 984
L00000069 G2C Homo sapiens BAYES-COLLINS-HUMAN-PSD-FULL Human cortex biopsy PSD full list 1461
L00000071 G2C Homo sapiens BAYES-COLLINS-MOUSE-PSD-FULL Mouse cortex PSD full list (ortho) 1556
© G2C 2014. The Genes to Cognition Programme received funding from The Wellcome Trust and the EU FP7 Framework Programmes:
EUROSPIN (FP7-HEALTH-241498), SynSys (FP7-HEALTH-242167) and GENCODYS (FP7-HEALTH-241995).

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