G2Cdb::Gene report

Gene id
Gene symbol
Homo sapiens
adaptor-related protein complex 2, alpha 1 subunit
G00000663 (Mus musculus)

Databases (9)

Curated Gene
OTTHUMG00000070490 (Vega human gene)
ENSG00000196961 (Ensembl human gene)
160 (Entrez Gene)
1085 (G2Cdb plasticity & disease)
AP2A1 (GeneCards)
601026 (OMIM)
Marker Symbol
Protein Expression
4306 (human protein atlas)
Protein Sequence
O95782 (UniProt)

Literature (50)

Pubmed - other

  • Competition model for upregulation of the major histocompatibility complex class II-associated invariant chain by human immunodeficiency virus type 1 Nef.

    Mitchell RS, Chaudhuri R, Lindwasser OW, Tanaka KA, Lau D, Murillo R, Bonifacino JS and Guatelli JC

    Department of Medicine,1 Division of Biology, University of California, San Diego, La Jolla, CA 92093-0679, USA. rsmitchell@ucsd.edu

    The human immunodeficiency virus type 1 (HIV-1) Nef protein upregulates the expression of the invariant chain (Ii)/major histocompatibility complex class II (MHC-II) complex at the cell surface. This complex appears to reach the antigen-loading endosomal compartment at least in part via an indirect pathway in which it is internalized from the cell surface via the adaptor protein 2 (AP-2) complex. Here we provide evidence for a competition model to explain how Nef upregulates the expression of Ii at the cell surface. In this model, Nef and Ii compete for binding to AP-2. In support of this model, Nef decreased the rate of internalization of Ii from the cell surface. The AP-binding dileucine motif in Nef, ENTSLL(165), was necessary and sufficient for the upregulation of Ii. In addition, two leucine-based AP-binding motifs in the Ii cytoplasmic tail, DDQRDLI(8) and EQLPML(17), were critical for the efficient upregulation of Ii by Nef. Experiments using Nef variants in which the native dileucine-based sorting motif was replaced with similar motifs from cellular transmembrane proteins allowed modulation of AP-binding specificity. Analysis of these variants suggested that the binding of Nef to AP-2 is sufficient to upregulate Ii at the plasma membrane. Finally, interference with the expression of AP-2 caused an upregulation of Ii at the plasma membrane, and this decreased the effect of Nef. These data indicate that Nef usurps AP-2 complexes to dysregulate Ii trafficking and potentially interfere with antigen presentation in the context of MHC-II.

    Funded by: Intramural NIH HHS; NIAID NIH HHS: AI 36214, AI07384, AI36214, AI38201, P30 AI036214, R01 AI038201, R21 AI038201, T32 AI007384

    Journal of virology 2008;82;16;7758-67

  • Inhibitory function of adapter-related protein complex 2 alpha 1 subunit in the process of nuclear translocation of human immunodeficiency virus type 1 genome.

    Kitagawa Y, Kameoka M, Shoji-Kawata S, Iwabu Y, Mizuta H, Tokunaga K, Fujino M, Natori Y, Yura Y and Ikuta K

    Department of Virology, Research Institute for Microbial Diseases and Osaka University, Osaka 565-0871, Japan.

    The transfection of human cells with siRNA against adapter-related protein complex 2 alpha 1 subunit (AP2alpha) was revealed to significantly up-regulate the replication of human immunodeficiency virus type 1 (HIV-1). This effect was confirmed by cell infection with vesicular stomatitis virus G protein-pseudotyped HIV-1 as well as CXCR4-tropic and CCR5-tropic HIV-1. Viral adsorption, viral entry and reverse transcription processes were not affected by cell transfection with siRNA against AP2alpha. In contrast, viral nuclear translocation as well as the integration process was significantly up-regulated in cells transfected with siRNA against AP2alpha. Confocal fluorescence microscopy revealed that a subpopulation of AP2alpha was not only localized in the cytoplasm but was also partly co-localized with lamin B, importin beta and Nup153, implying that AP2alpha negatively regulates HIV-1 replication in the process of nuclear translocation of viral DNA in the cytoplasm or the perinuclear region. We propose that AP2alpha may be a novel target for disrupting HIV-1 replication in the early stage of the viral life cycle.

    Virology 2008;373;1;171-80

  • A conserved dileucine motif mediates clathrin and AP-2-dependent endocytosis of the HIV-1 envelope protein.

    Byland R, Vance PJ, Hoxie JA and Marsh M

    Cell Biology Unit, MRC-Laboratory for Molecular Cell Biology and Department of Biochemistry and Molecular Biology, University College London, London WC1E 6BT, United Kingdom.

    During the assembly of enveloped viruses viral and cellular components essential for infectious particles must colocalize at specific membrane locations. For the human and simian immunodeficiency viruses (HIV and SIV), sorting of the viral envelope proteins (Env) to assembly sites is directed by trafficking signals located in the cytoplasmic domain of the transmembrane protein gp41 (TM). A membrane proximal conserved GYxxØ motif mediates endocytosis through interaction with the clathrin adaptor AP-2. However, experiments with SIV(mac239) Env indicate the presence of additional signals. Here we show that a conserved C-terminal dileucine in HIV(HxB2) also mediates endocytosis. Biochemical and morphological assays demonstrate that the C-terminal dileucine motif mediates internalization as efficiently as the GYxxØ motif and that both must be removed to prevent Env internalization. RNAi experiments show that depletion of the clathrin adaptor AP-2 leads to increased plasma membrane expression of HIV Env and that this adaptor is required for efficient internalization mediated by both signals. The redundancy of conserved endocytosis signals and the role of the SIV(mac239) Env GYxxØ motif in SIV pathogenesis, suggest that these motifs have functions in addition to endocytosis, possibly related to Env delivery to the site of viral assembly and/or incorporation into budding virions.

    Funded by: Medical Research Council: MC_U122665002, U.1226.00.003.00001.01(65002); NIAID NIH HHS: AI-49784, R01 AI049784

    Molecular biology of the cell 2007;18;2;414-25

  • Two mechanistically distinct forms of endocytosis in adrenal chromaffin cells: Differential effects of SH3 domains and amphiphysin antagonism.

    Elhamdani A, Azizi F, Solomaha E, Palfrey HC and Artalejo CR

    Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA. aelhamda@med.wayne.edu

    We previously identified two forms of endocytosis using capacitance measurements in chromaffin cells: rapid endocytosis (RE), dynamin-1 dependent but clathrin-independent and slow endocytosis (SE), dynamin-2 and clathrin-dependent. Various recombinant SH3 domains that interact with the proline-rich domain of dynamin were introduced into single cells via the patch pipette. GST-SH3 domains of amphiphysin-1, intersectin-IC, and endophilin-I inhibited SE but had no effect on RE. Grb2-SH3 (N-terminal) or a mutant of amphiphysin-1-SH3 was inactive on either process. These data confirm that dynamin-1 dependent RE is independent of clathrin and show that amphiphysin is exclusively associated with clathrin and dynamin-2-dependent SE.

    Funded by: NIDDK NIH HHS: DK-58921; NIGMS NIH HHS: GM-56396; NIMH NIH HHS: MH-47181

    FEBS letters 2006;580;13;3263-9

  • Interaction of HIV-1 Gag with the clathrin-associated adaptor AP-2.

    Batonick M, Favre M, Boge M, Spearman P, Höning S and Thali M

    Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT 05405, USA.

    The envelope glycoprotein (Env) of HIV-1 interacts with the clathrin-associated adaptor complex AP-2 during the late phase of the viral replication cycle. Upon its synthesis, Env, therefore, is retrieved from the cellular surface unless internalization is inhibited by viral Gag. Here we demonstrate that not only Env, but also HIV-1 Gag, specifically binds to AP-2. Gag-AP-2 association was found to depend on tyrosine residue 132 and valine residue 135 at the matrix-capsid junction in the Gag polyprotein. Results of a morphological analysis of viral egress from cells expressing dominant-negative AP-2 suggest an involvement of AP-2 in confining HIV-1 exit to distinct microdomains. Further, particle release from AP-2-mutant cells was enhanced compared to release from wild-type cells but the infectivity of virus released from these cells was moderately reduced. Together these data attribute a role to the AP-2 complex in the regulation of HIV-1 assembly/release.

    Funded by: NIAID NIH HHS: R01 AI047727, R01AI047727-04

    Virology 2005;342;2;190-200

  • 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

  • A human protein-protein interaction network: a resource for annotating the proteome.

    Stelzl U, Worm U, Lalowski M, Haenig C, Brembeck FH, Goehler H, Stroedicke M, Zenkner M, Schoenherr A, Koeppen S, Timm J, Mintzlaff S, Abraham C, Bock N, Kietzmann S, Goedde A, Toksöz E, Droege A, Krobitsch S, Korn B, Birchmeier W, Lehrach H and Wanker EE

    Max Delbrueck Center for Molecular Medicine, 13092 Berlin-Buch, Germany.

    Protein-protein interaction maps provide a valuable framework for a better understanding of the functional organization of the proteome. To detect interacting pairs of human proteins systematically, a protein matrix of 4456 baits and 5632 preys was screened by automated yeast two-hybrid (Y2H) interaction mating. We identified 3186 mostly novel interactions among 1705 proteins, resulting in a large, highly connected network. Independent pull-down and co-immunoprecipitation assays validated the overall quality of the Y2H interactions. Using topological and GO criteria, a scoring system was developed to define 911 high-confidence interactions among 401 proteins. Furthermore, the network was searched for interactions linking uncharacterized gene products and human disease proteins to regulatory cellular pathways. Two novel Axin-1 interactions were validated experimentally, characterizing ANP32A and CRMP1 as modulators of Wnt signaling. Systematic human protein interaction screens can lead to a more comprehensive understanding of protein function and cellular processes.

    Cell 2005;122;6;957-68

  • Human immunodeficiency virus Nef induces rapid internalization of the T-cell coreceptor CD8alphabeta.

    Stove V, Van de Walle I, Naessens E, Coene E, Stove C, Plum J and Verhasselt B

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

    Human immunodeficiency virus (HIV) Nef is a membrane-associated protein decreasing surface expression of CD4, CD28, and major histocompatibility complex class I on infected cells. We report that Nef strongly down-modulates surface expression of the beta-chain of the CD8alphabeta receptor by accelerated endocytosis, while CD8 alpha-chain expression is less affected. By mutational analysis of the cytoplasmic tail of the CD8 beta-chain, an FMK amino acid motif was shown to be critical for Nef-induced endocytosis. Although independent of CD4, endocytosis of the CD8 beta-chain was abrogated by the same mutations in Nef that affect CD4 down-regulation, suggesting common molecular interactions. The ability to down-regulate the human CD8 beta-chain was conserved in HIV-1, HIV-2, and simian immunodeficiency virus SIVmac239 Nef and required an intact AP-2 complex. The Nef-mediated internalization of receptors, such as CD4, major histocompatibility complex class I, CD28, and CD8alphabeta, may contribute to the subversion of the host immune system and progression towards AIDS.

    Journal of virology 2005;79;17;11422-33

  • PICK1 interacts with ABP/GRIP to regulate AMPA receptor trafficking.

    Lu W and Ziff EB

    Program in Neuroscience and Physiology, New York University School of Medicine, New York, New York 10016, USA.

    PICK1 and ABP/GRIP bind to the AMPA receptor (AMPAR) GluR2 subunit C terminus. Transfer of the receptor from ABP/GRIP to PICK1, facilitated by GluR2 S880 phosphorylation, may initiate receptor trafficking. Here we report protein interactions that regulate these steps. The PICK1 BAR domain interacts intermolecularly with the ABP/GRIP linker II region and intramolecularly with the PICK1 PDZ domain. Binding of PKCalpha or GluR2 to the PICK1 PDZ domain disrupts the intramolecular interaction and facilitates the PICK1 BAR domain association with ABP/GRIP. Interference with the PICK1-ABP/GRIP interaction impairs S880 phosphorylation of GluR2 by PKC and decreases the constitutive surface expression of GluR2, the NMDA-induced endocytosis of GluR2, and recycling of internalized GluR2. We suggest that the PICK1 interaction with ABP/GRIP is a critical step in controlling GluR2 trafficking.

    Funded by: NIMH NIH HHS: MH067229

    Neuron 2005;47;3;407-21

  • Yeast two-hybrid identification of prostatic proteins interacting with human sex hormone-binding globulin.

    Pope SN and Lee IR

    School of Biomedical Sciences, Curtin University of Technology, G.P.O. Box U1987, Perth, WA 6845, Australia.

    Yeast two-hybrid (Y2H) screening of a prostate cDNA library with the cDNA for sex hormone-binding globulin (SHBG) has been used to identify proteins through which SHBG may exert autocrine or paracrine effects on sex steroid target tissues. The library screen gave 230 positive interactions of which around 60 have been sequenced. Of the proteins identified to date from database (BLAST) searches of these sequences, SHBG is one of those occurring most frequently. Amongst the proteins of interest are the membrane-associated proteins flotillin-1 and PRV-1, the enzymes cathepsin D, kallikrein 4 and acid phosphatase, various metallothioneins and translation elongation factor 1 alpha. The significance of the interaction of SHBG with these proteins is discussed.

    The Journal of steroid biochemistry and molecular biology 2005;94;1-3;203-8

  • 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

  • Functional proteomics mapping of a human signaling pathway.

    Colland F, Jacq X, Trouplin V, Mougin C, Groizeleau C, Hamburger A, Meil A, Wojcik J, Legrain P and Gauthier JM

    Hybrigenics SA, 75014 Paris, France. fcolland@hybrigenics.fr

    Access to the human genome facilitates extensive functional proteomics studies. Here, we present an integrated approach combining large-scale protein interaction mapping, exploration of the interaction network, and cellular functional assays performed on newly identified proteins involved in a human signaling pathway. As a proof of principle, we studied the Smad signaling system, which is regulated by members of the transforming growth factor beta (TGFbeta) superfamily. We used two-hybrid screening to map Smad signaling protein-protein interactions and to establish a network of 755 interactions, involving 591 proteins, 179 of which were poorly or not annotated. The exploration of such complex interaction databases is improved by the use of PIMRider, a dedicated navigation tool accessible through the Web. The biological meaning of this network is illustrated by the presence of 18 known Smad-associated proteins. Functional assays performed in mammalian cells including siRNA knock-down experiments identified eight novel proteins involved in Smad signaling, thus validating this integrated functional proteomics approach.

    Genome research 2004;14;7;1324-32

  • HIV-1 Tat enters T cells using coated pits before translocating from acidified endosomes and eliciting biological responses.

    Vendeville A, Rayne F, Bonhoure A, Bettache N, Montcourrier P and Beaumelle B

    UMR 5539 CNRS, Département Biologie-Santé, Case 107, Université Montpellier II, 34095 Montpellier Cedex 5, France.

    The HIV-1 Tat protein is secreted by infected cells. Extracellular Tat can affect bystander uninfected T cells and induce numerous biological responses such as apoptosis and cytokine secretion. Tat is likely involved in several immune disorders during AIDS. Nevertheless, it is not known whether Tat triggers cell responses directly upon binding to signaling receptors at the plasma membrane or after delivery to the cytosol. The pathway that enables Tat to reach the cytosol is also unclear. Here we visualized Tat within T-cell-coated pits and endosomes. Moreover, inhibitors of clathrin/AP-2-mediated uptake such as chlorpromazine, activated RhoA, or dominant-negative mutants of Eps15, intersectin, dynamin, or rab5 impaired Tat delivery to the cytosol by preventing its endocytosis. Molecules neutralizing low endosomal pH or Hsp90 inhibitors abolished Tat entry at a later stage by blocking its endosomal translocation, as directly shown using a cell-free translocation assay. Finally, endosomal pH neutralization prevented Tat from inducing T-cell responses such as NF-kappaB activation, apoptosis, and interleukin secretion, indicating that cytosolic delivery is required for Tat signaling. Hence, Tat enters T cells essentially like diphtheria toxin, using clathrin-mediated endocytosis before low-pH-induced and Hsp90-assisted endosomal translocation. Cell responses are then induced from the cytosol.

    Molecular biology of the cell 2004;15;5;2347-60

  • The DNA sequence and biology of human chromosome 19.

    Grimwood J, Gordon LA, Olsen A, Terry A, Schmutz J, Lamerdin J, Hellsten U, Goodstein D, Couronne O, Tran-Gyamfi M, Aerts A, Altherr M, Ashworth L, Bajorek E, Black S, Branscomb E, Caenepeel S, Carrano A, Caoile C, Chan YM, Christensen M, Cleland CA, Copeland A, Dalin E, Dehal P, Denys M, Detter JC, Escobar J, Flowers D, Fotopulos D, Garcia C, Georgescu AM, Glavina T, Gomez M, Gonzales E, Groza M, Hammon N, Hawkins T, Haydu L, Ho I, Huang W, Israni S, Jett J, Kadner K, Kimball H, Kobayashi A, Larionov V, Leem SH, Lopez F, Lou Y, Lowry S, Malfatti S, Martinez D, McCready P, Medina C, Morgan J, Nelson K, Nolan M, Ovcharenko I, Pitluck S, Pollard M, Popkie AP, Predki P, Quan G, Ramirez L, Rash S, Retterer J, Rodriguez A, Rogers S, Salamov A, Salazar A, She X, Smith D, Slezak T, Solovyev V, Thayer N, Tice H, Tsai M, Ustaszewska A, Vo N, Wagner M, Wheeler J, Wu K, Xie G, Yang J, Dubchak I, Furey TS, DeJong P, Dickson M, Gordon D, Eichler EE, Pennacchio LA, Richardson P, Stubbs L, Rokhsar DS, Myers RM, Rubin EM and Lucas SM

    Stanford Human Genome Center, Department of Genetics, Stanford University School of Medicine, 975 California Avenue, Palo Alto, California 94304, USA. jane@shgc.stanford.edu

    Chromosome 19 has the highest gene density of all human chromosomes, more than double the genome-wide average. The large clustered gene families, corresponding high G + C content, CpG islands and density of repetitive DNA indicate a chromosome rich in biological and evolutionary significance. Here we describe 55.8 million base pairs of highly accurate finished sequence representing 99.9% of the euchromatin portion of the chromosome. Manual curation of gene loci reveals 1,461 protein-coding genes and 321 pseudogenes. Among these are genes directly implicated in mendelian disorders, including familial hypercholesterolaemia and insulin-resistant diabetes. Nearly one-quarter of these genes belong to tandemly arranged families, encompassing more than 25% of the chromosome. Comparative analyses show a fascinating picture of conservation and divergence, revealing large blocks of gene orthology with rodents, scattered regions with more recent gene family expansions and deletions, and segments of coding and non-coding conservation with the distant fish species Takifugu.

    Nature 2004;428;6982;529-35

  • 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

  • Identification and regulation of tissue-specific cis-acting elements associated with the human AP-2alpha gene.

    Zhang J and Williams T

    Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut, USA.

    Mice lacking transcription factor AP-2alpha exhibit defects in the formation of the head, body wall, heart, neural tube, eye, and limbs, reflecting important sites of AP-2alpha expression in the developing embryo. AP-2alpha is also expressed in the postnatal mammary gland and has been linked to tumor progression and defects in growth regulation in the breast. We have used a transgenic mouse approach to identify tissue-specific cis-acting sequences associated with expression of the human AP-2alpha gene. Our analysis indicates that multiple elements located throughout the gene contribute to expression in the trigeminal ganglia, spinal cord, mammary gland, and epidermis. A discrete cis-element located within the fifth intron is required for expression in the face and limbs, and we have derived a permanent line of AP-2alpha::lacZ transgenic mice to assess expression of this latter enhancer throughout morphogenesis. We also introduced this transgene into an AP-2alpha-null mouse background and detected subtle alterations of its expression within the progress zone and apical ectodermal ridge of the forelimbs. Similar changes in lacZ expression were observed within the zeugopod, and these correlated with defects in radius condensation in AP-2alpha-knockout mice. Taken together, these findings indicate that cell:cell communication within the forelimb is altered in the absence of AP-2alpha and reveal novel regulatory potential for AP-2alpha in limb development.

    Funded by: NCI NIH HHS: CA77833; NIDCR NIH HHS: DE12728

    Developmental dynamics : an official publication of the American Association of Anatomists 2003;228;2;194-207

  • CRMP-2 regulates polarized Numb-mediated endocytosis for axon growth.

    Nishimura T, Fukata Y, Kato K, Yamaguchi T, Matsuura Y, Kamiguchi H and Kaibuchi K

    Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, 65 Tsurumai, Showa, Nagoya, Aichi 466-8550, Japan.

    Axon growth during neural development is highly dependent on both cytoskeletal re-organization and polarized membrane trafficking. Previously, we demonstrated that collapsin response mediator protein-2 (CRMP-2) is critical for specifying axon/dendrite fate and axon growth in cultured hippocampal neurons, possibly by interacting with tubulin heterodimers and promoting microtubule assembly. Here, we identify Numb as a CRMP-2-interacting protein. Numb has been shown to interact with alpha-adaptin and to be involved in endocytosis. We found that Numb was associated with L1, a neuronal cell adhesion molecule that is endocytosed and recycled at the growth cone, where CRMP-2 and Numb were colocalized. Furthermore, expression of dominant-negative CRMP-2 mutants or knockdown of CRMP-2 message with small-interfering (si) RNA inhibited endocytosis of L1 at axonal growth cones and suppressed axon growth. These results suggest that in addition to regulating microtubule assembly, CRMP-2 is involved in polarized Numb-mediated endocytosis of proteins such as L1.

    Nature cell biology 2003;5;9;819-26

  • RLIP, an effector of the Ral GTPases, is a platform for Cdk1 to phosphorylate epsin during the switch off of endocytosis in mitosis.

    Rossé C, L'Hoste S, Offner N, Picard A and Camonis J

    Institut Curie, INSERM U528, Paris, France.

    The Ral signaling pathway is critically involved in Ras-dependent oncogenesis. One of its key actors, RLIP/RalBP1, which participates in receptor endocytosis during interphase, is also involved in mitotic processes when endocytosis is switched off. During mitosis, RLIP76 is located on the duplicated centrosomes and is required for their proper separation and movement to the poles. We have looked for actors that associate with RLIP during mitosis. We show here that RLIP/RalBP1 interacts with an active p34cdc2.cyclinB1 (cdk1) enzyme and that this interaction is crucial for the mitotic phosphorylation of Epsin that, once phosphorylated, is no longer competent for endocytosis. We show also that this latter phosphorylation is dependent on Ral signaling. We propose that RLIP/RalBP1 is used as a platform by the mitotic cdk1 to facilitate the phosphorylation of Epsin, which makes Epsin incompetent for endocytosis during mitosis, when endocytosis is switched off.

    The Journal of biological chemistry 2003;278;33;30597-604

  • The B cell coreceptor CD22 associates with AP50, a clathrin-coated pit adapter protein, via tyrosine-dependent interaction.

    John B, Herrin BR, Raman C, Wang YN, Bobbitt KR, Brody BA and Justement LB

    Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555, USA.

    The B cell coreceptor CD22 plays an important role in regulating signal transduction via the B cell Ag receptor. Studies have shown that surface expression of CD22 can be modulated in response to binding of ligand (i.e., mAb). Thus, it is possible that alterations in the level of CD22 expression following binding of natural ligand(s) may affect its ability to modulate the Ag receptor signaling threshold at specific points during B cell development and differentiation. Therefore, it is important to delineate the physiologic mechanism by which CD22 expression is controlled. In the current study, yeast two-hybrid analysis was used to demonstrate that CD22 interacts with AP50, the medium chain subunit of the AP-2 complex, via tyrosine-based internalization motifs in its cytoplasmic domain. This interaction was further characterized using yeast two-hybrid analysis revealing that Tyr(843) and surrounding amino acids in the cytoplasmic tail of CD22 comprise the primary binding site for AP50. Subsequent studies using transfectant Jurkat cell lines expressing wild-type or mutant forms of CD22 demonstrated that either Tyr(843) or Tyr(863) is sufficient for mAb-mediated internalization of CD22 and that these motifs are involved in its interaction with the AP-2 complex, as determined by coprecipitation of alpha-adaptin. Finally, experiments were performed demonstrating that treatment of B cells with either intact anti-Ig Ab or F(ab')(2) blocks ligand-mediated internalization of CD22. In conclusion, these studies demonstrate that internalization of CD22 is dependent on its association with the AP-2 complex via tyrosine-based internalization motifs.

    Funded by: NIAID NIH HHS: AI36401, R01 AI036401

    Journal of immunology (Baltimore, Md. : 1950) 2003;170;7;3534-43

  • Transcriptional activation by AP-2alpha is modulated by the oncogene DEK.

    Campillos M, García MA, Valdivieso F and Vázquez J

    Centro de Biología Molecular Severo Ochoa, CSIC-Universidad Autónoma de Madrid, 28049 Cantoblanco, Madrid, Spain.

    Cell differentiation and development are highly regulated processes at the transcriptional level. One of the main transcription factors that regulate these processes is AP-2alpha, a cell-type specific protein required for vertebrate development and embryogenesis. AP-2alpha also regulates apoptosis and cell-cycle specific events by interacting with the oncogene c-Myc. In searching for novel AP-2alpha- interacting factors, using an affinity chromatography approach, we have observed that oncoprotein DEK interacts with AP-2alpha in vitro. The existence of an interaction between AP-2alpha and DEK in cellular cultures was demonstrated by expression of a tagged AP-2alpha form followed by immunodetection. By transient co-expression experiments using a reporter for APOE promoter activity we have found that DEK stimulates the transactivation activity of AP-2alpha over APOE promoter. Finally, electrophoretic mobility shift assays suggested that DEK enhances the DNA-binding activity of AP-2alpha. Our data suggest a novel cellular function of DEK as a transcriptional co-activator.

    Nucleic acids research 2003;31;5;1571-5

  • Rab11-FIP2, an adaptor protein connecting cellular components involved in internalization and recycling of epidermal growth factor receptors.

    Cullis DN, Philip B, Baleja JD and Feig LA

    Department of Biochemistry, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.

    Rab11-FIP2 is a member of a newly identified family of Rab11-binding proteins that have been implicated in the function of recycling endosomes. Here we show that Rab11-FIP2 may also be involved with the process of receptor-mediated endocytosis. First we demonstrate that Rab11-FIP2 contains an NPF motif that allows it to bind Reps1, a member of a family of EH domain proteins involved in endocytosis. We also show that Rab11-FIP2 associates with the alpha-adaptin subunit of AP-2 complexes, which are known to recruit receptors into clathrin-coated vesicles. Finally, we find that overexpression of Rab11-FIP2 suppresses the internalization of epidermal growth factor receptors, but not transferrin receptors, through binding sites that promote complex formation with Rab11, Reps1, and alpha-adaptin. These findings suggest that Rab11-FIP2 may participate in the coupling of receptor-mediated endocytosis to the subsequent sorting of receptor-containing vesicles in endosomes.

    Funded by: PHS HHS: NIH R01 47717

    The Journal of biological chemistry 2002;277;51;49158-66

  • Clint: a novel clathrin-binding ENTH-domain protein at the Golgi.

    Kalthoff C, Groos S, Kohl R, Mahrhold S and Ungewickell EJ

    Department of Cell Biology, Center of Anatomy, Hannover Medical School, Hannover, Germany.

    We have characterized a novel clathrin-binding 68-kDa epsin N-terminal homology domain (ENTH-domain) protein that we name clathrin interacting protein localized in the trans-Golgi region (Clint). It localizes predominantly to the Golgi region of epithelial cells as well as to more peripheral vesicular structures. Clint colocalizes with AP-1 and clathrin only in the perinuclear area. Recombinantly expressed Clint interacts directly with the gamma-appendage domain of AP-1, with the clathrin N-terminal domain through the peptide motif (423)LFDLM, with the gamma-adaptin ear homology domain of Golgi-localizing, gamma-adaptin ear homology domain 2, with the appendage domain of beta2-adaptin and to a lesser extent with the appendage domain of alpha-adaptin. Moreover, the Clint ENTH-domain asssociates with phosphoinositide-containing liposomes. A significant amount of Clint copurifies with rat liver clathrin-coated vesicles. In rat kidney it is preferentially expressed in the apical region of epithelial cells that line the collecting duct. Clathrin and Clint also colocalize in the apical region of enterocytes along the villi of the small intestine. Apart from the ENTH-domain Clint has no similarities with the epsins AP180/CALM or Hip1/1R. A notable feature of Clint is a carboxyl-terminal methionine-rich domain (Met(427)-Met(605)), which contains >17% methionine. Our results suggest that Clint might participate in the formation of clathrin-coated vesicles at the level of the trans-Golgi network and remains associated with the vesicles longer than clathrin and adaptors.

    Molecular biology of the cell 2002;13;11;4060-73

  • Cloning, physical mapping and structural characterization of the human alpha(A)-adaptin gene.

    Scorilas A, Levesque MA, Ashworth LK and Diamandis EP

    Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, 600 University Avenue, Toronto, Ont. M5G 1X5, Canada.

    Adaptins are major structural components of heterotetrameric protein complexes called adaptors, which are involved in intracellular receptor transport via clathrin-coated vesicles. In mice, one of these adaptins has been shown to be encoded by two genes, alpha(A)-adaptin and alpha(C)-adaptin, the former of which is expressed as two alternatively spliced transcripts. Using positional cloning gene approaches, we were able to identify the human alpha(A)-adaptin gene, which consists of 24 exons spanning over 40 kb on chromosome 19q13.3 between the loci of the R-ras gene and the polynucleotide kinase phosphatase gene. The novel gene encodes a 977 amino acid, 107.6 kDa protein with 98% amino acid sequence identity to its murine ortholog. Human alpha(A)-adaptin is expressed as a full-length transcript in forebrain, skeletal muscle, spinal cord, cerebellum, salivary gland, heart and colon. It is also ubiquitously expressed in tissues and in ZR-75-1 breast cancer cells and LNCaP prostate carcinoma cells as a smaller variant generated by splicing out of an exon encoding 22 amino acids in the hinge region of the protein.

    Gene 2002;289;1-2;191-9

  • Multiple signals regulate trafficking of the mannose 6-phosphate-uncovering enzyme.

    Lee WS, Rohrer J, Kornfeld R and Kornfeld S

    Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

    The "uncovering enzyme," which catalyzes the second step in the formation of the mannose 6-phosphate recognition marker on lysosomal enzyme oligosaccharides, resides primarily in the trans-Golgi network and cycles between this compartment and the plasma membrane. An analysis of green fluorescent protein-uncovering enzyme chimeras revealed that the transmembrane segment and the first 11 residues of the 41-residue-cytoplasmic tail are sufficient for retention in the trans-Golgi network. The next eight residues ((486)YAYHPLQE(493)) facilitate exit from this compartment. Kinetic studies demonstrated that the (488)YHPL(491) sequence also mediates rapid internalization at the plasma membrane. This motif binds adaptor protein-2 in glutathione S-transferase-uncovering enzyme-cytoplasmic tail pull-down assays, indicating that the uncovering enzyme is endocytosed via clathrin-coated vesicles. Consistent with this finding, endogenous uncovering enzyme was detected in purified clathrin-coated vesicles. The enzyme with a Y486A mutation is internalized normally but accumulates on the cell surface because of increased recycling to the plasma membrane. This residue is required for efficient return of the enzyme from endosomes to the trans-Golgi network. These findings indicate that the YAYHPLQE motif is recognized at several sorting sites, including the trans-Golgi network, the plasma membrane, and the endosome.

    Funded by: NCI NIH HHS: CA08759

    The Journal of biological chemistry 2002;277;5;3544-51

  • HIP1 functions in clathrin-mediated endocytosis through binding to clathrin and adaptor protein 2.

    Metzler M, Legendre-Guillemin V, Gan L, Chopra V, Kwok A, McPherson PS and Hayden MR

    Centre for Molecular Medicine and Therapeutics, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada.

    Polyglutamine expansion in huntingtin is the underlying mutation leading to neurodegeneration in Huntington disease. This mutation influences the interaction of huntingtin with different proteins, including huntingtin-interacting protein 1 (HIP1), in which affinity to bind to mutant huntingtin is profoundly reduced. Here we demonstrate that HIP1 colocalizes with markers of clathrin-mediated endocytosis in neuronal cells and is highly enriched on clathrin-coated vesicles (CCVs) purified from brain homogenates. HIP1 binds to the clathrin adaptor protein 2 (AP2) and the terminal domain of the clathrin heavy chain, predominantly through a small fragment encompassing amino acids 276-335. This region, which contains consensus clathrin- and AP2-binding sites, functions in conjunction with the coiled-coil domain to target HIP1 to CCVs. Expression of various HIP1 fragments leads to a potent block of clathrin-mediated endocytosis. Our findings demonstrate that HIP1 is a novel component of the endocytic machinery.

    The Journal of biological chemistry 2001;276;42;39271-6

  • Adaptins: the final recount.

    Boehm M and Bonifacino JS

    Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.

    Adaptins are subunits of adaptor protein (AP) complexes involved in the formation of intracellular transport vesicles and in the selection of cargo for incorporation into the vesicles. In this article, we report the results of a survey for adaptins from sequenced genomes including those of man, mouse, the fruit fly Drosophila melanogaster, the nematode Caenorhabditis elegans, the plant Arabidopsis thaliana, and the yeasts, Saccharomyces cerevisiae and Schizosaccharomyces pombe. We find that humans, mice, and Arabidopsis thaliana have four AP complexes (AP-1, AP-2, AP-3, and AP-4), whereas D. melanogaster, C. elegans, S. cerevisiae, and S. pombe have only three (AP-1, AP-2, and AP-3). Additional diversification of AP complexes arises from the existence of adaptin isoforms encoded by distinct genes or resulting from alternative splicing of mRNAs. We complete the assignment of adaptins to AP complexes and provide information on the chromosomal localization, exon-intron structure, and pseudogenes for the different adaptins. In addition, we discuss the structural and evolutionary relationships of the adaptins and the genetic analyses of their function. Finally, we extend our survey to adaptin-related proteins such as the GGAs and stonins, which contain domains homologous to the adaptins.

    Molecular biology of the cell 2001;12;10;2907-20

  • Association of insulin-like growth factor 1 receptor with EHD1 and SNAP29.

    Rotem-Yehudar R, Galperin E and Horowitz M

    Department of Cell Research and Immunology, Tel-Aviv University, Ramat-Aviv, 69978, Tel-Aviv, Israel.

    Ligand-induced receptor-mediated endocytosis plays a central role in regulating signaling conveyed by tyrosine kinase receptors. This process depends on the recruitment of the adaptor protein 2 (AP-2) complex, clathrin, dynamin, and other accessory proteins to the ligand-bound receptor. We show here that besides AP-2 and clathrin, two other proteins participate in the endocytic process of the insulin-like growth factor receptor (IGF-1R); they are EHD1, an Eps15 homology (EH) domain-containing protein 1, and SNAP29, a synaptosomal-associated protein. EHD1 and SNAP29 form complexes with alpha-adaptin of AP-2 and co-localize in endocytic vesicles, indicating a role for them in endocytosis. EHD1 and SNAP29 interact directly with each other and are present in complexes with IGF-1R. After IGF-1 induction, EHD1 and IGF-1R co-localize intracellularly. Overexpression of EHD1 in Chinese hamster ovary cells represses IGF-1-mediated signaling, as measured by mitogen-activated protein kinase phosphorylation and Akt phosphorylation, indicating that EHD1 plays a role as a down-regulator in IGF-1 signaling pathway.

    The Journal of biological chemistry 2001;276;35;33054-60

  • The huntingtin interacting protein HIP1 is a clathrin and alpha-adaptin-binding protein involved in receptor-mediated endocytosis.

    Waelter S, Scherzinger E, Hasenbank R, Nordhoff E, Lurz R, Goehler H, Gauss C, Sathasivam K, Bates GP, Lehrach H and Wanker EE

    Max-Planck-Institut für Molekulare Genetik, Ihnestrasse 73, D-14195 Berlin (Dahlem), Germany.

    The huntingtin interacting protein (HIP1) is enriched in membrane-containing cell fractions and has been implicated in vesicle trafficking. It is a multidomain protein containing an N-terminal ENTH domain, a central coiled-coil forming region and a C-terminal actin-binding domain. In the present study we have identified three HIP1 associated proteins, clathrin heavy chain and alpha-adaptin A and C. In vitro binding studies revealed that the central coiled-coil domain is required for the interaction of HIP1 with clathrin, whereas DPF-like motifs located upstream to this domain are important for the binding of HIP1 to the C-terminal 'appendage' domain of alpha-adaptin A and C. Expression of full length HIP1 in mammalian cells resulted in a punctate cytoplasmic immunostaining characteristic of clathrin-coated vesicles. In contrast, when a truncated HIP1 protein containing both the DPF-like motifs and the coiled-coil domain was overexpressed, large perinuclear vesicle-like structures containing HIP1, huntingtin, clathrin and endocytosed transferrin were observed, indicating that HIP1 is an endocytic protein, the structural integrity of which is crucial for maintenance of normal vesicle size in vivo.

    Human molecular genetics 2001;10;17;1807-17

  • PACS-1 binding to adaptors is required for acidic cluster motif-mediated protein traffic.

    Crump CM, Xiang Y, Thomas L, Gu F, Austin C, Tooze SA and Thomas G

    Vollum Institute, L-474, Oregon Health Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR 97201-3098, USA.

    PACS-1 is a cytosolic protein involved in controlling the correct subcellular localization of integral membrane proteins that contain acidic cluster sorting motifs, such as furin and human immunodeficiency virus type 1 (HIV-1) NEF: We have now investigated the interaction of PACS-1 with heterotetrameric adaptor complexes. PACS-1 associates with both AP-1 and AP-3, but not AP-2, and forms a ternary complex between furin and AP-1. A short sequence within PACS-1 that is essential for binding to AP-1 has been identified. Mutation of this motif yielded a dominant-negative PACS-1 molecule that can still bind to acidic cluster motifs on cargo proteins but not to adaptor complexes. Expression of dominant-negative PACS-1 causes a mislocalization of both furin and mannose 6-phosphate receptor from the trans-Golgi network, but has no effect on the localization of proteins that do not contain acidic cluster sorting motifs. Furthermore, expression of dominant-negative PACS-1 inhibits the ability of HIV-1 Nef to downregulate MHC-I. These studies demonstrate the requirement for PACS-1 interactions with adaptor proteins in multiple processes, including secretory granule biogenesis and HIV-1 pathogenesis.

    Funded by: NIAID NIH HHS: AI49793, R01 AI048585, R01 AI048585-01A1, R01 AI048585-02, R01 AI048585-03, R01 AI048585-04, R01 AI048585-05, R01 AI049793; NIDDK NIH HHS: DK37274, R01 DK037274, R01 DK044629

    The EMBO journal 2001;20;9;2191-201

  • Shc mediates ligand-induced internalization of epidermal growth factor receptors.

    Sakaguchi K, Okabayashi Y and Kasuga M

    Second Department of Internal Medicine, Kobe University School of Medicine, Kobe, 650-0017, Japan.

    In order to clarify the physiological relevance of the interaction between Shc and adaptins, components of plasma membrane-coated pit adaptor complex AP2, we investigated the role of Shc in ligand-induced endocytosis of epidermal growth factor (EGF) receptors. In vitro peptide binding assay showed that alpha-adaptin bound to the wild-type peptide corresponding to amino acids 346-355 of Shc, RDLFDMKPFE, but not to the mutant peptide in which both phenylalanines at 349 and 354 were substituted for alanines (FA). Using adenovirus vectors carrying a herpes simplex virus epitope-tagged 52-kDa wild-type Shc and Shc FA, we examined the interaction between Shc, AP2, and EGF receptors in intact cells. Alpha-adaptin bound to wild-type Shc in an EGF-dependent manner, whereas EGF-dependent association of alpha-adaptin with Shc FA was markedly reduced. In addition, EGF increased the amount of alpha-adaptin coprecipitated with EGF receptors in cells expressing wild-type Shc but not Shc FA. These results suggest that EGF stimulates Shc-AP2 complex formation and association of Shc-AP2 complexes with EGF receptors. Internalization assay showed that (125)I-EGF internalization was reduced in cells overexpressing Shc FA. Immunofluorescence study showed that punctate staining along the plasma membrane border as well as punctate pattern characteristic of cytoplasmic vesicles near the plasma membrane was enhanced in cells expressing wild-type Shc. These results suggest, therefore, the implication of Shc in ligand-induced endocytosis of EGF receptors in intact cells.

    Biochemical and biophysical research communications 2001;282;5;1154-60

  • Toward a catalog of human genes and proteins: sequencing and analysis of 500 novel complete protein coding human cDNAs.

    Wiemann S, Weil B, Wellenreuther R, Gassenhuber J, Glassl S, Ansorge W, Böcher M, Blöcker H, Bauersachs S, Blum H, Lauber J, Düsterhöft A, Beyer A, Köhrer K, Strack N, Mewes HW, Ottenwälder B, Obermaier B, Tampe J, Heubner D, Wambutt R, Korn B, Klein M and Poustka A

    Molecular Genome Analysis, German Cancer Research Center, 69120 Heidelberg, Germany. s.wiemann@dkfz.de

    With the complete human genomic sequence being unraveled, the focus will shift to gene identification and to the functional analysis of gene products. The generation of a set of cDNAs, both sequences and physical clones, which contains the complete and noninterrupted protein coding regions of all human genes will provide the indispensable tools for the systematic and comprehensive analysis of protein function to eventually understand the molecular basis of man. Here we report the sequencing and analysis of 500 novel human cDNAs containing the complete protein coding frame. Assignment to functional categories was possible for 52% (259) of the encoded proteins, the remaining fraction having no similarities with known proteins. By aligning the cDNA sequences with the sequences of the finished chromosomes 21 and 22 we identified a number of genes that either had been completely missed in the analysis of the genomic sequences or had been wrongly predicted. Three of these genes appear to be present in several copies. We conclude that full-length cDNA sequencing continues to be crucial also for the accurate identification of genes. The set of 500 novel cDNAs, and another 1000 full-coding cDNAs of known transcripts we have identified, adds up to cDNA representations covering 2%--5 % of all human genes. We thus substantially contribute to the generation of a gene catalog, consisting of both full-coding cDNA sequences and clones, which should be made freely available and will become an invaluable tool for detailed functional studies.

    Genome research 2001;11;3;422-35

  • Association of Trk neurotrophin receptors with components of the cytoplasmic dynein motor.

    Yano H, Lee FS, Kong H, Chuang J, Arevalo J, Perez P, Sung C and Chao MV

    Molecular Neurobiology Program, Skirball Institute for Biomolecular Medicine, Departments of Cell Biology , New York, New York 10016, USA.

    Nerve growth factor (NGF) initiates its trophic effects by long-range signaling through binding, internalization, and transport of a ligand-receptor complex from the axon terminal to the cell body. However, the mechanism by which retrograde transport of NGF takes place has not been elucidated. Here we describe an interaction between the Trk receptor tyrosine kinase and a 14 kDa light chain of cytoplasmic dynein. After transfection in human embryonic kidney 293 cells, this 14 kDa dynein light chain was found to bind to TrkA, TrkB, and TrkC receptors. Mapping experiments indicated that the 14 kDa dynein light chain binds to the distal region of the TrkA juxtamembrane domain. Coimmunoprecipitation experiments in vivo indicate that Trk receptors are in a complex with the 14 kDa light chain and 74 kDa intermediate chain of dynein. Confirming the physiological relevance of this association, a marked accumulation of Trk with the 14 kDa and the 74 kDa dynein components was observed after ligation of the sciatic nerve. The association of Trk receptors with components of cytoplasmic dynein suggests that transport of neurotrophins during vesicular trafficking may occur through a direct interaction of the Trk receptor with the dynein motor machinery.

    Funded by: NEI NIH HHS: EY11307, R01 EY011307; NICHD NIH HHS: HD233-5; NINDS NIH HHS: NS21072

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2001;21;3;RC125

  • Identification of a motif in the carboxyl terminus of CXCR2 that is involved in adaptin 2 binding and receptor internalization.

    Fan GH, Yang W, Wang XJ, Qian Q and Richmond A

    Veterans Affairs Medical Center, Nashville, Tennessee 37212-2637, USA.

    Agonist treatment of cells expressing the chemokine receptor, CXCR2, induces receptor phosphorylation and internalization through a dynamin-dependent mechanism. In the present study, we demonstrate that a carboxyl terminus-truncated mutant of CXCR2 (331T), which no longer undergoes agonist-induced phosphorylation, continues to undergo ligand-induced internalization in HEK293 cells. This mutant receptor exhibits reduced association with beta-arrestin 1 but continues to exhibit association with adaptin 2 alpha and beta subunits. Replacing Leu320-321 and/or Ile323-Leu324 with Ala (LL320,321AA, IL323,324AA, and LLIL320,321,323,324AAAA) in wild-type CXCR2 or 331T causes little change in ligand binding and signaling through Ca(2+) mobilization but greatly impairs the agonist-induced receptor sequestration and ligand-mediated chemotaxis. The LL320,321AA, IL323,324AA, and LLIL320,321,323,324AAAA mutants of CXCR2 exhibit normal binding to beta-arrestin 1 but exhibit decreased binding to adaptin 2alpha and beta. These data demonstrate a role for the LLKIL motif in the carboxyl terminus of CXCR2 in receptor internalization and cell chemotaxis and imply a role for adaptin 2 in the endocytosis of CXCR2.

    Funded by: NCI NIH HHS: CA34590, CA68485, P30 CA068485, R01 CA034590, R01 CA034590-17, R01 CA034590-18

    Biochemistry 2001;40;3;791-800

  • Clathrin.

    Kirchhausen T

    Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA. Kirchhausen@crystal.harvard.edu

    Clathrin was discovered nearly 25 years ago. Since then, a large number of other proteins that participate in the process by which clathrin-coated vesicles retrieve synaptic membranes or take up endocytic receptors have been identified. The functional relationships among these disparate components remain, in many cases, obscure. High-resolution structures of parts of clathrin, determined by X-ray crystallography, and lower-resolution images of assembled coats, determined by electron cryomicroscopy, now provide the information necessary to integrate various lines of evidence and to design experiments that test specific mechanistic notions. This review summarizes and illustrates the recent structural results and outlines what is known about coated-vesicle assembly in the context of this information.

    Annual review of biochemistry 2000;69;699-727

  • The epsins define a family of proteins that interact with components of the clathrin coat and contain a new protein module.

    Rosenthal JA, Chen H, Slepnev VI, Pellegrini L, Salcini AE, Di Fiore PP and De Camilli P

    Howard Hughes Medical Institute and Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.

    Epsin (epsin 1) is an interacting partner for the EH domain-containing region of Eps15 and has been implicated in conjunction with Eps15 in clathrin-mediated endocytosis. We report here the characterization of a similar protein (epsin 2), which we have cloned from human and rat brain libraries. Epsin 1 and 2 are most similar in their NH(2)-terminal region, which represents a module (epsin NH(2) terminal homology domain, ENTH domain) found in a variety of other proteins of the data base. The multiple DPW motifs, typical of the central region of epsin 1, are only partially conserved in epsin 2. Both proteins, however, interact through this central region with the clathrin adaptor AP-2. In addition, we show here that both epsin 1 and 2 interact with clathrin. The three NPF motifs of the COOH-terminal region of epsin 1 are conserved in the corresponding region of epsin 2, consistent with the binding of both proteins to Eps15. Epsin 2, like epsin 1, is enriched in brain, is present in a brain-derived clathrin-coated vesicle fraction, is concentrated in the peri-Golgi region and at the cell periphery of transfected cells, and partially colocalizes with clathrin. High overexpression of green fluorescent protein-epsin 2 mislocalizes components of the clathrin coat and inhibits clathrin-mediated endocytosis. The epsins define a new protein family implicated in membrane dynamics at the cell surface.

    Funded by: NCI NIH HHS: CA46128; NINDS NIH HHS: NS1024-01, NS36251; ...

    The Journal of biological chemistry 1999;274;48;33959-65

  • A beta-turn endocytic code is required for optimal internalization of the growth hormone receptor but not for alpha-adaptin association.

    Vleurick L, Pezet A, Kühn ER, Decuypere E and Edery M

    INSERM U344, Faculté de Médecine Necker, Paris, France.

    Intracellular trafficking of GH and its receptor, more particularly the chicken GH receptor (cGHR), was examined in COS-7 cells using biochemical and structural studies. Internalization of radioactive GH by the cGHR is reduced as compared with the rat GHR. On the contrary, activation of gene transcription through Janus kinase-2 was similar for both species. Secondary structures of the cytoplasmic domain of chicken and rat GHR were compared, since beta-turns were reported as internalization signals. The substitution of Pro335-Asp335, present in mammalian GH receptors, with Thr307-Gln308 in the cGHR leads to the loss of a beta-turn within a conserved cytoplasmic region. Mutational analysis indicated that the lower rate of internalization of cGHR, as compared with mammalian GHR, was due to this motif. Our data further show that alpha-adaptin, a subunit of adaptor protein AP-2, associates with the GHR upon hormone stimulation. The clathrin-coated pit pathway therefore seems to be involved in the endocytosis of cGHR, as AP-2 is known to intervene in the recruitment of receptors to these pits. Interaction with alpha-adaptin may occur through a common epitope of the chicken and mammalian GHR, since receptors from both species bind similar amounts of alpha-adaptin; alternatively, two different epitopes with similar affinity may be involved. Therefore, not alpha-adaptin but an uncharacterized factor, presumably interacting with the identified beta-turn endocytic code, is responsible for the difference in internalization kinetics. Finally, the present study illustrates that functional amino acid motifs of receptors can be derived from comparative studies.

    Molecular endocrinology (Baltimore, Md.) 1999;13;11;1823-31

  • Clathrin assembly lymphoid myeloid leukemia (CALM) protein: localization in endocytic-coated pits, interactions with clathrin, and the impact of overexpression on clathrin-mediated traffic.

    Tebar F, Bohlander SK and Sorkin A

    Department of Pharmacology, University of Colorado Health Science Center, Denver, Colorado 80111, USA.

    The clathrin assembly lymphoid myeloid leukemia (CALM) gene encodes a putative homologue of the clathrin assembly synaptic protein AP180. Hence the biochemical properties, the subcellular localization, and the role in endocytosis of a CALM protein were studied. In vitro binding and coimmunoprecipitation demonstrated that the clathrin heavy chain is the major binding partner of CALM. The bulk of cellular CALM was associated with the membrane fractions of the cell and localized to clathrin-coated areas of the plasma membrane. In the membrane fraction, CALM was present at near stoichiometric amounts relative to clathrin. To perform structure-function analysis of CALM, we engineered chimeric fusion proteins of CALM and its fragments with the green fluorescent protein (GFP). GFP-CALM was targeted to the plasma membrane-coated pits and also found colocalized with clathrin in the Golgi area. High levels of expression of GFP-CALM or its fragments with clathrin-binding activity inhibited the endocytosis of transferrin and epidermal growth factor receptors and altered the steady-state distribution of the mannose-6-phosphate receptor in the cell. In addition, GFP-CALM overexpression caused the loss of clathrin accumulation in the trans-Golgi network area, whereas the localization of the clathrin adaptor protein complex 1 in the trans-Golgi network remained unaffected. The ability of the GFP-tagged fragments of CALM to affect clathrin-mediated processes correlated with the targeting of the fragments to clathrin-coated areas and their clathrin-binding capacities. Clathrin-CALM interaction seems to be regulated by multiple contact interfaces. The C-terminal part of CALM binds clathrin heavy chain, although the full-length protein exhibited maximal ability for interaction. Altogether, the data suggest that CALM is an important component of coated pit internalization machinery, possibly involved in the regulation of clathrin recruitment to the membrane and/or the formation of the coated pit.

    Funded by: NCI NIH HHS: CA-46934, P30 CA046934; NIDDK NIH HHS: DK-46817

    Molecular biology of the cell 1999;10;8;2687-702

  • Splice variants of intersectin are components of the endocytic machinery in neurons and nonneuronal cells.

    Hussain NK, Yamabhai M, Ramjaun AR, Guy AM, Baranes D, O'Bryan JP, Der CJ, Kay BK and McPherson PS

    Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada.

    We recently identified and cloned intersectin, a protein containing two Eps15 homology (EH) domains and five Src homology 3 (SH3) domains. Using a newly developed intersectin antibody, we demonstrate that endogenous COS-7 cell intersectin localizes to clathrin-coated pits, and transfection studies suggest that the EH domains may direct this localization. Through alternative splicing in a stop codon, a long form of intersectin is generated with a C-terminal extension containing Dbl homology (DH), pleckstrin homology (PH), and C2 domains. Western blots reveal that the long form of intersectin is expressed specifically in neurons, whereas the short isoform is expressed at lower levels in glia and other nonneuronal cells. Immunofluorescence analysis of cultured hippocampal neurons reveals that intersectin is found at the plasma membrane where it is co-localized with clathrin. Ibp2, a protein identified based on its interactions with the EH domains of intersectin, binds to clathrin through the N terminus of the heavy chain, suggesting a mechanism for the localization of intersectin at clathrin-coated pits. Ibp2 also binds to the clathrin adaptor AP2, and antibodies against intersectin co-immunoprecipitate clathrin, AP2, and dynamin from brain extracts. These data suggest that the long and short forms of intersectin are components of the endocytic machinery in neurons and nonneuronal cells.

    The Journal of biological chemistry 1999;274;22;15671-7

  • Interactions of the cytoplasmic domains of human and simian retroviral transmembrane proteins with components of the clathrin adaptor complexes modulate intracellular and cell surface expression of envelope glycoproteins.

    Berlioz-Torrent C, Shacklett BL, Erdtmann L, Delamarre L, Bouchaert I, Sonigo P, Dokhelar MC and Benarous R

    CJF 97/03 INSERM, Interactions Moléculaires, Hôte-Pathogène, Institut Cochin de Génétique Moléculaire, 75014 Paris, France.

    The cytoplasmic domains of the transmembrane (TM) envelope proteins (TM-CDs) of most retroviruses have a Tyr-based motif, YXXO, in their membrane-proximal regions. This signal is involved in the trafficking and endocytosis of membrane receptors via clathrin-associated AP-1 and AP-2 adaptor complexes. We have used CD8-TM-CD chimeras to investigate the role of the Tyr-based motif of human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus (SIV), and human T-leukemia virus type 1 (HTLV-1) TM-CDs in the cell surface expression of the envelope glycoprotein. Flow cytometry and confocal microscopy studies showed that this motif is a major determinant of the cell surface expression of the CD8-HTLV chimera. The YXXO motif also plays a key role in subcellular distribution of the envelope of lentiviruses HIV-1 and SIV. However, these viruses, which encode TM proteins with a long cytoplasmic domain, have additional determinants distal to the YXXO motif that participate in regulating cell surface expression. We have also used the yeast two-hybrid system and in vitro binding assays to demonstrate that all three retroviral YXXO motifs interact with the micro1 and micro2 subunits of AP complexes and that the C-terminal regions of HIV-1 and SIV TM proteins interact with the beta2 adaptin subunit. The TM-CDs of HTLV-1, HIV-1, and SIV also interact with the whole AP complexes. These results clearly demonstrate that the cell surface expression of retroviral envelope glycoproteins is governed by interactions with adaptor complexes. The YXXO-based signal is the major determinant of this interaction for the HTLV-1 TM, which contains a short cytoplasmic domain, whereas the lentiviruses HIV-1 and SIV have additional determinants distal to this signal that are also involved.

    Journal of virology 1999;73;2;1350-61

  • Epsin is an EH-domain-binding protein implicated in clathrin-mediated endocytosis.

    Chen H, Fre S, Slepnev VI, Capua MR, Takei K, Butler MH, Di Fiore PP and De Camilli P

    Howard Hughes Medical Institute and Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.

    During endocytosis, clathrin and the clathrin adaptor protein AP-2, assisted by a variety of accessory factors, help to generate an invaginated bud at the cell membrane. One of these factors is Eps15, a clathrin-coat-associated protein that binds the alpha-adaptin subunit of AP-2. Here we investigate the function of Eps15 by characterizing an important binding partner for its region containing EH domains; this protein, epsin, is closely related to the Xenopus mitotic phosphoprotein MP90 and has a ubiquitous tissue distribution. It is concentrated together with Eps15 in presynaptic nerve terminals, which are sites specialized for the clathrin-mediated endocytosis of synaptic vesicles. The central region of epsin binds AP-2 and its carboxy-terminal region binds Eps15. Epsin is associated with clathrin coats in situ, can be co-precipitated with AP-2 and Eps15 from brain extracts, but does not co-purify with clathrin coat components in a clathrin-coated vesicle fraction. When epsin function is disrupted, clathrin-mediated endocytosis is blocked. We propose that epsin may participate, together with Eps15, in the molecular rearrangement of the clathrin coats that are required for coated-pit invagination and vesicle fission.

    Nature 1998;394;6695;793-7

  • Clathrin interacts specifically with amphiphysin and is displaced by dynamin.

    McMahon HT, Wigge P and Smith C

    Neurobiology Division, MRC-LMB, Cambridge, UK. hmm@mrc-lmb.cam.ac.uk

    Amphiphysin is an SH3 domain protein that has been implicated in synaptic vesicle endocytosis. We have recently cloned a second amphiphysin isoform, Amph2 (sequence submitted to GenBank, Y13380). Proteins capable of forming a complex with amphiphysin were isolated from rat brain by using recombinant GST-Amph2 for binding experiments. As well as interacting with dynamin I, the full-length protein bound to a weaker 180-kDa band. Immunoblotting demonstrated this protein to be clathrin. To address whether this is a direct interaction, the clathrin binding to amphiphysin was reconstituted in vitro with purified proteins. The N-terminal domain of Amph2 is sufficient for clathrin binding. Dynamin, which interacts with the SH3 domain of Amph2, displaces clathrin from the N-terminus. We propose a model that may explain how clathrin and dynamin are recruited to non-overlapping sites of the coated pit.

    FEBS letters 1997;413;2;319-22

  • Association and colocalization of Eps15 with adaptor protein-2 and clathrin.

    van Delft S, Schumacher C, Hage W, Verkleij AJ and van Bergen en Henegouwen PM

    Department of Molecular Cell Biology, Institute of Biomembranes, Utrecht University, The Netherlands.

    Eps15 has been identified as a substrate of the EGF receptor tyrosine kinase. In this report, we show that activation of the EGF receptor by either EGF or TGF-alpha results in phosphorylation of Eps15. Stimulation of cells with PDGF or insulin did not lead to Eps15 phosphorylation, suggesting that phosphorylation of Eps15 is a receptor-specific process. We demonstrate that Eps15 is constitutively associated with both alpha-adaptin and clathrin. Upon EGF stimulation, Eps15 and alpha-adaptin are recruited to the EGF receptor. Using a truncated EGF receptor mutant, we demonstrate that the regulatory domain of the cytoplasmic tail of the EGF receptor is essential for the binding of Eps15. Fractionation studies reveal that Eps15 is present in cell fractions enriched for plasma membrane and endosomal membranes. Immunofluorescence studies show that Eps15 colocalizes with adaptor protein-2 (AP-2) and partially with clathrin. No colocalization of Eps15 was observed with the early endosomal markers rab4 and rab5. These observations indicate that Eps15 is present in coated pits and coated vesicles of the clathrin-mediated endocytic pathway, but not in early endosomes. Neither AP-2 nor clathrin are required for the binding of Eps15 to coated pits or coated vesicles, since in membranes lacking AP-2 and clathrin, Eps15 still shows the same staining pattern. These findings suggest that Eps15 may play a critical role in the recruitment of active EGF receptors into coated pit regions before endocytosis of ligand-occupied EGF receptors.

    The Journal of cell biology 1997;136;4;811-21

  • The ear of alpha-adaptin interacts with the COOH-terminal domain of the Eps 15 protein.

    Benmerah A, Bégue B, Dautry-Varsat A and Cerf-Bensussan N

    Développement Normal et Pathologique de Système Immunitaire, INSERM U429, Paris, France.

    The role of Eps15 in clathrin-mediated endocytosis is supported by two observations. First, it interacts specifically and constitutively with the plasma membrane adaptor AP-2. Second, its NH2 terminus shows significant homology to the NH2 terminus of yeast End3p, necessary for endocytosis of alpha-factor. To gain further insight into the role of Eps15-AP-2 association, we have now delineated their sites of interactions. AP-2 binds to a domain of 72 amino acids (767-739) present in the COOH terminus of Eps15. This domain contains 4 of the 15 DPF repeats characteristic of the COOH-terminal domain of Eps15 and shares no homology with known proteins, including the related Epsl5r protein. Precipitation of proteolytic fragments of AP-2 with Eps15-derived fusion proteins containing the binding site for AP-2 showed that Eps15 binds specifically to a 40-kDa fragment corresponding to the ear of alpha-adaptin, a result confirmed by precipitation of Eps15 by alpha-adaptin-derived fusion proteins. Our data indicate that this specific part of AP-2 binds to a cellular component and provide the tools for investigating the functions of the association between AP-2 and Eps15.

    The Journal of biological chemistry 1996;271;20;12111-6

  • Interaction of Shc with adaptor protein adaptins.

    Okabayashi Y, Sugimoto Y, Totty NF, Hsuan J, Kido Y, Sakaguchi K, Gout I, Waterfield MD and Kasuga M

    Second Department of Internal Medicine, Kobe University School of Medicine, Kobe 650, Japan.

    The role of Shc as a substrate of receptors for growth factors and cytokines is well established. To gain further insight into the function of Shc in signal transduction, we used an affinity method to identify potential Shc-binding proteins. Incubation of bovine brain lysates with a glutathione S-transferase (GST)-Shc fusion protein immobilized on glutathione-Sepharose beads resulted in the binding of cellular proteins of approximately 115, 110, and 100 kDa as well as those of 50 and 17 kDa. Amino acid sequencing of tryptic peptides revealed that the 100-kDa protein was almost identical to beta-adaptin and that the 110- and 115-kDa proteins were almost identical to alphaA-adaptin. Using immunoblot analysis, anti-alpha-adaptin antibody recognized several proteins of 100 approximately 115 kDa, and anti-beta-adaptin antibody recognized a 100-kDa protein, suggesting that alphaA-, alphaC-, and beta-adaptins are bound to the GST-Shc fusion protein. Immunoblot analysis with anti-alpha-adaptin antibody revealed that alpha-adaptin was coimmunoprecipitated with Shc from PC12, KB, and COS cell lysates, suggesting a specific interaction of Shc and adaptins in intact cells. A binding study using mutant GST-Shc fusion proteins revealed that the collagen homologous region (amino acids 233-377) of Shc was required for adaptin binding. Conversely, the collagen homologous region of Shc inhibited the binding of adaptins to GST-Shc. In addition, adaptin was able to bind mutant fusion proteins containing amino acids 233-369, 233-355, 346-369, and 346-355 of Shc, but failed to bind a mutant containing amino acids 233-345, suggesting that amino acids 346-355 (RDLFDMKPFE) in the collagen homologous region of Shc are required for adaptin binding. Thus, this study indicates the specific interaction of Shc with alpha- and beta-adaptin components of plasma membrane adaptor proteins that are thought to be involved in receptor endocytosis.

    The Journal of biological chemistry 1996;271;9;5265-9

  • Targeting signals and subunit interactions in coated vesicle adaptor complexes.

    Page LJ and Robinson MS

    Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, England.

    There are two clathrin-coated vesicle adaptor complexes in the cell, one associated with the plasma membrane and one associated with the TGN. The subunit composition of the plasma membrane adaptor complex is alpha-adaptin, beta-adaptin, AP50, and AP17; while that of the TGN adaptor complex is gamma-adaptin, beta'-adaptin, AP47, and AP19. To search for adaptor targeting signals, we have constructed chimeras between alpha-adaptin and gamma-adaptin within their NH2-terminal domains. We have identified stretches of sequence in the two proteins between amino acids approximately 130 and 330-350 that are essential for targeting. Immunoprecipitation reveals that this region determines whether a construct coassemblies with AP50 and AP17, or with AP47 and AP19. These observations suggest that these other subunits may play an important role in targeting. In contrast, beta- and beta'-adaptins are clearly not involved in this event. Chimeras between the alpha- and gamma-adaptin COOH-terminal domains reveal the presence of a second targeting signal. We have further investigated the interactions between the adaptor subunits using the yeast two-hybrid system. Interactions can be detected between the beta/beta'-adaptins and the alpha/gamma-adaptins, between the beta/beta'-adaptins and the AP50/AP47 subunits, between alpha-adaptin and AP17, and between gamma-adaptin and AP19. These results indicate that the adaptor subunits act in concert to target the complex to the appropriate membrane.

    Funded by: Wellcome Trust

    The Journal of cell biology 1995;131;3;619-30

  • The alpha chain of the AP-2 adaptor is a clathrin binding subunit.

    Goodman OB and Keen JH

    Department of Pharmacology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.

    We have utilized a rabbit reticulocyte lysate coupled transcription-translation system to express the large subunits of the clathrin associated protein-2 (AP-2) complex so that their individual functions may be studied separately. Appropriate folding of each subunit into N-terminal core and C-terminal appendage domains was confirmed by limited proteolysis. Translated beta 2 subunit bound to both assembled clathrin cages and immobilized clathrin trimers, confirming and extending earlier studies with preparations obtained by chemical denaturation-renaturation. Translated alpha a exhibited rapid, reversible and specific binding to clathrin cages. As with native AP-2, proteolysis of alpha a bound to clathrin cages released the appendages, while cores were retained. Further digestion revealed a approximately 29-kDa alpha a clathrin-binding fragment that remained tightly cage-associated. Translated alpha a also bound to immobilized clathrin trimers, although with greater sensitivity to increasing pH than the translated beta 2 subunit. Clathrin binding by both the alpha and beta subunits is consistent with a bivalent cross-linking model for lattice assembly (Keen, J. H. (1987) Cell Biol. 105, 1989). It also raises the possibility that the alpha-clathrin interaction may have other consequences, such as modulation of lattice stability or shape, or other alpha functions.

    Funded by: NCI NIH HHS: CA09662; NIGMS NIH HHS: GM-28526

    The Journal of biological chemistry 1995;270;40;23768-73

  • Ca(2+)-dependent and -independent activities of neural and non-neural synaptotagmins.

    Li C, Ullrich B, Zhang JZ, Anderson RG, Brose N and Südhof TC

    Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas 75235, USA.

    Synaptotagmins (Syts) are brain-specific Ca2+/phospholipid-binding proteins. In hippocampal synapses, Syt I is essential for fast Ca(2+)-dependent synaptic vesicle exocytosis but not for Ca(2+)-independent exocytosis. In vertebrates and invertebrates, Syt may therefore participate in Ca(2+)-dependent synaptic membrane fusion, either by serving as the Ca2+ sensor in the last step of fast Ca(2+)-triggered neurotransmitter release, or by collaborating with an additional Ca2+ sensor. While Syt I binds Ca2+ (refs 10, 11), its phospholipid binding is triggered at lower calcium concentrations (EC50 = 3-6 microM) than those required for exocytosis. Furthermore, Syts bind clathrin-AP2 with high affinity, indicating that they may play a general role in endocytosis rather than being confined to a specialized function in regulated exocytosis. Here we resolve this apparent contradiction by describing four Syts, three of which (Syt VI, VII and VIII) are widely expressed in non-neural tissues. All Syts tested share a common domain structure, with a cytoplasmic region composed of two C2 domains that interacts with clathrin-AP2 (Kd = 0.1-1.0 nM) and with neural and non-neural syntaxins. The first C2 domains of Syt I, II, III, V and VII, but not of IV, VI or VIII, bind phospholipids with a similar Ca(2+)-concentration dependence (EC50 = 3-6 microM). The same C2 domains also bind syntaxin as a function of Ca2+ but the Ca(2+)-concentration dependence of Syt I, II and V (> 200 microM) differs from that of Syt III and VII (< 10 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

    Nature 1995;375;6532;594-9

  • Serine phosphorylation-independent downregulation of cell-surface CD4 by nef.

    Garcia JV and Miller AD

    Program in molecular Medicine, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.

    A decline in the T-cell population usually marks the onset of progressive immunological disease in individuals infected with the human immunodeficiency virus (HIV). Because CD4+ cells help to coordinate efficient immune responses, some of the defects in the immune function in advanced cases of AIDS may be explained by the disappearance of these cells. Therefore, an understanding of the mechanisms used by HIV to induce the reduction of CD4+ cells is important. Here we use a Moloney murine leukaemia virus-based retroviral vector in order to express the nef gene of HIV-1 in three lymphocytic cell lines expressing CD4. In all cases we find that cell-surface CD4 expression is inversely related to nef expression. However, nef does not alter steady-state levels of CD4 RNA or CD4 protein. Also, nef can downregulate a CD4 triple mutant (Ser----Ala) that is neither phosphorylated nor down-regulated by phorbol esters, indicating that nef is acting by a different mechanism.

    Nature 1991;350;6318;508-11

  • Cloning of cDNAs encoding two related 100-kD coated vesicle proteins (alpha-adaptins).

    Robinson MS

    Medical Research Council Laboratory of Molecular Biology, Cambridge, England.

    Coat proteins of approximately 100-kD (adaptins) are components of the adaptor complexes which link clathrin to receptors in coated vesicles. The alpha-adaptins, which are found exclusively in endocytic coated vesicles, separate into two bands on SDS gels, designated A and C (Robinson, M. S., 1987. J. Cell Biol. 104:887-895). Two distinct cDNAs (sequences 1 and 2) encoding the two alpha-adaptins were cloned from a mouse brain cDNA library. Southern blotting indicates that there is one copy of each of the two alpha-adaptin genes, and that there are no additional closely related genes. Based on the size of the predicted protein products of the two genes (108 and 104 kD), the relative abundance of the two messages in brain and liver, and the reactivity of a sequence 1 fusion protein with different antibodies, it was possible to conclude that sequence 1 codes for A and sequence 2 for C. The two protein sequences are strikingly homologous to each other (84% identical amino acids), the major difference being an additional stretch of 41 amino acids, rich in prolines and acidic residues, inserted into the COOH-terminal half of A. In situ hybridization carried out on mouse brain sections indicates that the same cell type may express both transcripts, but that their relative expressions vary. Antipeptide antibodies are now being raised to find out whether the proteins are localized in functionally distinct populations of endocytic coated vesicles.

    The Journal of cell biology 1989;108;3;833-42

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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