G2Cdb::Gene report

Gene id
Gene symbol
Homo sapiens
adaptor-related protein complex 2, beta 1 subunit
G00000677 (Mus musculus)

Databases (7)

ENSG00000006125 (Ensembl human gene)
163 (Entrez Gene)
1087 (G2Cdb plasticity & disease)
AP2B1 (GeneCards)
601025 (OMIM)
Marker Symbol
Protein Sequence
P63010 (UniProt)

Literature (45)

Pubmed - other

  • Molecular basis for association of PIPKI gamma-p90 with clathrin adaptor AP-2.

    Kahlfeldt N, Vahedi-Faridi A, Koo SJ, Schäfer JG, Krainer G, Keller S, Saenger W, Krauss M and Haucke V

    Institute of Chemistry and Biochemistry, Department of Membrane Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany.

    Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) is an essential determinant in clathrin-mediated endocytosis (CME). In mammals three type I phosphatidylinositol-4-phosphate 5-kinase (PIPK) enzymes are expressed, with the I gamma-p90 isoform being highly expressed in the brain where it regulates synaptic vesicle (SV) exo-/endocytosis at nerve terminals. How precisely PI(4,5)P(2) metabolism is controlled spatially and temporally is still uncertain, but recent data indicate that direct interactions between type I PIPK and components of the endocytic machinery, in particular the AP-2 adaptor complex, are involved. Here we demonstrated that PIPKI gamma-p90 associates with both the mu and beta2 subunits of AP-2 via multiple sites. Crystallographic data show that a peptide derived from the splice insert of the human PIPKI gamma-p90 tail binds to a cognate recognition site on the sandwich subdomain of the beta2 appendage. Partly overlapping aromatic and hydrophobic residues within the same peptide also can engage the C-terminal sorting signal binding domain of AP-2mu, thereby potentially competing with the sorting of conventional YXXØ motif-containing cargo. Biochemical and structure-based mutagenesis analysis revealed that association of the tail domain of PIPKI gamma-p90 with AP-2 involves both of these sites. Accordingly the ability of overexpressed PIPKI gamma tail to impair endocytosis of SVs in primary neurons largely depends on its association with AP-2 beta and AP-2mu. Our data also suggest that interactions between AP-2 and the tail domain of PIPKI gamma-p90 may serve to regulate complex formation and enzymatic activity. We postulate a model according to which multiple interactions between PIPKI gamma-p90 and AP-2 lead to spatiotemporally controlled PI(4,5)P(2) synthesis during clathrin-mediated SV endocytosis.

    The Journal of biological chemistry 2010;285;4;2734-49

  • Defining the human deubiquitinating enzyme interaction landscape.

    Sowa ME, Bennett EJ, Gygi SP and Harper JW

    Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.

    Deubiquitinating enzymes (Dubs) function to remove covalently attached ubiquitin from proteins, thereby controlling substrate activity and/or abundance. For most Dubs, their functions, targets, and regulation are poorly understood. To systematically investigate Dub function, we initiated a global proteomic analysis of Dubs and their associated protein complexes. This was accomplished through the development of a software platform called CompPASS, which uses unbiased metrics to assign confidence measurements to interactions from parallel nonreciprocal proteomic data sets. We identified 774 candidate interacting proteins associated with 75 Dubs. Using Gene Ontology, interactome topology classification, subcellular localization, and functional studies, we link Dubs to diverse processes, including protein turnover, transcription, RNA processing, DNA damage, and endoplasmic reticulum-associated degradation. This work provides the first glimpse into the Dub interaction landscape, places previously unstudied Dubs within putative biological pathways, and identifies previously unknown interactions and protein complexes involved in this increasingly important arm of the ubiquitin-proteasome pathway.

    Funded by: NIA NIH HHS: AG085011, R01 AG011085, R01 AG011085-16; NIGMS NIH HHS: GM054137, GM67945, R01 GM054137, R01 GM054137-14, R01 GM067945

    Cell 2009;138;2;389-403

  • Immunohistochemical detection of EGFR, fibrillin-2, P-cadherin and AP2beta as biomarkers for rhabdomyosarcoma diagnostics.

    Grass B, Wachtel M, Behnke S, Leuschner I, Niggli FK and Schäfer BW

    Department of Oncology, University Children's Hospital, Zurich, Switzerland.

    Aims: Subclassification of rhabdomyosarcoma (RMS) has clinical relevance, as the two major subclasses embryonal (ERMS) and alveolar (ARMS) rhabdomyosarcoma differ greatly in terms of aggressiveness and prognosis. However, histological analysis is not always sufficient for an unequivocal subclassification of RMS. Furthermore, clinical presentation of ARMS has been reported to mimic other tumour types, specifically lymphoma. The aim was to determine the role of four biomarkers in the diagnosis of rhabdomyosarcoma.

    Recently, we identified four potential biomarkers to subclassify RMS with high sensitivity and specificity. These included epidermal growth factor receptor (EGFR) and fibrillin-2 as markers for ERMS, and AP2beta and P-cadherin as markers for translocation-positive ARMS. Here, we further validate the potential of these four markers in a second, independent patient cohort by immunohistochemistry on 80 sections of RMS biopsy specimens as well as a tissue microarray representing 18 different additional tumour types, including seven lymphomas. The combination of EGFR and fibrillin-2 was able to detect ERMS with a specificity of 76% and sensitivity of 90%. The combination of AP2beta and P-cadherin detected ARMS with a specificity of 97% and sensitivity of 90%, data very similar to our previous study. Furthermore, all lymphomas were clearly negative for AP2beta and P-cadherin.

    Conclusions: These four biomarkers are suitable for clinical implementation in the future diagnosis of RMS.

    Histopathology 2009;54;7;873-9

  • Role of activation of PIP5Kgamma661 by AP-2 complex in synaptic vesicle endocytosis.

    Nakano-Kobayashi A, Yamazaki M, Unoki T, Hongu T, Murata C, Taguchi R, Katada T, Frohman MA, Yokozeki T and Kanaho Y

    Department of Physiological Chemistry, Graduate School of Comprehensive Human Sciences and Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, Japan.

    Synaptic vesicles (SVs) are retrieved by clathrin-mediated endocytosis at the nerve terminals. Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] drives this event by recruiting the components of the endocytic machinery. However, the molecular mechanisms that result in local generation of PI(4,5)P2 remain unclear. We demonstrate here that AP-2 complex directly interacts with phosphatidylinositol 4-phosphate 5-kinase gamma661 (PIP5Kgamma661), the major PI(4,5)P2-producing enzyme in the brain. The beta2 subunit of AP-2 was found to bind to the C-terminal tail of PIP5Kgamma661 and cause PIP5Kgamma661 activation. The interaction is regulated by PIP5Kgamma661 dephosphorylation, which is triggered by depolarization in mouse hippocampal neurons. Finally, overexpression of the PIP5Kgamma661 C-terminal region in hippocampal neurons suppresses depolarization-dependent SV endocytosis. These findings provide evidence for the molecular mechanism through which PIP5Kgamma661 locally generates PI(4,5)P2 in hippocampal neurons and suggest a model in which the interaction trigger SV endocytosis.

    Funded by: NIGMS NIH HHS: R01 GM071520, R01 GM71520

    The EMBO journal 2007;26;4;1105-16

  • 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_U122663296, 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

  • Large-scale mapping of human protein-protein interactions by mass spectrometry.

    Ewing RM, Chu P, Elisma F, Li H, Taylor P, Climie S, McBroom-Cerajewski L, Robinson MD, O'Connor L, Li M, Taylor R, Dharsee M, Ho Y, Heilbut A, Moore L, Zhang S, Ornatsky O, Bukhman YV, Ethier M, Sheng Y, Vasilescu J, Abu-Farha M, Lambert JP, Duewel HS, Stewart II, Kuehl B, Hogue K, Colwill K, Gladwish K, Muskat B, Kinach R, Adams SL, Moran MF, Morin GB, Topaloglou T and Figeys D

    Protana, Toronto, Ontario, Canada.

    Mapping protein-protein interactions is an invaluable tool for understanding protein function. Here, we report the first large-scale study of protein-protein interactions in human cells using a mass spectrometry-based approach. The study maps protein interactions for 338 bait proteins that were selected based on known or suspected disease and functional associations. Large-scale immunoprecipitation of Flag-tagged versions of these proteins followed by LC-ESI-MS/MS analysis resulted in the identification of 24,540 potential protein interactions. False positives and redundant hits were filtered out using empirical criteria and a calculated interaction confidence score, producing a data set of 6463 interactions between 2235 distinct proteins. This data set was further cross-validated using previously published and predicted human protein interactions. In-depth mining of the data set shows that it represents a valuable source of novel protein-protein interactions with relevance to human diseases. In addition, via our preliminary analysis, we report many novel protein interactions and pathway associations.

    Molecular systems biology 2007;3;89

  • Role of the AP2 beta-appendage hub in recruiting partners for clathrin-coated vesicle assembly.

    Schmid EM, Ford MG, Burtey A, Praefcke GJ, Peak-Chew SY, Mills IG, Benmerah A and McMahon HT

    Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom.

    Adaptor protein complex 2 alpha and beta-appendage domains act as hubs for the assembly of accessory protein networks involved in clathrin-coated vesicle formation. We identify a large repertoire of beta-appendage interactors by mass spectrometry. These interact with two distinct ligand interaction sites on the beta-appendage (the "top" and "side" sites) that bind motifs distinct from those previously identified on the alpha-appendage. We solved the structure of the beta-appendage with a peptide from the accessory protein Eps15 bound to the side site and with a peptide from the accessory cargo adaptor beta-arrestin bound to the top site. We show that accessory proteins can bind simultaneously to multiple appendages, allowing these to cooperate in enhancing ligand avidities that appear to be irreversible in vitro. We now propose that clathrin, which interacts with the beta-appendage, achieves ligand displacement in vivo by self-polymerisation as the coated pit matures. This changes the interaction environment from liquid-phase, affinity-driven interactions, to interactions driven by solid-phase stability ("matricity"). Accessory proteins that interact solely with the appendages are thereby displaced to areas of the coated pit where clathrin has not yet polymerised. However, proteins such as beta-arrestin (non-visual arrestin) and autosomal recessive hypercholesterolemia protein, which have direct clathrin interactions, will remain in the coated pits with their interacting receptors.

    Funded by: Medical Research Council: G0100100, MC_U105178795

    PLoS biology 2006;4;9;e262

  • Clathrin adaptor AP2 regulates thrombin receptor constitutive internalization and endothelial cell resensitization.

    Paing MM, Johnston CA, Siderovski DP and Trejo J

    Department of Pharmacology, University of North Carolina at Chapel Hill, 1106 Mary Ellen Jones Bldg., Chapel Hill, NC 27599-7365. USA.

    Protease-activated receptor 1 (PAR1), a G protein-coupled receptor for the coagulant protease thrombin, is irreversibly activated by proteolysis. Unactivated PAR1 cycles constitutively between the plasma membrane and intracellular stores, thereby providing a protected receptor pool that replenishes the cell surface after thrombin exposure and leads to rapid resensitization to thrombin signaling independent of de novo receptor synthesis. Here, we show that AP2, a clathrin adaptor, binds directly to a tyrosine-based motif in the cytoplasmic tail of PAR1 and is essential for constitutive receptor internalization and cellular recovery of thrombin signaling. Expression of a PAR1 tyrosine mutant or depletion of AP2 by RNA interference leads to significant inhibition of PAR1 constitutive internalization, loss of intracellular uncleaved PAR1, and failure of endothelial cells and other cell types to regain thrombin responsiveness. Our findings establish a novel role for AP2 in direct regulation of PAR1 trafficking, a process critically important to the temporal and spatial aspects of thrombin signaling.

    Funded by: NHLBI NIH HHS: HL 067967, HL 073328, K01 HL067697, R01 HL073328; NIGMS NIH HHS: GM 065533, P01 GM065533

    Molecular and cellular biology 2006;26;8;3231-42

  • 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

  • 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

  • Expression of a novel beta adaptin subunit mRNA splice variant in human testes.

    Zhang XD, Yin LL, Zheng Y, Lu L, Zhou ZM and Sha JH

    Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing 210029, China.

    Aim: To identify a novel isoform of adaptin 2 beta subunit (named Ap2beta-NY) and to investigate its relationship with testicular development and spermatogenesis.

    Methods: Using a human testis cDNA microarray, a clone (Ap2beta-NY), which was strongly expressed in adult testes but weakly expressed in embryo testes, was sequenced and analyzed. Using polymerase chain reaction (PCR), the tissue distribution and expression time pattern of Ap2beta-NY were determined.

    Results: Ap2beta-NY was identified and has been deposited in the GenBank (AY341427). The expression level of Ap2beta-NY in the adult testis was about 3-fold higher than that in the embryo testis. PCR analysis using multi-tissue cDNA indicated that Ap2beta-NY was highly expressed in the testis, spleen, thymus, prostate, ovary, blood leukocyte and brain, but not in the heart, placenta, lung, liver, skeletal muscle, kidney and pancreas. In addition, Ap2beta-NY was variably expressed in the testes of patients with spermatogenesis-disturbance and spermatogenesis-arrest but not expressed in those of Sertoli-cell-only syndrome, which implied that, in the testis, Ap2beta-NY was restrictively expressed in germ cells.

    Conclusion: Ap2beta-NY is an isoform of Ap2beta and may be involved in regulating the process of spermatogenesis and testis development.

    Asian journal of andrology 2005;7;2;179-88

  • High-throughput mapping of a dynamic signaling network in mammalian cells.

    Barrios-Rodiles M, Brown KR, Ozdamar B, Bose R, Liu Z, Donovan RS, Shinjo F, Liu Y, Dembowy J, Taylor IW, Luga V, Przulj N, Robinson M, Suzuki H, Hayashizaki Y, Jurisica I and Wrana JL

    Program in Molecular Biology and Cancer, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada, M5G 1X5.

    Signaling pathways transmit information through protein interaction networks that are dynamically regulated by complex extracellular cues. We developed LUMIER (for luminescence-based mammalian interactome mapping), an automated high-throughput technology, to map protein-protein interaction networks systematically in mammalian cells and applied it to the transforming growth factor-beta (TGFbeta) pathway. Analysis using self-organizing maps and k-means clustering identified links of the TGFbeta pathway to the p21-activated kinase (PAK) network, to the polarity complex, and to Occludin, a structural component of tight junctions. We show that Occludin regulates TGFbeta type I receptor localization for efficient TGFbeta-dependent dissolution of tight junctions during epithelial-to-mesenchymal transitions.

    Funded by: NIGMS NIH HHS: P50 GM-62413

    Science (New York, N.Y.) 2005;307;5715;1621-5

  • Huntingtin-interacting protein 1 (Hip1) and Hip1-related protein (Hip1R) bind the conserved sequence of clathrin light chains and thereby influence clathrin assembly in vitro and actin distribution in vivo.

    Chen CY and Brodsky FM

    G. W. Hooper Foundation, Department of Biopharmaceutical Sciences, University of California, San Francisco, CA 94143-0552, USA.

    Clathrin heavy and light chains form triskelia, which assemble into polyhedral coats of membrane vesicles that mediate transport for endocytosis and organelle biogenesis. Light chain subunits regulate clathrin assembly in vitro by suppressing spontaneous self-assembly of the heavy chains. The residues that play this regulatory role are at the N terminus of a conserved 22-amino acid sequence that is shared by all vertebrate light chains. Here we show that these regulatory residues and others in the conserved sequence mediate light chain interaction with Hip1 and Hip1R. These related proteins were previously found to be enriched in clathrin-coated vesicles and to promote clathrin assembly in vitro. We demonstrate Hip1R binding preference for light chains associated with clathrin heavy chain and show that Hip1R stimulation of clathrin assembly in vitro is blocked by mutations in the conserved sequence of light chains that abolish interaction with Hip1 and Hip1R. In vivo overexpression of a fragment of clathrin light chain comprising the Hip1R-binding region affected cellular actin distribution. Together these results suggest that the roles of Hip1 and Hip1R in affecting clathrin assembly and actin distribution are mediated by their interaction with the conserved sequence of clathrin light chains.

    Funded by: NCI NIH HHS: CA09043; NIGMS NIH HHS: GM38093

    The Journal of biological chemistry 2005;280;7;6109-17

  • Immunoaffinity profiling of tyrosine phosphorylation in cancer cells.

    Rush J, Moritz A, Lee KA, Guo A, Goss VL, Spek EJ, Zhang H, Zha XM, Polakiewicz RD and Comb MJ

    Cell Signaling Technology Inc., 166B Cummings Center, Beverly, Massachusetts 01915, USA.

    Tyrosine kinases play a prominent role in human cancer, yet the oncogenic signaling pathways driving cell proliferation and survival have been difficult to identify, in part because of the complexity of the pathways and in part because of low cellular levels of tyrosine phosphorylation. In general, global phosphoproteomic approaches reveal small numbers of peptides containing phosphotyrosine. We have developed a strategy that emphasizes the phosphotyrosine component of the phosphoproteome and identifies large numbers of tyrosine phosphorylation sites. Peptides containing phosphotyrosine are isolated directly from protease-digested cellular protein extracts with a phosphotyrosine-specific antibody and are identified by tandem mass spectrometry. Applying this approach to several cell systems, including cancer cell lines, shows it can be used to identify activated protein kinases and their phosphorylated substrates without prior knowledge of the signaling networks that are activated, a first step in profiling normal and oncogenic signaling networks.

    Funded by: NCI NIH HHS: 1R43CA101106

    Nature biotechnology 2005;23;1;94-101

  • 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

  • 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 AP-2 complex is excluded from the dynamic population of plasma membrane-associated clathrin.

    Rappoport JZ, Taha BW, Lemeer S, Benmerah A and Simon SM

    The Laboratory of Cellular Biophysics, The Rockefeller University, New York, New York 10021, USA.

    Numerous biologically relevant substrates are selectively internalized via clathrin-mediated endocytosis. At the plasma membrane the AP-2 complex plays a major role in clathrin coat formation, interacting with both cargo and clathrin. Utilizing simultaneous dual-channel total internal reflection fluorescence microscopy we have analyzed components of the AP-2 complex (alpha- and beta 2-adaptin) during clathrin-mediated endocytosis. Although in static images enhanced green fluorescent protein-tagged AP-2 markers significantly co-localized with clathrin and other components of clathrin-coated pits, AP-2 did not seem to be present in clathrin spots that appeared to undergo internalization or motility parallel to the plane of the plasma membrane. Two populations of clathrin at the plasma membrane seem to exist, the dynamic and the static, and AP-2 appears to be only found within the latter. These results suggest that colocalized clathrin/AP-2 puncta may represent loci for coated pit production and that previous models that assumed AP-2 was retained within clathrin coats during endocytosis may need to be re-evaluated.

    Funded by: NIGMS NIH HHS: 1 F32 GM069200-01

    The Journal of biological chemistry 2003;278;48;47357-60

  • Tyrosine phosphorylation of the beta2 subunit of clathrin adaptor complex AP-2 reveals the role of a di-leucine motif in the epidermal growth factor receptor trafficking.

    Huang F, Jiang X and Sorkin A

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

    Tyrosine phosphorylation of the beta2 subunit of clathrin adaptor complex AP-2 was detected in three types of cells treated with epidermal growth factor (EGF). The tyrosine phosphorylation was observed during recruitment of EGF receptors into coated pits at 4 degrees C and reached maximum at 37 degrees C at post-recruitment stages of endocytosis. An inhibitor of EGF receptor kinase completely abolished this phosphorylation in all cell types, whereas the inhibitor of Src family kinases partially inhibited beta2 phosphorylation in A-431 cells but not in HeLa cells. By using beta2 subunit tagged with yellow fluorescent protein that is effectively assembled into AP-2 complex, the major phosphorylation site of beta2 was mapped to Tyr-6. Analysis of cells expressing dominant-interfering mutant mu2 subunit of AP-2 suggested that beta2 phosphorylation is partially mediated by the receptor interaction with the mu2 subunit. Mutation of leucine residues 1010 and 1011 motif in the EGF receptor resulted in the severe inhibition of beta2 tyrosine phosphorylation. From these data, we propose that interactions of the EGF receptor with AP-2 mediated by the receptor 974YRAL and di-leucine motifs may contribute to beta2 tyrosine phosphorylation. Surprisingly, mutation of the Leu-1010/Leu-1011 motif resulted in impaired degradation of EGF receptors, suggesting the role of this motif in lysosomal targeting of the receptor.

    Funded by: NCI NIH HHS: CA089151

    The Journal of biological chemistry 2003;278;44;43411-7

  • Molecular and functional characterization of clathrin- and AP-2-binding determinants within a disordered domain of auxilin.

    Scheele U, Alves J, Frank R, Duwel M, Kalthoff C and Ungewickell E

    Departments of Cell Biology and Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany.

    Uncoating of clathrin-coated vesicles requires the J-domain protein auxilin for targeting hsc70 to the clathrin coats and for stimulating the hsc70 ATPase activity. This results in the release of hsc70-complexed clathrin triskelia and concomitant dissociation of the coat. To understand the complex role of auxilin in uncoating and clathrin assembly in more detail, we analyzed the molecular organization of its clathrin-binding domain (amino acids 547-813). CD spectroscopy of auxilin fragments revealed that the clathrin-binding domain is almost completely disordered in solution. By systematic mapping using synthetic peptides and by site-directed mutagenesis, we identified short peptide sequences involved in clathrin heavy chain and AP-2 binding and evaluated their significance for the function of auxilin. Some of the binding determinants, including those containing sequences 674DPF and 636WDW, showed dual specificity for both clathrin and AP-2. In contrast, the two DLL motifs within the clathrin-binding domain were exclusively involved in clathrin binding. Surprisingly, they interacted not only with the N-terminal domain of the heavy chain, but also with the distal domain. Moreover, both DLL peptides proved to be essential for clathrin assembly and uncoating. In addition, we found that the motif 726NWQ is required for efficient clathrin assembly activity. Auxilin shares a number of protein-protein interaction motifs with other endocytic proteins, including AP180. We demonstrate that AP180 and auxilin compete for binding to the alpha-ear domain of AP-2. Like AP180, auxilin also directly interacts with the ear domain of beta-adaptin. On the basis of our data, we propose a refined model for the uncoating mechanism of clathrin-coated vesicles.

    The Journal of biological chemistry 2003;278;28;25357-68

  • The beta2-adaptin clathrin adaptor interacts with the mitotic checkpoint kinase BubR1.

    Cayrol C, Cougoule C and Wright M

    Institut de Pharmacologie et de Biologie Structurale du CNRS-UMR 5089, 205 route de Narbonne, 31077 Toulouse, France. Corinne.Cayrol@ipbs.fr

    The adaptor AP2 is a heterotetrameric complex that associates with clathrin and regulatory proteins to mediate rapid endocytosis from the plasma membrane. Here, we report the identification of the mitotic checkpoint kinase BubR1 as a novel binding partner of beta2-adaptin, one of the AP2 large subunits. Using two-hybrid experiments and in vitro binding assays, we show that beta2-adaptin binds to BubR1 through its amino-terminal beta2-'trunk' domain, while the beta2-binding region of BubR1 maps to the carboxy-terminal kinase domain. Subcellular immunolocalization studies suggest that the interaction between BubR1 and beta2-adaptin could take place in the cytosol at any time during the cell cycle. In addition, we found that BubR1 and the BubR1-related kinase, Bub1, also bind to beta-adaptins of other AP complexes. Together, these results support a model in which the mitotic checkpoint kinases BubR1 and BuB1, by binding to beta-adaptins, may play novel roles in the regulation of vesicular intracellular traffic.

    Biochemical and biophysical research communications 2002;298;5;720-30

  • ARH is a modular adaptor protein that interacts with the LDL receptor, clathrin, and AP-2.

    He G, Gupta S, Yi M, Michaely P, Hobbs HH and Cohen JC

    McDermott Center for Human Growth and Development, the Howard Hughes Medical Institute, University of Texas Southwestern Medical Center at Dallas, 75290, USA.

    Mutations in the phosphotyrosine binding domain protein ARH cause autosomal recessive hypercholesterolemia, a disorder caused by defective internalization of low density lipoprotein receptors (LDLR) in the liver. To examine the function of ARH, we used pull-down experiments to test for interactions between ARH, the LDLR, and proteins involved in clathrin-mediated endocytosis. The phosphotyrosine binding domain of ARH interacted with the internalization sequence (NPVY) in the cytoplasmic tail of LDLR in a sequence-specific manner. Mutations in the NPVY sequence that were previously shown to decrease LDLR internalization abolished in vitro binding to ARH. Recombinant ARH bound purified bovine clathrin with high affinity (K(D), approximately 44 nm). The interaction between ARH and clathrin was mapped to a canonical clathrin box sequence (LLDLE) in ARH and to the N-terminal domain of the clathrin heavy chain. A highly conserved 20-amino acid sequence in the C-terminal region of ARH bound the beta(2)-adaptin subunit of AP-2. Mutation of a glutamic acid residue in the appendage domain of beta(2)-adaptin that is required for interaction with the adapter protein beta-arrestin markedly reduced binding to ARH. These data are consistent with the hypothesis that ARH functions as an adaptor protein that couples LDLR to the endocytic machinery.

    Funded by: NHLBI NIH HHS: HL20948, HL53917

    The Journal of biological chemistry 2002;277;46;44044-9

  • 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

  • Transforming growth factor-beta receptors interact with AP2 by direct binding to beta2 subunit.

    Yao D, Ehrlich M, Henis YI and Leof EB

    Department of Biochemistry and Molecular Biology and Thoracic Diseases Research Unit, Mayo Clinic, Rochester, Minnesota 55905, USA.

    Transforming growth factor-beta (TGF-beta) superfamily members regulate a wide range of biological processes by binding to two transmembrane serine/threonine kinase receptors, type I and type II. We have previously shown that the internalization of these receptors is inhibited by K(+) depletion, cytosol acidification, or hypertonic medium, suggesting the involvement of clathrin-coated pits. However, the involvement of the clathrin-associated adaptor complex AP2 and the identity of the AP2 subunit that binds the receptors were not known. Herein, we have studied these issues by combining studies on intact cells with in vitro assays. Using fluorescence photobleaching recovery to measure the lateral mobility of the receptors on live cells (untreated or treated to alter their coated pit structure), we demonstrated that their mobility is restricted by interactions with coated pits. These interactions were transient and mediated through the receptors' cytoplasmic tails. To measure direct binding of the receptors to specific AP2 subunits, we used yeast two-hybrid screens and in vitro biochemical assays. In contrast to most other plasma membrane receptors that bind to AP2 via the mu2 subunit, AP2/TGF-beta receptor binding was mediated by a direct interaction between the beta2-adaptin N-terminal trunk domain and the cytoplasmic tails of the receptors; no binding was observed to the mu2, alpha, or sigma2 subunits of AP2 or to mu1 of AP1. The data uniquely demonstrate both in vivo and in vitro the ability of beta2-adaptin to directly couple TGF-beta receptors to AP2 and to clathrin-coated pits, providing the first in vivo evidence for interactions of a transmembrane receptor with beta2-adaptin.

    Funded by: NIGMS NIH HHS: GM-54200, GM-55816, R01 GM054200, R01 GM055816, R37 GM055816

    Molecular biology of the cell 2002;13;11;4001-12

  • Differential roles of arrestin-2 interaction with clathrin and adaptor protein 2 in G protein-coupled receptor trafficking.

    Kim YM and Benovic JL

    Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA.

    The non-visual arrestins, arrestin-2 and arrestin-3, play a critical role in regulating the signaling and trafficking of many G protein-coupled receptors (GPCRs). Molecular insight into the role of arrestins in GPCR trafficking has suggested that arrestin interaction with clathrin, beta(2)-adaptin (the beta-subunit of the adaptor protein AP2), and phosphoinositides contributes to this process. In the present study, we have attempted to better define the molecular basis and functional role of arrestin-2 interaction with clathrin and beta(2)-adaptin. Site-directed mutagenesis revealed that the C-terminal region of arrestin-2 mediated beta(2)-adaptin and clathrin interaction with Phe-391 and Arg-395 having an essential role in beta(2)-adaptin binding and LIELD (residues 376-380) having an essential role in clathrin binding. Interestingly, arrestin-2-R169E, an activated form of arrestin that binds to GPCRs in a phosphorylation-independent manner, has significantly enhanced binding to beta(2)-adaptin and clathrin. This suggests that receptor-induced conformational changes in the C-terminal tail of arrestin-2 will likely play a major role in mediating arrestin interaction with clathrin-coated pits. In an effort to clarify the role of these interactions in GPCR trafficking we generated arrestin mutants that were completely and selectively defective in either clathrin (arrestin-2-DeltaLIELD) or beta(2)-adaptin (arrestin-2-F391A) interaction. Analysis of these mutants in COS-1 cells revealed that arrestin/clathrin interaction was essential for agonist-promoted internalization of the beta(2)-adrenergic receptor, while arrestin/beta(2)-adaptin interaction appeared less critical. Arrestin-2 mutants defective in both clathrin and beta(2)-adaptin binding functioned as effective dominant negatives in HEK293 cells and significantly attenuated beta(2)-adrenergic receptor internalization. These mutants should prove useful in better defining the role of arrestins in mediating receptor trafficking.

    Funded by: NHLBI NIH HHS: HL 67663; NIGMS NIH HHS: GM 47419

    The Journal of biological chemistry 2002;277;34;30760-8

  • Molecular architecture and functional model of the endocytic AP2 complex.

    Collins BM, McCoy AJ, Kent HM, Evans PR and Owen DJ

    Cambridge Institute for Medical Research, University of Cambridge, Department of Clinical Biochemistry, Wellcome Trust/MRC Building, Hills Road, United Kingdom.

    AP2 is the best-characterized member of the family of heterotetrameric clathrin adaptor complexes that play pivotal roles in many vesicle trafficking pathways within the cell. AP2 functions in clathrin-mediated endocytosis, the process whereby cargo enters the endosomal system from the plasma membrane. We describe the structure of the 200 kDa AP2 "core" (alpha trunk, beta2 trunk, mu2, and sigma2) complexed with the polyphosphatidylinositol headgroup mimic inositolhexakisphosphate at 2.6 A resolution. Two potential polyphosphatidylinositide binding sites are observed, one on alpha and one on mu2. The binding site for Yxxphi endocytic motifs is buried, indicating that a conformational change, probably triggered by phosphorylation in the disordered mu2 linker, is necessary to allow Yxxphi motif binding. A model for AP2 recruitment and activation is proposed.

    Cell 2002;109;4;523-35

  • beta-Arrestin/AP-2 interaction in G protein-coupled receptor internalization: identification of a beta-arrestin binging site in beta 2-adaptin.

    Laporte SA, Miller WE, Kim KM and Caron MG

    Howard Hughes Medical Institute Laboratories, the Department of Cell Biology, and the Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.

    beta-Arrestins, proteins involved in the turn-off of G protein-coupled receptor (GPCR) activation, bind to the beta(2)-adaptin subunit of the clathrin adaptor AP-2. The interaction of beta(2)-adaptin with beta-arrestin involves critical arginine residues in the C-terminal domain of beta-arrestin and plays an important role in initiating clathrin-mediated endocytosis of the beta(2)-adrenergic receptor (beta(2)AR) (Laporte, S. A., Oakley, R. H., Holt, J. A., Barak, L. S., and Caron, M. G. (2000) J. Biol. Chem. 275, 23120--23126). However, the beta-arrestin-binding site in beta(2)-adaptin has not been identified, and little is known about the role of beta-arrestin/AP-2 interaction in the endocytosis of other GPCRs. Using in vitro binding assays, we have identified two glutamate residues (Glu-849 and Glu-902) in beta(2)-adaptin that are important in beta-arrestin binding. These residues are located in the platform subdomain of the C terminus of beta(2)-adaptin, where accessory/adapter endocytic proteins for other classes of receptors interact, distinct from the main site where clathrin interacts. The functional significance of the beta-arrestin/AP-2/clathrin complex in the endocytosis of GPCRs such as the beta(2)AR and vasopressin type II receptor was evaluated using mutant constructs of the beta(2)-adaptin C terminus containing either the clathrin and the beta-arrestin binding domains or the beta-arrestin-binding domain alone. When expressed in human embryonic kidney 293 cells, both constructs acted as dominant negatives inhibiting the agonist-induced internalization of the beta(2)AR and the vasopressin type II receptor. In addition, although the beta(2)-adaptin construct containing both the clathrin and beta-arrestin binding domains was able to block the endocytosis of transferrin receptors, a beta(2)-adaptin construct capable of associating with beta-arrestin but lacking its high affinity clathrin interaction did not interfere with transferrin receptor endocytosis. These results suggest that the interaction of beta-arrestin with beta(2)-adaptin represents a selective endocytic trigger for several members of the GPCR family.

    Funded by: NINDS NIH HHS: NS 19576

    The Journal of biological chemistry 2002;277;11;9247-54

  • Structure--function relationships in HIV-1 Nef.

    Geyer M, Fackler OT and Peterlin BM

    Howard Hughes Medical Institute, University of California, San Francisco 94143-0703, CA, USA. mgeyer@cc.ucsf.edu

    The accessory Nef protein of HIV and SIV is essential for viral pathogenesis, yet it is perplexing in its multitude of molecular functions. In this review we analyse the structure-function relationships of motifs recently proposed to play roles in aspects of Nef modification, signalling and trafficking, and thereby to impinge on the ability of the virus to survive in, and to manipulate, its cellular host. Based on the full-length structure assembly of HIV Nef, we correlate surface accessibility with secondary structure elements and sequence conservation. Motifs involved in Nef-mediated CD4 and MHC I downregulation are located in flexible regions of Nef, suggesting that the formation of the transient trafficking complexes involved in these processes depends on the recognition of primary sequences. In contrast, the interaction sites for signalling molecules that contain SH3 domains or the p21-activated kinases are associated with the well folded core domain, suggesting the recognition of highly structured protein surfaces.

    EMBO reports 2001;2;7;580-5

  • Mechanism for down-regulation of CD28 by Nef.

    Swigut T, Shohdy N and Skowronski J

    Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.

    SIV and HIV Nef proteins disrupt T-cell receptor machinery by down-modulating cell surface expression of CD4 and expression or signaling of CD3-TCR. Nef also down-modulates class I major histocompatibility complex (MHC) surface expression. We show that SIV and HIV-1 Nefs down-modulate CD28, a major co-stimulatory receptor that mediates effective T-cell activation, by accelerating CD28 endocytosis. The effects of Nef on CD28, CD4, CD3 and class I MHC expression are all genetically separable, indicating that all are selected independently. In cells expressing a Nef-green fluorescent protein (GFP) fusion, CD28 co-localizes with the AP-2 clathrin adaptor and Nef-GFP. Mutations that disrupt Nef interaction with AP-2 disrupt CD28 down-regulation. Furthermore, HIV and SIV Nefs use overlapping but distinct target sites in the membrane-proximal region of the CD28 cytoplasmic domain. Thus, Nef probably induces CD28 endocytosis via the AP-2 pathway, and this involves a ternary complex containing Nef, AP-2 and CD28. The likely consequence of the concerted down-regulation of CD28, CD4 and/or CD3 by Nef is disruption of antigen-specific signaling machineries in infected T cells following a productive antigen recognition event.

    Funded by: NIAID NIH HHS: AI-42561, R01 AI042561

    The EMBO journal 2001;20;7;1593-604

  • 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

  • The structure and function of the beta 2-adaptin appendage domain.

    Owen DJ, Vallis Y, Pearse BM, McMahon HT and Evans PR

    MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH, UK.

    The heterotetrameric AP2 adaptor (alpha, beta 2, mu 2 and sigma 2 subunits) plays a central role in clathrin-mediated endocytosis. We present the protein recruitment function and 1.7 A resolution structure of its beta 2-appendage domain to complement those previously determined for the mu 2 subunit and alpha appendage. Using structure-directed mutagenesis, we demonstrate the ability of the beta 2 appendage alone to bind directly to clathrin and the accessory proteins AP180, epsin and eps15 at the same site. Clathrin polymerization is promoted by binding of clathrin simultaneously to the beta 2-appendage site and to a second site on the adjacent beta 2 hinge. This results in the displacement of the other ligands from the beta 2 appendage. Thus clathrin binding to an AP2-accessory protein complex would cause the controlled release of accessory proteins at sites of vesicle formation.

    The EMBO journal 2000;19;16;4216-27

  • 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

  • The beta2-adrenergic receptor/betaarrestin complex recruits the clathrin adaptor AP-2 during endocytosis.

    Laporte SA, Oakley RH, Zhang J, Holt JA, Ferguson SS, Caron MG and Barak LS

    Howard Hughes Medical Institute Laboratories and Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.

    betaarrestins mediate the desensitization of the beta2-adrenergic receptor (beta2AR) and many other G protein-coupled receptors (GPCRs). Additionally, betaarrestins initiate the endocytosis of these receptors via clathrin coated-pits and interact directly with clathrin. Consequently, it has been proposed that betaarrestins serve as clathrin adaptors for the GPCR family by linking these receptors to clathrin lattices. AP-2, the heterotetrameric clathrin adaptor protein, has been demonstrated to mediate the internalization of many types of plasma membrane proteins other than GPCRs. AP-2 interacts with the clathrin heavy chain and cytoplasmic domains of receptors such as those for epidermal growth factor and transferrin. In the present study we demonstrate the formation of an agonist-induced multimeric complex containing a GPCR, betaarrestin 2, and the beta2-adaptin subunit of AP-2. beta2-Adaptin binds betaarrestin 2 in a yeast two-hybrid assay and coimmunoprecipitates with betaarrestins and beta2AR in an agonist-dependent manner in HEK-293 cells. Moreover, beta2-adaptin translocates from the cytosol to the plasma membrane in response to the beta2AR agonist isoproterenol and colocalizes with beta2AR in clathrin-coated pits. Finally, expression of betaarrestin 2 minigene constructs containing the beta2-adaptin interacting region inhibits beta2AR endocytosis. These findings point to a role for AP-2 in GPCR endocytosis, and they suggest that AP-2 functions as a clathrin adaptor for the endocytosis of diverse classes of membrane receptors.

    Funded by: NHLBI NIH HHS: HL 03422; NINDS NIH HHS: NS 19576, R01 NS019576

    Proceedings of the National Academy of Sciences of the United States of America 1999;96;7;3712-7

  • 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

  • A dileucine motif in HIV-1 Nef is essential for sorting into clathrin-coated pits and for downregulation of CD4.

    Greenberg M, DeTulleo L, Rapoport I, Skowronski J and Kirchhausen T

    Cold Spring Harbor Laboratory, New York 11724, USA.

    Nef, a approximately 200 residue multifunctional regulatory protein of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV), interacts with components of host cell signal transduction and clathrin-dependent protein sorting pathways. The downregulation of surface CD4 molecules and major histocompatibility complex (MHC) class I antigens by Nef is believed to be important in AIDS pathogenesis [1-7]. Nef contains a globular core domain and two disordered segments--a myristylated arm at the amino terminus and a carboxy-terminal loop projecting from the globular core [8,9]. Here, we aimed to determine the sorting signals in HIV-1 Nef that were responsible for its involvement in the clathrin-mediated pathway. We found that a sequence in the carboxy-terminal disordered loop of Nef is essential for downregulation of CD4. This sequence resembles the dileucine motif, one of two well-characterized sorting signals that target membrane proteins to clathrin-coated vesicles. The dileucine-motif-containing segment of Nef bound directly and specifically to the beta-adaptin subunit of the clathrin adaptor complexes AP-1 and AP-2, which are responsible for recruiting sorted proteins into coated pits. Unlike wild-type Nef, a mutant form of Nef that lacked the dileucine motif did not localize to clathrin-coated pits and did not downregulate CD4 expression, although it could downregulate MHC class I surface expression. Thus, the dileucine motif in HIV-1 is required for CD4 downregulation and for interaction with clathrin adaptor complexes.

    Funded by: NIAID NIH HHS: AI42561; NIGMS NIH HHS: GM36548

    Current biology : CB 1998;8;22;1239-42

  • ATM binds to beta-adaptin in cytoplasmic vesicles.

    Lim DS, Kirsch DG, Canman CE, Ahn JH, Ziv Y, Newman LS, Darnell RB, Shiloh Y and Kastan MB

    Oncology Center, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA.

    Inherited mutations in the ATM gene lead to a complex clinical phenotype characterized by neuronal degeneration, oculocutaneous telangiectasias, immune dysfunction, and cancer predisposition. Using the yeast two-hybrid system, we demonstrate that ataxia telangiectasia mutated (ATM) binds to beta-adaptin, one of the components of the AP-2 adaptor complex, which is involved in clathrin-mediated endocytosis of receptors. The interaction between ATM and beta-adaptin was confirmed in vitro, and coimmunoprecipitation and colocalization studies show that the proteins also associate in vivo. ATM also interacts in vitro with beta-NAP, a neuronal-specific beta-adaptin homolog that was identified as an autoantigen in a patient with cerebellar degeneration. Our data describing the association of ATM with beta-adaptin in vesicles indicate that ATM may play a role in intracellular vesicle and/or protein transport mechanisms.

    Funded by: NCI NIH HHS: CA71387, R01 CA071387; NIGMS NIH HHS: GM07309, T32 GM007309

    Proceedings of the National Academy of Sciences of the United States of America 1998;95;17;10146-51

  • Co-localization of HIV-1 Nef with the AP-2 adaptor protein complex correlates with Nef-induced CD4 down-regulation.

    Greenberg ME, Bronson S, Lock M, Neumann M, Pavlakis GN and Skowronski J

    Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.

    The nef gene of human and simian immunodeficiency viruses is critical for AIDS pathogenesis. Its function in vivo is unknown, but in vitro natural isolates of Nef down-regulate expression of the cell surface CD4 molecule, a component of the T cell antigen receptor and the viral receptor, by accelerating its endocytosis. We have used chimeric proteins comprised of the natural HIV-1 NA7 Nef fused to a strongly fluorescing mutant of green fluorescent protein (GFP) to correlate Nef function with intracellular localization in human CD4-positive Jurkat T cells. The NA7-GFP fusion protein co-localizes with components of the clathrin coat, including clathrin and the beta-subunit of the AP-2 adaptor protein complex, at discrete locations that are consistent with the normal cellular distribution of clathrin coats at the plasma membrane. The NA7-GFP protein is also found in the perinuclear region of the cell, which is likely to reflect the Golgi apparatus. Evidence from a CD4-negative fibroblast cell line indicates that co-localization of NA7-GFP with components of the clathrin coat does not require expression of the CD4 molecule. Analysis of a large panel of chimeric molecules containing mutant Nef moieties demonstrated that the N-terminal membrane targeting signal cooperates with additional element(s) in the disordered loops in the Nef molecule to co-localize the Nef protein with AP-2 adaptor complexes at the cell margin. This localization of NA7-GFP correlates with, but is not sufficient for, down-regulation of surface CD4 and at least one additional function of Nef is required. In T cells co-expressing CD4 and NA7-GFP, CD4 at the cell surface is redistributed into a discrete pattern that co-localizes with that of NA7-GFP. Our observations place NA7-GFP in physical proximity to AP-2-containing clathrin coat at the plasma membrane and imply that Nef interacts, either directly or indirectly, with a component of the AP-2-containing coat at this location. This evidence supports a model whereby Nef recruits CD4 to the endocytic machinery via AP-2-containing clathrin coats at the plasma membrane.

    Funded by: PHS HHS: IA-35394

    The EMBO journal 1997;16;23;6964-76

  • Chromosome localization of human genes for clathrin adaptor polypeptides AP2 beta and AP50 and the clathrin-binding protein, VCP.

    Druck T, Gu Y, Prabhala G, Cannizzaro LA, Park SH, Huebner K and Keen JH

    Jefferson Cancer Institute, Jefferson Medical College, Philadelphia, Pennsylvania 19107, USA.

    Clathrin-coated vesicles, involved in endocytosis and Golgi processing, have a surface lattice containing clathrin triskelia and stoichiometric amounts of additional components termed "assembly proteins," or APs. The AP form at the plasma membrane, AP2, is composed of two large subunits of 100-115 kDa, denoted AP2 alpha and AP2 beta, a medium chain of 50 kDa, designated AP50, and a small chain. We have determined human chromosomal locations of genes for a large AP2 beta (CLAPB1) and a medium (CLAPM1) AP subunit and of a novel clathrin-binding protein, VCP, that binds clathrin simultaneously with APs. Chromosomal in situ hybridization of a human genomic clone demonstrated that the CLAPM1 gene mapped to chromosome region 3q28. The gene for the CLAPB1 large subunit was mapped to 17q11.2-q12 by PCR amplification of an AP2 beta fragment from a panel of rodent-human hybrid DNAs. To map the human VCP sequence, a human-specific probe was made by RT-PCR of human mRNA using oligonucleotide primers from conserved regions of the porcine sequence. The amplified human fragment served as probe on Southern blots of hybrid DNAs to determine that the human VCP locus maps to chromosome region 9pter-q34.

    Funded by: NCI NIH HHS: CA51083; NIGMS NIH HHS: GM-28526, GM49217

    Genomics 1995;30;1;94-7

  • The beta 1 and beta 2 subunits of the AP complexes are the clathrin coat assembly components.

    Gallusser A and Kirchhausen T

    Harvard Medical School, Department of Cell Biology, Boston, MA 02115.

    The beta 1 and beta 2 subunits are the closely-related large chains of the trans-Golgi network AP-1 and the plasma membrane AP-2 clathrin-associated protein complexes, respectively. Recombinant beta 1 and beta 2 subunits have been generated in Escherichia coli. It was found that, in the absence of all the other AP subunits, beta 1 and beta 2 interact with clathrin and drive the efficient assembly of clathrin coats. In addition, beta 2 subunits and AP complexes compete for the same clathrin binding site. The appearance of the clathrin/beta coats is the same as the barrel-shaped structures formed with native AP complexes. It is proposed that the principal function of the beta subunits is to initiate coat formation, while the remaining subunits of the AP complexes have other roles in coated pit and coated vesicle function.

    The EMBO journal 1993;12;13;5237-44

  • 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

  • Conservation and diversity in families of coated vesicle adaptins.

    Ponnambalam S, Robinson MS, Jackson AP, Peiperl L and Parham P

    Department of Cell Biology, Stanford University Medical School, California 94305.

    The complete sequence of the beta adaptin subunit of the plasma membrane adaptor complex from coated vesicles has been elucidated. Complementary cDNA clones from human fibroblasts, rat lymphocytes, and bovine lymphocytes have been isolated, sequenced, and compared with each other and with beta adaptin sequences from rat brain (Kirchhausen, T., Nathanson, K.L., Matsui, W., Vaisberg, A., Chow, E.P., Burne, C., Keen, J.H., and Davis, A.E. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 2612-2616). Surprisingly, the 937-amino acid beta adaptin polypeptide is totally conserved between species. This remarkable homology contrasts with the absence of significant sequence similarity between the alpha (Robinson, M.S. (1989) J. Cell Biol. 108, 833-842) and beta adaptins of the plasma membrane adaptor complex. Diversity within each adaptin family is created by the expression of different genes and by tissue-specific differential splicing. The structures of the beta and alpha adaptins can both be divided into two globular domains interconnected by a variable and potentially flexible stalk domain.

    The Journal of biological chemistry 1990;265;9;4814-20

Gene lists (7)

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
L00000013 G2C Homo sapiens Human mGluR5 Human orthologues of mouse mGluR5 complex adapted from Collins et al (2006) 52
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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