151
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Wagener BM, Marjon NA, Revankar CM, Prossnitz ER. Adaptor protein-2 interaction with arrestin regulates GPCR recycling and apoptosis. Traffic 2009; 10:1286-300. [PMID: 19602204 DOI: 10.1111/j.1600-0854.2009.00957.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
G protein-coupled receptors (GPCRs) are integral to cellular function in nearly all physiologic and many pathologic processes. GPCR signaling represents an intricate balance between receptor activation, inactivation (desensitization, internalization and degradation) and resensitization (recycling and de novo synthesis). Complex formation between phosphorylated GPCRs, arrestins and an ever-increasing number of effector molecules is known to regulate cellular function. Previous studies have demonstrated that, although N-formyl peptide receptor (FPR) internalization occurs in the absence of arrestins, FPR recycling is arrestin-dependent. Furthermore, FPR stimulation in the absence of arrestins leads to receptor accumulation in perinuclear endosomes and apoptosis. In this study, we show that the interaction of GPCR-bound arrestin with adaptor protein-2 (AP-2) is a critical anti-apoptotic event. In addition, AP-2 associates with the receptor-arrestin complex in perinuclear endosomes and is required for proper post-endocytic GPCR trafficking. Finally, we observed that depletion of endogenous AP-2 results in the initiation of apoptosis upon stimulation of multiple GPCRs, including P2Y purinergic receptors and CXCR2, but not CXCR4. We propose a model in which the abnormal accumulation of internalized GPCR-arrestin complexes in recycling endosomes, resulting from defective arrestin-AP-2 interactions, leads to the specific initiation of aberrant signaling pathways and apoptosis.
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Affiliation(s)
- Brant M Wagener
- Department of Cell Biology and Physiology and UNM Cancer Research and Treatment Center, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
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152
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Christensen EI, Verroust PJ, Nielsen R. Receptor-mediated endocytosis in renal proximal tubule. Pflugers Arch 2009; 458:1039-48. [PMID: 19499243 DOI: 10.1007/s00424-009-0685-8] [Citation(s) in RCA: 170] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Accepted: 05/19/2009] [Indexed: 01/08/2023]
Abstract
Proteins filtered in renal glomeruli are removed from the tubular fluid by endocytosis in the proximal tubule mediated by the two receptors megalin and cubilin. After endocytic uptake, the proteins are transferred to lysosomes for degradation, while the receptors are returned to the apical cell membrane by receptor recycling in dense apical tubules. In the renal proximal tubule, there is no significant transcellular transport of protein. The reabsorptive process is extremely efficient as evidenced by the virtual protein free urine in humans. The two receptors bind a variety of ligands. The process serves not only to remove the proteins from the ultrafiltrate but also to conserve a variety of essential substances such as vitamins and trace elements carried by plasma proteins. The endocytic apparatus is highly developed in the proximal tubule demonstrating the high capacity of the cells; however, under certain circumstances like diseases affecting the glomeruli, the system is overloaded resulting in proteinuria.
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Affiliation(s)
- Erik Ilsø Christensen
- Section of Cell Biology, Department of Anatomy, University of Aarhus, Wilh. Meyers Allé, Building 1234, 8000, Aarhus C, Denmark.
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153
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Masuyama N, Kuronita T, Tanaka R, Muto T, Hirota Y, Takigawa A, Fujita H, Aso Y, Amano J, Tanaka Y. HM1.24 is internalized from lipid rafts by clathrin-mediated endocytosis through interaction with alpha-adaptin. J Biol Chem 2009; 284:15927-41. [PMID: 19359243 DOI: 10.1074/jbc.m109.005124] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
HM1.24/Bst2/CD317 is a protein highly expressed in multiple myeloma cells and has unique topology with two membrane anchor domains, an NH2-terminal transmembrane domain and a glycosylphosphatidylinositol attached to the COOH terminus. We show here that human HM1.24 is localized not only on the cell surface but also in the trans-Golgi network and/or recycling endosomes, where it resides in detergent-resistant microdomains, lipid rafts. In contrast to other glycosylphosphatidylinositol-anchored proteins, HM1.24 was internalized from lipid rafts on the cell surface by clathrin-mediated endocytosis. Interestingly, a non-canonical tyrosine-based motif, which contains two tyrosine residues, Tyr-6 and Tyr-8, present in the NH2-terminal cytoplasmic tail, was essential for endocytosis through interaction with an Deltaa-adaptin, but not mu2-subunit, of the AP-2 complex. Indeed, an appendage domain of alpha-adaptin was identified as a protein interacting with the cytoplasmic tail of HM1.24. Furthermore, overexpression of the appendage domain of alpha-adaptin in cells depleted of alpha-adaptin could rescue the clathrin-mediated endocytosis of HM1.24 but not of the transferrin receptor. Taken together, our findings suggest that clathrin-dependent endocytosis of human HM1.24 from the cell surface lipid rafts is mediated by direct interaction with alpha-adaptin.
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Affiliation(s)
- Naoko Masuyama
- Division of Pharmaceutical Cell Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Fukuoka 812-8582, Japan
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154
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Abstract
Endocytic mechanisms control the lipid and protein composition of the plasma membrane, thereby regulating how cells interact with their environments. Here, we review what is known about mammalian endocytic mechanisms, with focus on the cellular proteins that control these events. We discuss the well-studied clathrin-mediated endocytic mechanisms and dissect endocytic pathways that proceed independently of clathrin. These clathrin-independent pathways include the CLIC/GEEC endocytic pathway, arf6-dependent endocytosis, flotillin-dependent endocytosis, macropinocytosis, circular doral ruffles, phagocytosis, and trans-endocytosis. We also critically review the role of caveolae and caveolin1 in endocytosis. We highlight the roles of lipids, membrane curvature-modulating proteins, small G proteins, actin, and dynamin in endocytic pathways. We discuss the functional relevance of distinct endocytic pathways and emphasize the importance of studying these pathways to understand human disease processes.
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Affiliation(s)
- Gary J Doherty
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
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155
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Thieman JR, Mishra SK, Ling K, Doray B, Anderson RA, Traub LM. Clathrin regulates the association of PIPKIgamma661 with the AP-2 adaptor beta2 appendage. J Biol Chem 2009; 284:13924-13939. [PMID: 19287005 DOI: 10.1074/jbc.m901017200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The AP-2 clathrin adaptor differs fundamentally from the related AP-1, AP-3, and AP-4 sorting complexes because membrane deposition does not depend directly on an Arf family GTPase. Instead phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)) appears to act as the principal compartmental cue for AP-2 placement at the plasma membrane as well as for the docking of numerous other important clathrin coat components at the nascent bud site. This PtdIns(4,5)P(2) dependence makes type I phosphatidylinositol 4-phosphate 5-kinases (PIPKIs) lynchpin enzymes in the assembly of clathrin-coated structures at the cell surface. PIPKIgamma is the chief 5-kinase at nerve terminals, and here we show that the 26-amino acid, alternatively spliced C terminus of PIPKIgamma661 is an intrinsically unstructured polypeptide that binds directly to the sandwich subdomain of the AP-2 beta2 subunit appendage. An aromatic side chain-based, extended interaction motif that also includes the two bulky C-terminal residues of the short PIPKIgamma635 variant is necessary for beta2 appendage engagement. The clathrin heavy chain accesses the same contact surface on the AP-2 beta2 appendage, but because of additional clathrin binding sites located within the unstructured hinge segment of the beta2 subunit, clathrin binds the beta2 chain with a higher apparent affinity than PIPKIgamma661. A clathrin-regulated interaction with AP-2 could allow PIPKIgamma661 to be strategically positioned for regional PtdIns(4,5)P(2) generation during clathrin-coated vesicle assembly at the synapse.
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Affiliation(s)
- James R Thieman
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Sanjay K Mishra
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Kun Ling
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Balraj Doray
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Richard A Anderson
- Department of Pharmacology, University of Wisconsin School of Medicine, Madison, Wisconsin 53706
| | - Linton M Traub
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261.
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156
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Rudinskiy N, Grishchuk Y, Vaslin A, Puyal J, Delacourte A, Hirling H, Clarke PGH, Luthi-Carter R. Calpain hydrolysis of alpha- and beta2-adaptins decreases clathrin-dependent endocytosis and may promote neurodegeneration. J Biol Chem 2009; 284:12447-58. [PMID: 19240038 DOI: 10.1074/jbc.m804740200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Clathrin-dependent endocytosis is mediated by a tightly regulated network of molecular interactions that provides essential protein-protein and protein-lipid binding activities. Here we report the hydrolysis of the alpha- and beta2-subunits of the tetrameric adaptor protein complex 2 by calpain. Calcium-dependent alpha- and beta2-adaptin hydrolysis was observed in several rat tissues, including brain and primary neuronal cultures. Neuronal alpha- and beta2-adaptin cleavage was inducible by glutamate stimulation and was accompanied by the decreased endocytosis of transferrin. Heterologous expression of truncated forms of the beta2-adaptin subunit significantly decreased the membrane recruitment of clathrin and inhibited clathrin-mediated receptor endocytosis. Moreover, the presence of truncated beta2-adaptin sensitized neurons to glutamate receptor-mediated excitotoxicity. Proteolysis of alpha- and beta2-adaptins, as well as the accessory clathrin adaptors epsin 1, adaptor protein 180, and the clathrin assembly lymphoid myeloid leukemia protein, was detected in brain tissues after experimentally induced ischemia and in cases of human Alzheimer disease. The present study further clarifies the central role of calpain in regulating clathrin-dependent endocytosis and provides evidence for a novel mechanism through which calpain activation may promote neurodegeneration: the sensitization of cells to glutamate-mediated excitotoxicity via the decreased internalization of surface receptors.
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Affiliation(s)
- Nikita Rudinskiy
- Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne, Station 15, Lausanne CH1015, Switzerland
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157
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Sone M, Uchida A, Komatsu A, Suzuki E, Ibuki I, Asada M, Shiwaku H, Tamura T, Hoshino M, Okazawa H, Nabeshima YI. Loss of yata, a novel gene regulating the subcellular localization of APPL, induces deterioration of neural tissues and lifespan shortening. PLoS One 2009; 4:e4466. [PMID: 19209226 PMCID: PMC2635962 DOI: 10.1371/journal.pone.0004466] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Accepted: 01/02/2009] [Indexed: 11/24/2022] Open
Abstract
Background The subcellular localization of membrane and secreted proteins is finely and dynamically regulated through intracellular vesicular trafficking for permitting various biological processes. Drosophila Amyloid precursor protein like (APPL) and Hikaru genki (HIG) are examples of proteins that show differential subcellular localization among several developmental stages. Methodology/Principal Findings During the study of the localization mechanisms of APPL and HIG, we isolated a novel mutant of the gene, CG1973, which we named yata. This molecule interacted genetically with Appl and is structurally similar to mouse NTKL/SCYL1, whose mutation was reported to cause neurodegeneration. yata null mutants showed phenotypes that included developmental abnormalities, progressive eye vacuolization, brain volume reduction, and lifespan shortening. Exogenous expression of Appl or hig in neurons partially rescued the mutant phenotypes of yata. Conversely, the phenotypes were exacerbated in double null mutants for yata and Appl. We also examined the subcellular localization of endogenous APPL and exogenously pulse-induced APPL tagged with FLAG by immunostaining the pupal brain and larval motor neurons in yata mutants. Our data revealed that yata mutants showed impaired subcellular localization of APPL. Finally, yata mutant pupal brains occasionally showed aberrant accumulation of Sec23p, a component of the COPII coat of secretory vesicles traveling from the endoplasmic reticulum (ER) to the Golgi. Conclusion/Significance We identified a novel gene, yata, which is essential for the normal development and survival of tissues. Loss of yata resulted in the progressive deterioration of the nervous system and premature lethality. Our genetic data showed a functional relationship between yata and Appl. As a candidate mechanism of the abnormalities, we found that yata regulates the subcellular localization of APPL and possibly other proteins.
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Affiliation(s)
- Masaki Sone
- Medical Top Track Program, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.
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158
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Gsponer J, Madan Babu M. The rules of disorder or why disorder rules. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2009; 99:94-103. [DOI: 10.1016/j.pbiomolbio.2009.03.001] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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159
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Salazar G, Zlatic S, Craige B, Peden AA, Pohl J, Faundez V. Hermansky-Pudlak syndrome protein complexes associate with phosphatidylinositol 4-kinase type II alpha in neuronal and non-neuronal cells. J Biol Chem 2009; 284:1790-802. [PMID: 19010779 PMCID: PMC2615517 DOI: 10.1074/jbc.m805991200] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Revised: 11/04/2008] [Indexed: 11/06/2022] Open
Abstract
The Hermansky-Pudlak syndrome is a disorder affecting endosome sorting. Disease is triggered by defects in any of 15 mouse gene products, which are part of five distinct cytosolic molecular complexes: AP-3, homotypic fusion and vacuole protein sorting, and BLOC-1, -2, and -3. To identify molecular associations of these complexes, we used in vivo cross-linking followed by purification of cross-linked AP-3 complexes and mass spectrometric identification of associated proteins. AP-3 was co-isolated with BLOC-1, BLOC-2, and homotypic fusion and vacuole protein sorting complex subunits; clathrin; and phosphatidylinositol-4-kinase type II alpha (PI4KIIalpha). We previously reported that this membrane-anchored enzyme is a regulator of AP-3 recruitment to membranes and a cargo of AP-3 ( Craige, B., Salazar, G., and Faundez, V. (2008) Mol. Biol. Cell 19, 1415-1426 ). Using cells deficient in different Hermansky-Pudlak syndrome complexes, we identified that BLOC-1, but not BLOC-2 or BLOC-3, deficiencies affect PI4KIIalpha inclusion into AP-3 complexes. BLOC-1, PI4KIIalpha, and AP-3 belong to a tripartite complex, and down-regulation of either PI4KIIalpha, BLOC-1, or AP-3 complexes led to similar LAMP1 phenotypes. Our analysis indicates that BLOC-1 complex modulates the association of PI4KIIalpha with AP-3. These results suggest that AP-3 and BLOC-1 act, either in concert or sequentially, to specify sorting of PI4KIIalpha along the endocytic route.
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Affiliation(s)
- Gloria Salazar
- Departments of Cell Biology and
Medicine, Division of Cardiology,
the Graduate Program in Biochemistry,
Cell, and Developmental Biology, the
Center for
Neurodegenerative Diseases, and the
Microchemical Facility, Emory University,
Atlanta, Georgia 30322 and the
Cambridge Institute for Medical
Research, University of Cambridge, Hills Road, Cambridge CB20XY, United
Kingdom
| | - Stephanie Zlatic
- Departments of Cell Biology and
Medicine, Division of Cardiology,
the Graduate Program in Biochemistry,
Cell, and Developmental Biology, the
Center for
Neurodegenerative Diseases, and the
Microchemical Facility, Emory University,
Atlanta, Georgia 30322 and the
Cambridge Institute for Medical
Research, University of Cambridge, Hills Road, Cambridge CB20XY, United
Kingdom
| | - Branch Craige
- Departments of Cell Biology and
Medicine, Division of Cardiology,
the Graduate Program in Biochemistry,
Cell, and Developmental Biology, the
Center for
Neurodegenerative Diseases, and the
Microchemical Facility, Emory University,
Atlanta, Georgia 30322 and the
Cambridge Institute for Medical
Research, University of Cambridge, Hills Road, Cambridge CB20XY, United
Kingdom
| | - Andrew A. Peden
- Departments of Cell Biology and
Medicine, Division of Cardiology,
the Graduate Program in Biochemistry,
Cell, and Developmental Biology, the
Center for
Neurodegenerative Diseases, and the
Microchemical Facility, Emory University,
Atlanta, Georgia 30322 and the
Cambridge Institute for Medical
Research, University of Cambridge, Hills Road, Cambridge CB20XY, United
Kingdom
| | - Jan Pohl
- Departments of Cell Biology and
Medicine, Division of Cardiology,
the Graduate Program in Biochemistry,
Cell, and Developmental Biology, the
Center for
Neurodegenerative Diseases, and the
Microchemical Facility, Emory University,
Atlanta, Georgia 30322 and the
Cambridge Institute for Medical
Research, University of Cambridge, Hills Road, Cambridge CB20XY, United
Kingdom
| | - Victor Faundez
- Departments of Cell Biology and
Medicine, Division of Cardiology,
the Graduate Program in Biochemistry,
Cell, and Developmental Biology, the
Center for
Neurodegenerative Diseases, and the
Microchemical Facility, Emory University,
Atlanta, Georgia 30322 and the
Cambridge Institute for Medical
Research, University of Cambridge, Hills Road, Cambridge CB20XY, United
Kingdom
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160
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Abstract
Clathrin-mediated endocytosis sorts for degradation of more than 50 different growth factor receptors capable of relaying growth and differentiation signals by means of their cytoplasm-facing, intrinsic tyrosine kinase activity. The kinetics and alternative routings of receptor endocytosis critically regulate growth factor signaling, which underscores the importance of understanding mechanisms underlying fail-safe operation (robustness) and fidelity of the pathway. Like other robust systems, a layered hub-centric network controls receptor endocytosis. Characteristically, the modular hubs (e.g., AP2-Eps15 and Hrs) contain a membrane-anchoring lipid-binding domain, an ubiquitin-binding module, which recruits ubiquitinylated cargo, and a machinery enabling homo-assembly. Scheduled hub transitions, as well as cascades of Rab family guanosine triphosphatases and membrane bending machineries, define points of commitment to vesicle budding, thereby securing unidirectional trafficking. System's bistability permits stimulation by a growth factor, which oscillates a series of switches based on posttranslational protein modifications (i.e., phosphorylation, ubiquitinylation and neddylation), as well as transient low-affinity/high-avidity protein assemblies. Cbl family ubiquitin ligases, along with a set of phosphotyrosine-binding adaptors (e.g., Grb2), integrate receptor endocytosis into the densely wired networks of signal transduction pathways, which are involved in health and disease.
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Affiliation(s)
- Yaara Zwang
- Department of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
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161
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Hennies HC, Kornak U, Zhang H, Egerer J, Zhang X, Seifert W, Kühnisch J, Budde B, Nätebus M, Brancati F, Wilcox WR, Müller D, Kaplan PB, Rajab A, Zampino G, Fodale V, Dallapiccola B, Newman W, Metcalfe K, Clayton-Smith J, Tassabehji M, Steinmann B, Barr FA, Nürnberg P, Wieacker P, Mundlos S. Gerodermia osteodysplastica is caused by mutations in SCYL1BP1, a Rab-6 interacting golgin. Nat Genet 2008; 40:1410-2. [PMID: 18997784 PMCID: PMC3122266 DOI: 10.1038/ng.252] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Accepted: 09/03/2008] [Indexed: 11/10/2022]
Abstract
Gerodermia osteodysplastica is an autosomal recessive disorder characterized by wrinkly skin and osteoporosis. Here we demonstrate that gerodermia osteodysplastica is caused by loss-of-function mutations in SCYL1BP1, which is highly expressed in skin and osteoblasts. The protein localizes to the Golgi apparatus and interacts with Rab6, identifying SCYL1BP1 as a golgin. These results associate abnormalities of the secretory pathway with age-related changes in connective tissues.
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Affiliation(s)
- Hans Christian Hennies
- Cologne Center for Genomics (CCG), University of Cologne, 50674 Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, 50931 Cologne, Germany
| | - Uwe Kornak
- Institute for Medical Genetics, Charité University Medicine of Berlin, 13353 Berlin, Germany
- Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
| | - Haikuo Zhang
- Institute for Medical Genetics, Charité University Medicine of Berlin, 13353 Berlin, Germany
- Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
| | - Johannes Egerer
- Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
- Max Planck Institute for Biochemistry, 82152 Munich, Germany
| | - Xin Zhang
- Institute for Medical Genetics, Charité University Medicine of Berlin, 13353 Berlin, Germany
- Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
| | - Wenke Seifert
- Cologne Center for Genomics (CCG), University of Cologne, 50674 Cologne, Germany
- Institute for Medical Genetics, Charité University Medicine of Berlin, 13353 Berlin, Germany
| | - Jirko Kühnisch
- Institute for Medical Genetics, Charité University Medicine of Berlin, 13353 Berlin, Germany
| | - Birgit Budde
- Cologne Center for Genomics (CCG), University of Cologne, 50674 Cologne, Germany
| | - Marc Nätebus
- Cologne Center for Genomics (CCG), University of Cologne, 50674 Cologne, Germany
| | - Francesco Brancati
- IRCCS-CSS, San Giovanni Rotondo and CSS-Mendel Institute, 00198 Rome, Italy and Department of Biomedical Sciences and Aging Research Center, Ce.S.I., G. d’Annunzio University Foundation, Chieti, Italy
| | - William R. Wilcox
- Medical Genetics Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA, 90048
| | - Dietmar Müller
- Institute of Medical Genetics, Klinikum Chemnitz, 09116 Chemnitz, Germany
| | - Paige B. Kaplan
- Section of Metabolic Diseases, Children’s Hospital of Philadelphia, University of Pennsylvania, PA 19104, USA
| | - Anna Rajab
- Genetic Unit, Directorate General of Health Affairs, Ministry of Health, Muscat 113, Sultanate of Oman
| | - Giuseppe Zampino
- Istituto di Clinica Pediatrica, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
| | - Valentina Fodale
- Dipartimento di Biologia Cellulare e Neuroscienze, Istituto Superiore di Sanità, 00161 Rome, Italy
| | - Bruno Dallapiccola
- IRCCS-CSS, San Giovanni Rotondo and CSS-Mendel Institute, 00198 Rome, Italy and Department of Biomedical Sciences and Aging Research Center, Ce.S.I., G. d’Annunzio University Foundation, Chieti, Italy
| | - William Newman
- Medical Genetics, St Mary’s Hospital, University of Manchester, Manchester, M13 0JH, UK
| | - Kay Metcalfe
- Medical Genetics, St Mary’s Hospital, University of Manchester, Manchester, M13 0JH, UK
| | - Jill Clayton-Smith
- Medical Genetics, St Mary’s Hospital, University of Manchester, Manchester, M13 0JH, UK
| | - May Tassabehji
- Medical Genetics, St Mary’s Hospital, University of Manchester, Manchester, M13 0JH, UK
| | - Beat Steinmann
- Division of Metabolism and Molecular Pediatrics, University Children's Hospital, 8032 Zurich, Switzerland
| | - Francis A. Barr
- Max Planck Institute for Biochemistry, 82152 Munich, Germany
- Cancer Research Centre, University of Liverpool, L3 9TA Liverpool, UK
| | - Peter Nürnberg
- Cologne Center for Genomics (CCG), University of Cologne, 50674 Cologne, Germany
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Peter Wieacker
- Institut für Humangenetik, Westfälische Wilhelms-Universität, 48149 Münster, Germany
| | - Stefan Mundlos
- Institute for Medical Genetics, Charité University Medicine of Berlin, 13353 Berlin, Germany
- Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
- Berlin-Brandenburg Center for Regenerative Therapies, 14195 Berlin, Germany
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162
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Sorting of lysosomal proteins. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1793:605-14. [PMID: 19046998 DOI: 10.1016/j.bbamcr.2008.10.016] [Citation(s) in RCA: 585] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Revised: 10/07/2008] [Accepted: 10/30/2008] [Indexed: 11/24/2022]
Abstract
Lysosomes are composed of soluble and transmembrane proteins that are targeted to lysosomes in a signal-dependent manner. The majority of soluble acid hydrolases are modified with mannose 6-phosphate (M6P) residues, allowing their recognition by M6P receptors in the Golgi complex and ensuing transport to the endosomal/lysosomal system. Other soluble enzymes and non-enzymatic proteins are transported to lysosomes in an M6P-independent manner mediated by alternative receptors such as the lysosomal integral membrane protein LIMP-2 or sortilin. Sorting of cargo receptors and lysosomal transmembrane proteins requires sorting signals present in their cytosolic domains. These signals include dileucine-based motifs, DXXLL or [DE]XXXL[LI], and tyrosine-based motifs, YXXØ, which interact with components of clathrin coats such as GGAs or adaptor protein complexes. In addition, phosphorylation and lipid modifications regulate signal recognition and trafficking of lysosomal membrane proteins. The complex interaction of both luminal and cytosolic signals with recognition proteins guarantees the specific and directed transport of proteins to lysosomes.
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163
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Keyel PA, Thieman JR, Roth R, Erkan E, Everett ET, Watkins SC, Heuser JE, Traub LM. The AP-2 adaptor beta2 appendage scaffolds alternate cargo endocytosis. Mol Biol Cell 2008; 19:5309-26. [PMID: 18843039 DOI: 10.1091/mbc.e08-07-0712] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The independently folded appendages of the large alpha and beta2 subunits of the endocytic adaptor protein (AP)-2 complex coordinate proper assembly and operation of endocytic components during clathrin-mediated endocytosis. The beta2 subunit appendage contains a common binding site for beta-arrestin or the autosomal recessive hypercholesterolemia (ARH) protein. To determine the importance of this interaction surface in living cells, we used small interfering RNA-based gene silencing. The effect of extinguishing beta2 subunit expression on the internalization of transferrin is considerably weaker than an AP-2 alpha subunit knockdown. We show the mild sorting defect is due to fortuitous substitution of the beta2 chain with the closely related endogenous beta1 subunit of the AP-1 adaptor complex. Simultaneous silencing of both beta1 and beta2 subunit transcripts recapitulates the strong alpha subunit RNA interference (RNAi) phenotype and results in loss of ARH from endocytic clathrin coats. An RNAi-insensitive beta2-yellow fluorescent protein (YFP) expressed in the beta1 + beta2-silenced background restores cellular AP-2 levels, robust transferrin internalization, and ARH colocalization with cell surface clathrin. The importance of the beta appendage platform subdomain over clathrin for precise deposition of ARH at clathrin assembly zones is revealed by a beta2-YFP with a disrupted ARH binding interface, which does not restore ARH colocalization with clathrin. We also show a beta-arrestin 1 mutant, which engages coated structures in the absence of any G protein-coupled receptor stimulation, colocalizes with beta2-YFP and clathrin even in the absence of an operational clathrin binding sequence. These findings argue against ARH and beta-arrestin binding to a site upon the beta2 appendage platform that is later obstructed by polymerized clathrin. We conclude that ARH and beta-arrestin depend on a privileged beta2 appendage site for proper cargo recruitment to clathrin bud sites.
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Affiliation(s)
- Peter A Keyel
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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164
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Chaineau M, Danglot L, Proux-Gillardeaux V, Galli T. Role of HRB in clathrin-dependent endocytosis. J Biol Chem 2008; 283:34365-73. [PMID: 18819912 DOI: 10.1074/jbc.m804587200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human immunodeficiency virus Rev-binding protein (HRB), also called human Rev-interacting protein (hRIP) or Rev/Rex activation domain binding (RAB) is a partner of the tyrosine kinase substrate EPS15, and it has been recovered in the AP-2 interactome. EPS15 and AP-2 are involved in endocytosis, but the function of HRB in this process is still unknown. Here we identified HRB as a partner of the vesicular SNARE tetanus neurotoxin-insensitive vesicle-associated membrane protein (TI-VAMP, also called VAMP7) in yeast two-hybrid screens and using biochemical assays. In HeLa cells, HRB localized both in the nucleus and in the cytoplasm. In the cytoplasm, HRB colocalized with clathrin-, AP-2-, EPS15-, and transferrin receptor-containing vesicles. We did not see significant colocalization between HRB and TI-VAMP in HeLa cells, and we saw partial colocalization with green fluorescent protein-TI-VAMP in stably expressing Madin-Darby canine kidney cells. Nevertheless using a pHLuorin-tagged TI-VAMP construct, we found that HRB and TI-VAMP colocalize close to the plasma membrane after 5 min of anti-green fluorescent protein antibody uptake. These results suggest that TI-VAMP and HRB may interact only during the early stages of endocytosis. Furthermore uptake experiments followed by fluorescence-activated cell sorting showed that the endocytosis of fluorescent transferrin and pHLuorin-TI-VAMP is strongly reduced in HRB knockdown cells. Altogether these results suggest that HRB is involved in clathrin-dependent endocytosis and recruits TI-VAMP in this process.
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Affiliation(s)
- Mathilde Chaineau
- "Membrane Traffic in Neuronal and Epithelial Morphogenesis," INSERM Avenir Team and Institut Jacques Monod, CNRS UMR7592, Universities Paris 6 and Paris 7, Paris, F-75005 France
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165
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Pryor PR, Jackson L, Gray SR, Edeling MA, Thompson A, Sanderson CM, Evans PR, Owen DJ, Luzio JP. Molecular basis for the sorting of the SNARE VAMP7 into endocytic clathrin-coated vesicles by the ArfGAP Hrb. Cell 2008; 134:817-27. [PMID: 18775314 PMCID: PMC2648964 DOI: 10.1016/j.cell.2008.07.023] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2008] [Revised: 06/06/2008] [Accepted: 07/15/2008] [Indexed: 11/18/2022]
Abstract
SNAREs provide the specificity and energy for the fusion of vesicles with their target membrane, but how they are sorted into the appropriate vesicles on post-Golgi trafficking pathways is largely unknown. We demonstrate that the clathrin-mediated endocytosis of the SNARE VAMP7 is directly mediated by Hrb, a clathrin adaptor and ArfGAP. Hrb wraps 20 residues of its unstructured C-terminal tail around the folded VAMP7 longin domain, demonstrating that unstructured regions of clathrin adaptors can select cargo. Disrupting this interaction by mutation of the VAMP7 longin domain or depletion of Hrb causes VAMP7 to accumulate on the cell's surface. However, the SNARE helix of VAMP7 binds back onto its longin domain, outcompeting Hrb for binding to the same groove and suggesting that Hrb-mediated endocytosis of VAMP7 occurs only when VAMP7 is incorporated into a cis-SNARE complex. These results elucidate the mechanism of retrieval of a postfusion SNARE complex in clathrin-coated vesicles.
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Affiliation(s)
- Paul R. Pryor
- Cambridge Institute for Medical Research and Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
| | - Lauren Jackson
- Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | - Sally R. Gray
- Cambridge Institute for Medical Research and Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
| | - Melissa A. Edeling
- Cambridge Institute for Medical Research and Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
| | - Amanda Thompson
- Medical Research Council Rosalind Franklin Centre for Genomics Research, Hinxton, Cambridge CB10 1SB, UK
| | - Christopher M. Sanderson
- Medical Research Council Rosalind Franklin Centre for Genomics Research, Hinxton, Cambridge CB10 1SB, UK
| | - Philip R. Evans
- Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | - David J. Owen
- Cambridge Institute for Medical Research and Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
| | - J. Paul Luzio
- Cambridge Institute for Medical Research and Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
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166
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Kasprowicz J, Kuenen S, Miskiewicz K, Habets RLP, Smitz L, Verstreken P. Inactivation of clathrin heavy chain inhibits synaptic recycling but allows bulk membrane uptake. ACTA ACUST UNITED AC 2008; 182:1007-16. [PMID: 18762582 PMCID: PMC2528586 DOI: 10.1083/jcb.200804162] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Synaptic vesicle reformation depends on clathrin, an abundant protein that polymerizes around newly forming vesicles. However, how clathrin is involved in synaptic recycling in vivo remains unresolved. We test clathrin function during synaptic endocytosis using clathrin heavy chain (chc) mutants combined with chc photoinactivation to circumvent early embryonic lethality associated with chc mutations in multicellular organisms. Acute inactivation of chc at stimulated synapses leads to substantial membrane internalization visualized by live dye uptake and electron microscopy. However, chc-inactivated membrane cannot recycle and participate in vesicle release, resulting in a dramatic defect in neurotransmission maintenance during intense synaptic activity. Furthermore, inactivation of chc in the context of other endocytic mutations results in membrane uptake. Our data not only indicate that chc is critical for synaptic vesicle recycling but they also show that in the absence of the protein, bulk retrieval mediates massive synaptic membrane internalization.
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Affiliation(s)
- Jaroslaw Kasprowicz
- Department of Molecular and Developmental Genetics, VIB Flemish Institute for Biotechnology, 3000 Leuven, Belgium
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167
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Abstract
Investigations into the mechanisms which regulate entry of integral membrane proteins, and associated ligands, into the cell through vesicular carriers (endocytosis) have greatly benefited from the application of live-cell imaging. Several excellent recent reviews have detailed specific aspects of endocytosis, such as entry of particular cargo, or the different routes of internalization. The aim of the present review is to highlight how advances in live-cell fluorescence microscopy have affected the study of clathrin-mediated endocytosis. The last decade has seen a tremendous increase in the development and dissemination of methods for imaging endocytosis in live cells, and this has been followed by a dramatic shift in the way this critical cellular pathway is studied and understood. The present review begins with a description of the technical advances which have permitted new types of experiment to be performed, as well as potential pitfalls of these new technologies. Subsequently, advances in the understanding of three key endocytic proteins will be addressed: clathrin, dynamin and AP-2 (adaptor protein 2). Although great strides have clearly been made in these areas in recent years, as is often the case, each answer has bred numerous questions. Furthermore, several examples are highlighted where, because of seemingly minor differences in experimental systems, what appear at first to be very similar studies have, at times, yielded vastly differing results and conclusions. Thus this is an exceedingly exciting time to study endocytosis, and this area serves as a clear demonstration of the power of applying live-cell imaging to answer fundamental biological questions.
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168
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Burman JL, Bourbonniere L, Philie J, Stroh T, Dejgaard SY, Presley JF, McPherson PS. Scyl1, mutated in a recessive form of spinocerebellar neurodegeneration, regulates COPI-mediated retrograde traffic. J Biol Chem 2008; 283:22774-86. [PMID: 18556652 DOI: 10.1074/jbc.m801869200] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Scy1-like 1 (Scyl1), a member of the Scy1-like family of catalytically inactive protein kinases, was recently identified as the gene product altered in muscle-deficient mice, which suffer from motor neuron degeneration and cerebellar atrophy. To determine the function of Scyl1, we have now used a mass spectrometry-based screen to search for Scyl1-binding partners and identified components of coatomer I (COPI) coats. The interaction was confirmed in pull-down assays, and Scyl1 co-immunoprecipitates with betaCOP from brain lysates. Interestingly, and unique for a non-transmembrane domain protein, Scyl1 binds COPI coats using a C-terminal RKLD-COO(-) sequence, similar to the KKXX-COO(-) COPI-binding motif found in transmembrane endoplasmic reticulum (ER) proteins. Scyl1 co-localizes with betaCOP and is localized, in an Arf1-independent manner, to the ER-Golgi intermediate compartment and the cis-Golgi, sites of COPI-mediated membrane budding. The localization and binding properties of Scyl1 strongly suggest a function in COPI transport, and inhibitory RNA-mediated knock down of the protein disrupts COPI-mediated retrograde traffic of the KDEL receptor to the ER without affecting anterograde traffic from the ER. Our data demonstrate a function for Scyl1 as an accessory factor in COPI trafficking and suggest for the first time that alterations in the COPI pathway result in neurodegenerative disease.
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Affiliation(s)
- Jonathon L Burman
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC H3A 2B4, Canada
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169
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Abstract
The ability to localize proteins of interest in live cells through imaging inherently fluorescent protein tags has provided an unprecedented level of information on cellular organization. However, there are numerous cases where fluorescent tags alter the localization and/or function of the proteins to which they are appended. Clathrin-mediated endocytosis from the plasma membrane is a physiologically important process evolutionarily conserved from yeast to humans. Some proteins that are associated with the machinery of clathrin-mediated endocytosis have been tagged with fluorescent proteins. However, it has not yet been possible to study this process through a protein marker that is specific to this step and still fully functional when linked to a fluorescent protein. In this study, we present the first demonstration that one of these proteins, in this case a green fluorescent protein (GFP) fusion to alpha-adaptin, a marker of the adaptor protein-2 complex, functionally complements knockdown of endogenous protein through small interfering RNA silencing. GFP-alpha-adaptin, as well as the techniques used to test the fusion protein, represents an important contribution to the cell biologist's toolbox, which will permit a greater understanding of vesicle trafficking in live cells.
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Affiliation(s)
- Joshua Z Rappoport
- Laboratory of Cellular Biophysics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
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170
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Abstract
Epsin has been suggested to act as an alternate adaptor in several endocytic pathways. Its role in synaptic vesicle recycling remains, however, unclear. Here, we examined the role of epsin in this process by using the lamprey reticulospinal synapse as a model system. We characterized a lamprey ortholog of epsin 1 and showed that it is accumulated at release sites at rest and also at clathrin-coated pits in the periactive zone during synaptic activity. Disruption of epsin interactions, by presynaptic microinjection of antibodies to either the epsin-N-terminal homology domain (ENTH) or the clathrin/AP2 binding region (CLAP), caused profound loss of vesicles in stimulated synapses. CLAP antibody-injected synapses displayed a massive accumulation of distorted coated structures, including coated vacuoles, whereas in synapses perturbed with ENTH antibodies, very few coated structures were found. In both cases coated pits on the plasma membrane showed a shift to early intermediates (shallow coated pits) and an increase in size. Moreover, in CLAP antibody-injected synapses flat clathrin-coated patches occurred on the plasma membrane. We conclude that epsin is involved in clathrin-mediated synaptic vesicle endocytosis. Our results support a model, based on in vitro studies, suggesting that epsin coordinates curvature generation with coat assembly and further indicating that epsin limits clathrin coat assembly to the size of newly formed vesicles. We propose that these functions of epsin 1 provide an additional mechanism for generation of uniformly sized synaptic vesicles.
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171
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Mishra SK, Jha A, Steinhauser AL, Kokoza VA, Washabaugh CH, Raikhel AS, Foster WA, Traub LM. Internalization of LDL-receptor superfamily yolk-protein receptors during mosquito oogenesis involves transcriptional regulation of PTB-domain adaptors. J Cell Sci 2008; 121:1264-74. [DOI: 10.1242/jcs.025833] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
In the anautogenous disease vector mosquitoes Anopheles gambiae and Aedes aegypti, egg development is nutritionally controlled. A blood meal permits further maturation of developmentally repressed previtellogenic egg chambers. This entails massive storage of extraovarian yolk precursors by the oocyte, which occurs through a burst of clathrin-mediated endocytosis. Yolk precursors are concentrated at clathrin-coated structures on the oolemma by two endocytic receptors, the vitellogenin and lipophorin receptors. Both these mosquito receptors are members of the low-density-lipoprotein-receptor superfamily that contain FxNPxY-type internalization signals. In mammals, this tyrosine-based signal is not decoded by the endocytic AP-2 adaptor complex directly. Instead, two functionally redundant phosphotyrosine-binding domain adaptors, Disabled 2 and the autosomal recessive hypercholesterolemia protein (ARH) manage the internalization of the FxNPxY sorting signal. Here, we report that a mosquito ARH-like protein, which we designate trephin, possess similar functional properties to the orthologous vertebrate proteins despite engaging AP-2 in an atypical manner, and that mRNA expression in the egg chamber is strongly upregulated shortly following a blood meal. Temporally regulated trephin transcription and translation suggests a mechanism for controlling yolk uptake when vitellogenin and lipophorin receptors are expressed and clathrin coats operate in previtellogenic ovaries.
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Affiliation(s)
- Sanjay K. Mishra
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Anupma Jha
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Amie L. Steinhauser
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Vladimir A. Kokoza
- Department of Entomology, University of California, Riverside, CA 92521, USA
| | - Charles H. Washabaugh
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | | | | | - Linton M. Traub
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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172
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Håberg K, Lundmark R, Carlsson SR. SNX18 is an SNX9 paralog that acts as a membrane tubulator in AP-1-positive endosomal trafficking. J Cell Sci 2008; 121:1495-505. [PMID: 18411244 DOI: 10.1242/jcs.028530] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
SNX9, SNX18 and SNX30 constitute a separate subfamily of PX-BAR-containing sorting nexin (SNX) proteins. We show here that most tissues express all three paralogs, and immunoprecipitation and immunofluorescence experiments demonstrated that the SNX9-family proteins act as individual entities in cells. Their SH3 domains displayed a high selectivity for dynamin 2, and the PX-BAR units had the capacity to tubulate membranes when expressed in HeLa cells. As previously described for the PX-BAR domain of SNX9 (SNX9-PX-BAR), purified SNX18-PX-BAR caused liposome tubulation in vitro and had a binding preference for PtdIns(4,5)P(2). However, contrary to SNX9, which primarily acts in clathrin-mediated endocytosis at the plasma membrane, endogenous SNX18 localized to AP-1- and PACS1-positive endosomal structures, which were devoid of clathrin and resistant to Brefeldin A. Moreover, a gamma-adaptin recognition motif was defined in a low-complexity region of SNX18, and a complex of endogenous SNX18 and AP-1 could be immunoprecipitated after Brefeldin A treatment. Overexpression of SNX18 sequestered AP-1 from peripheral endosomes and resulted in the formation of short SNX18-decorated tubes with distinct dynamin puncta. The results indicate that SNX9-family members make up discrete membrane-scission units together with dynamin, and suggest that SNX18 mediates budding of carriers for AP-1-positive endosomal trafficking.
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Affiliation(s)
- Karin Håberg
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
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173
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Olesen LE, Ford MG, Schmid EM, Vallis Y, Babu MM, Li PH, Mills IG, McMahon HT, Praefcke GJ. Solitary and Repetitive Binding Motifs for the AP2 Complex α-Appendage in Amphiphysin and Other Accessory Proteins. J Biol Chem 2008; 283:5099-109. [DOI: 10.1074/jbc.m708621200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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174
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DeRegis CJ, Rahl PB, Hoffman GR, Cerione RA, Collins RN. Mutational analysis of betaCOP (Sec26p) identifies an appendage domain critical for function. BMC Cell Biol 2008; 9:3. [PMID: 18211691 PMCID: PMC2262067 DOI: 10.1186/1471-2121-9-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2007] [Accepted: 01/22/2008] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The appendage domain of the gammaCOP subunit of the COPI vesicle coat bears a striking structural resemblance to adaptin-family appendages despite limited primary sequence homology. Both the gammaCOP appendage domain and an equivalent region on betaCOP contain the FxxxW motif; the conservation of this motif suggested the existence of a functional appendage domain in betaCOP. RESULTS Sequence comparisons in combination with structural prediction tools show that the fold of the COOH-terminus of Sec26p is strongly predicted to closely mimic that of adaptin-family appendages. Deletion of the appendage domain of Sec26p results in inviability in yeast, over-expression of the deletion construct is dominant negative and mutagenesis of this region identifies residues critical for function. The ArfGAP Glo3p was identified via suppression screening as a potential downstream modulator of Sec26p in a manner that is independent of the GAP activity of Glo3p but requires the presence of the COOH-terminal ISS motifs. CONCLUSION Together, these results indicate an essential function for the predicted betaCOP appendage and suggest that both COPI appendages perform a biologically active regulatory role with a structure related to adaptin-family appendage domains.
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Affiliation(s)
- Carol J DeRegis
- Graduate Program in Comparative Biomedical Sciences, Cornell University, Ithaca NY 14853, USA
| | - Peter B Rahl
- Graduate Program in Pharmacology, Cornell University, Ithaca, NY 14853, USA
| | - Gregory R Hoffman
- Graduate Program in Biophysics, Cornell University, Ithaca, NY 14853, USA
| | - Richard A Cerione
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Ruth N Collins
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
- Department of Molecular Medicine, Cornell University, C4-109 Veterinary Medical Center, Ithaca, NY 14853, USA
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175
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Structure of the Eps15-stonin2 complex provides a molecular explanation for EH-domain ligand specificity. EMBO J 2008; 27:558-69. [PMID: 18200045 DOI: 10.1038/sj.emboj.7601980] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2007] [Accepted: 12/17/2007] [Indexed: 11/09/2022] Open
Abstract
Eps15 homology (EH) domain-containing proteins play a key regulatory role in intracellular membrane trafficking and cell signalling. EH domains serve as interaction platforms for short peptide motifs comprising the residues NPF within natively unstructured regions of accessory proteins. The EH-NPF interactions described thus far are of very low affinity and specificity. Here, we identify the presynaptic endocytic sorting adaptor stonin2 as a high-affinity ligand for the second EH domain (EH2) of the clathrin accessory protein Eps15. Calorimetric data indicate that both NPF motifs within stonin2 interact with EH2 simultaneously and with sub-micromolar affinity. The solution structure of this complex reveals that the first NPF motif binds to the conserved site on the EH domain, whereas the second motif inserts into a novel hydrophobic pocket. Our data show how combination of two EH-attachment sites provides a means for modulating specificity and allows discrimination from a large pool of potential binding partners containing NPF motifs.
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176
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Ritter B, Denisov AY, Philie J, Allaire PD, Legendre-Guillemin V, Zylbergold P, Gehring K, McPherson PS. The NECAP PHear domain increases clathrin accessory protein binding potential. EMBO J 2007; 26:4066-77. [PMID: 17762867 PMCID: PMC2230672 DOI: 10.1038/sj.emboj.7601836] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2007] [Accepted: 07/30/2007] [Indexed: 11/08/2022] Open
Abstract
AP-2 is a key regulator of the endocytic protein machinery driving clathrin-coated vesicle (CCV) formation. One critical function, mediated primarily by the AP-2 alpha-ear, is the recruitment of accessory proteins. NECAPs are alpha-ear-binding proteins that enrich on CCVs. Here, we have solved the structure of the conserved N-terminal region of NECAP 1, revealing a unique module in the pleckstrin homology (PH) domain superfamily, which we named the PHear domain. The PHear domain binds accessory proteins bearing FxDxF motifs, which were previously thought to bind exclusively to the AP-2 alpha-ear. Structural analysis of the PHear domain reveals the molecular surface for FxDxF motif binding, which was confirmed by site-directed mutagenesis. The reciprocal analysis of the FxDxF motif in amphiphysin I identified distinct binding requirements for binding to the alpha-ear and PHear domain. We show that NECAP knockdown compromises transferrin uptake and establish a functional role for NECAPs in clathrin-mediated endocytosis. Our data uncover a striking convergence of two evolutionarily and structurally distinct modules to recognize a common peptide motif and promote efficient endocytosis.
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Affiliation(s)
- Brigitte Ritter
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Alexei Yu Denisov
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | - Jacynthe Philie
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Patrick D Allaire
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Valerie Legendre-Guillemin
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Peter Zylbergold
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Kalle Gehring
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
- Department of Biochemistry, McGill University, 3655 Promenade Sir William Osler, Montreal, Canada H3G 1Y6. Tel.: +514 398 7287; Fax: +514 847 0220; E-mail:
| | - Peter S McPherson
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, Canada H3A 2B4. Tel.: +514 398 7355; Fax: +514 398 8106; E-mail:
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177
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Young A. Structural insights into the clathrin coat. Semin Cell Dev Biol 2007; 18:448-58. [PMID: 17702618 DOI: 10.1016/j.semcdb.2007.07.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Accepted: 07/05/2007] [Indexed: 11/25/2022]
Abstract
Clathrin is a cytoplasmic protein best known for its role in endocytosis and intracellular trafficking. The diverse nature of clathrin has recently become apparent, with strong evidence available suggesting roles in both chromosome segregation and reassembly of the Golgi apparatus during mitosis. Clathrin functions as a heterohexamer, adopting a three-legged triskelion structure of three clathrin light chains and three heavy chains. During endocytosis clathrin forms a supportive network about the invaginating membrane, interacting with itself and numerous adapter proteins. Advances in the field of structural biology have led us to a greater understanding of clathrin in its assembled state, the clathrin lattice. Combining techniques such as X-ray crystallography, NMR, and cryo-electron microscopy has allowed us to piece together the intricate nature of clathrin-coated vesicles and the interactions of clathrin with its many binding partners. In this review I outline the roles of clathrin within the cell and the recent structural advances that have improved our understanding of clathrin-clathrin and clathrin-protein interactions.
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Affiliation(s)
- Anna Young
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, West Midlands, UK.
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178
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Abstract
The strength of network biology lies in its ability to derive cell biological information without a priori mechanistic or molecular knowledge. It is shown here how a careful understanding of a given biological pathway can refine an interactome approach. This permits the elucidation of additional design principles and of spatio-temporal dynamics behind pathways, and aids in experimental design and interpretation.
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Affiliation(s)
- Eva M Schmid
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
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179
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Wessels E, Simpson JC. Impact of live cell imaging on coated vesicle research. Semin Cell Dev Biol 2007; 18:412-23. [PMID: 17689276 DOI: 10.1016/j.semcdb.2007.07.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2007] [Revised: 06/29/2007] [Accepted: 07/02/2007] [Indexed: 11/21/2022]
Abstract
The role of membrane traffic is to transfer cargo between distinct subcellular compartments. Each individual trafficking event involves the creation, transport and fusion of vesicular and tubular carriers that are formed and regulated via cytoplasmic coat protein complexes. The dynamic nature of this process is therefore highly suitable for studying using live cell imaging techniques. Although these approaches have raised further questions for the field, they have also been instrumental in providing essential new information, in particular relating to the morphology of transport carriers and the exchange kinetics of coat proteins and their regulators on membranes. Here, we present an overview of live cell-imaging experiments that have been used in the study of coated-vesicle transport, and provide specific examples of their impact on our understanding of coat function.
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Affiliation(s)
- Els Wessels
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany.
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180
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Ungewickell EJ, Hinrichsen L. Endocytosis: clathrin-mediated membrane budding. Curr Opin Cell Biol 2007; 19:417-25. [PMID: 17631994 DOI: 10.1016/j.ceb.2007.05.003] [Citation(s) in RCA: 179] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Revised: 05/14/2007] [Accepted: 05/16/2007] [Indexed: 01/18/2023]
Abstract
Clathrin-dependent endocytosis is the major pathway for the uptake of nutrients and signaling molecules in higher eukaryotic cells. The long-held tenet that clathrin-coated vesicles are created from flat coated plasma membrane patches by a sequential process of invagination, bud formation and fission recently received strong support from the results of advanced live cell fluorescence microscopy. The data on the critical components that deform the plasma membrane locally into a coated bud suggest that membrane bending is a team effort requiring membrane-curving protein domains, actin dynamics and, last but not least, clathrin. The scission step requires the mechano-enzymatic function of dynamin, actin dynamics and possibly myosin motor proteins. Finally, a burst of auxilin/GAK initiates the uncoating of the vesicle.
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Affiliation(s)
- Ernst J Ungewickell
- Department of Cell Biology, Center of Anatomy, Hannover Medical School, Carl-Neuberg Street 1, D-30625 Hannover, Germany.
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181
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Mills IG. The interplay between clathrin-coated vesicles and cell signalling. Semin Cell Dev Biol 2007; 18:459-70. [PMID: 17692542 DOI: 10.1016/j.semcdb.2007.07.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2007] [Revised: 06/28/2007] [Accepted: 07/02/2007] [Indexed: 01/26/2023]
Abstract
Internalization of cargo proteins and lipids at the cell surface occurs in both a constitutive and signal-regulated manner through clathrin-mediated and other endocytic pathways. Clathrin-coated vesicle formation is a principal uptake route in response to signalling events. Protein-lipid and protein-protein interactions control both the targeting of signalling molecules and their binding partners to membrane compartments and the assembly of clathrin coats. An emerging aspect of membrane trafficking research is now addressing how signalling cascades and vesicle coat assembly and subsequently disassembly are integrated.
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Affiliation(s)
- Ian G Mills
- Cancer Research UK, Cambridge Research Institute, Robinson Way, Cambridge CB2 ORE, UK.
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182
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Abstract
Neurons are communication specialists that convert electrical into chemical signals at specialized cell-cell junctions termed synapses. Arrival of an action potential triggers calcium-regulated exocytosis of neurotransmitter (NT) from small synaptic vesicles (SVs), which then diffuses across the synaptic cleft and binds to postsynaptic receptors to elicit specific changes within the postsynaptic cell. Endocytosis of pre- and postsynaptic membrane proteins including SV components and postsynaptic NT receptors is essential for the proper functioning of the synapse. During the past several years, we have witnessed enormous progress in our understanding of the mechanics of clathrin-mediated endocytosis (CME) and its role in regulating exo-endocytic vesicle cycling at synapses. Here we summarize the molecular machinery used for recognition of synaptic membrane protein cargo and its clathrin-dependent internalization, and describe the inventory of tools that can be used to monitor vesicle cycling at synapses or to inhibit CME in a stage-specific manner.
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Affiliation(s)
- Nadja Jung
- Department of Membrane Biochemistry, Institute of Chemistry & Biochemistry, Freie Universität Berlin, Takustrasse 6, 14195 Berlin, Germany
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183
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Burtey A, Schmid EM, Ford MGJ, Rappoport JZ, Scott MGH, Marullo S, Simon SM, McMahon HT, Benmerah A. The conserved isoleucine-valine-phenylalanine motif couples activation state and endocytic functions of beta-arrestins. Traffic 2007; 8:914-31. [PMID: 17547696 DOI: 10.1111/j.1600-0854.2007.00578.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Beta-arrestins (betaarrs) play a central role in the regulation of G-protein-coupled receptors (GPCRs). Their binding to phosphorylated activated GPCRs induces a conformational transition to an active state resulting in the release of their flexible C-terminal tail. Binding sites for clathrin and the adaptor protein (AP)-2 clathrin adaptor complex are then unmasked, which drive the recruitment of betaarrs-GPCR complexes into clathrin-coated pits (CCPs). A conserved isoleucine-valine-phenylalanine (IVF) motif of the C-terminal tail controls betaarr activation through intramolecular interactions. Here, we provide structural, biochemical and functional evidence in living cells that the IVF motif also controls binding to AP-2. While the F residue is directly involved in AP-2 binding, substitutions of I and V residues, markedly enhanced affinity for AP-2 resulting in active betaarr mutants, which are constitutively targeted to CCPs in the absence of any GPCR activation. Conformational change and endocytic functions of betaarrs thus appear to be coordinated via the complex molecular interactions established by the IVF motif.
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Affiliation(s)
- Anne Burtey
- Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris, France
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184
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Kolokoltsov AA, Deniger D, Fleming EH, Roberts NJ, Karpilow JM, Davey RA. Small interfering RNA profiling reveals key role of clathrin-mediated endocytosis and early endosome formation for infection by respiratory syncytial virus. J Virol 2007; 81:7786-800. [PMID: 17494077 PMCID: PMC1933373 DOI: 10.1128/jvi.02780-06] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Respiratory syncytial virus (RSV) is a common cause of respiratory tract infections in infants and the elderly. Like many other pH-independent enveloped viruses, RSV is thought to enter at the cell surface, independently of common endocytic pathways. We have used a targeted small interfering RNA (siRNA) library to identify key cellular genes involved in cytoskeletal dynamics and endosome trafficking that are important for RSV infection. Surprisingly, RSV infection was potently inhibited by siRNAs targeting genes associated with clathrin-mediated endocytosis, including clathrin light chain. The important role of clathrin-mediated endocytosis was confirmed by the expression of well-characterized dominant-negative mutants of genes in this pathway and by using the clathrin endocytosis inhibitor chlorpromazine. We conclude that, while RSV may be competent to enter at the cell surface, clathrin function and endocytosis are a necessary and important part of a productive RSV infection, even though infection is strictly independent of pH. These findings raise the possibility that other pH-independent viruses may share a similar dependence on endocytosis for infection and provide a new potential avenue for treatment of infection.
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Affiliation(s)
- Andrey A Kolokoltsov
- Department of Microbiology and Immunology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA
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185
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Traub LM, Lukacs GL. Decoding ubiquitin sorting signals for clathrin-dependent endocytosis by CLASPs. J Cell Sci 2007; 120:543-53. [PMID: 17287393 DOI: 10.1242/jcs.03385] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Cargo selectivity is a hallmark of clathrin-mediated endocytosis. A wide range of structurally unrelated internalization signals specify the preferential clustering of transmembrane cargo into clathrin coats forming on the plasma membrane. Intriguingly, the classical endocytic adaptor AP-2 appears to recognize only a subset of these endocytic sorting signals. New data now reveal the molecular basis for recognition of other internalization signals, including post-translationally appended ubiquitin, by clathrin-coat-associated sorting proteins (CLASPs). Curiously, structurally related ubiquitin-recognition modules are shared by select CLASPs and the 26S proteasome, and recent work indicates that both display similar requirements for ubiquitin binding. During endocytosis, these modules engage oligoubiquitylated cargo in the form of polyubiquitin chains and/or multiple single ubiquitin molecules appended to different acceptor lysines. Functional separation between clathrin-mediated endocytosis and proteasome-dependent proteolysis is probably ensured by temporally regulated, local assembly of ubiquitin-tagged membrane cargo at sorting stations on the cell surface, shielding ubiquitin sorting signals from the proteasome. Thus, an expanded repertoire of CLASPs couples the process of clathrin-coat assembly with high-fidelity incorporation of assorted, cargo-specific sorting signals.
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Affiliation(s)
- Linton M Traub
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, PA 15261, USA, and Program in Cell and Lung Biology, Hospital for Sick Children Research Institute, Toronto, Ontario, Canada.
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186
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Abstract
The ATP-dependent dissociation of clathrin from clathrin-coated vesicles (CCVs) by the molecular chaperone Hsc70 requires J-domain cofactor proteins, either auxilin or cyclin-G-associated kinase (GAK). Both the nerve-specific auxilin and the ubiquitous GAK induce CCVs to bind to Hsc70. The removal of auxilin or GAK from various organisms and cells has provided definitive evidence that Hsc70 uncoats CCVs in vivo. In addition, evidence from various studies has suggested that Hsc70 and auxilin are involved in several other key processes that occur during clathrin-mediated endocytosis. First, Hsc70 and auxilin are required for the clathrin exchange that occurs during coated-pit invagination and constriction; this clathrin exchange may catalyze any rearrangement of the clathrin-coated pit (CCP) structure that is required during invagination and constriction. Second, Hsc70 and auxilin may chaperone clathrin after it dissociates from CCPs so that it does not aggregate in the cytosol. Third, auxilin and Hsc70 may be involved in the rebinding of clathrin to the plasma membrane to form new CCPs and independently appear to chaperone adaptor proteins so that they can also rebind to membranes to nucleate the formation of new CCPs. Finally, if formation of the curved clathrin coat induces membrane curvature, then Hsc70 and auxilin provide the energy for this curvature by inducing ATP-dependent clathrin exchange and rearrangement during endocytosis and ATP-dependent dissociation of clathrin at the end of the cycle so that it is energetically primed to rebind to the plasma membrane.
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Affiliation(s)
- Evan Eisenberg
- Laboratory of Cell Biology, National Heart Lung Blood Institute, National Institutes of Health, Bethesda, MD 20892-0301, USA
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187
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Abstract
Because of the discovery of coated pits and vesicles more than 40 years ago and the identification of clathrin as a major component of the coat, it has been assumed that clathrin-coated pits (CCPs) are responsible for the uptake of most plasma membrane receptors undergoing internalization. The recent molecular characterization of clathrin-independent routes of endocytosis confirms that several alternative endocytic pathways operate at the plasma membrane of mammalian cells. This heterogeneous view of endocytosis has been expanded still further by recent studies, suggesting that different subpopulations of CCPs responsible for the internalization of specific sets of cargo may coexist. In the present review, we have discussed the experimental evidence in favor or against the existence of distinct parallel clathrin-dependent pathways at the plasma membrane.
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Affiliation(s)
- Alexandre Benmerah
- Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), 75014 Paris, France, and INSERM, U567, 75014 Paris, France.
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188
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Fessart D, Simaan M, Zimmerman B, Comeau J, Hamdan FF, Wiseman PW, Bouvier M, Laporte SA. Src-dependent phosphorylation of beta2-adaptin dissociates the beta-arrestin-AP-2 complex. J Cell Sci 2007; 120:1723-32. [PMID: 17456551 DOI: 10.1242/jcs.03444] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Beta-arrestins are known to act as endocytic adaptors by recruiting the clathrin adaptor protein 2 (AP-2) complex to G-protein-coupled receptors (GPCRs), linking them to clathrin-coated pits (CCPs) for internalization. They also act as signaling molecules connecting GPCRs to different downstream effectors. We have previously shown that stimulation of the angiotensin II (Ang II) type 1 receptor (AGTR1, hereafter referred to as AT1R), a member of the GPCR family, promotes the formation of a complex between beta-arrestin, the kinase Src and AP-2. Here, we report that formation of such a complex is involved in the AT1R-mediated tyrosine phosphorylation of beta2-adaptin, the subunit of AP-2 involved in binding beta-arrestin. We identify a crucial tyrosine residue in the ear domain of beta2-adaptin and show in vitro that the phosphorylation of this site regulates the interaction between beta-arrestin and beta2-adaptin. Using fluorescently tagged proteins combined with resonance energy transfer and image cross-correlation spectroscopy approaches, we show in live cells that beta2-adaptin phosphorylation is an important regulatory process for the dissociation of beta-arrestin-AP-2 complexes in CCPs. Finally, we show that beta2-adaptin phosphorylation is involved in the early steps of receptor internalization. Our findings not only unveil beta2-adaptin as a new Src target during AT1R internalization, but also support the role of receptor-mediated signaling in the control of clathrin-dependent endocytosis of receptors.
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Affiliation(s)
- Delphine Fessart
- Hormones and Cancer Research Unit, Department of Medicine, Royal Victoria Hospital, Montréal, QC, H3A 1A1, Canada
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189
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Allaire PD, Ritter B, Thomas S, Burman JL, Denisov AY, Legendre-Guillemin V, Harper SQ, Davidson BL, Gehring K, McPherson PS. Connecdenn, a novel DENN domain-containing protein of neuronal clathrin-coated vesicles functioning in synaptic vesicle endocytosis. J Neurosci 2006; 26:13202-12. [PMID: 17182770 PMCID: PMC6674997 DOI: 10.1523/jneurosci.4608-06.2006] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2005] [Revised: 11/07/2006] [Accepted: 11/07/2006] [Indexed: 11/21/2022] Open
Abstract
Clathrin-coated vesicles (CCVs) are responsible for the endocytosis of multiple cargo, including synaptic vesicle membranes. We now describe a new CCV protein, termed connecdenn, that contains an N-terminal DENN (differentially expressed in neoplastic versus normal cells) domain, a poorly characterized protein module found in multiple proteins of unrelated function and a C-terminal peptide motif domain harboring three distinct motifs for binding the alpha-ear of the clathrin adaptor protein 2 (AP-2). Connecdenn coimmunoprecipitates and partially colocalizes with AP-2, and nuclear magnetic resonance and peptide competition studies reveal that all three alpha-ear-binding motifs contribute to AP-2 interactions. In addition, connecdenn contains multiple Src homology 3 (SH3) domain-binding motifs and coimmunoprecipitates with the synaptic SH3 domain proteins intersectin and endophilin A1. Interestingly, connecdenn is enriched on neuronal CCVs and is present in the presynaptic compartment of neurons. Moreover, connecdenn has a uniquely stable association with CCV membranes because it resists extraction with Tris and high-salt buffers, unlike most other CCV proteins, but it is not detected on purified synaptic vesicles. Together, these observations suggest that connecdenn functions on the endocytic limb of the synaptic vesicle cycle. Accordingly, disruption of connecdenn interactions with its binding partners through overexpression of the C-terminal peptide motif domain or knock down of connecdenn through lentiviral delivery of small hairpin RNA both lead to defects in synaptic vesicle endocytosis in cultured hippocampal neurons. Thus, we identified connecdenn as a component of the endocytic machinery functioning in synaptic vesicle endocytosis, providing the first evidence of a role for a DENN domain-containing protein in endocytosis.
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Affiliation(s)
- Patrick D. Allaire
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada, H3A 2B4
| | - Brigitte Ritter
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada, H3A 2B4
| | - Sebastien Thomas
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada, H3A 2B4
| | - Jonathon L. Burman
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada, H3A 2B4
| | - Alexei Yu. Denisov
- Department of Biochemistry and Montreal Joint Centre for Structural Biology, McGill University, Montreal, Quebec, Canada, H3G 1Y6, and
| | - Valerie Legendre-Guillemin
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada, H3A 2B4
| | - Scott Q. Harper
- Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa 52242
| | - Beverly L. Davidson
- Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa 52242
| | - Kalle Gehring
- Department of Biochemistry and Montreal Joint Centre for Structural Biology, McGill University, Montreal, Quebec, Canada, H3G 1Y6, and
| | - Peter S. McPherson
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada, H3A 2B4
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190
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Keyel PA, Mishra SK, Roth R, Heuser JE, Watkins SC, Traub LM. A single common portal for clathrin-mediated endocytosis of distinct cargo governed by cargo-selective adaptors. Mol Biol Cell 2006; 17:4300-17. [PMID: 16870701 PMCID: PMC1635374 DOI: 10.1091/mbc.e06-05-0421] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Sorting of transmembrane cargo into clathrin-coated vesicles requires endocytic adaptors, yet RNA interference (RNAi)-mediated gene silencing of the AP-2 adaptor complex only disrupts internalization of a subset of clathrin-dependent cargo. This suggests alternate clathrin-associated sorting proteins participate in cargo capture at the cell surface, and a provocative recent proposal is that discrete endocytic cargo are sorted into compositionally and functionally distinct clathrin coats. We show here that the FXNPXY-type internalization signal within cytosolic domain of the LDL receptor is recognized redundantly by two phosphotyrosine-binding domain proteins, Dab2 and ARH; diminishing both proteins by RNAi leads to conspicuous LDL receptor accumulation at the cell surface. AP-2-dependent uptake of transferrin ensues relatively normally in the absence of Dab2 and ARH, clearly revealing delegation of sorting operations at the bud site. AP-2, Dab2, ARH, transferrin, and LDL receptors are all present within the vast majority of clathrin structures at the surface, challenging the general existence of specialized clathrin coats for segregated internalization of constitutively internalized cargo. However, Dab2 expression is exceptionally low in hepatocytes, likely accounting for the pathological hypercholesterolemia that accompanies ARH loss.
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Affiliation(s)
- Peter A. Keyel
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
| | - Sanjay K. Mishra
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
| | - Robyn Roth
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - John E. Heuser
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Simon C. Watkins
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
| | - Linton M. Traub
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
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191
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Brett TJ, Traub LM. Molecular structures of coat and coat-associated proteins: function follows form. Curr Opin Cell Biol 2006; 18:395-406. [PMID: 16806884 DOI: 10.1016/j.ceb.2006.06.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2006] [Accepted: 06/08/2006] [Indexed: 10/24/2022]
Abstract
Endocytic clathrin-coated vesicles arise through the deformation of a small region of plasma membrane encapsulated by a cytosol-oriented clathrin lattice. The coat assembles from soluble protomers in a rapid and highly cooperative process, and invagination is tightly linked to the selective enrichment of cargo molecules within the nascent bud. Recent structural and functional studies demonstrate that coat assembly, membrane deformation, local actin dynamics and the final scission event are intricately coupled, and begin to reveal how key multifunctional, modular proteins are responsible for this linkage. An emerging mechanistic theme is how sequential engagement of common interaction surfaces or network hubs can evict prior binding partners from the assembly zone to ensure vectorial progression of the coat assembly process.
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Affiliation(s)
- Tom J Brett
- Department of Pathology and Immunology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
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