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Reincke M, Sbiera S, Hayakawa A, Theodoropoulou M, Osswald A, Beuschlein F, Meitinger T, Mizuno-Yamasaki E, Kawaguchi K, Saeki Y, Tanaka K, Wieland T, Graf E, Saeger W, Ronchi CL, Allolio B, Buchfelder M, Strom TM, Fassnacht M, Komada M. Mutations in the deubiquitinase gene USP8 cause Cushing's disease. Nat Genet 2014; 47:31-8. [PMID: 25485838 DOI: 10.1038/ng.3166] [Citation(s) in RCA: 361] [Impact Index Per Article: 36.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 11/17/2014] [Indexed: 12/13/2022]
Abstract
Cushing's disease is caused by corticotroph adenomas of the pituitary. To explore the molecular mechanisms of endocrine autonomy in these tumors, we performed exome sequencing of 10 corticotroph adenomas. We found somatic mutations in the USP8 deubiquitinase gene in 4 of 10 adenomas. The mutations clustered in the 14-3-3 protein binding motif and enhanced the proteolytic cleavage and catalytic activity of USP8. Cleavage of USP8 led to increased deubiqutination of the EGF receptor, impairing its downregulation and sustaining EGF signaling. USP8 mutants enhanced promoter activity of the gene encoding proopiomelanocortin. In summary, our data show that dominant mutations in USP8 cause Cushing's disease via activation of EGF receptor signaling.
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Affiliation(s)
- Martin Reincke
- Medizinische Klinik und Poliklinik IV, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Silviu Sbiera
- 1] Medizinische Klinik und Poliklinik IV, Ludwig-Maximilians-Universität München, Munich, Germany. [2] Department of Medicine I, Endocrine and Diabetes Unit, University Hospital, University of Würzburg, Würzburg, Germany
| | - Akira Hayakawa
- Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan
| | | | - Andrea Osswald
- Medizinische Klinik und Poliklinik IV, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Felix Beuschlein
- Medizinische Klinik und Poliklinik IV, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Thomas Meitinger
- 1] Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany. [2] Institute of Human Genetics, Technische Universität München, Munich, Germany. [3] DZHK (German Centre for Cardiovascular Research) partner site, Munich Heart Alliance, Munich, Germany
| | - Emi Mizuno-Yamasaki
- Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan
| | - Kohei Kawaguchi
- Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan
| | - Yasushi Saeki
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Keiji Tanaka
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Thomas Wieland
- Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany
| | - Elisabeth Graf
- Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany
| | - Wolfgang Saeger
- Institut für Neuropathologie der Universität Hamburg, Hamburg, Germany
| | - Cristina L Ronchi
- Comprehensive Cancer Center Mainfranken, University of Würzburg, Würzburg, Germany
| | - Bruno Allolio
- 1] Department of Medicine I, Endocrine and Diabetes Unit, University Hospital, University of Würzburg, Würzburg, Germany. [2] Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany
| | - Michael Buchfelder
- Neurochirurgische Klinik, Klinikum der Universität Erlangen, Erlangen, Germany
| | - Tim M Strom
- 1] Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany. [2] Institute of Human Genetics, Technische Universität München, Munich, Germany
| | - Martin Fassnacht
- 1] Medizinische Klinik und Poliklinik IV, Ludwig-Maximilians-Universität München, Munich, Germany. [2] Department of Medicine I, Endocrine and Diabetes Unit, University Hospital, University of Würzburg, Würzburg, Germany. [3] Comprehensive Cancer Center Mainfranken, University of Würzburg, Würzburg, Germany
| | - Masayuki Komada
- Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan
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2
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Lee SM, Chin LS, Li L. Charcot-Marie-Tooth disease-linked protein SIMPLE functions with the ESCRT machinery in endosomal trafficking. ACTA ACUST UNITED AC 2012; 199:799-816. [PMID: 23166352 PMCID: PMC3514783 DOI: 10.1083/jcb.201204137] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
SIMPLE functions with the ESCRT machinery to promote endosome-to-lysosome trafficking, and this function is impaired by Charcot-Marie-Tooth disease–associated mutations. Mutations in small integral membrane protein of lysosome/late endosome (SIMPLE) cause autosomal dominant, Charcot-Marie-Tooth disease (CMT) type 1C. The cellular function of SIMPLE is unknown and the pathogenic mechanism of SIMPLE mutations remains elusive. Here, we report that SIMPLE interacted and colocalized with endosomal sorting complex required for transport (ESCRT) components STAM1, Hrs, and TSG101 on early endosomes and functioned with the ESCRT machinery in the control of endosome-to-lysosome trafficking. Our analyses revealed that SIMPLE was required for efficient recruitment of ESCRT components to endosomal membranes and for regulating endosomal trafficking and signaling attenuation of ErbB receptors. We found that the ability of SIMPLE to regulate ErbB trafficking and signaling was impaired by CMT-linked SIMPLE mutations via a loss-of-function, dominant-negative mechanism, resulting in prolonged activation of ERK1/2 signaling. Our findings indicate a function of SIMPLE as a regulator of endosomal trafficking and provide evidence linking dysregulated endosomal trafficking to CMT pathogenesis.
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Affiliation(s)
- Samuel M Lee
- Department of Pharmacology and Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, GA 30322, USA
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3
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Ying H, Yue BYJT. Cellular and molecular biology of optineurin. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 294:223-58. [PMID: 22364875 DOI: 10.1016/b978-0-12-394305-7.00005-7] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Optineurin is a gene linked to glaucoma, amyotrophic lateral sclerosis, other neurodegenerative diseases, and Paget's disease of bone. This review describes the characteristics of optineurin and summarizes the cellular and molecular biology investigations conducted so far on optineurin. Data from a number of laboratories indicate that optineurin is a cytosolic protein containing 577 amino acid residues. Interacting with proteins such as myosin VI, Rab8, huntingtin, transferrin receptor, and TANK-binding kinase 1, optineurin is involved in basic cellular functions including protein trafficking, maintenance of the Golgi apparatus, as well as NF-κB pathway, antiviral, and antibacteria signaling. Mutation or alteration of homeostasis of optineurin (such as overexpression or knockdown) results in adverse consequences in the cells, leading to the development of neurodegenerative diseases including glaucoma.
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Affiliation(s)
- Hongyu Ying
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, College of Medicine, Chicago, Illinois, USA
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4
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Wu CY, Jhingory S, Taneyhill LA. The tight junction scaffolding protein cingulin regulates neural crest cell migration. Dev Dyn 2011; 240:2309-23. [PMID: 21905165 DOI: 10.1002/dvdy.22735] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/21/2011] [Indexed: 01/11/2023] Open
Abstract
Neural crest cells give rise to a diverse range of structures during vertebrate development. These cells initially exist in the dorsal neuroepithelium and subsequently acquire the capacity to migrate. Although studies have documented the importance of adherens junctions in regulating neural crest cell migration, little attention has been paid to tight junctions during this process. We now identify the tight junction protein cingulin as a key regulator of neural crest migration. Cingulin knock-down increases the migratory neural crest cell domain, which is correlated with a disruption of the neural tube basal lamina. Overexpression of cingulin also augments neural crest cell migration and is associated with similar basal lamina changes and an expansion of the premigratory neural crest population. Cingulin overexpression causes aberrant ventrolateral neuroepithelial cell delamination, which is linked to laminin loss and a decrease in RhoA. Together, our results highlight a novel function for cingulin in the neural crest.
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Affiliation(s)
- Chyong-Yi Wu
- Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, USA
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5
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Malerød L, Pedersen NM, Sem Wegner CE, Lobert VH, Leithe E, Brech A, Rivedal E, Liestøl K, Stenmark H. Cargo-dependent degradation of ESCRT-I as a feedback mechanism to modulate endosomal sorting. Traffic 2011; 12:1211-26. [PMID: 21564451 DOI: 10.1111/j.1600-0854.2011.01220.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ligand-mediated lysosomal degradation of growth factor receptors, mediated by the endosomal sorting complex required for transport (ESCRT) machinery, is a mechanism that attenuates the cellular response to growth factors. In this article, we present a novel regulatory mechanism that involves ligand-mediated degradation of a key component of the sorting machinery itself. We have investigated the endosomal localization of subunits of the four ESCRTs-Hrs (ESCRT-0), Tsg101 (ESCRT-I), EAP30/Vps22 (ESCRT-II) and charged multivesicular body protein 3/Vps24 (ESCRT-III). All the components were detected on the limiting membrane of multivesicular endosomes (MVEs). Surprisingly, however, Tsg101 and other ESCRT-I subunits were also detected within intraluminal vesicles (ILVs) of MVEs. Tsg101 was sequestered along with cargo during endosomal sorting into ILVs and further degraded in lysosomes. Importantly, ESCRT-mediated downregulation of two distinct cargoes, epidermal growth factor receptor (EGFR) and connexin43, mutually made cells refractory to degradation of the other cargo. Our observations indicate that the degradation of a key ESCRT component along with cargo represents a novel feedback control of endosomal sorting by preventing collateral degradation of cell surface receptors following stimulation of one specific pathway.
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Affiliation(s)
- Lene Malerød
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway
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Berlin I, Schwartz H, Nash PD. Regulation of epidermal growth factor receptor ubiquitination and trafficking by the USP8·STAM complex. J Biol Chem 2010; 285:34909-21. [PMID: 20736164 PMCID: PMC2966105 DOI: 10.1074/jbc.m109.016287] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2009] [Revised: 08/02/2010] [Indexed: 11/06/2022] Open
Abstract
Reversible ubiquitination of activated receptor complexes signals their sorting between recycling and degradation and thereby dictates receptor fate. The deubiquitinating enzyme ubiquitin-specific protease 8 (USP8/UBPy) has been previously implicated in the regulation of the epidermal growth factor receptor (EGFR); however, the molecular mechanisms governing its recruitment and activity in this context remain unclear. Herein, we investigate the role of USP8 in countering ligand-induced ubiquitination and down-regulation of EGFR and characterize a subset of protein-protein interaction determinants critical for this function. USP8 depletion accelerates receptor turnover, whereas loss of hepatocyte growth factor-regulated substrate (Hrs) rescues this phenotype, indicating that USP8 protects EGFR from degradation via an Hrs-dependent pathway. Catalytic inactivation of USP8 incurs EGFR hyperubiquitination and promotes receptor localization to endosomes marked by high ubiquitin content. These phenotypes require the central region of USP8, containing three extended Arg-X-X-Lys (RXXK) motifs that specify direct low affinity interactions with the SH3 domain(s) of ESCRT-0 proteins, STAM1/2. The USP8·STAM complex critically impinges on receptor ubiquitination status and modulates ubiquitin dynamics on EGFR-positive endosomes. Consequently, USP8-mediated deubiquitination slows progression of EGFR past the early-to-recycling endosome circuit in a manner dependent upon the RXXK motifs. Collectively, these findings demonstrate a role for the USP8·STAM complex as a protective mechanism regulating early endosomal sorting of EGFR between pathways destined for lysosomal degradation and recycling.
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Affiliation(s)
- Ilana Berlin
- From the Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois 60637
| | - Heather Schwartz
- From the Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois 60637
| | - Piers D. Nash
- From the Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois 60637
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7
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Park B, Ying H, Shen X, Park JS, Qiu Y, Shyam R, Yue BYJT. Impairment of protein trafficking upon overexpression and mutation of optineurin. PLoS One 2010; 5:e11547. [PMID: 20634958 PMCID: PMC2902519 DOI: 10.1371/journal.pone.0011547] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Accepted: 06/17/2010] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Glaucoma is a major blinding disease characterized by progressive loss of retinal ganglion cells (RGCs) and axons. Optineurin is one of the candidate genes identified so far. A mutation of Glu(50) to Lys (E50K) has been reported to be associated with a more progressive and severe disease. Optineurin, known to interact with Rab8, myosin VI and transferrin receptor (TfR), was speculated to have a role in protein trafficking. Here we determined whether, and how optineurin overexpression and E50K mutation affect the internalization of transferrin (Tf), widely used as a marker for receptor-mediated endocytosis. METHODOLOGY/PRINCIPAL FINDINGS Human retinal pigment epithelial (RPE) and rat RGC5 cells transfected to overexpress wild type optineurin were incubated with Texas Red-Tf to evaluate Tf uptake. Granular structures or dots referred to as foci formed in perinuclear regions after transfection. An impairment of the Tf uptake was in addition observed in transfected cells. Compared to overexpression of the wild type, E50K mutation yielded an increased foci formation and a more pronounced defect in Tf uptake. Co-transfection with TfR, but not Rab8 or myosin VI, construct rescued the optineurin inhibitory effect, suggesting that TfR was the factor involved in the trafficking phenotype. Forced expression of both wild type and E50K optineurin rendered TfR to colocalize with the foci. Surface biotinylation experiments showed that the surface level of TfR was also reduced, leading presumably to an impeded Tf uptake. A non-consequential Leu(157) to Ala (L157A) mutation that displayed much reduced foci formation and TfR binding had normal TfR distribution, normal surface TfR level and normal Tf internalization. CONCLUSIONS/SIGNIFICANCE The present study demonstrates that overexpression of wild type optineurin results in impairment of the Tf uptake in RPE and RGC5 cells. The phenotype is related to the optineurin interaction with TfR. Our results further indicate that E50K induces more dramatic effects than the wild type optineurin, and is thus a gain-of-function mutation. The defective protein trafficking may be one of the underlying bases why glaucoma pathology develops in patients with E50K mutation.
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Affiliation(s)
- BumChan Park
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine, Chicago, Illinois, United States of America
| | - Hongyu Ying
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine, Chicago, Illinois, United States of America
| | - Xiang Shen
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine, Chicago, Illinois, United States of America
| | - Jeong-Seok Park
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine, Chicago, Illinois, United States of America
| | - Ye Qiu
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine, Chicago, Illinois, United States of America
| | - Rajalekshmy Shyam
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine, Chicago, Illinois, United States of America
| | - Beatrice Y. J. T. Yue
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine, Chicago, Illinois, United States of America
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8
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Duex JE, Mullins MR, Sorkin A. Recruitment of Uev1B to Hrs-containing endosomes and its effect on endosomal trafficking. Exp Cell Res 2010; 316:2136-51. [PMID: 20420830 DOI: 10.1016/j.yexcr.2010.04.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 04/09/2010] [Accepted: 04/19/2010] [Indexed: 11/28/2022]
Abstract
Endocytosis of signaling receptors, such as epidermal growth factor receptor (EGFR), tightly controls the signal transduction process triggered by ligand activation of these receptors. To identify new regulators of the endocytic trafficking of EGFR an RNA interference screen was performed for genes involved in ubiquitin conjugation and down-regulation of EGFR. The screen revealed that small interfering RNAs (siRNAs) that target the conserved ubiquitin-binding domain Uev1 increased down-regulation of EGFR. Since these siRNAs simultaneously targeted multiple genes containing a Uev1 domain, we analyzed the role of these gene products by overexpressing individual Uev1-related proteins. This analysis revealed that overexpression of Uev1A (UBE2V1) has no effect on the degradation of EGFR:EGF complexes. In contrast, overexpression of Uev1B (TMEM189-UBE2V1 isoform 2) slowed the degradation of EGF:receptor complexes. The Uev1B protein was found to strongly colocalize and associate with ubiquitin and Hrs in endosomes. Moreover, overexpression of Uev1B abrogated the ability of Hrs to colocalize with EGFR. The B-domain of Uev1B, and not the UEV-domain, was mainly responsible for the observed phenotypes suggesting the presence of a novel endosomal targeting sequence within the B-domain. Together, the data show that elevated levels of Uev1B protein in cells lead to decreased efficiency of endosomal sorting by associating with ubiquitinated proteins and Hrs.
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Affiliation(s)
- Jason E Duex
- Department of Pharmacology, University of Colorado Denver Medical School, Aurora, Colorado, USA
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9
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Jovic M, Sharma M, Rahajeng J, Caplan S. The early endosome: a busy sorting station for proteins at the crossroads. Histol Histopathol 2010; 25:99-112. [PMID: 19924646 DOI: 10.14670/hh-25.99] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Endocytosis marks the entry of internalized receptors into the complex network of endocytic trafficking pathways. Endocytic vesicles are rapidly targeted to a distinct membrane-bound endocytic organelle referred to as the early endosome. Despite the existence of numerous internalization routes, early endosomes (EE) serve as a focal point of the endocytic pathway. Sorting events initiated at this compartment determine the subsequent fate of internalized proteins and lipids, destining them either for recycling to the plasma membrane, degradation in lysosomes or delivery to the trans-Golgi network. Sorting of endocytic cargo to the latter compartments is accomplished through the formation of distinct microdomains within early endosomes, through the coordinate recruitment and assembly of the sorting machinery. An elaborate network of interactions between endocytic regulatory proteins ensures synchronized sorting of cargo to microdomains followed by morphological changes at the early endosomal membranes. Consequently, the cargo targeted either for recycling back to the plasma membrane, or for retrograde transport to the trans-Golgi network, localizes to newly-formed tubular membranes. With a high ratio of membrane surface to lumenal volume, these tubules effectively concentrate the recycling cargo, ensuring efficient transport out of the EE. Conversely, receptors sorted for degradation cluster at the flat clathrin lattices involved in invaginations of the limiting membrane, associating with newly formed intralumenal vesicles. In this review we will discuss the characteristics of early endosomes, their role in the regulation of endocytic transport, and their aberrant function in a variety of diseases.
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Affiliation(s)
- Marko Jovic
- Department of Biochemistry and Molecular Biology and Eppley Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198-5870, USA
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10
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Belleudi F, Leone L, Maggio M, Torrisi MR. Hrs regulates the endocytic sorting of the fibroblast growth factor receptor 2b. Exp Cell Res 2009; 315:2181-91. [DOI: 10.1016/j.yexcr.2009.03.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Revised: 03/27/2009] [Accepted: 03/29/2009] [Indexed: 11/28/2022]
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11
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12
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Huang SH, Zhao L, Sun ZP, Li XZ, Geng Z, Zhang KD, Chao MV, Chen ZY. Essential role of Hrs in endocytic recycling of full-length TrkB receptor but not its isoform TrkB.T1. J Biol Chem 2009; 284:15126-36. [PMID: 19351881 DOI: 10.1074/jbc.m809763200] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Brain-derived neurotrophic factor (BDNF) signaling through its receptor, TrkB, modulates survival, differentiation, and synaptic activity of neurons. Both full-length TrkB (TrkB-FL) and its isoform T1 (TrkB.T1) receptors are expressed in neurons; however, whether they follow the same endocytic pathway after BDNF treatment is not known. In this study we report that TrkB-FL and TrkB.T1 receptors traverse divergent endocytic pathways after binding to BDNF. We provide evidence that in neurons TrkB.T1 receptors predominantly recycle back to the cell surface by a "default" mechanism. However, endocytosed TrkB-FL receptors recycle to a lesser extent in a hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs)-dependent manner which relies on its tyrosine kinase activity. The distinct role of Hrs in promoting recycling of internalized TrkB-FL receptors is independent of its ubiquitin-interacting motif. Moreover, Hrs-sensitive TrkB-FL recycling plays a role in BDNF-induced prolonged mitogen-activated protein kinase (MAPK) activation. These observations provide evidence for differential postendocytic sorting of TrkB-FL and TrkB.T1 receptors to alternate intracellular pathways.
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Affiliation(s)
- Shu-Hong Huang
- Department of Neurobiology, Key Laboratory of Medical Neurobiology, School of Medicine, Jinan, Shandong 250012, China
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13
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Pridgeon JW, Webber EA, Sha D, Li L, Chin LS. Proteomic analysis reveals Hrs ubiquitin-interacting motif-mediated ubiquitin signaling in multiple cellular processes. FEBS J 2009; 276:118-31. [PMID: 19019082 DOI: 10.1111/j.1742-4658.2008.06760.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Despite the critical importance of protein ubiquitination in the regulation of diverse cellular processes, the molecular mechanisms by which cells recognize and transmit ubiquitin signals remain poorly understood. The endosomal sorting machinery component hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) contains a ubiquitin-interacting motif (UIM), which is believed to bind ubiquitinated membrane cargo proteins and mediate their sorting to the lysosomal degradation pathway. To gain insight into the role of Hrs UIM-mediated ubiquitin signaling in cells, we performed a proteomic screen for Hrs UIM-interacting ubiquitinated proteins in human brain by using an in vitro expression cloning screening approach. We have identified 48 ubiquitinated proteins that are specifically recognized by the UIM domain of Hrs. Among them, 12 are membrane proteins that are likely to be Hrs cargo proteins, and four are membrane protein-associated adaptor proteins whose ubiquitination may act as a signal to target their associated membrane cargo for Hrs-mediated endosomal sorting. Other classes of the identified proteins include components of the vesicular trafficking machinery, cell signaling molecules, proteins associated with the cytoskeleton and cytoskeleton-dependent transport, and enzymes involved in ubiquitination and metabolism, suggesting the involvement of Hrs UIM-mediated ubiquitin signaling in the regulation of multiple cellular processes. We have characterized the ubiquitination of two identified proteins, Munc18-1 and Hsc70, and their interaction with Hrs UIM, and provided functional evidence supporting a role for Hsc70 in the regulation of Hrs-mediated endosome-to-lysosome trafficking.
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Affiliation(s)
- Julia W Pridgeon
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
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14
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Webber E, Li L, Chin LS. Hypertonia-associated protein Trak1 is a novel regulator of endosome-to-lysosome trafficking. J Mol Biol 2008; 382:638-51. [PMID: 18675823 DOI: 10.1016/j.jmb.2008.07.045] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Revised: 07/16/2008] [Accepted: 07/17/2008] [Indexed: 12/11/2022]
Abstract
Hypertonia, which is characterized by stiff gait, abnormal posture, jerky movements, and tremor, is associated with a number of neurological disorders, including cerebral palsy, dystonia, Parkinson's disease, stroke, and spinal cord injury. Recently, a spontaneous mutation in the gene encoding trafficking protein, kinesin-binding 1 (Trak1), was identified as the genetic defect that causes hypertonia in mice. The subcellular localization and biological function of Trak1 remain unclear. Here we report that Trak1 interacts with hepatocyte-growth-factor-regulated tyrosine kinase substrate (Hrs), an essential component of the endosomal sorting and trafficking machinery. Double-label immunofluorescence confocal studies show that the endogenous Trak1 protein partially colocalizes with Hrs on early endosomes. Like Hrs, both overexpression and small-interfering-RNA-mediated knockdown of Trak1 inhibit degradation of internalized epidermal growth factor receptors through a block in endosome-to-lysosome trafficking. Our findings support a role for Trak1 in the regulation of Hrs-mediated endosomal sorting and have important implications for understanding hypertonia associated with neurological disorders.
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Affiliation(s)
- Elizabeth Webber
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322-4218, USA
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15
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Hanyaloglu AC, von Zastrow M. Regulation of GPCRs by endocytic membrane trafficking and its potential implications. Annu Rev Pharmacol Toxicol 2008; 48:537-68. [PMID: 18184106 DOI: 10.1146/annurev.pharmtox.48.113006.094830] [Citation(s) in RCA: 447] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The endocytic pathway tightly controls the activity of G protein-coupled receptors (GPCRs). Ligand-induced endocytosis can drive receptors into divergent lysosomal and recycling pathways, producing essentially opposite effects on the strength and duration of cellular signaling via heterotrimeric G proteins, and may also promote distinct signaling events from intracellular membranes. This chapter reviews recent developments toward understanding the molecular machinery and functional implications of GPCR sorting in the endocytic pathway, focusing on mammalian GPCRs whose ligand-induced endocytosis is mediated primarily by clathrin-coated pits. Lysosomal sorting of a number of GPCRs occurs via a highly conserved mechanism requiring covalent tagging of receptors with ubiquitin. There is increasing evidence that additional, noncovalent mechanisms control the sorting of endocytosed GPCRs to lysosomes in mammalian cells. Recycling of several GPCRs to the plasma membrane is also specifically sorted, via a mechanism requiring both receptor-specific and shared sorting proteins. The current data reveal an unprecedented degree of specificity and plasticity in the cellular regulation of mammalian GPCRs by endocytic membrane trafficking. These developments have fundamental implications for GPCR pharmacology, and suggest new mechanisms that could be exploited in GPCR-directed pharmacotherapy.
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Affiliation(s)
- Aylin C Hanyaloglu
- Institute of Reproductive Biology and Development, Imperial College London, Hammersmith Campus, London, United Kingdom
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16
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Raiborg C, Malerød L, Pedersen NM, Stenmark H. Differential functions of Hrs and ESCRT proteins in endocytic membrane trafficking. Exp Cell Res 2007; 314:801-13. [PMID: 18031739 DOI: 10.1016/j.yexcr.2007.10.014] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Revised: 10/17/2007] [Accepted: 10/17/2007] [Indexed: 10/22/2022]
Abstract
A ubiquitin-binding endosomal protein machinery is responsible for sorting endocytosed membrane proteins into intraluminal vesicles of multivesicular endosomes (MVEs) for subsequent degradation in lysosomes. The Hrs-STAM complex and endosomal sorting complex required for transport (ESCRT)-I, -II and -III are central components of this machinery. Here, we have performed a systematic analysis of their importance in four trafficking pathways through endosomes. Neither Hrs, Tsg101 (ESCRT-I), Vps22/EAP30 (ESCRT-II), nor Vps24/CHMP3 (ESCRT-III) was required for ligand-mediated internalization of epidermal growth factor (EGF) receptors (EGFRs) or for recycling of cation-independent mannose 6-phosphate receptors (CI-M6PRs) from endosomes to the trans-Golgi network (TGN). In contrast, both Hrs and ESCRT subunits were equally required for degradation of both endocytosed EGF and EGFR. Whereas depletion of Hrs or Tsg101 caused enhanced recycling of endocytosed EGFRs, this was not the case with depletion of Vps22 or Vps24. Depletion of Vps24 instead caused a strong increase in the levels of CI-M6PRs and a dramatic redistribution of the Golgi and the TGN. These results indicate that, although Hrs-STAM and ESCRT-I, -II and -III have a common function in degradative protein sorting, they play differential roles in other trafficking pathways, probably reflecting their functions at distinct stages of the endocytic pathway.
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Affiliation(s)
- Camilla Raiborg
- Centre for Cancer Biomedicine, University of Oslo, and Department of Biochemistry, the Norwegian Radium Hospital, Rikshospitalet, Norway
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17
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Malerød L, Stuffers S, Brech A, Stenmark H. Vps22/EAP30 in ESCRT-II mediates endosomal sorting of growth factor and chemokine receptors destined for lysosomal degradation. Traffic 2007; 8:1617-29. [PMID: 17714434 DOI: 10.1111/j.1600-0854.2007.00630.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ubiquitin-binding protein Hrs and endosomal sorting complex required for transport (ESCRT)-I and ESCRT-III are involved in sorting endocytosed and ubiquitinated receptors to lysosomes for degradation and efficient termination of signaling. In this study, we have investigated the role of the ESCRT-II subunit Vps22/EAP30 in degradative protein sorting of ubiquitinated receptors. Vps22 transiently expressed in HeLa cells was detected in endosomes containing endocytosed epidermal growth factor receptors (EGFRs) as well as Hrs and ESCRT-I and ESCRT-III. Depletion of Vps22 by small interfering RNA, which was accompanied by decreased levels of other ESCRT-II subunits, greatly reduced degradation of EGFR and its ligand EGF as well as the chemokine receptor CXCR4. EGFR accumulated on the limiting membranes of early endosomes and aberrantly small multivesicular bodies in Vps22-depleted cells. Phosphorylation and nuclear translocation of extracellular-signal-regulated kinase1/2 downstream of the EGF-activated receptor were sustained by depletion of Hrs or the ESCRT-I subunit Tsg101. In contrast, this was not the case when Vps22 was depleted. These results indicate an important role for Vps22 in ligand-induced EGFR and CXCR4 turnover and suggest that termination of EGF signaling occurs prior to ESCRT-II engagement.
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Affiliation(s)
- Lene Malerød
- Centre for Cancer Biomedicine, University of Oslo, Montebello, N-0310 Oslo, Norway
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18
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Hasdemir B, Bunnett NW, Cottrell GS. Hepatocyte growth factor-regulated tyrosine kinase substrate (HRS) mediates post-endocytic trafficking of protease-activated receptor 2 and calcitonin receptor-like receptor. J Biol Chem 2007; 282:29646-57. [PMID: 17675298 DOI: 10.1074/jbc.m702974200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The E3 ligase c-Cbl ubiquitinates protease-activated receptor 2 (PAR(2)), which is required for post-endocytic sorting of PAR(2) to lysosomes, where degradation arrests signaling. The mechanisms of post-endocytic sorting of ubiquitinated receptors are incompletely understood. Here, we investigated the role of hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), in post-endocytic sorting and signaling of PAR(2). In HEK-PAR(2) cells, PAR(2) activating peptide (PAR(2)-AP) induced PAR(2) trafficking from the cell surface to early endosomes containing endogenous HRS, and then to lysosomes. HRS overexpression or knockdown with small interfering RNA caused formation of enlarged HRS-positive endosomes, where activated PAR(2) and c-Cbl accumulated, and PAR(2) failed to traffic to lysosomes. Overexpression of HRS prevented PAR(2)-AP-induced degradation of PAR(2), as determined by Western blotting. Overexpression of HRS mutant lacking an ubiquitin-binding motif similarly caused retention of PAR(2) in enlarged endosomes. Moreover, HRS overexpression or knockdown caused retention of ubiquitin-resistant PAR(2)Delta14K/R in enlarged HRS-containing endosomes, preventing recycling and resensitization of PAR(2)Delta14K/R. HRS overexpression or knockdown similarly prevented lysosomal trafficking and recycling of calcitonin receptor-like receptor, a non-ubiquitinated receptor that traffics to lysosomes after sustained activation and recycles after transient activation. Thus, HRS plays a critically important role in the post-endocytic sorting of single receptors, PAR(2) and CLR, to both degradative and recycling pathways. This sorting role for HRS is independent of its ubiquitin-interacting motif, and it can regulate trafficking of both ubiquitinated and non-ubiquitinated PAR(2) and non-ubiquitinated CLR. The ultimate sorting decision to degradative or recycling pathways appears to occur downstream from HRS.
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Affiliation(s)
- Burcu Hasdemir
- Department of Surgery, University of California, San Francisco, California 94143-0660, USA
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19
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Mizuno E, Kitamura N, Komada M. 14-3-3-dependent inhibition of the deubiquitinating activity of UBPY and its cancellation in the M phase. Exp Cell Res 2007; 313:3624-34. [PMID: 17720156 DOI: 10.1016/j.yexcr.2007.07.028] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2007] [Revised: 07/26/2007] [Accepted: 07/27/2007] [Indexed: 10/23/2022]
Abstract
The deubiquitinating enzyme UBPY, also known as USP8, regulates cargo sorting and membrane traffic at early endosomes. Here we demonstrate the regulatory mechanism of the UBPY catalytic activity. We identified 14-3-3 epsilon, gamma, and zeta as UBPY-binding proteins using co-immunoprecipitation followed by mass spectrometric analysis. The 14-3-3 binding of UBPY was inhibited by mutating the consensus 14-3-3-binding motif RSYS(680)SP, by phosphatase treatment, and by competition with the Ser(680)-phosphorylated RSYS(680)SP peptide. Metabolic labeling with [(32)P]orthophosphate and immunoblotting using antibody against the phosphorylated 14-3-3-binding motif showed that Ser(680) is a major phosphorylation site in UBPY. These results indicated that 14-3-3s bind to the region surrounding Ser(680) in a phosphorylation-dependent manner. The mutation at Ser(680) led to enhanced ubiquitin isopeptidase activity of UBPY toward poly-ubiquitin chains and a cellular substrate, epidermal growth factor receptor, in vitro and in vivo. Moreover, addition of 14-3-3epsilon inhibited the UBPY activity in vitro. Finally, UBPY was dephosphorylated at Ser(680) and dissociated from 14-3-3s in the M phase, resulting in enhanced activity of UBPY during cell division. We conclude that UBPY is catalytically inhibited in a phosphorylation-dependent manner by 14-3-3s during the interphase, and this regulation is cancelled in the M phase.
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Affiliation(s)
- Emi Mizuno
- Department of Biological Sciences, Tokyo Institute of Technology, 4259-B-16 Nagatsuta, Yokohama, Japan
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20
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Kutateladze TG. Mechanistic similarities in docking of the FYVE and PX domains to phosphatidylinositol 3-phosphate containing membranes. Prog Lipid Res 2007; 46:315-27. [PMID: 17707914 PMCID: PMC2211451 DOI: 10.1016/j.plipres.2007.06.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Phosphatidylinositol 3-phosphate [PtdIns(3)P], a phospholipid produced by PI 3-kinases in early endosomes and multivesicular bodies, often serves as a marker of endosomal membranes. PtdIns(3)P recruits and activates effector proteins containing the FYVE or PX domain and therefore regulates a variety of biological processes including endo- and exocytosis, membrane trafficking, protein sorting, signal transduction and cytoskeletal rearrangement. Structures and PtdIns(3)P binding modes of several FYVE and PX domains have recently been characterized, unveiling the molecular basis underlying multiple cellular functions of these proteins. Here, structural and functional aspects and current mechanisms of the multivalent membrane anchoring by the FYVE and PX domains are reviewed and compared.
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Affiliation(s)
- Tatiana G Kutateladze
- Department of Pharmacology, University of Colorado Health Sciences Center, Aurora, CO 80045, USA.
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21
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Hasseine LK, Murdaca J, Suavet F, Longnus S, Giorgetti-Peraldi S, Van Obberghen E. Hrs is a positive regulator of VEGF and insulin signaling. Exp Cell Res 2007; 313:1927-42. [PMID: 17445799 DOI: 10.1016/j.yexcr.2007.02.034] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2006] [Revised: 02/20/2007] [Accepted: 02/22/2007] [Indexed: 12/25/2022]
Abstract
Both VEGF and insulin are implicated in the pathogenesis of diabetic retinopathy. While it has been established for many years that the number of cell surface receptors impacts upon VEGF and insulin action, little is known about the precise machinery and proteins driving VEGF-R2 and IR degradation. Here, we investigate the role of Hepatocyte growth factor-Regulated tyrosine kinase Substrate (Hrs), a regulator of RTK trafficking, in VEGF and insulin signaling. We report that ectopic expression of Hrs increases VEGF-R2 and IR number and tyrosine phosphorylation, leading to amplification of their downstream signaling. The UIM (Ubiquitin Interacting Motif) domain of Hrs is required for Hrs-induced increases in VEGF-R2, but not in IR. Furthermore, Hrs is tyrosine-phosphorylated in response to VEGF and insulin. We show that the UIM domain is required for Hrs phosphorylation in response to VEGF, but not to insulin. Importantly, Hrs co-localizes with both VEGF-R2 and IR and co-immunoprecipitates with both in a manner independent of the Hrs-UIM domain. Finally, we demonstrate that Hrs inhibits Nedd4-mediated VEGF-R2 degradation and acts additively with Grb10. We conclude that Hrs is a positive regulator of VEGF-R2 and IR signaling and that ectopic expression of Hrs protects both VEGF-R2 and IR from degradation.
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22
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Bakowska JC, Jupille H, Fatheddin P, Puertollano R, Blackstone C. Troyer syndrome protein spartin is mono-ubiquitinated and functions in EGF receptor trafficking. Mol Biol Cell 2007; 18:1683-92. [PMID: 17332501 PMCID: PMC1855030 DOI: 10.1091/mbc.e06-09-0833] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Troyer syndrome is an autosomal recessive hereditary spastic paraplegia caused by mutation in the spartin (SPG20) gene, which encodes a widely expressed protein of unknown function. This mutation results in premature protein truncation and thus might signify a loss-of-function disease mechanism. In this study, we have found that spartin is mono-ubiquitinated and functions in degradation of the epidermal growth factor receptor (EGFR). Upon EGF stimulation, spartin translocates from the cytoplasm to the plasma membrane and colocalizes with internalized EGF-Alexa. Knockdown of spartin by small interfering RNA decreases the rate of EGFR degradation and also affects EGFR internalization, recycling, or both. Furthermore, overexpression of spartin results in a prominent decrease in EGFR degradation. Taken together, our data suggest that spartin is involved in the intracellular trafficking of EGFR and that impaired endocytosis may underlie the pathogenesis of Troyer syndrome.
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Affiliation(s)
- Joanna C. Bakowska
- *Cellular Neurology Unit, National Institute of Neurological Disorders and Stroke, and
| | - Henri Jupille
- *Cellular Neurology Unit, National Institute of Neurological Disorders and Stroke, and
| | - Parvin Fatheddin
- *Cellular Neurology Unit, National Institute of Neurological Disorders and Stroke, and
| | - Rosa Puertollano
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Craig Blackstone
- *Cellular Neurology Unit, National Institute of Neurological Disorders and Stroke, and
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23
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Kirk E, Chin LS, Li L. GRIF1 binds Hrs and is a new regulator of endosomal trafficking. J Cell Sci 2006; 119:4689-701. [PMID: 17062640 DOI: 10.1242/jcs.03249] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Endosomal sorting of internalized cell surface receptors to the lysosomal pathway plays a crucial role in the control of cell signaling and function. Here we report the identification of GABA(A) receptor interacting factor-1 (GRIF1), a recently discovered protein of unknown function, as a new regulator of endosome-to-lysosome trafficking. Yeast two-hybrid screen and co-immunoprecipitation analysis reveal that GRIF1 interacts with hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs), an essential component of the endosomal sorting machinery. We have mapped the binding domains of GRIF1 and Hrs that mediate their association and shown the colocalization of GRIF1 with Hrs on early endosomes. Like Hrs, both overexpression and siRNA-mediated depletion of GRIF1 inhibit the degradation of internalized epidermal growth factor receptors and block the trafficking of the receptors from early endosomes to the lysosomal pathway. Our results indicate, for the first time, a functional role for GRIF1 in the regulation of endosomal trafficking. Interestingly, overexpression of full-length GRIF1, but not the Hrs- or kinesin-interacting GRIF1 deletion mutants, causes a perinuclear clustering of early endosomes. Our findings suggest that GRIF1 may also participate in microtubule-based transport of early endosomes by acting as an adaptor linking Hrs-containing endosomes to kinesin.
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Affiliation(s)
- Elizabeth Kirk
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
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24
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Welsch S, Habermann A, Jäger S, Müller B, Krijnse-Locker J, Kräusslich HG. Ultrastructural analysis of ESCRT proteins suggests a role for endosome-associated tubular-vesicular membranes in ESCRT function. Traffic 2006; 7:1551-66. [PMID: 17014699 DOI: 10.1111/j.1600-0854.2006.00489.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The endosomal sorting complex required for transport (ESCRT) is thought to support the formation of intralumenal vesicles of multivesicular bodies (MVBs). The ESCRT is also required for the budding of HIV and has been proposed to be recruited to the HIV-budding site, the plasma membrane of T cells and MVBs in macrophages. Despite increasing data on the function of ESCRT, the ultrastructural localization of its components has not been determined. We therefore localized four proteins of the ESCRT machinery in human T cells and macrophages by quantitative electron microscopy. All the proteins were found throughout the endocytic pathway, including the plasma membrane, with only around 10 and 3% of the total labeling in the cytoplasm and on the MVBs, respectively. The majority of the labeling (45%) was unexpectedly found on tubular-vesicular endosomal membranes rather than on endosomes themselves. The ESCRT labeling was twice as concentrated on early and late endosomes/lysosomes in macrophages compared with that in T cells, where it was twice more abundant at the plasma membrane. The ESCRT proteins were not redistributed on HIV infection, suggesting that the amount of ESCRT proteins located at the budding site suffices for HIV release. These results represent the first systematic ultrastructural localization of ESCRT and provide insights into its role in uninfected and HIV-infected cells.
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Affiliation(s)
- Sonja Welsch
- Department of Virology, Heidelberg University, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
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25
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Mizuno E, Kobayashi K, Yamamoto A, Kitamura N, Komada M. A deubiquitinating enzyme UBPY regulates the level of protein ubiquitination on endosomes. Traffic 2006; 7:1017-31. [PMID: 16771824 DOI: 10.1111/j.1600-0854.2006.00452.x] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Monoubiquitination of endocytosed cell surface receptors serves as a sorting signal for their trafficking from endosomes to lysosomes. The sorting of ubiquitinated proteins is executed by concerted actions of class E vacuolar protein sorting (Vps) proteins. Some proteins in the sorting machinery undergo monoubiquitination, suggesting that their functions are also regulated by ubiquitination. The Hrs-STAM complex, a class E Vps protein complex essential for the initial step of the sorting pathway, binds two deubiquitinating enzymes, UBPY and AMSH. Here we examined the effects of inactivating UBPY on protein ubiquitination at endosomes. Overexpression of a catalytically inactive UBPY mutant or depletion of UBPY by RNA interference resulted in the accumulation of ubiquitinated proteins on morphologically aberrant endosomes. Electron microscopy showed that they are aggregates of multivesicular endosomes. Among the sorting machinery proteins that undergo ubiquitination, Eps15 was monoubiquitinated at an elevated level in UBPY-inactivated cells. UBPY also deubiquitinated Eps15 in vitro, suggesting that Eps15 is a cellular substrate for UBPY. Furthermore, inactivation of UBPY caused the accumulation of Eps15 on the endosomal aggregates. These results suggest that UBPY regulates the level of protein ubiquitination on endosomes, which is required for maintaining the morphology of the organelle.
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Affiliation(s)
- Emi Mizuno
- Department of Biological Sciences, Tokyo Institute of Technology, Yokohama 226-8501, Japan
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26
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Neil SJD, Eastman SW, Jouvenet N, Bieniasz PD. HIV-1 Vpu promotes release and prevents endocytosis of nascent retrovirus particles from the plasma membrane. PLoS Pathog 2006; 2:e39. [PMID: 16699598 PMCID: PMC1458960 DOI: 10.1371/journal.ppat.0020039] [Citation(s) in RCA: 218] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Accepted: 03/30/2006] [Indexed: 12/31/2022] Open
Abstract
The human immunodeficiency virus (HIV) type-1 viral protein U (Vpu) protein enhances the release of diverse retroviruses from human, but not monkey, cells and is thought to do so by ablating a dominant restriction to particle release. Here, we determined how Vpu expression affects the subcellular distribution of HIV-1 and murine leukemia virus (MLV) Gag proteins in human cells where Vpu is, or is not, required for efficient particle release. In HeLa cells, where Vpu enhances HIV-1 and MLV release approximately 10-fold, concentrations of HIV-1 Gag and MLV Gag fused to cyan fluorescent protein (CFP) were initially detected at the plasma membrane, but then accumulated over time in early and late endosomes. Endosomal accumulation of Gag-CFP was prevented by Vpu expression and, importantly, inhibition of plasma membrane to early endosome transport by dominant negative mutants of Rab5a, dynamin, and EPS-15. Additionally, accumulation of both HIV and MLV Gag in endosomes required a functional late-budding domain. In human HOS cells, where HIV-1 and MLV release was efficient even in the absence of Vpu, Gag proteins were localized predominantly at the plasma membrane, irrespective of Vpu expression or manipulation of endocytic transport. While these data indicated that Vpu inhibits nascent virion endocytosis, Vpu did not affect transferrin endocytosis. Moreover, inhibition of endocytosis did not restore Vpu-defective HIV-1 release in HeLa cells, but instead resulted in accumulation of mature virions that could be released from the cell surface by protease treatment. Thus, these findings suggest that a specific activity that is present in HeLa cells, but not in HOS cells, and is counteracted by Vpu, traps assembled retrovirus particles at the cell surface. This entrapment leads to subsequent endocytosis by a Rab5a- and clathrin-dependent mechanism and intracellular sequestration of virions in endosomes.
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Affiliation(s)
- Stuart J D Neil
- Aaron Diamond AIDS Research Center, Laboratory of Retrovirology, Rockefeller University, New York, New York, USA
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27
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Kutateladze TG. Phosphatidylinositol 3-phosphate recognition and membrane docking by the FYVE domain. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:868-77. [PMID: 16644267 PMCID: PMC2740714 DOI: 10.1016/j.bbalip.2006.03.011] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2006] [Revised: 03/07/2006] [Accepted: 03/09/2006] [Indexed: 12/17/2022]
Abstract
The FYVE domain is a small zinc binding module that recognizes phosphatidylinositol 3-phosphate [PtdIns(3)P], a phospholipid enriched in membranes of early endosomes and other endocytic vesicles. It is usually present as a single module or rarely as a tandem repeat in eukaryotic proteins involved in a variety of biological processes including endo- and exocytosis, membrane trafficking and phosphoinositide metabolism. A number of FYVE domain-containing proteins are recruited to endocytic membranes through the specific interaction of their FYVE domains with PtdIns(3)P. Structures and PtdIns(3)P binding modes of several FYVE domains have recently been characterized, shedding light on the molecular basis underlying multiple cellular functions of these proteins. Here, structural and functional aspects and the current mechanism of the multivalent membrane anchoring by monomeric or dimeric FYVE domain are reviewed. This mechanism involves stereospecific recognition of PtdIns(3)P that is facilitated by non-specific electrostatic contacts and modulated by the histidine switch, and is accompanied by hydrophobic insertion. Contributions of each component to the FYVE domain specificity and affinity for PtdIns(3)P-containing membranes are discussed.
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Affiliation(s)
- Tatiana G Kutateladze
- Department of Pharmacology, University of Colorado Health Sciences Center, 12801 East 17th Avenue, Aurora, CO 80045, USA.
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28
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da Rocha AA, Giorgi RR, de Sa SV, Correa-Giannella ML, Fortes MA, Cavaleiro AM, Machado MC, Cescato VA, Bronstein MD, Giannella-Neto D. Hepatocyte growth factor-regulated tyrosine kinase substrate (HGS) and guanylate kinase 1 (GUK1) are differentially expressed in GH-secreting adenomas. Pituitary 2006; 9:83-92. [PMID: 16832584 DOI: 10.1007/s11102-006-9277-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Pituitary tumors, adenomas in their vast majority, represent around 10-15% of the intracranial neoplasms. Pituitary carcinomas are exceedingly rare. Clinically, these neoplasms cause hormonal dysfunctions, and mass effect symptoms as headache and visual disorders in the case of macroadenomas. Pituitary tumorigenesis is still poorly understood. In order to investigate the expression of cancer-related genes in pituitary tumors, we employed a human cancer cDNA macroarray membrane with 1176 well-characterized human genes related to cancer and tumor biology. We were able to identify several differentially expressed genes, among them hepatocyte growth factor-regulated tyrosine kinase substrate (HGS) and guanylate kinase 1 (GUK1) which were over expressed in a pool of clinically nonfunctioning pituitary adenomas, compared with a spinal cord metastasis of a nonfunctioning pituitary carcinoma. HGS and GUK1 mRNA expression were chosen to be validated by quantitative RT-qPCR, however, only GUK1 had the differential expression confirmed between the adenomas and the metastasis of a pituitary carcinoma. We have also investigated HGS and GUK1 mRNA expressions in a series of 46 pituitary adenomas (18 nonfunctioning, 12 GH-secreting, nine PRL-secreting, and seven ACTH-secreting adenomas). HGS and GUK1 were significantly over expressed in GH-secreting adenomas, compared with ACTH-secreting adenomas and nonfunctioning tumors, and with PRL-secreting adenomas, respectively. We have shown that these genes, involved in tumorigenesis in other tissues, are as well over expressed in the pituitary tumors, however, their role in the oncogenesis of these tumors need to be further investigated.
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Affiliation(s)
- Anderson Alves da Rocha
- Laboratory for Cellular and Molecular Endocrinology-LIM/25, University of Sao Paulo Medical School, Sao Paulo-SP, Brazil
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29
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Rayala SK, Hollander PD, Balasenthil S, Molli PR, Bean AJ, Vadlamudi RK, Wang RA, Kumar R. Hepatocyte growth factor-regulated tyrosine kinase substrate (HRS) interacts with PELP1 and activates MAPK. J Biol Chem 2005; 281:4395-403. [PMID: 16352611 DOI: 10.1074/jbc.m510368200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PELP1 (proline-, glutamic acid-, and leucine-rich protein-1) (also known as the modulator of nongenomic activity of estrogen receptor) plays a role in genomic functions of the estrogen receptor via histone interactions and in nongenomic functions via its influence on the MAPK-Src pathway. However, recent studies have shown that differential compartmentalization of PELP1 could play a crucial role in modulating the status of nongenomic signaling by using molecular mechanisms that remain poorly understood. Hepatocyte growth factor-regulated tyrosine kinase substrate (HRS) is an early endosomal protein that plays a role in regulating the trafficking of growth factor-receptor complexes through early endosomes. By using a yeast two-hybrid screen, we identified HRS as a novel PELP1-binding protein providing evidence of a physiologic interaction between HRS and PELP1. The noted HRS-PELP1 interaction was accompanied by inhibition of the basal coactivator function of PELP1 upon estrogen receptor transactivation. HRS was found to sequester PELP1 in the cytoplasm, leading to the activation of MAPK in a manner that is dependent on the epidermal growth factor receptor but independent of the estrogen receptor, Shc, and Src. In addition, stimulation of MAPK and the subsequent activation of its downstream effector pathway, Elk-1, by HRS or PELP1 were found to depend on the presence of endogenous PELP1 or HRS. Furthermore, HRS was overexpressed and correlated well with the cytoplasmic PELP1, increased MAPK, and EGFR status in breast tumors. These findings highlight a novel role of HRS in up-regulating MAPK, presumably involving interaction with PELP1.
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Affiliation(s)
- Suresh K Rayala
- Department of Molecular and Cellular Oncology, the University of Texas MD Anderson Cancer Center, Houston, 77030, USA
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30
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Scoles DR, Qin Y, Nguyen V, Gutmann DH, Pulst SM. HRS inhibits EGF receptor signaling in the RT4 rat schwannoma cell line. Biochem Biophys Res Commun 2005; 335:385-92. [PMID: 16083858 DOI: 10.1016/j.bbrc.2005.07.083] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2005] [Accepted: 07/16/2005] [Indexed: 10/25/2022]
Abstract
Hepatocyte growth factor-regulated tyrosine kinase substrate (HRS) is required for trafficking of cell surface receptors to the lysosome. Previously, we identified HRS as a protein that interacts with the neurofibromatosis 2 tumor suppressor schwannomin. In the present study, we established modified RT4 schwannoma cell lines that inducibly express HRS and constitutively express epidermal growth factor receptor (EGFR) fused to the green fluorescent protein. We demonstrated that HRS expression reduced EGFR abundance and EGF-mediated Stat3 activation. HRS expression also targeted EGFR to late endosomes. Schwannomin inhibited EGF-mediated Stat3 activation, consistent with HRS and schwannomin interacting in the same signaling pathway. Paradoxically, past studies have shown that HRS overexpression blocked EGFR trafficking to the late endosome and EGFR downregulation contrary to predictions of HRS function in HRS knockout studies. This study is the first to show that HRS can reduce the abundance of total and active EGFR and may reflect cell type-specific HRS function.
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Affiliation(s)
- Daniel R Scoles
- Rose Moss Neurogenetics Laboratory and Division of Neurology, Burns and Allen Research Institute, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, CA 90048, USA.
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Strick DJ, Elferink LA. Rab15 effector protein: a novel protein for receptor recycling from the endocytic recycling compartment. Mol Biol Cell 2005; 16:5699-709. [PMID: 16195351 PMCID: PMC1289414 DOI: 10.1091/mbc.e05-03-0204] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Sorting endosomes and the endocytic recycling compartment are critical intracellular stores for the rapid recycling of internalized membrane receptors to the cell surface in multiple cell types. However, the molecular mechanisms distinguishing fast receptor recycling from sorting endosomes and slow receptor recycling from the endocytic recycling compartment remain poorly understood. We previously reported that Rab15 differentially regulates transferrin receptor trafficking through sorting endosomes and the endocytic recycling compartment, suggesting a role for distinct Rab15-effector interactions at these endocytic compartments. In this study, we identified the novel protein Rab15 effector protein (REP15) as a binding partner for Rab15-GTP. REP15 is compartment specific, colocalizing with Rab15 and Rab11 on the endocytic recycling compartment but not with Rab15, Rab4, or early endosome antigen 1 on sorting endosomes. REP15 interacts directly with Rab15-GTP but not with Rab5 or Rab11. Consistent with its localization, REP15 overexpression and small interfering RNA-mediated depletion inhibited transferrin receptor recycling from the endocytic recycling compartment, without affecting receptor entry into or recycling from sorting endosomes. Our data identify REP15 as a compartment-specific protein for receptor recycling from the endocytic recycling compartment, highlighting that the rapid and slow modes of transferrin receptor recycling are mechanistically distinct pathways.
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Affiliation(s)
- David J Strick
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555-1043, USA
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Mizuno E, Iura T, Mukai A, Yoshimori T, Kitamura N, Komada M. Regulation of epidermal growth factor receptor down-regulation by UBPY-mediated deubiquitination at endosomes. Mol Biol Cell 2005; 16:5163-74. [PMID: 16120644 PMCID: PMC1266416 DOI: 10.1091/mbc.e05-06-0560] [Citation(s) in RCA: 215] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Ligand-activated receptor tyrosine kinases undergo endocytosis and are transported via endosomes to lysosomes for degradation. This "receptor down-regulation" process is crucial to terminate the cell proliferation signals produced by activated receptors. During the process, ubiquitination of the receptors serves as a sorting signal for their trafficking from endosomes to lysosomes. Here, we describe the role of a deubiquitinating enzyme UBPY/USP8 in the down-regulation of epidermal growth factor (EGF) receptor (EGFR). Overexpression of UBPY reduced the ubiquitination level of EGFR and delayed its degradation in EGF-stimulated cells. Immunopurified UBPY deubiquitinated EGFR in vitro. In EGF-stimulated cells, UBPY underwent ubiquitination and bound to EGFR. Overexpression of Hrs or a dominant-negative mutant of SKD1, proteins that play roles in the endosomal sorting of ubiquitinated receptors, caused the accumulation of endogenous UBPY on exaggerated endosomes. A catalytically inactive UBPY mutant clearly localized on endosomes, where it overlapped with EGFR when cells were stimulated with EGF. Finally, depletion of endogenous UBPY by RNA interference resulted in elevated ubiquitination and accelerated degradation of EGF-activated EGFR. We conclude that UBPY negatively regulates the rate of EGFR down-regulation by deubiquitinating EGFR on endosomes.
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Affiliation(s)
- Emi Mizuno
- Department of Biological Sciences, Tokyo Institute of Technology, Yokohama 226-8501, Japan
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Hanyaloglu AC, McCullagh E, von Zastrow M. Essential role of Hrs in a recycling mechanism mediating functional resensitization of cell signaling. EMBO J 2005; 24:2265-83. [PMID: 15944737 PMCID: PMC1173141 DOI: 10.1038/sj.emboj.7600688] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2004] [Accepted: 04/28/2005] [Indexed: 12/13/2022] Open
Abstract
Hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) is well known to terminate cell signaling by sorting activated receptors to the MVB/lysosomal pathway. Here we identify a distinct role of Hrs in promoting rapid recycling of endocytosed signaling receptors to the plasma membrane. This function of Hrs is specific for receptors that recycle in a sequence-directed manner, in contrast to default recycling by bulk membrane flow, and is distinguishable in several ways from previously identified membrane-trafficking functions of Hrs/Vps27p. In particular, Hrs function in sequence-directed recycling does not require other mammalian Class E gene products involved in MVB/lysosomal sorting, nor is receptor ubiquitination required. Mutational studies suggest that the VHS domain of Hrs plays an important role in sequence-directed recycling. Disrupting Hrs-dependent recycling prevented functional resensitization of the beta(2)-adrenergic receptor, converting the temporal profile of cell signaling by this prototypic G protein-coupled receptor from sustained to transient. These studies identify a novel function of Hrs in a cargo-specific recycling mechanism, which is critical to controlling functional activity of the largest known family of signaling receptors.
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MESH Headings
- ATPases Associated with Diverse Cellular Activities
- Adenosine Triphosphatases/metabolism
- Adrenergic beta-2 Receptor Agonists
- Adrenergic beta-2 Receptor Antagonists
- Cell Membrane/metabolism
- DNA-Binding Proteins/metabolism
- Endocytosis/physiology
- Endosomal Sorting Complexes Required for Transport
- HeLa Cells
- Humans
- Membrane Proteins/metabolism
- Mutation
- Phosphoproteins/genetics
- Phosphoproteins/metabolism
- Protein Sorting Signals
- Protein Structure, Tertiary
- Receptors, Adrenergic, beta-2/metabolism
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/metabolism
- Repressor Proteins/metabolism
- Signal Transduction/physiology
- Transcription Factors/metabolism
- Vacuolar Proton-Translocating ATPases
- Vesicular Transport Proteins
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Affiliation(s)
| | | | - Mark von Zastrow
- University of California, San Francisco, CA, USA
- Department of Psychiatry and Department of Cellular and Molecular Pharmacology, UCSF, N212 Genentech Hall, San Francisco, CA 94143-2140, USA. Tel.: +1 415 476 7855; Fax: +1 415 514 0169; E-mail:
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