1
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Zhang R, Pan S, Zheng S, Liao Q, Jiang Z, Wang D, Li X, Hu A, Li X, Zhu Y, Shen X, Lei J, Zhong S, Zhang X, Huang L, Wang X, Huang L, Shen L, Song BL, Zhao JW, Wang Z, Yang B, Guo X. Lipid-anchored proteasomes control membrane protein homeostasis. SCIENCE ADVANCES 2023; 9:eadj4605. [PMID: 38019907 PMCID: PMC10686573 DOI: 10.1126/sciadv.adj4605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Accepted: 10/30/2023] [Indexed: 12/01/2023]
Abstract
Protein degradation in eukaryotic cells is mainly carried out by the 26S proteasome, a macromolecular complex not only present in the cytosol and nucleus but also associated with various membranes. How proteasomes are anchored to the membrane and the biological meaning thereof have been largely unknown in higher organisms. Here, we show that N-myristoylation of the Rpt2 subunit is a general mechanism for proteasome-membrane interaction. Loss of this modification in the Rpt2-G2A mutant cells leads to profound changes in the membrane-associated proteome, perturbs the endomembrane system, and undermines critical cellular processes such as cell adhesion, endoplasmic reticulum-associated degradation and membrane protein trafficking. Rpt2G2A/G2A homozygous mutation is embryonic lethal in mice and is sufficient to abolish tumor growth in a nude mice xenograft model. These findings have defined an evolutionarily conserved mechanism for maintaining membrane protein homeostasis and underscored the significance of compartmentalized protein degradation by myristoyl-anchored proteasomes in health and disease.
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Affiliation(s)
- Ruizhu Zhang
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Shuxian Pan
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Suya Zheng
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Qingqing Liao
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Zhaodi Jiang
- National Institute of Biological Sciences, Beijing 102206, China
- Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing 100084, China
| | - Dixian Wang
- Department of Human Anatomy, Histology and Embryology, System Medicine Research Center, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
- Cryo-Electron Microscopy Center, Zhejiang University, Hangzhou 310058, China
| | - Xuemei Li
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Ao Hu
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Taikang Center for Life and Medical Sciences, Taikang Medical School, Wuhan University, Wuhan 430072, China
| | - Xinran Li
- Zhejiang University-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 311200, China
| | - Yezhang Zhu
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Xiaoqi Shen
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Jing Lei
- Department of Neurobiology and Department of Neurology of Second Affiliated Hospital, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou 310058, China
- The MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Brain Science and Brain Medicine, Hangzhou 310058, China
| | - Siming Zhong
- Zhejiang University-University of Edinburgh Institute, Zhejiang University, Haining 314400, China
- Deanery of Biomedical Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9YL, UK
| | - Xiaomei Zhang
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Lingyun Huang
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Xiaorong Wang
- Department of Physiology and Biophysics, University of California-Irvine, Irvine, CA 92697, USA
- Department of Developmental and Cell Biology, University of California-Irvine, Irvine, CA 92697, USA
| | - Lan Huang
- Department of Physiology and Biophysics, University of California-Irvine, Irvine, CA 92697, USA
- Department of Developmental and Cell Biology, University of California-Irvine, Irvine, CA 92697, USA
| | - Li Shen
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Bao-Liang Song
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Taikang Center for Life and Medical Sciences, Taikang Medical School, Wuhan University, Wuhan 430072, China
| | - Jing-Wei Zhao
- Department of Human Anatomy, Histology and Embryology, System Medicine Research Center, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
- Cryo-Electron Microscopy Center, Zhejiang University, Hangzhou 310058, China
| | - Zhiping Wang
- Department of Neurobiology and Department of Neurology of Second Affiliated Hospital, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou 310058, China
- The MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Brain Science and Brain Medicine, Hangzhou 310058, China
| | - Bing Yang
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Xing Guo
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
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2
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Li H, Santos MS, Park CK, Dobry Y, Voglmaier SM. VGLUT2 Trafficking Is Differentially Regulated by Adaptor Proteins AP-1 and AP-3. Front Cell Neurosci 2017; 11:324. [PMID: 29123471 PMCID: PMC5662623 DOI: 10.3389/fncel.2017.00324] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2017] [Accepted: 09/28/2017] [Indexed: 01/25/2023] Open
Abstract
Release of the major excitatory neurotransmitter glutamate by synaptic vesicle exocytosis depends on glutamate loading into synaptic vesicles by vesicular glutamate transporters (VGLUTs). The two principal isoforms, VGLUT1 and 2, exhibit a complementary pattern of expression in adult brain that broadly distinguishes cortical (VGLUT1) and subcortical (VGLUT2) systems, and correlates with distinct physiological properties in synapses expressing these isoforms. Differential trafficking of VGLUT1 and 2 has been suggested to underlie their functional diversity. Increasing evidence suggests individual synaptic vesicle proteins use specific sorting signals to engage specialized biochemical mechanisms to regulate their recycling. We observed that VGLUT2 recycles differently in response to high frequency stimulation than VGLUT1. Here we further explore the trafficking of VGLUT2 using a pHluorin-based reporter, VGLUT2-pH. VGLUT2-pH exhibits slower rates of both exocytosis and endocytosis than VGLUT1-pH. VGLUT2-pH recycling is slower than VGLUT1-pH in both hippocampal neurons, which endogenously express mostly VGLUT1, and thalamic neurons, which endogenously express mostly VGLUT2, indicating that protein identity, not synaptic vesicle membrane or neuronal cell type, controls sorting. We characterize sorting signals in the C-terminal dileucine-like motif, which plays a crucial role in VGLUT2 trafficking. Disruption of this motif abolishes synaptic targeting of VGLUT2 and essentially eliminates endocytosis of the transporter. Mutational and biochemical analysis demonstrates that clathrin adaptor proteins (APs) interact with VGLUT2 at the dileucine-like motif. VGLUT2 interacts with AP-2, a well-studied adaptor protein for clathrin mediated endocytosis. In addition, VGLUT2 also interacts with the alternate adaptors, AP-1 and AP-3. VGLUT2 relies on distinct recycling mechanisms from VGLUT1. Abrogation of these differences by pharmacological and molecular inhibition reveals that these mechanisms are dependent on the adaptor proteins AP-1 and AP-3. Further, shRNA-mediated knockdown reveals differential roles for AP-1 and AP-3 in VGLUT2 recycling.
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Affiliation(s)
- Haiyan Li
- Department of Psychiatry, School of Medicine, Weill Institute for Neurosciences, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, United States
| | - Magda S Santos
- Department of Psychiatry, School of Medicine, Weill Institute for Neurosciences, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, United States
| | - Chihyung K Park
- Department of Psychiatry, School of Medicine, Weill Institute for Neurosciences, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, United States
| | - Yuriy Dobry
- Department of Psychiatry, School of Medicine, Weill Institute for Neurosciences, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, United States
| | - Susan M Voglmaier
- Department of Psychiatry, School of Medicine, Weill Institute for Neurosciences, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, United States
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3
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Cottam NP, Ungar D. Retrograde vesicle transport in the Golgi. PROTOPLASMA 2012; 249:943-55. [PMID: 22160157 DOI: 10.1007/s00709-011-0361-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Accepted: 11/29/2011] [Indexed: 05/23/2023]
Abstract
The Golgi apparatus is the central sorting and biosynthesis hub of the secretory pathway, and uses vesicle transport for the recycling of its resident enzymes. This system must operate with high fidelity and efficiency for the correct modification of secretory glycoconjugates. In this review, we discuss recent advances on how coats, tethers, Rabs and SNAREs cooperate at the Golgi to achieve vesicle transport. We cover the well understood vesicle formation process orchestrated by the COPI coat, and the comprehensively documented fusion process governed by a set of Golgi localised SNAREs. Much less clear are the steps in-between formation and fusion of vesicles, and we therefore provide a much needed update of the latest findings about vesicle tethering. The interplay between Rab GTPases, golgin family coiled-coil tethers and the conserved oligomeric Golgi (COG) complex at the Golgi are thoroughly evaluated.
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Affiliation(s)
- Nathanael P Cottam
- Department of Biology (Area 9), University of York, Heslington, York, YO10 5DD, UK
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4
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Popoff V, Langer JD, Reckmann I, Hellwig A, Kahn RA, Brügger B, Wieland FT. Several ADP-ribosylation factor (Arf) isoforms support COPI vesicle formation. J Biol Chem 2011; 286:35634-35642. [PMID: 21844198 DOI: 10.1074/jbc.m111.261800] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Newly synthesized proteins and lipids are transported in vesicular carriers along the secretory pathway. Arfs (ADP-ribosylation factors), a family of highly conserved GTPases within the Ras superfamily, control recruitment of molecular coats to membranes, the initial step of coated vesicle biogenesis. Arf1 and coatomer constitute the minimal cytosolic machinery leading to COPI vesicle formation from Golgi membranes. Although some functional redundancies have been suggested, other Arf isoforms have been poorly analyzed in this context. In this study, we found that Arf1, Arf4, and Arf5, but not Arf3 and Arf6, associate with COPI vesicles generated in vitro from Golgi membranes and purified cytosol. Using recombinant myristoylated proteins, we show that Arf1, Arf4, and Arf5 each support COPI vesicle formation individually. Unexpectedly, we found that Arf3 could also mediate vesicle biogenesis. However, Arf3 was excluded from the vesicle fraction in the presence of the other isoforms, highlighting a functional competition between the different Arf members.
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Affiliation(s)
- Vincent Popoff
- Heidelberg University Biochemistry Center (BZH), University of Heidelberg, INF 364, 69120 Heidelberg, Germany.
| | - Julian D Langer
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - Ingeborg Reckmann
- Heidelberg University Biochemistry Center (BZH), University of Heidelberg, INF 364, 69120 Heidelberg, Germany
| | - Andrea Hellwig
- Department of Neurobiology IZN, University of Heidelberg, INF 364, 69120 Heidelberg, Germany
| | - Richard A Kahn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Britta Brügger
- Heidelberg University Biochemistry Center (BZH), University of Heidelberg, INF 364, 69120 Heidelberg, Germany
| | - Felix T Wieland
- Heidelberg University Biochemistry Center (BZH), University of Heidelberg, INF 364, 69120 Heidelberg, Germany
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5
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β-Subunit myristoylation is the gatekeeper for initiating metabolic stress sensing by AMP-activated protein kinase (AMPK). Proc Natl Acad Sci U S A 2010; 107:19237-41. [PMID: 20974912 DOI: 10.1073/pnas.1009705107] [Citation(s) in RCA: 242] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The AMP-activated protein kinase (AMPK) is an αβγ heterotrimer that acts as a master metabolic regulator to maintain cellular energy balance following increased energy demand and increases in the AMP/ATP ratio. This regulation provides dynamic control of energy metabolism, matching energy supply with demand that is essential for the function and survival of organisms. AMPK is inactive unless phosphorylated on Thr172 in the α-catalytic subunit activation loop by upstream kinases (LKB1 or calcium-calmodulin-dependent protein kinase kinase β). How a rise in AMP levels triggers AMPK α-Thr172 phosphorylation and activation is incompletely understood. Here we demonstrate unequivocally that AMP directly stimulates α-Thr172 phosphorylation provided the AMPK β-subunit is myristoylated. Loss of the myristoyl group abolishes AMP activation and reduces the extent of α-Thr172 phosphorylation. Once AMPK is phosphorylated, AMP further activates allosterically but this activation does not require β-subunit myristoylation. AMP and glucose deprivation also promote membrane association of myristoylated AMPK, indicative of a myristoyl-switch mechanism. Our results show that AMP regulates AMPK activation at the initial phosphorylation step, and that β-subunit myristoylation is important for transducing the metabolic stress signal.
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6
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Hsu VW, Yang JS. Mechanisms of COPI vesicle formation. FEBS Lett 2009; 583:3758-63. [PMID: 19854177 DOI: 10.1016/j.febslet.2009.10.056] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Revised: 10/15/2009] [Accepted: 10/20/2009] [Indexed: 10/20/2022]
Abstract
Coat Protein I (COPI) is one of the most intensely investigated coat complexes. Numerous studies have contributed to a general understanding of how coat proteins act to initiate intracellular vesicular transport. This review highlights key recent findings that have shaped our current understanding of how COPI vesicles are formed.
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Affiliation(s)
- Victor W Hsu
- Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA 02115, USA.
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7
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Beck R, Ravet M, Wieland F, Cassel D. The COPI system: Molecular mechanisms and function. FEBS Lett 2009; 583:2701-9. [DOI: 10.1016/j.febslet.2009.07.032] [Citation(s) in RCA: 214] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 07/07/2009] [Accepted: 07/13/2009] [Indexed: 02/03/2023]
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8
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Beck R, Adolf F, Weimer C, Bruegger B, Wieland FT. ArfGAP1 Activity and COPI Vesicle Biogenesis. Traffic 2009; 10:307-15. [DOI: 10.1111/j.1600-0854.2008.00865.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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9
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Liu Y, Kahn RA, Prestegard JH. Structure and membrane interaction of myristoylated ARF1. Structure 2009; 17:79-87. [PMID: 19141284 PMCID: PMC2659477 DOI: 10.1016/j.str.2008.10.020] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Revised: 10/25/2008] [Accepted: 10/29/2008] [Indexed: 11/22/2022]
Abstract
ADP-ribosylation factors (ARFs) are small (21 kDa), monomeric GTPases that are important regulators of membrane traffic. When membrane bound, they recruit soluble adaptors to membranes and trigger the assembly of coating complexes involved in cargo selection and vesicular budding. N-myristoylation is a conserved feature of all ARF proteins that is required for its biological functions, although the mechanism(s) by which the myristate acts in ARF functions is not fully understood. Here we present the structure of a myristoylated ARF1 protein, determined by solution NMR methods, and an assessment of the influence of myristoylation on association of ARF1.GDP and ARF1.GTP with lipid bilayers. A model in which myristoylation contributes to both the regulation of guanine nucleotide exchange and stable membrane association is supported.
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Affiliation(s)
- Yizhou Liu
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, Georgia 30602-4712
| | - Richard A. Kahn
- Emory University School of Medicine, Department of Biochemistry, 1510 Clifton Rd., Atlanta, GA 30322-3050
| | - James H. Prestegard
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, Georgia 30602-4712
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10
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Membrane curvature induced by Arf1-GTP is essential for vesicle formation. Proc Natl Acad Sci U S A 2008; 105:11731-6. [PMID: 18689681 DOI: 10.1073/pnas.0805182105] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The GTPase Arf1 is considered as a molecular switch that regulates binding and release of coat proteins that polymerize on membranes to form transport vesicles. Here, we show that Arf1-GTP induces positive membrane curvature and find that the small GTPase can dimerize dependent on GTP. Investigating a possible link between Arf dimerization and curvature formation, we isolated an Arf1 mutant that cannot dimerize. Although it was capable of exerting the classical role of Arf1 as a coat receptor, it could not mediate the formation of COPI vesicles from Golgi-membranes and was lethal when expressed in yeast. Strikingly, this mutant was not able to deform membranes, suggesting that GTP-induced dimerization of Arf1 is a critical step inducing membrane curvature during the formation of coated vesicles.
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11
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Sun Z, Anderl F, Fröhlich K, Zhao L, Hanke S, Brügger B, Wieland F, Béthune J. Multiple and stepwise interactions between coatomer and ADP-ribosylation factor-1 (Arf1)-GTP. Traffic 2008; 8:582-93. [PMID: 17451557 DOI: 10.1111/j.1600-0854.2007.00554.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The small GTPase ADP-ribosylation factor-1 (Arf1) plays a key role in the formation of coat protein I (COP I)-coated vesicles. Upon recruitment to the donor Golgi membrane by interaction with dimeric p24 proteins, Arf1's GDP is exchanged for GTP. Arf1-GTP then dissociates from p24, and together with other Golgi membrane proteins, it recruits coatomer, the heptameric coat protein complex of COP I vesicles, from the cytosol. In this process, Arf1 was shown to specifically interact with the coatomer beta and gamma-COP subunits through its switch I region, and with epsilon-COP. Here, we mapped the interaction of the Arf1-GTP switch I region to the trunk domains of beta and gamma-COP. Site-directed photolabeling at position 167 in the C-terminal helix of Arf1 revealed a novel interaction with coatomer via a putative longin domain of delta-COP. Thus, coatomer is linked to the Golgi through multiple interfaces with membrane-bound Arf1-GTP. These interactions are located within the core, adaptor-like domain of coatomer, indicating an organizational similarity between the COP I coat and clathrin adaptor complexes.
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Affiliation(s)
- Zhe Sun
- Biochemie-Zentrum der Universität Heidelberg (BZH), Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany
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12
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Wong TA, Fairn GD, Poon PP, Shmulevitz M, McMaster CR, Singer RA, Johnston GC. Membrane metabolism mediated by Sec14 family members influences Arf GTPase activating protein activity for transport from the trans-Golgi. Proc Natl Acad Sci U S A 2005; 102:12777-82. [PMID: 16126894 PMCID: PMC1200303 DOI: 10.1073/pnas.0506156102] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The budding yeast Saccharomyces cerevisiae contains a family of Arf (ADP-ribosylation factor) GTPase activating protein (GAP) proteins with the Gcs1 + Age2 ArfGAP pair providing essential overlapping function for the movement of transport vesicles from the trans-Golgi network. We have generated a temperature-sensitive but stable version of the Gcs1 protein that is impaired only for trans-Golgi transport and find that deleterious effects of this enfeebled Gcs1-4 mutant protein are relieved by increased gene dosage of the gcs1-4 mutant gene itself or by the SFH2 gene (also called CSR1), encoding a phosphatidylinositol transfer protein (PITP). This effect was not seen for the SEC14 gene, encoding the founding member of the yeast PITP protein family, even though the Gcs1 and Age2 ArfGAPs are known to be downstream effectors of Sec14-mediated activity for trans-Golgi transport. Sfh2-mediated suppression of inadequate Gcs1-4 function depended on phospholipase D, whereas inadequate Gcs1-4 activity was relieved by increasing levels of diacylglycerol (DAG). Recombinant Gcs1 protein was found to bind certain phospholipids but not DAG. Our findings favor a model of Gcs1 localization through binding to specific phospholipids and activation of ArfGAP activity by DAG-mediated membrane curvature as the transport vesicle is formed. Thus, ArfGAPs are subject to both temporal and spatial regulation that is facilitated by Sfh2-mediated modulation of the lipid environment.
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Affiliation(s)
- Tania A Wong
- Department of Microbiology and Immunology, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada B3H 1X5
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13
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Lay D, L Grosshans B, Heid H, Gorgas K, Just WW. Binding and functions of ADP-ribosylation factor on mammalian and yeast peroxisomes. J Biol Chem 2005; 280:34489-99. [PMID: 16100119 DOI: 10.1074/jbc.m503497200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have analyzed in vitro the binding characteristics of members of the ADP-ribosylation factor (ARF) family of proteins to a highly purified rat liver peroxisome preparation void of Golgi membranes and studied in vivo a role these proteins play in the proliferation of yeast peroxisomes. Although both ARF1 and ARF6 were found on peroxisomes, coatomer recruitment only depended on ARF1-GTP. Recruitment of ARF1 and coatomer to peroxisomes was significantly affected both by pretreating the animals with peroxisome proliferators and by ATP and a cytosolic fraction designated the intermediate pool fraction depleted of ARF and coatomer. In the presence of ATP, the concentrations of ARF1 and coatomer on peroxisomes were reduced, whereas intermediate pool fraction led to a concentration-dependent decrease in ARF and increase in coatomer. Brefeldin A, a fungal toxin that is known to reduce ARF1 binding to Golgi membranes, did not affect ARF1 binding to peroxisomes. In Saccharomyces cerevisiae, both ScARF1 and ScARF3, the yeast orthologs of mammalian ARF1 and ARF6, were implicated in the control of peroxisome proliferation. ScARF1 regulated this process in a positive manner, and ScARF3 regulated it in a negative manner.
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Affiliation(s)
- Dorothee Lay
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany
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14
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Lee SY, Yang JS, Hong W, Premont RT, Hsu VW. ARFGAP1 plays a central role in coupling COPI cargo sorting with vesicle formation. ACTA ACUST UNITED AC 2005; 168:281-90. [PMID: 15657398 PMCID: PMC2171589 DOI: 10.1083/jcb.200404008] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Examining how key components of coat protein I (COPI) transport participate in cargo sorting, we find that, instead of ADP ribosylation factor 1 (ARF1), its GTPase-activating protein (GAP) plays a direct role in promoting the binding of cargo proteins by coatomer (the core COPI complex). Activated ARF1 binds selectively to SNARE cargo proteins, with this binding likely to represent at least a mechanism by which activated ARF1 is stabilized on Golgi membrane to propagate its effector functions. We also find that the GAP catalytic activity plays a critical role in the formation of COPI vesicles from Golgi membrane, in contrast to the prevailing view that this activity antagonizes vesicle formation. Together, these findings indicate that GAP plays a central role in coupling cargo sorting and vesicle formation, with implications for simplifying models to describe how these two processes are coupled during COPI transport.
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Affiliation(s)
- Stella Y Lee
- Division of Rheumatology, Immunology, and Allergy, Brigham and Women's Hospital, and Department of Medicine, Harvard Medical School, Boston, MA 02115
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15
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Lewis SM, Poon PP, Singer RA, Johnston GC, Spang A. The ArfGAP Glo3 is required for the generation of COPI vesicles. Mol Biol Cell 2004; 15:4064-72. [PMID: 15254269 PMCID: PMC515341 DOI: 10.1091/mbc.e04-04-0316] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2004] [Revised: 06/25/2004] [Accepted: 07/01/2004] [Indexed: 11/11/2022] Open
Abstract
The small GTPase Arf and coatomer (COPI) are required for the generation of retrograde transport vesicles. Arf activity is regulated by guanine exchange factors (ArfGEF) and GTPase-activating proteins (ArfGAPs). The ArfGAPs Gcs1 and Glo3 provide essential overlapping function for retrograde vesicular transport from the Golgi to the endoplasmic reticulum. We have identified Glo3 as a component of COPI vesicles. Furthermore, we find that a mutant version of the Glo3 protein exerts a negative effect on retrograde transport, even in the presence of the ArfGAP Gcs1. Finally, we present evidence supporting a role for ArfGAP protein in the generation of COPI retrograde transport vesicles.
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Affiliation(s)
- Stephen M Lewis
- Departments of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 1X5
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16
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Memon AR. The role of ADP-ribosylation factor and SAR1 in vesicular trafficking in plants. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2004; 1664:9-30. [PMID: 15238254 DOI: 10.1016/j.bbamem.2004.04.005] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2003] [Revised: 03/22/2004] [Accepted: 04/19/2004] [Indexed: 12/27/2022]
Abstract
Ras-like small GTP binding proteins regulate a wide variety of intracellular signalling and vesicular trafficking pathways in eukaryotic cells including plant cells. They share a common structure that operates as a molecular switch by cycling between active GTP-bound and inactive GDP-bound conformational states. The active GTP-bound state is regulated by guanine nucleotide exchange factors (GEF), which promote the exchange of GDP for GTP. The inactive GDP-bound state is promoted by GTPase-activating proteins (GAPs) which accelerate GTP hydrolysis by orders of magnitude. Two types of small GTP-binding proteins, ADP-ribosylation factor (Arf) and secretion-associated and Ras-related (Sar), are major regulators of vesicle biogenesis in intracellular traffic and are founding members of a growing family that also includes Arf-related proteins (Arp) and Arf-like (Arl) proteins. The most widely involved small GTPase in vesicular trafficking is probably Arf1, which not only controls assembly of COPI- and AP1, AP3, and AP4/clathrin-coated vesicles but also recruits other proteins to membranes, including some that may be components of further coats. Recent molecular, structural and biochemical studies have provided a wealth of detail of the interactions between Arf and the proteins that regulate its activity as well as providing clues for the types of effector molecules which are controlled by Arf. Sar1 functions as a molecular switch to control the assembly of protein coats (COPII) that direct vesicle budding from ER. The crystallographic analysis of Sar1 reveals a number of structurally unique features that dictate its function in COPII vesicle formation. In this review, I will summarize the current knowledge of Arf and Sar regulation in vesicular trafficking in mammalian and yeast cells and will highlight recent advances in identifying the elements involved in vesicle formation in plant cells. Additionally, I will briefly discuss the similarities and dissimilarities of vesicle traffic in plant, mammalian and yeast cells.
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Affiliation(s)
- Abdul R Memon
- TUBITAK, Research Institute for Genetic Engineering and Biotechnology, P.O. Box 21, 41470 Gebze, Kocaeli, Turkey.
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Crottet P, Meyer DM, Rohrer J, Spiess M. ARF1.GTP, tyrosine-based signals, and phosphatidylinositol 4,5-bisphosphate constitute a minimal machinery to recruit the AP-1 clathrin adaptor to membranes. Mol Biol Cell 2002; 13:3672-82. [PMID: 12388765 PMCID: PMC129974 DOI: 10.1091/mbc.e02-05-0309] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2002] [Revised: 07/09/2002] [Accepted: 07/16/2002] [Indexed: 11/11/2022] Open
Abstract
At the trans-Golgi network, clathrin coats containing AP-1 adaptor complexes are formed in an ARF1-dependent manner, generating vesicles transporting cargo proteins to endosomes. The mechanism of site-specific targeting of AP-1 and the role of cargo are poorly understood. We have developed an in vitro assay to study the recruitment of purified AP-1 adaptors to chemically defined liposomes presenting peptides corresponding to tyrosine-based sorting motifs. AP-1 recruitment was found to be dependent on myristoylated ARF1, GTP or nonhydrolyzable GTP-analogs, tyrosine signals, and small amounts of phosphoinositides, most prominently phosphatidylinositol 4,5-bisphosphate, in the absence of any additional cytosolic or membrane bound proteins. AP-1 from cytosol could be recruited to a tyrosine signal independently of the lipid composition, but the rate of recruitment was increased by phosphatidylinositol 4,5-bisphosphate. The results thus indicate that cargo proteins are involved in coat recruitment and that the local lipid composition contributes to specifying the site of vesicle formation.
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Affiliation(s)
- Pascal Crottet
- Biozentrum, University of Basel, CH-4056 Basel, Switzerland
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18
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Fucini RV, Chen JL, Sharma C, Kessels MM, Stamnes M. Golgi vesicle proteins are linked to the assembly of an actin complex defined by mAbp1. Mol Biol Cell 2002; 13:621-31. [PMID: 11854417 PMCID: PMC65654 DOI: 10.1091/mbc.01-11-0547] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Recent studies indicate that regulation of the actin cytoskeleton is important for protein trafficking, but its precise role is unclear. We have characterized the ARF1-dependent assembly of actin on the Golgi apparatus. Actin recruitment involves Cdc42/Rac and requires the activation of the Arp2/3 complex. Although the actin-binding proteins mAbp1 (SH3p7) and drebrin share sequence homology, they are differentially segregated into two distinct ARF-dependent actin complexes. The binding of Cdc42 and mAbp1, which localize to the Golgi apparatus, but not drebrin, is blocked by occupation of the p23 cargo-protein-binding site on coatomer. Exogenously expressed mAbp1 is mislocalized and inhibits Golgi transport in whole cells. The ability of ARF, vesicle-coat proteins, and cargo to direct the assembly of cytoskeletal structures helps explain how only a handful of vesicle types can mediate the numerous trafficking steps in the cell.
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Affiliation(s)
- Raymond V Fucini
- Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA
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19
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Gommel DU, Memon AR, Heiss A, Lottspeich F, Pfannstiel J, Lechner J, Reinhard C, Helms J, Nickel W, Wieland FT. Recruitment to Golgi membranes of ADP-ribosylation factor 1 is mediated by the cytoplasmic domain of p23. EMBO J 2001; 20:6751-60. [PMID: 11726511 PMCID: PMC125325 DOI: 10.1093/emboj/20.23.6751] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Binding to Golgi membranes of ADP ribosylation factor 1 (ARF1) is the first event in the initiation of COPI coat assembly. Based on binding studies, a proteinaceous receptor has been proposed to be critical for this process. We now report that p23, a member of the p24 family of Golgi-resident transmembrane proteins, is involved in ARF1 binding to membranes. Using a cross-link approach based on a photolabile peptide corresponding to the cytoplasmic domain of p23, the GDP form of ARF1 (ARF1-GDP) is shown to interact with p23 whereas ARF1-GTP has no detectable affinity to p23. The p23 binding is shown to localize specifically to a 22 amino acid C-terminal fragment of ARF1. While a monomeric form of a non-photolabile p23 peptide does not significantly inhibit formation of the cross-link product, the corresponding dimeric form does compete efficiently for this interaction. Consistently, the dimeric p23 peptide strongly inhibits ARF1 binding to native Golgi membranes suggesting that an oligomeric form of p23 acts as a receptor for ARF1 before nucleotide exchange takes place.
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Affiliation(s)
- Daniel U. Gommel
- Biochemie-Zentrum Heidelberg, Ruprecht-Karls-Universität, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany Present address: Marmara Research Center, Institute for Genetic Engineering and Biotechnology, 41470 Gebze, Kocaeli, Turkey Present address: Max-Planck-Institute for Biochemistry, Am Klopferspitz, D-82152 Martinsried, Germany Corresponding authors e-mail: or D.U.Gommel and A.R.Memon contributed equally to this work
| | - Abdul R. Memon
- Biochemie-Zentrum Heidelberg, Ruprecht-Karls-Universität, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany Present address: Marmara Research Center, Institute for Genetic Engineering and Biotechnology, 41470 Gebze, Kocaeli, Turkey Present address: Max-Planck-Institute for Biochemistry, Am Klopferspitz, D-82152 Martinsried, Germany Corresponding authors e-mail: or D.U.Gommel and A.R.Memon contributed equally to this work
| | - Armin Heiss
- Biochemie-Zentrum Heidelberg, Ruprecht-Karls-Universität, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany Present address: Marmara Research Center, Institute for Genetic Engineering and Biotechnology, 41470 Gebze, Kocaeli, Turkey Present address: Max-Planck-Institute for Biochemistry, Am Klopferspitz, D-82152 Martinsried, Germany Corresponding authors e-mail: or D.U.Gommel and A.R.Memon contributed equally to this work
| | - Friedrich Lottspeich
- Biochemie-Zentrum Heidelberg, Ruprecht-Karls-Universität, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany Present address: Marmara Research Center, Institute for Genetic Engineering and Biotechnology, 41470 Gebze, Kocaeli, Turkey Present address: Max-Planck-Institute for Biochemistry, Am Klopferspitz, D-82152 Martinsried, Germany Corresponding authors e-mail: or D.U.Gommel and A.R.Memon contributed equally to this work
| | - Jens Pfannstiel
- Biochemie-Zentrum Heidelberg, Ruprecht-Karls-Universität, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany Present address: Marmara Research Center, Institute for Genetic Engineering and Biotechnology, 41470 Gebze, Kocaeli, Turkey Present address: Max-Planck-Institute for Biochemistry, Am Klopferspitz, D-82152 Martinsried, Germany Corresponding authors e-mail: or D.U.Gommel and A.R.Memon contributed equally to this work
| | - Johannes Lechner
- Biochemie-Zentrum Heidelberg, Ruprecht-Karls-Universität, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany Present address: Marmara Research Center, Institute for Genetic Engineering and Biotechnology, 41470 Gebze, Kocaeli, Turkey Present address: Max-Planck-Institute for Biochemistry, Am Klopferspitz, D-82152 Martinsried, Germany Corresponding authors e-mail: or D.U.Gommel and A.R.Memon contributed equally to this work
| | - Constanze Reinhard
- Biochemie-Zentrum Heidelberg, Ruprecht-Karls-Universität, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany Present address: Marmara Research Center, Institute for Genetic Engineering and Biotechnology, 41470 Gebze, Kocaeli, Turkey Present address: Max-Planck-Institute for Biochemistry, Am Klopferspitz, D-82152 Martinsried, Germany Corresponding authors e-mail: or D.U.Gommel and A.R.Memon contributed equally to this work
| | - J.Bernd Helms
- Biochemie-Zentrum Heidelberg, Ruprecht-Karls-Universität, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany Present address: Marmara Research Center, Institute for Genetic Engineering and Biotechnology, 41470 Gebze, Kocaeli, Turkey Present address: Max-Planck-Institute for Biochemistry, Am Klopferspitz, D-82152 Martinsried, Germany Corresponding authors e-mail: or D.U.Gommel and A.R.Memon contributed equally to this work
| | - Walter Nickel
- Biochemie-Zentrum Heidelberg, Ruprecht-Karls-Universität, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany Present address: Marmara Research Center, Institute for Genetic Engineering and Biotechnology, 41470 Gebze, Kocaeli, Turkey Present address: Max-Planck-Institute for Biochemistry, Am Klopferspitz, D-82152 Martinsried, Germany Corresponding authors e-mail: or D.U.Gommel and A.R.Memon contributed equally to this work
| | - Felix T. Wieland
- Biochemie-Zentrum Heidelberg, Ruprecht-Karls-Universität, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany Present address: Marmara Research Center, Institute for Genetic Engineering and Biotechnology, 41470 Gebze, Kocaeli, Turkey Present address: Max-Planck-Institute for Biochemistry, Am Klopferspitz, D-82152 Martinsried, Germany Corresponding authors e-mail: or D.U.Gommel and A.R.Memon contributed equally to this work
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20
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Ahluwalia JP, Topp JD, Weirather K, Zimmerman M, Stamnes M. A role for calcium in stabilizing transport vesicle coats. J Biol Chem 2001; 276:34148-55. [PMID: 11435443 DOI: 10.1074/jbc.m105398200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calcium has been implicated in regulating vesicle fusion reactions, but its potential role in regulating other aspects of protein transport, such as vesicle assembly, is largely unexplored. We find that treating cells with the membrane-permeable calcium chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester) (BAPTA-AM), leads to a dramatic redistribution of the vesicle coat protein, coatomer, in the cell. We have used the cell-free reconstitution of coat-protomer I (COPI) vesicle assembly to characterize the mechanisms of this redistribution. We find that the recovery of COPI-coated Golgi vesicles is inhibited by the addition of BAPTA to the cell-free vesicle budding assay. When coatomer-coated membranes are incubated in the presence of calcium chelators, the membranes "uncoat," indicating that calcium is necessary for maintaining the integrity of the coat. This uncoating is reversed by the addition of calcium. Interestingly, BAPTA, a calcium chelator with fast binding kinetics, is more potent at uncoating the coatomer-coated membrane than EGTA, suggesting that a calcium transient or a calcium gradient is important for stabilizing COPI vesicle coat. The primary target for the effects of calcium on coatomer recruitment is a step that occurs after ADP-ribosylation factor binding to the membrane. We suggest that a calcium gradient may serve to regulate the timing of vesicle uncoating.
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Affiliation(s)
- J P Ahluwalia
- Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA
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21
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Nickel W, Wieland FT. Receptor-dependent formation of COPI-coated vesicles from chemically defined donor liposomes. Methods Enzymol 2001; 329:388-404. [PMID: 11210558 DOI: 10.1016/s0076-6879(01)29100-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- W Nickel
- Biochemie-Zentrum Heidelberg, Ruprecht-Karls Universität, Heidelberg D-69120, Germany
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22
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Austin C, Hinners I, Tooze SA. Direct and GTP-dependent interaction of ADP-ribosylation factor 1 with clathrin adaptor protein AP-1 on immature secretory granules. J Biol Chem 2000; 275:21862-9. [PMID: 10807927 DOI: 10.1074/jbc.m908875199] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ADP-ribosylation factor 1 (ARF1) mediates clathrin coat formation on PC12 immature secretory granules (ISGs). We have used two approaches to investigate whether ARF1 interacts directly with the clathrin adaptor protein, AP-1. Using an in vitro recruitment assay and co-immunoprecipitation, we could isolate an AP-1.ARF1 complex. Then we used a site-directed photocross-linking approach to determine the components that act downstream of ARF1 in clathrin coat formation on ISGs. Myristoylated ARF1, with a photolabile phenylalanine analogue incorporated into its putative effector domain (switch 1), showed a specific, GTP-dependent interaction with both the gamma- and beta-adaptin subunits of AP-1 on ISGs. These experiments provide evidence for a direct interaction of ARF1 with AP-1. On mature secretory granules myristoylated ARF1 does not bind, and hence clathrin coat formation cannot be initiated, supporting the hypothesis that molecules involved in coat recruitment are removed during ISG maturation.
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Affiliation(s)
- C Austin
- Secretory Pathway Laboratory, Imperial Cancer Research Fund, 44 Lincoln's Inn Fields, London, WC2A 3PX, United Kingdom
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23
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Martin ME, Hidalgo J, Rosa JL, Crottet P, Velasco A. Effect of protein kinase A activity on the association of ADP-ribosylation factor 1 to golgi membranes. J Biol Chem 2000; 275:19050-9. [PMID: 10858454 DOI: 10.1074/jbc.275.25.19050] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The small GTP-binding protein ADP-ribosylation factor 1 (ARF1) is an essential component of the molecular machinery that catalyzes the formation of membrane-bound transport intermediates. By using an in vitro assay that reproduces recruitment of cytosolic proteins onto purified, high salt-washed Golgi membranes, we have analyzed the role of cAMP-dependent protein kinase A (PKA) on ARF1 incorporation. Addition to this assay of either pure catalytic subunits of PKA (C-PKA) or cAMP increased ARF1 binding. By contrast, ARF1 association was inhibited following C-PKA inactivation with either PKA inhibitory peptide or RIIalpha as well as after cytosol depletion of C-PKA. C-PKA also stimulated recruitment and activation of a recombinant form of human ARF1 in the absence of additional cytosolic components. The binding step could be dissociated from the activation reaction and found to be independent of guanine nucleotides and saturable. This step was stimulated by C-PKA in an ATP-dependent manner. Dephosphorylated Golgi membranes exhibited a decreased ability to recruit ARF1, and this effect was reverted by addition of C-PKA. Following an increase in the intracellular level of cAMP, ARF proteins redistributed from cytosol to the perinuclear Golgi region of intact cells. Collectively, the results show that PKA exerts a key regulatory role in the recruitment of ARF1 onto Golgi membranes. In contrast, PKA modulators did not affect recruitment of beta-COP onto Golgi membranes containing prebound ARF1.
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Affiliation(s)
- M E Martin
- Department of Cell Biology, University of Seville, 41012 Seville, Spain
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24
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Abstract
Sorting signals on cargo proteins are recognized by coatomer for selective uptake into COPI (coatomer)-coated vesicles. This study shows that coatomer couples sorting signal recognition to the GTP hydrolysis reaction on ARF1. Coatomer responds differently to different signals. The cytoplasmic signal sequence of hp24a inhibits coatomer-dependent GTP hydrolysis. By contrast, the dilysine retrieval signal, which competes for the same binding site on coatomer, has no effect on GTPase activity. It is inferred that, in vivo, sorting signal selection is under kinetic control, with coatomer governing a GTPase discard pathway that excludes dilysine-tagged proteins from one class of COPI-coated vesicles. The concept of competing sets of sorting signals that act positively and negatively during vesicle budding through a GTPase switch in the COPI coat complex suggests mechanisms for cargo segregation in which specificity is conferred by GTP hydrolysis.
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Affiliation(s)
- J Goldberg
- Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
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25
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Scales SJ, Gomez M, Kreis TE. Coat proteins regulating membrane traffic. INTERNATIONAL REVIEW OF CYTOLOGY 1999; 195:67-144. [PMID: 10603575 DOI: 10.1016/s0074-7696(08)62704-7] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
This review focuses on the roles of coat proteins in regulating the membrane traffic of eukaryotic cells. Coat proteins are recruited to the donor organelle membrane from a cytosolic pool by specific small GTP-binding proteins and are required for the budding of coated vesicles. This review first describes the four types of coat complexes that have been characterized so far: clathrin and its adaptors, the adaptor-related AP-3 complex, COPI, and COPII. It then discusses the ascribed functions of coat proteins in vesicular transport, including the physical deformation of the membrane into a bud, the selection of cargo, and the targeting of the budded vesicle. It also mentions how the coat proteins may function in an alternative model for transport, namely via tubular connections, and how traffic is regulated. Finally, this review outlines the evidence that related coat proteins may regulate other steps of membrane traffic.
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Affiliation(s)
- S J Scales
- Department of Cell Biology, University of Geneva, Switzerland
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26
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Gillingham AK, Koumanov F, Pryor PR, Reaves BJ, Holman GD. Association of AP1 adaptor complexes with GLUT4 vesicles. J Cell Sci 1999; 112 ( Pt 24):4793-800. [PMID: 10574726 DOI: 10.1242/jcs.112.24.4793] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Nycodenz gradients have been used to examine the in vitro effects of GTP-(gamma)-S on adaptor complex association with GLUT4 vesicles. On addition of GTP-(gamma)-S, GLUT4 fractionates as a heavier population of vesicles, which we suggest is due to a budding or coating reaction. Under these conditions there is an increase in co-sedimentation of GLUT4 with AP1, but not with AP3. Western blotting of proteins associated with isolated GLUT4 vesicles shows the presence of high levels of AP1 and some AP3 but very little AP2 adaptor complexes. Cell free, in vitro association of the AP1 complex with GLUT4 vesicles is increased approximately 4-fold by the addition of GTP-(gamma)-S and an ATP regenerating system. Following GTP-(gamma)-S treatment in vitro, ARF is also recruited to GLUT4 vesicles, and the temperature dependence of ARF recruitment closely parallels that of AP1. The recruitment of both AP1 and ARF are partially blocked by brefeldin A. These data demonstrate that the coating of GLUT4 vesicles can be studied in isolated cell-free fractions. Furthermore, at least two distinct adaptor complexes can associate with the GLUT4 vesicles and it is likely that these adaptors are involved in mediating distinct intracellular sorting events at the level of TGN and endosomes.
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Affiliation(s)
- A K Gillingham
- Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK
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27
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Malsam J, Gommel D, Wieland FT, Nickel W. A role for ADP ribosylation factor in the control of cargo uptake during COPI-coated vesicle biogenesis. FEBS Lett 1999; 462:267-72. [PMID: 10622709 DOI: 10.1016/s0014-5793(99)01543-4] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
ARF-mediated hydrolysis of GTP has been demonstrated to regulate coat disassembly of Golgi-derived COPI transport vesicles (Tanigawa, G., Orci, L., Amherdt, M., Ravazzola, M., Helms, J.B. and Rothman, J.E. (1993) J. Cell Biol. 123, 1365-1371). In addition, a requirement for GTP hydrolysis at an early stage of COPI vesicle biogenesis has been established since cargo uptake is impaired in the presence of GTPgammaS (Nickel, W., Malsam, J., Gorgas, K., Ravazzola, M., Jenne, N., Helms, J.B. and Wieland, F.T. (1998) J. Cell Sci. 111, 3081-3090), a non-hydrolyzable analogue of GTP. We now demonstrate that the GTPase involved in the regulation of cargo uptake is ARF, revealing a multi-functional role of this GTPase in COPI-mediated vesicular transport. The molecular mechanism of cargo uptake as well as the functional implications of these findings on the overall process of COPI vesicle biogenesis are discussed.
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Affiliation(s)
- J Malsam
- Biochemie Zentrum Heidelberg, Ruprecht Karls-Universität Heidelberg, Germany
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28
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Jones AT, Spiro DJ, Kirchhausen T, Melançon P, Wessling-Resnick M. Studies on the inhibition of endosome fusion by GTPgammaS-bound ARF. J Cell Sci 1999; 112 ( Pt 20):3477-85. [PMID: 10504296 DOI: 10.1242/jcs.112.20.3477] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Using a cell free assay, we have previously shown that ARF is not required for endosome fusion but that inhibition of fusion by GTPgammaS is dependent on a cytosolic pool of ARFs. Since ARF is proposed to function in intracellular membrane traffic by promoting vesicle biogenesis, and components of clathrin- and COP-coated vesicles have been localized on endosomal structures, we investigated whether ARF-mediated inhibition of early endosome fusion involves the recruitment or irreversible association of these proteins onto endosomal membranes. We now report that depletion of components of clathrin coated vesicles (clathrin, AP-1 and AP-2) or COPI vesicles (beta COP) does not affect the capacity of GTPgammaS-activated ARF to inhibit endosome fusion. Inhibition of fusion by activated ARF is also independent of endosomal acidification since assays performed in the presence of the vacuolar ATPase inhibitor bafilomycin A1 are equally sensitive to GTPgammaS-bound ARF. Finally, in contrast to reported effects on lysosomes, we demonstrate that ARF-GTPgammaS does not induce endosomal lysis. These combined data argue that sequestration of known coat proteins to membranes by activated ARF is not involved in the inhibition of early endosome fusion and that its capacity to inhibit fusion involves other specific interactions with the endosome surface. These results contrast with the mechanistic action of ARF on intra-Golgi transport and nuclear envelope assembly.
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Affiliation(s)
- A T Jones
- Department of Nutrition, Harvard School of Public Health, Boston, MA 02115, USA.
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29
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Zhao L, Helms JB, Brunner J, Wieland FT. GTP-dependent binding of ADP-ribosylation factor to coatomer in close proximity to the binding site for dilysine retrieval motifs and p23. J Biol Chem 1999; 274:14198-203. [PMID: 10318838 DOI: 10.1074/jbc.274.20.14198] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A site-directed photocross-linking approach was employed to determine components that act downstream of ADP-ribosylation factor (ARF). To this end, a photolabile phenylalanine analog was incorporated at various positions of the putative effector region of the ARF molecule. Depending on the position of incorporation, we find specific and GTP-dependent interactions of ARF with two subunits of the coatomer complex, beta-COP and gamma-COP, as well as an interaction with a cytosolic protein (approximately 185 kDa). In addition, we observe homodimer formation of ARF molecules at the Golgi membrane. These data suggest that the binding site of ARF to coatomer is at the interface of its beta- and gamma-subunits, and this is in close proximity to the second site of interaction of coatomer with the Golgi membrane, the binding site within gamma-COP for cytosolic dibasic/diphenylalanine motifs.
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Affiliation(s)
- L Zhao
- Biochemie-Zentrum Heidelberg, University of Heidelberg, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
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30
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Abstract
Insulin modulates many intracellular processes including cellular metabolism, cell proliferation and cell differentiation. Some of these processes involve significant changes in the traffic of intracellular vesicles or in the structural organization of the cell. These phenomena have been linked to the activity of regulatory GTP-binding proteins. Most, if not all functions, of the insulin receptor are associated with its tyrosine kinase activity. Thus, over the past few years, a significant effort has been dedicated to elucidate the cross-talk between the tyrosine kinase activity of the receptor and the regulation of G protein-mediated pathways. Recent progress indicates that G proteins may mediate the control of several of insulin's intracellular functions. These include the regulation of the MAP kinase pathway, the activation of phospholipase D and the regulation of glucose uptake. This article discusses some recent advances in this area.
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Affiliation(s)
- M A Rizzo
- Department of Pharmacology, University of Pittsburgh School of Medicine, PA 15261, USA
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31
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Bremser M, Nickel W, Schweikert M, Ravazzola M, Amherdt M, Hughes CA, Söllner TH, Rothman JE, Wieland FT. Coupling of coat assembly and vesicle budding to packaging of putative cargo receptors. Cell 1999; 96:495-506. [PMID: 10052452 DOI: 10.1016/s0092-8674(00)80654-6] [Citation(s) in RCA: 241] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
COPI-coated vesicle budding from lipid bilayers whose composition resembles mammalian Golgi membranes requires coatomer, ARF, GTP, and cytoplasmic tails of putative cargo receptors (p24 family proteins) or membrane cargo proteins (containing the KKXX retrieval signal) emanating from the bilayer surface. Liposome-derived COPI-coated vesicles are similar to their native counterparts with respect to diameter, buoyant density, morphology, and the requirement for an elevated temperature for budding. These results suggest that a bivalent interaction of coatomer with membrane-bound ARF[GTP] and with the cytoplasmic tails of cargo or putative cargo receptors is the molecular basis of COPI coat assembly and provide a simple mechanism to couple uptake of cargo to transport vesicle formation.
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Affiliation(s)
- M Bremser
- Biochemie-Zentrum Heidelberg, University of Heidelberg, Germany
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Aridor M, Bannykh SI, Rowe T, Balch WE. Cargo can modulate COPII vesicle formation from the endoplasmic reticulum. J Biol Chem 1999; 274:4389-99. [PMID: 9933643 DOI: 10.1074/jbc.274.7.4389] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The COPII coat complex found on endoplasmic reticulum (ER)-derived vesicles plays a critical role in cargo selection. We now address the potential role of biosynthetic cargo in modulating COPII coat assembly and vesicle budding. The ER accumulation of vesicular stomatitis glycoprotein (VSV-G), a transmembrane protein, or the soluble PiZ variant of alpha1-antitrypsin, reduced levels of general COPII vesicle formation in vivo. Consistent with this result, conditions that prevent the export of VSV-G from the ER led to a significant inhibition of general COPII vesicle budding from ER microsomes and the export of an endogenous recycling protein p58 in vitro. In contrast, synchronized export of VSV-G stimulated COPII vesicle budding both in vivo and in vitro. Under conditions where VSV-G is retained in the ER, we find that it can to be recovered in pre-budding complexes containing COPII components. These results suggest that the export of biosynthetic cargo is integrated with ER functions involved in protein folding and oligomerization. The ability of biosynthetic cargo to prevent or enhance ER export suggests that interactions of cargo with the COPII machinery contribute to the formation of vesicles budding from the ER.
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Affiliation(s)
- M Aridor
- Departments of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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33
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Stamnes M, Schiavo G, Stenbeck G, Söllner TH, Rothman JE. ADP-ribosylation factor and phosphatidic acid levels in Golgi membranes during budding of coatomer-coated vesicles. Proc Natl Acad Sci U S A 1998; 95:13676-80. [PMID: 9811859 PMCID: PMC24878 DOI: 10.1073/pnas.95.23.13676] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The finding that ADP-ribosylation factor (ARF) can activate phospholipase D has led to debate as to whether ARF recruits coat proteins through direct binding or indirectly by catalytically increasing phosphatidic acid production. Here we test critical aspects of these hypotheses. We find that Golgi membrane phosphatidic acid levels do not rise-in fact they decline-during cell-free budding reactions. We confirm that the level of membrane-bound ARF can be substantially reduced without compromising coat assembly [Ktistakis, N. T., Brown, H. A., Waters, M. G., Sternweis, P. C. & Roth, M. G. (1996) J. Cell Biol. 134, 295-306], but find that under all conditions, ARF is present on the Golgi membrane in molar excess over bound coatomer. These results do not support the possibility that the activation of coat assembly by ARF is purely catalytic, and they are consistent with ARF forming direct interactions with coatomer. We suggest that ARF, like many other G proteins, is a multifunctional protein with roles in trafficking and phospholipid signaling.
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Affiliation(s)
- M Stamnes
- Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA.
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34
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Robinson DG, Hinz G, Holstein SE. The molecular characterization of transport vesicles. PLANT MOLECULAR BIOLOGY 1998; 38:49-76. [PMID: 9738960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Secretion, endocytosis and transport to the lytic compartment are fundamental, highly coordinated features of the eukaryotic cell. These intracellular transport processes are facilitated by vesicles, many of which are small (100 nm or less in diameter) and 'coated' on their cytoplasmic surface. Research into the structure of the coat proteins and how they interact with the components of the vesicle membrane to ensure the selective packaging of the cargo molecules and their correct targeting, has been quite extensive in mammalian and yeast cell biology. By contrast, our knowledge of the corresponding types of transport vesicles in plant cells is limited. Nevertheless, the available data indicate that a considerable homology between plant and non-plant coat polypeptides exists, and it is also suggestive of a certain similarity in the mechanisms underlying targeting in all eukaryotes. In this article we shall concentrate on three major types of transport vesicles: clathrin-coated vesicles, COP-coated vesicles, and 'dense' vesicles, the latter of which are responsible for the transport of vacuolar storage proteins in maturing legume cotyledons. For each we will summarize the current literature on animal and yeast cells, and then present the relevant data derived from work on plant cells. In addition, we briefly review the evidence in support of the 'SNARE' hypothesis, which explains how vesicles find and fuse with their target membrane.
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Affiliation(s)
- D G Robinson
- Abteilung Strukturelle Zellphysiologie, Albrecht-von-Haller Institut für Pflanzen-wissenschaften, Universität Göttingen, Germany.
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35
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Cuconati A, Molla A, Wimmer E. Brefeldin A inhibits cell-free, de novo synthesis of poliovirus. J Virol 1998; 72:6456-64. [PMID: 9658088 PMCID: PMC109807 DOI: 10.1128/jvi.72.8.6456-6464.1998] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/1997] [Accepted: 05/05/1998] [Indexed: 02/08/2023] Open
Abstract
Brefeldin A (BFA), an inhibitor of intracellular vesicle-dependent secretory transport, is a potent inhibitor of poliovirus RNA replication in infected cells. We have determined that the unknown mechanism of BFA inhibition of replication is reproduced in the cell-free poliovirus translation, replication, and encapsidation system. Furthermore, we provide evidence suggesting that the cellular mechanism targeted by BFA, the GTP-dependent synthesis of secretory transport vesicles, may be involved in viral RNA replication in the system via a soluble cellular GTP-binding and -hydrolyzing activity. This activity is related to the ARF (ADP-ribosylation factor) family of GTP-binding proteins. ARFs are required for the formation of several classes of secretory vesicles, and some family members are indirectly inactivated by BFA. Peptides that function as competitive inhibitors of ARF activity in cell-free transport systems also inhibit poliovirus RNA replication, and this inhibitory effect can be countered by the addition of exogenous ARF. We suggest that BFA inhibition of replication is diagnostic of a requirement for ARF activity in the cell-free system.
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Affiliation(s)
- A Cuconati
- Department of Molecular Genetics and Microbiology, School of Medicine, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
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36
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Ooi CE, Dell'Angelica EC, Bonifacino JS. ADP-Ribosylation factor 1 (ARF1) regulates recruitment of the AP-3 adaptor complex to membranes. J Biophys Biochem Cytol 1998; 142:391-402. [PMID: 9679139 PMCID: PMC2133064 DOI: 10.1083/jcb.142.2.391] [Citation(s) in RCA: 164] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Small GTP-binding proteins such as ADP- ribosylation factor 1 (ARF1) and Sar1p regulate the membrane association of coat proteins involved in intracellular membrane trafficking. ARF1 controls the clathrin coat adaptor AP-1 and the nonclathrin coat COPI, whereas Sar1p controls the nonclathrin coat COPII. In this study, we demonstrate that membrane association of the recently described AP-3 adaptor is regulated by ARF1. Association of AP-3 with membranes in vitro was enhanced by GTPgammaS and inhibited by brefeldin A (BFA), an inhibitor of ARF1 guanine nucleotide exchange. In addition, recombinant myristoylated ARF1 promoted association of AP-3 with membranes. The role of ARF1 in vivo was examined by assessing AP-3 subcellular localization when the intracellular level of ARF1-GTP was altered through overexpression of dominant ARF1 mutants or ARF1- GTPase-activating protein (GAP). Lowering ARF1-GTP levels resulted in redistribution of AP-3 from punctate membrane-bound structures to the cytosol as seen by immunofluorescence microscopy. In contrast, increasing ARF1-GTP levels prevented redistribution of AP-3 to the cytosol induced by BFA or energy depletion. Similar experiments with mutants of ARF5 and ARF6 showed that these other ARF family members had little or no effect on AP-3. Taken together, our results indicate that membrane recruitment of AP-3 is promoted by ARF1-GTP. This finding suggests that ARF1 is not a regulator of specific coat proteins, but rather is a ubiquitous molecular switch that acts as a transducer of diverse signals influencing coat assembly.
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Affiliation(s)
- C E Ooi
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health (NIH), Bethesda, Maryland 20892, USA
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37
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Zhu Y, Traub LM, Kornfeld S. ADP-ribosylation factor 1 transiently activates high-affinity adaptor protein complex AP-1 binding sites on Golgi membranes. Mol Biol Cell 1998; 9:1323-37. [PMID: 9614177 PMCID: PMC25353 DOI: 10.1091/mbc.9.6.1323] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/1998] [Accepted: 03/10/1998] [Indexed: 12/20/2022] Open
Abstract
Association of the Golgi-specific adaptor protein complex 1 (AP-1) with the membrane is a prerequisite for clathrin coat assembly on the trans-Golgi network (TGN). The AP-1 adaptor is efficiently recruited from cytosol onto the TGN by myristoylated ADP-ribosylation factor 1 (ARF1) in the presence of the poorly hydrolyzable GTP analog guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS). Substituting GTP for GTPgammaS, however, results in only poor AP-1 binding. Here we show that both AP-1 and clathrin can be recruited efficiently onto the TGN in the presence of GTP when cytosol is supplemented with ARF1. Optimal recruitment occurs at 4 microM ARF1 and with 1 mM GTP. The AP-1 recruited by ARF1.GTP is released from the Golgi membrane by treatment with 1 M Tris-HCl (pH 7) or upon reincubation at 37 degreesC, whereas AP-1 recruited with GTPgammaS or by a constitutively active point mutant, ARF1(Q71L), remains membrane bound after either treatment. An incubation performed with added ARF1, GTP, and AlFn, used to block ARF GTPase-activating protein activity, results in membrane-associated AP-1, which is largely insensitive to Tris extraction. Thus, ARF1. GTP hydrolysis results in lower-affinity binding of AP-1 to the TGN. Using two-stage assays in which ARF1.GTP first primes the Golgi membrane at 37 degreesC, followed by AP-1 binding on ice, we find that the high-affinity nucleating sites generated in the priming stage are rapidly lost. In addition, the AP-1 bound to primed Golgi membranes during a second-stage incubation on ice is fully sensitive to Tris extraction, indicating that the priming stage has passed the ARF1.GTP hydrolysis point. Thus, hydrolysis of ARF1.GTP at the priming sites can occur even before AP-1 binding. Our finding that purified clathrin-coated vesicles contain little ARF1 supports the concept that ARF1 functions in the coat assembly process rather than during the vesicle-uncoating step. We conclude that ARF1 is a limiting factor in the GTP-stimulated recruitment of AP-1 in vitro and that it appears to function in a stoichiometric manner to generate high-affinity AP-1 binding sites that have a relatively short half-life.
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Affiliation(s)
- Y Zhu
- Division of Hematology, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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38
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Katayama T, Imaizumi K, Tsuda M, Mori Y, Takagi T, Tohyama M. Expression of an ADP-ribosylation factor like gene, ARF4L, is induced after transient forebrain ischemia in the gerbil. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1998; 56:66-75. [PMID: 9602063 DOI: 10.1016/s0169-328x(98)00030-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
To elucidate the molecular mechanisms underlying post-ischemic phenomena including delayed neuronal death, we screened for genes which were induced in the hippocampus after transient global ischemia in the Mongolian gerbil by a differential display method, and cloned a gerbil homologue of human ADP-ribosylation factor 4L (ARF4L). Although the physiological roles of ARF4L are unknown, it is likely that ARF4L participates in vesicle transport between the endoplasmic reticulum (ER) and Golgi complex as it contains a GTP binding site, myristoylation site and coatmer binding motif (KKXX). In situ hybridization analysis indicated that the expression of ARF4L mRNA was elevated in neurons of the dentate gyrus (DG) and CA1 regions. In DG, the signals were detected 3 h after ischemia and peaked at 6 h with subsequent gradual reduction. On the other hand, in the CA1 region where cell death occurs in this model, ARF4L mRNA was slightly detected from 1 to 2 days after ischemia but was absent after 3 days. Other vesicle transport-related genes such as ARF1, ARL4 and beta-COP were also induced after 5-min ischemia, suggesting that vesicle transport was activated in hippocampal neurons after ischemic stress. To determine the cause of the induction of ARF4L gene expression after transient ischemia, we examined the changes in ARF4L mRNA expression in HEK 293 cells under hypoxic conditions compared with HSP70. The expression of ARF4L mRNA was elevated at 12 h after hypoxia exposure, similarly to HSP70. These results will help to elucidate the association of upregulation of vesicle transport systems including ARF4L and stress responses of neurons after transient ischemia.
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Affiliation(s)
- T Katayama
- Department of Molecular Neurobiology (TANABE), Osaka University Medical School, Osaka, Japan.
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39
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Abstract
Synaptic vesicles can be coated in vitro in a reaction that is ARF-, ATP-, and temperature-dependent and requires synaptic vesicle membrane proteins. The coat is largely made up of the heterotetrameric complex, adaptor protein 3, recently implicated in Golgi-to-vacuole traffic in yeast. Depletion of AP3 from brain cytosol inhibits small vesicle formation from PC12 endosomes in vitro. Budding from washed membranes can be reconstituted with purified AP3 and recombinant ARF1. We conclude that AP3 coating is involved in at least one pathway of small vesicle formation from endosomes.
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Affiliation(s)
- V Faúndez
- Department of Biochemistry and Biophysics and Hormone Research Institute, University of California, San Francisco 94143-0534, USA
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40
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Vasudevan C, Han W, Tan Y, Nie Y, Li D, Shome K, Watkins SC, Levitan ES, Romero G. The distribution and translocation of the G protein ADP-ribosylation factor 1 in live cells is determined by its GTPase activity. J Cell Sci 1998; 111 ( Pt 9):1277-85. [PMID: 9547306 DOI: 10.1242/jcs.111.9.1277] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
ADP-ribosylation factors (ARF) are small G proteins that play key roles in vesicular transport processes. We have studied the distribution of ARF1 in live cells using chimeras of ARF1 mutants (wild type (wt) ARF1; Q71L-ARF1 (reduced GTPase); T31N (low affinity for GTP); and (Delta)Nwt (deletion of amino acids 2–18)) with green fluorescent protein (GFP). Confocal microscopy studies showed that the wt and Q71L proteins were localized in the Golgi and cytoplasm. The (Delta)Nwt and the T31N mutants were exclusively cytoplasmic. The behavior of the wt and Q71L proteins was studied in detail. About 15% of wt-ARF1-GFP was bound to the Golgi. Bound wt-ARF1-GFP dissociated rapidly after addition of Brefeldin A (BFA). This process did not appear to be a consequence of BFA-induced disappearance of the Golgi. Photobleaching recovery showed that essentially all the ARF-GFP was mobile, although it diffused very slowly. In contrast, about 40–50% of the Q71L mutant was found in the Golgi, and its rate of dissociation in the presence of BFA was slow and biphasic. Q71L-ARF1-GFP diffused more slowly than the wt. We conclude that ARF1 proteins exist in a dynamic equilibrium between Golgi-bound and cytosolic pools, and that the translocation of ARF in live cells requires the hydrolysis of GTP by the Golgi-bound protein.
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Affiliation(s)
- C Vasudevan
- Department of Pharmacology, University of Pittsburgh, Pittsburgh, PA 15261, USA
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41
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Hsuan JJ, Minogue S, dos Santos M. Phosphoinositide 4- and 5-kinases and the cellular roles of phosphatidylinositol 4,5-bisphosphate. Adv Cancer Res 1998; 74:167-216. [PMID: 9561269 DOI: 10.1016/s0065-230x(08)60767-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- J J Hsuan
- Ludwig Institute for Cancer Research, University College London Medical School, London, United Kingdom
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42
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Pavel J, Harter C, Wieland FT. Reversible dissociation of coatomer: functional characterization of a beta/delta-coat protein subcomplex. Proc Natl Acad Sci U S A 1998; 95:2140-5. [PMID: 9482852 PMCID: PMC19276 DOI: 10.1073/pnas.95.5.2140] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
COPI-coated vesicles mediate protein transport within the early secretory pathway. Their coat consists of ADP ribosylation factor (ARF1, a small guanosine nucleotide binding protein), and coatomer, a cytosolic complex composed of seven subunits, alpha- to zeta-coat proteins (COPs). For coat formation that initiates budding of a vesicle, ARF1 is recruited to the Golgi membrane from the cytosol in its GTP-bound form, and subsequently, coatomer can bind to the membrane. To identify a minimal structure of coatomer capable to bind to Golgi membranes in an ARF1-dependent manner, we have established a procedure to dissociate coatomer under conditions that allow reassociation of the subunits to a complete and functional complex. After dissociation, subunits or subcomplexes can be isolated and may be expected to be functional. Herein we describe isolation of a subcomplex of coatomer consisting of beta- and delta-COPs that is able to bind to Golgi membranes in an ARF1- and GTP-dependent manner.
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Affiliation(s)
- J Pavel
- Biochemie-Zentrum Heidelberg Ruprecht-Karls-Universität, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
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43
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Aoe T, Cukierman E, Lee A, Cassel D, Peters PJ, Hsu VW. The KDEL receptor, ERD2, regulates intracellular traffic by recruiting a GTPase-activating protein for ARF1. EMBO J 1997; 16:7305-16. [PMID: 9405360 PMCID: PMC1170331 DOI: 10.1093/emboj/16.24.7305] [Citation(s) in RCA: 143] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The small GTPase ADP-ribosylation factor 1 (ARF1) is a key regulator of intracellular membrane traffic. Regulators of ARF1, its GTPase-activating protein (GAP) and its guanine nucleotide exchange factor have been identified recently. However, it remains uncertain whether these regulators drive the GTPase cycle of ARF1 autonomously or whether their activities can be regulated by other proteins. Here, we demonstrate that the intracellular KDEL receptor, ERD2, self-oligomerizes and interacts with ARF1 GAP, and thereby regulates the recruitment of cytosolic ARF1 GAP to membranes. Because ERD2 overexpression enhances the recruitment of GAP to membranes and results in a phenotype that reflects ARF1 inactivation, our findings suggest that ERD2 regulates ARF1 GAP, and thus regulates ARF1-mediated transport.
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Affiliation(s)
- T Aoe
- Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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44
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Hauri H, Schweizer A. The
ER
–Golgi Membrane System: Compartmental Organization and Protein Traffic. Compr Physiol 1997. [DOI: 10.1002/cphy.cp140115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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45
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Abstract
Biosynthetic protein transport and sorting along the secretory pathway represents the last step in biosynthesis of a variety of proteins. Proteins destined for delivery to the cell surface are inserted cotranslationally into the endoplasmic reticulum (ER) and, after their correct folding, are transported out of the ER towards their final destinations. The successive compartments of the secretory pathway are connected by vesicular shuttles that mediate delivery of cargo. The formation of these carrier vesicles depends on the recruitment of cytosolic coat proteins that are thought to act as a mechanical device to shape a flattened donor membrane into a spherical vesicle. A general molecular machinery that mediates targeting and fusion of carrier vesicles has also been identified. This review is focused on COPI-coated vesicles that operate in protein transport within the early secretory pathway. Rather than representing a general overview of the role of COPI-coated vesicles, this mini-review will discuss mechanisms specifically related to the biogenesis of COPI-coated vesicles: (i) a possible role of phospholipase D in the formation of COPI-coated vesicles, (ii) a functional role of a novel family of transmembrane proteins, the p24 family, in the initiation of COPI assembly, and (iii) the direction COPI-coated vesicles may take within the early secretory pathway.
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Affiliation(s)
- W Nickel
- Biochemie-Zentrum Heidelberg, Ruprecht-Karls-Universität Heidelberg, Germany
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46
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Miaczynska M, Lorenzetti S, Bialek U, Benito-Moreno RM, Schweyen RJ, Ragnini A. The yeast Rab escort protein binds intracellular membranes in vivo and in vitro. J Biol Chem 1997; 272:16972-7. [PMID: 9202009 DOI: 10.1074/jbc.272.27.16972] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In both mammals and yeast, intracellular vesicular transport depends on the correct shuttling between membrane and cytosol of the Rab/Ypt small G proteins. Membrane association of these proteins requires prenylation by the Rab geranylgeranyl transferase that recognizes a complex formed by the Rab/Ypt protein and the Rab escort protein (REP). After prenylation the Rab/Ypt protein is delivered to the target membranes by REP. Little is known about the early steps of the Rab-REP complex formation and where this association occurs in the cell. Although prenylation is believed to take place in the cytosol, we show that the yeast Rab escort protein Mrs6 is present in both soluble and particulate fractions of cell extracts. Mrs6p is associated with the heavy microsomal fraction that contains endoplasmic reticulum-Golgi membranes but is absent in the plasma membrane, vacuoles, mitochondria, and microsomal subfraction associated with mitochondria. The solubilization pattern of the particulate pool of Mrs6p implies that this protein is peripherally but tightly associated with membranes via hydrophobic interactions and metal ions. We also report that the C terminus of Mrs6p is important for maintaining the solubility of the protein because its deletion or replacement with the C terminus of RabGDI results in a protein that localizes only to membranes.
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Affiliation(s)
- M Miaczynska
- Vienna Biocenter, Institute of Microbiology and Genetics, University of Vienna, A-1030 Vienna, Austria
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47
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Abstract
BACKGROUND ADP-ribosylation factors (ARFs) have been shown to activate phospholipase D (PLD), an enzyme modulated by extracellular signals, including several growth factors and, in particular, insulin. We have tested the hypothesis that ARF proteins are involved specifically in insulin-induced activation of PLD. RESULTS We found that in membranes obtained from HIRcB cells, a cell line derived from Rat-1 fibroblasts that overexpresses normal human insulin receptors, binding of the GTP analogue GTPgammaS to purified bovine or recombinant ARF was enhanced in the presence of insulin. Membranes obtained from cells that overexpressed a mutated, nonfunctional insulin receptor failed to stimulate ARF activation. Insulin promoted the association of ARF proteins with membranes in the presence of GTPgammaS in permeabilized cells. Insulin activated PLD in permeabilized HIRcB cells by a process that required GTPgammaS and ARF. Azido-gamma[32P]-GTP labelling of immunoprecipitated receptors revealed the presence of a unique 19 kD band; ARF proteins are approximately this size, and analysis using specific monoclonal antibodies demonstrated that ARF proteins coimmunoprecipitated with the insulin receptor. Coimmunoprecipitation of ARF with the receptor was inhibited by guanine nucleotides and stimulated by insulin. No evidence of the coprecipitation of ARF with mutant receptors could be obtained using azido-gamma[32P]-GTP or anti-ARF antibodies. CONCLUSIONS The activation of ARF proteins is stimulated by insulin and this process plays an important role in insulin-mediated regulation of PLD.
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Affiliation(s)
- K Shome
- Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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48
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Zhao L, Helms JB, Brügger B, Harter C, Martoglio B, Graf R, Brunner J, Wieland FT. Direct and GTP-dependent interaction of ADP ribosylation factor 1 with coatomer subunit beta. Proc Natl Acad Sci U S A 1997; 94:4418-23. [PMID: 9114004 PMCID: PMC20737 DOI: 10.1073/pnas.94.9.4418] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A site-directed photocrosslink approach was used to elucidate components that interact directly with ADP- ribosylation factor (ARF)-GTP during coat assembly. Two ARF mutants were generated that contain a photolabile amino acid at positions distant to each other within the ARF molecule. Here we show that one of the two positions specifically interacts with coatomer subunit beta both on Golgi membranes and in isolated coat protein complex type I (COPI)-coated vesicles. Thus, a direct and GTP-dependent interaction of coatomer via beta-coat protein complex (COP) with ARF is involved in the coating of COPI-coated vesicles. These data implicate a bivalent interaction of the complex with the donor membrane during vesicle formation.
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Affiliation(s)
- L Zhao
- Biochemie-Zentrum Heidelberg, Universität Heidelberg, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany
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49
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Marshansky V, Bourgoin S, Londoño I, Bendayan M, Vinay P. Identification of ADP-ribosylation factor-6 in brush-border membrane and early endosomes of human kidney proximal tubules. Electrophoresis 1997; 18:538-47. [PMID: 9150938 DOI: 10.1002/elps.1150180334] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The expression and distribution of ADP-ribosylation factor (ARF) small GTP-binding proteins in kidney tissue was examined. Various anti-ARF antibodies were raised against purified rec-ARF 1 and rec-ARF 6 and their specificity was determined. Using indirect immunofluorescence analysis of intact kidney, ARF proteins were found to be predominantly expressed in kidney tubules as compared to glomeruli. This result was further supported by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis of purified human kidney glomeruli and proximal tubules. Both ARF 1 and ARF 6 were detected in purified human glomeruli and proximal tubules; however, ARF 1 was more abundant than ARF 6 in these kidney structures. Brush-border membrane vesicles (BBMV) and early endosomes (EE) derived from the receptor-mediated endocytosis pathway were isolated from purified proximal tubules of rat, dog and human kidney using a combination of magnesium precipitation and wheat-germ agglutinin negative selection techniques. We demonstrated that ARF 6 is associated with BBMV and with EE derived from receptor-mediated endocytosis pathway of human kidney proximal tubules. Using a combination of SDS-PAGE and quantitative enhanced chemiluminescence Western blot analysis, the quantification of the ARF 6 distribution in membrane and cytoplasmic fractions of proximal tubules was made and its predominance in membrane fractions was demonstrated. By analogy with the functional role of ARF 1 in Golgi protein transport, we suggest that ARF 6 may play an important role in the regulation of receptor-mediated endocytosis and protein reabsorption by kidney proximal tubules.
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Affiliation(s)
- V Marshansky
- Laboratory of Renal Biochemistry, Centre de Recherche L.-C. Simard, Centre Hospitalier, Université de Montréal, Québec, Canada.
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50
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Kanoh H, Williger BT, Exton JH. Arfaptin 1, a putative cytosolic target protein of ADP-ribosylation factor, is recruited to Golgi membranes. J Biol Chem 1997; 272:5421-9. [PMID: 9038142 DOI: 10.1074/jbc.272.9.5421] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
ADP-ribosylation factors (ARFs) have been implicated in vesicle transport in the Golgi complex. Employing yeast two-hybrid screening of an HL60 cDNA library using a constitutively active mutant of ARF3 (ARF3.Q71L), as a probe, we have identified a cDNA encoding a novel protein with a calculated molecular mass of 38.6 kDa, which we have named arfaptin 1. The mRNA of arfaptin 1 was ubiquitously expressed, and recombinant arfaptin 1 bound preferentially to class I ARFs, especially ARF1, but only in the GTP-bound form. The interactions were independent of myristoylation of ARF. Arfaptin 1 in cytosol was recruited to Golgi membranes by ARF in a guanosine 5'-O-(3-thiotriphosphate)-dependent and brefeldin A-sensitive manner. When expressed in COS cells, arfaptin 1 was localized to the Golgi complex. The yeast two-hybrid system yielded another clone, which encoded a putative protein, which we have named arfaptin 2. This consisted of the same number of amino acids as arfaptin 1 and was 60% identical to it. Arfaptin 2 was also ubiquitously expressed and bound to the GTP-, but not GDP-liganded form of class I ARFs, especially ARF1. These results suggest that arfaptins 1 and 2 may be direct target proteins of class 1 ARFs. Arfaptin 1 may be involved in Golgi function along with ARF1.
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Affiliation(s)
- H Kanoh
- Howard Hughes Medical Institute and the Department of Molecular Physiology and Biophysics and Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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