101
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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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102
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Donaldson JG, Honda A, Weigert R. Multiple activities for Arf1 at the Golgi complex. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1744:364-73. [PMID: 15979507 DOI: 10.1016/j.bbamcr.2005.03.001] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 12/23/2004] [Revised: 02/28/2005] [Accepted: 03/01/2005] [Indexed: 10/25/2022]
Abstract
The Arf family of GTPases regulates membrane traffic and organelle structure. At the Golgi complex, Arf proteins facilitate membrane recruitment of many cytoplasmic coat proteins to allow sorting of membrane proteins for transport, stimulate the activity of enzymes that modulate the lipid composition of the Golgi, and assemble a cytoskeletal scaffold on the Golgi. Arf1 is the Arf family member most closely studied for its function at the Golgi complex. A number of regulators that activate and inactivate Arf1 on the Golgi have been described that localize to different regions of the organelle. This spatial distribution of Arf regulators may facilitate the recruitment of the coat proteins and other Arf effectors to different regions of the Golgi complex.
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Affiliation(s)
- Julie G Donaldson
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Building 50, Room 2503, Bethesda, MD 20892, USA.
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103
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Jiang S, Storrie B. Cisternal rab proteins regulate Golgi apparatus redistribution in response to hypotonic stress. Mol Biol Cell 2005; 16:2586-96. [PMID: 15758030 PMCID: PMC1087260 DOI: 10.1091/mbc.e04-10-0861] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
We show that a physiological role of the extensively studied cisternal Golgi rab protein, rab6, is modulation of Golgi apparatus response to stress. Taking exposure of cells to hypotonic media as the best-known example of mammalian Golgi stress response, we found that hypotonic-induced tubule extension from the Golgi apparatus was sensitive to GDP-rab6a expression. Similarly, we found that Golgi tubulation induced by brefeldin A, a known microtubule-dependent process, was inhibited by GDP-restricted rab6a, rab6a', and rab33b, the most commonly studied cisternal rab proteins. These GDP-rab levels were sufficient to inhibit rab-induced redistribution of Golgi glycosyltransferases into the endoplasmic reticulum (ER), also a microtubule-dependent process, and to depress Golgi membrane association of the GTP-conformer of rab6. Nocodazole-induced Golgi scattering, a microtubule-independent process, also was inhibited by GDP-rab6a expression. In comparison, we found similar GDP-rab expression levels had little inhibitory effect on another microtubule-independent process, constitutive recycling of Golgi resident proteins to the ER. We conclude that Golgi cisternal rabs, and in particular rab6a, are regulators of the Golgi response to stress and presumably the molecular targets of stress-activated signaling pathway(s). Moreover, we conclude that rab6a can regulate select microtubule-independent processes as well as microtubule-dependent processes.
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Affiliation(s)
- Shu Jiang
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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104
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Abstract
Coiled-coil proteins of the golgin family have been implicated in intra-Golgi transport through tethering coat protein complex I (COPI) vesicles. The p115-golgin tether is the best studied, and here we characterize the golgin-84-CASP tether. The vesicles bound by this tether were strikingly different from those bound by the p115-golgin tether in that they lacked members of the p24 family of putative cargo receptors and contained enzymes instead of anterograde cargo. Microinjected golgin-84 or CASP also inhibited Golgi-enzyme transport to the endoplasmic reticulum, further implicating this tether in retrograde transport. These and other golgins may modulate the flow patterns within the Golgi stack.
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Affiliation(s)
- Jörg Malsam
- Department of Cell Biology, Ludwig Institute for Cancer Research, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8002, USA
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105
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Zolov SN, Lupashin VV. Cog3p depletion blocks vesicle-mediated Golgi retrograde trafficking in HeLa cells. ACTA ACUST UNITED AC 2005; 168:747-59. [PMID: 15728195 PMCID: PMC2171815 DOI: 10.1083/jcb.200412003] [Citation(s) in RCA: 200] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The conserved oligomeric Golgi (COG) complex is an evolutionarily conserved multi-subunit protein complex that regulates membrane trafficking in eukaryotic cells. In this work we used short interfering RNA strategy to achieve an efficient knockdown (KD) of Cog3p in HeLa cells. For the first time, we have demonstrated that Cog3p depletion is accompanied by reduction in Cog1, 2, and 4 protein levels and by accumulation of COG complex-dependent (CCD) vesicles carrying v-SNAREs GS15 and GS28 and cis-Golgi glycoprotein GPP130. Some of these CCD vesicles appeared to be vesicular coat complex I (COPI) coated. A prolonged block in CCD vesicles tethering is accompanied by extensive fragmentation of the Golgi ribbon. Fragmented Golgi membranes maintained their juxtanuclear localization, cisternal organization and are competent for the anterograde trafficking of vesicular stomatitis virus G protein to the plasma membrane. In a contrast, Cog3p KD resulted in inhibition of retrograde trafficking of the Shiga toxin. Furthermore, the mammalian COG complex physically interacts with GS28 and COPI and specifically binds to isolated CCD vesicles.
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Affiliation(s)
- Sergey N Zolov
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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106
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Lee MCS, Miller EA, Goldberg J, Orci L, Schekman R. Bi-directional protein transport between the ER and Golgi. Annu Rev Cell Dev Biol 2005; 20:87-123. [PMID: 15473836 DOI: 10.1146/annurev.cellbio.20.010403.105307] [Citation(s) in RCA: 686] [Impact Index Per Article: 36.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The endoplasmic reticulum (ER) and the Golgi comprise the first two steps in protein secretion. Vesicular carriers mediate a continuous flux of proteins and lipids between these compartments, reflecting the transport of newly synthesized proteins out of the ER and the retrieval of escaped ER residents and vesicle machinery. Anterograde and retrograde transport is mediated by distinct sets of cytosolic coat proteins, the COPII and COPI coats, respectively, which act on the membrane to capture cargo proteins into nascent vesicles. We review the mechanisms that govern coat recruitment to the membrane, cargo capture into a transport vesicle, and accurate delivery to the target organelle.
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Affiliation(s)
- Marcus C S Lee
- Howard Hughes Medical Institute and Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA.
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107
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de Graffenried CL, Bertozzi CR. The roles of enzyme localisation and complex formation in glycan assembly within the Golgi apparatus. Curr Opin Cell Biol 2005; 16:356-63. [PMID: 15261667 DOI: 10.1016/j.ceb.2004.06.007] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Cell surface glycans govern numerous cell-cell interactions are therefore key determinants of multicellular biology. They originate from biosynthetic pathways comprising an assembly line of glycosyltransferases within the Golgi compartment. Although the mechanisms of Golgi enzyme localisation are still under debate, the distribution of these enzymes among the Golgi cisternae can dictate the overall structures produced by the cell. Fine-tuning of glycan biosynthetic pathways is further accomplished by specific associations among glycosyltransferases. Together, localisation and association govern the assembly of complex glycans and thereby regulate interactions at the cell surface.
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108
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He CY, Ho HH, Malsam J, Chalouni C, West CM, Ullu E, Toomre D, Warren G. Golgi duplication in Trypanosoma brucei. ACTA ACUST UNITED AC 2004; 165:313-21. [PMID: 15138289 PMCID: PMC2172185 DOI: 10.1083/jcb.200311076] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Duplication of the single Golgi apparatus in the protozoan parasite Trypanosoma brucei has been followed by tagging a putative Golgi enzyme and a matrix protein with variants of GFP. Video microscopy shows that the new Golgi appears de novo, near to the old Golgi, about two hours into the cell cycle and grows over a two-hour period until it is the same size as the old Golgi. Duplication of the endoplasmic reticulum (ER) export site follows exactly the same time course. Photobleaching experiments show that the new Golgi is not the exclusive product of the new ER export site. Rather, it is supplied, at least in part, by material directly from the old Golgi. Pharmacological experiments show that the site of the new Golgi and ER export is determined by the location of the new basal body.
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Affiliation(s)
- Cynthia Y He
- Department of Cell Biology, Ludwig Institute for Cancer Research, Yale University School of Medicine, 333 Cedar St., P.O. Box 208002, New Haven, CT 06520-8002, USA
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109
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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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110
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Fauré J, Stalder R, Borel C, Sobo K, Piguet V, Demaurex N, Gruenberg J, Trono D. ARF1 regulates Nef-induced CD4 degradation. Curr Biol 2004; 14:1056-64. [PMID: 15202998 DOI: 10.1016/j.cub.2004.06.021] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2003] [Revised: 03/03/2004] [Accepted: 03/30/2004] [Indexed: 10/26/2022]
Abstract
BACKGROUND The HIV Nef protein downregulates CD4 through sequential connection with clathrin-coated pits and the COP1 coatomer, resulting in accelerated endocytosis and lysosomal targeting. RESULTS Here we report that the small GTPase ARF1 controls the Nef-induced, COP-mediated late-endosomal targeting of CD4. We find that Nef binds ARF1 directly and can recruit the GTPase onto endosomal membranes. Furthermore, a complex comprising Nef, ARF1, and betaCOP can be immunoprecipitated from cells expressing the viral protein. Residues in a C-terminal loop of the viral protein facilitate both these interactions and the targeting of Nef and CD4 to acidic late endosomes, whereas other residues primarily involved in mediating CD4 endocytosis are dispensable for this process. Finally, a dominant-negative ARF1 mutant blocks the migration of the Nef-CD4 complex to lysosomes. CONCLUSIONS Our results support a model in which ARF1 is the immediate downstream partner of Nef for CD4 lysosomal targeting.
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Affiliation(s)
- Julien Fauré
- Department of Biochemistry, University of Geneva, 1211 Geneva, Switzerland
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111
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Kweon HS, Beznoussenko GV, Micaroni M, Polishchuk RS, Trucco A, Martella O, Di Giandomenico D, Marra P, Fusella A, Di Pentima A, Berger EG, Geerts WJC, Koster AJ, Burger KNJ, Luini A, Mironov AA. Golgi enzymes are enriched in perforated zones of golgi cisternae but are depleted in COPI vesicles. Mol Biol Cell 2004; 15:4710-24. [PMID: 15282336 PMCID: PMC519161 DOI: 10.1091/mbc.e03-12-0881] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In the most widely accepted version of the cisternal maturation/progression model of intra-Golgi transport, the polarity of the Golgi complex is maintained by retrograde transport of Golgi enzymes in COPI-coated vesicles. By analyzing enzyme localization in relation to the three-dimensional ultrastructure of the Golgi complex, we now observe that Golgi enzymes are depleted in COPI-coated buds and 50- to 60-nm COPI-dependent vesicles in a variety of different cell types. Instead, we find that Golgi enzymes are concentrated in the perforated zones of cisternal rims both in vivo and in a cell-free system. This lateral segregation of Golgi enzymes is detectable in some stacks during steady-state transport, but it was significantly prominent after blocking endoplasmic reticulum-to-Golgi transport. Delivery of transport carriers to the Golgi after the release of a transport block leads to a diminution in Golgi enzyme concentrations in perforated zones of cisternae. The exclusion of Golgi enzymes from COPI vesicles and their transport-dependent accumulation in perforated zones argues against the current vesicle-mediated version of the cisternal maturation/progression model.
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Affiliation(s)
- Hee-Seok Kweon
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, 66030 Santa Maria Imbaro (Chieti), Italy
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112
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Contreras I, Ortiz-Zapater E, Aniento F. Sorting signals in the cytosolic tail of membrane proteins involved in the interaction with plant ARF1 and coatomer. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 38:685-698. [PMID: 15125774 DOI: 10.1111/j.1365-313x.2004.02075.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In mammals and yeast, a cytosolic dilysine motif is critical for endoplasmic reticulum (ER) localization of type I membrane proteins. Retrograde transport of type I membrane proteins containing dilysine motifs at their cytoplasmic carboxy (C)-terminal tail involves the interaction of these motifs with the COPI coat. The C-terminal dilysine motif has also been shown to confer ER localization to type I membrane proteins in plant cells. Using in vitro binding assays, we have analyzed sorting motifs in the cytosolic tail of membrane proteins, which may be involved in the interaction with components of the COPI coat in plant cells. We show that a dilysine motif in the -3,-4 position (relative to the cytosolic C-terminus) recruits in a very specific manner all the subunits of the plant coatomer complex. Lysines cannot be replaced by arginines or histidines to bind plant coatomer. A diphenylalanine motif in the -7,-8 position, which by itself has a low ability to bind plant coatomer, shows a clear cooperativity with the dilysine motif. Both dilysine and diphenylalanine motifs are present in the cytosolic tail of several proteins of the p24 family of putative cargo receptors, which has several members in plant cells. The cytosolic tail of a plant p24 protein is shown to recruit not only coatomer but also ADP ribosylation factor 1 (ARF1), a process which depends on both dilysine and diphenylalanine motifs. ARF1 binding increases twofold upon treatment with brefeldin A (BFA) and is completely abolished upon treatment with GTPgammaS, suggesting that ARF1 can only interact with the cytosolic tail of p24 proteins in its GDP-bound form.
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Affiliation(s)
- Inmaculada Contreras
- Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Valencia, Avenida Vicente Andrés Estellés s/n, E-46100 Burjassot, Valencia, Spain
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113
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Abstract
Adaptors select cargo for inclusion into coated vesicles in the late secretory and endocytic pathways. Although originally there were thought to be just two adaptors, AP-1 and AP-2, it is now clear that there are many more: two additional adaptor complexes, AP-3 and AP-4, which might function independently of clathrin; a family of monomeric adaptors, the GGAs; and an ever-growing number of cargo-specific adaptors. The adaptors are targeted to the appropriate membrane at least in part by interacting with phosphoinositides, and, once on the membrane, they form interconnected networks to get different types of cargo into the same vesicle. Adaptors participate in trafficking pathways shared by all cells, and they are also used to generate specialized organelles and to influence cell fate during development.
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Affiliation(s)
- Margaret S Robinson
- University of Cambridge, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Hills Road, Cambridge, UK CB2 2XY.
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114
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Randazzo PA, Hirsch DS. Arf GAPs: multifunctional proteins that regulate membrane traffic and actin remodelling. Cell Signal 2004; 16:401-13. [PMID: 14709330 DOI: 10.1016/j.cellsig.2003.09.012] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The ADP-ribosylation factor (Arf) Arf GTPase-activating proteins (GAPs) are a family of proteins that induce hydrolysis of GTP bound to Arf. A conserved domain containing a zinc finger motif mediates catalysis. The substrate, Arf.GTP, affects membrane trafficking and actin remodelling. Consistent with activity as an Arf regulator, the Arf GAPs affect both of these pathways. However, the Arf GAPs are likely to have Arf-independent activities that contribute to their cellular functions. Structures of the Arf GAPs are diverse containing catalytic, protein-protein interaction and lipid interaction domains in addition to the Arf GAP domain. Some Arf GAPs have been identified and characterized on the basis of activities other than Arf GAP. Here, we describe the Arf GAP family, enzymology of some members of the Arf GAP family and known functions of the proteins. The results discussed illustrate roles for both Arf-dependent and -independent activities in the regulation of cellular architecture.
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Affiliation(s)
- Paul A Randazzo
- Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, Building. 37 Room 4118, Bethesda, MD 20892, USA.
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115
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van der Wouden JM, Maier O, van IJzendoorn SCD, Hoekstra D. Membrane dynamics and the regulation of epithelial cell polarity. INTERNATIONAL REVIEW OF CYTOLOGY 2004; 226:127-64. [PMID: 12921237 DOI: 10.1016/s0074-7696(03)01003-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Plasma membranes of epithelial cells consist of two domains, an apical and a basolateral domain, the surfaces of which differ in composition. The separation of these domains by a tight junction and the fact that specific transport pathways exist for intracellular communication between these domains and distinct intracellular compartments relevant to cell polarity development, have triggered extensive research on issues that focus on how the polarity is generated and maintained. Apart from proper assembly of tight junctions, their potential functioning as landmark for the transport machinery, cell-cell adhesion is obviously instrumental in barrier formation. In recent years, distinct endocytic compartments, defined as subapical compartment or common endosome, were shown to play a prominent role in regulating membrane trafficking to and from polarized membrane domains. Sorting devices remain to be determined but likely include distinct rab proteins, and evidence is accumulating to indicate that signaling events may direct intracellular membrane transport, intimately involved in the biogenesis and maintenance of polarized membrane domains and hence the development of cell polarity.
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Affiliation(s)
- Johanna M van der Wouden
- Department of Membrane Cell Biology, University of Groningen, Antonius Deusinglaan 1, 9713AV Groningen, The Netherlands
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116
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Affiliation(s)
- Joost C M Holthuis
- Department of Membrane Enzymology, Institute of Biomembranes, Padualaan 8, 3584 CH Utrecht, The Netherlands
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117
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Bäck N, Litonius E, Mains RE, Eipper BA. Fluoride causes reversible dispersal of Golgi cisternae and matrix in neuroendocrine cells. Eur J Cell Biol 2004; 83:389-402. [PMID: 15506563 DOI: 10.1078/0171-9335-00405] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A role for heterotrimeric G proteins in the regulation of Golgi function and formation of secretory granules is generally accepted. We set out to study the effect of activation of heterotrimeric G proteins by aluminum fluoride on secretory granule formation in AtT-20 corticotropic tumor cells and in melanotrophs from the rat pituitary. In AtT-20 cells, treatment with aluminum fluoride or fluoride alone for 60 min induced complete dispersal of Golgi, ER-Golgi intermediate compartment and Golgi matrix markers, while betaCOP immunoreactiviy retained a juxtanuclear position and TGN38 was unaffected. Electron microscopy showed compression of Golgi cisternae followed by conversion of the Golgi stacks into clusters of tubular and vesicular elements. In the melanotroph of the rat pituitary a similar compression of Golgi cisternae was observed, followed by a progressive loss of cisternae from the stacks. As shown in other cells, brefeldin A induced redistribution of the Golgi matrix protein GM130 to punctate structures in the cytoplasm in AtT-20 cells, while mannosidase II immunoreactivity was completely dispersed. Fluoride induced a complete dispersal of mannosidase II and GM130 immunoreactivity. The effect of fluoride was fully reversible with reestablishment of normal mannosidase II and GM130 immunoreactivity within 2 h. After 1 h of recovery, showing varying stages of reassembly, the patterns of mannosidase II and GM130 immunoreactivity were identical in individual cells, indicating that Golgi matrix and cisternae reassemble with similar kinetics during recovery from fluoride treatment. Instead of a specific aluminum fluoride effect on secretory granule formation in the trans-Golgi network, we thus observe a unique form of Golgi dispersal induced by fluoride alone, possibly via its action as a phosphatase inhibitor.
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Affiliation(s)
- Nils Bäck
- Department of Anatomy, Institute of Biomedicine, Biomedicum Helsinki, University of Helsinki, Finland.
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118
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Andag U, Schmitt HD. Dsl1p, an Essential Component of the Golgi-Endoplasmic Reticulum Retrieval System in Yeast, Uses the Same Sequence Motif to Interact with Different Subunits of the COPI Vesicle Coat. J Biol Chem 2003; 278:51722-34. [PMID: 14504276 DOI: 10.1074/jbc.m308740200] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dsl1p is required for Golgi-endoplasmic reticulum (ER) retrograde transport in yeast. It interacts with the ER resident protein Tip20p and with delta-COP, a subunit of coatomer, the coat complex of COPI vesicles. To test the significance of these interactions, we mapped the different binding sites and created mutant versions of Dsl1p and delta-COP, which are unable to bind directly to each other. Three domains were identified in Dsl1p: a Tip20p binding region within the N-terminal 200 residues, a highly acidic region in the center of Dsl1p containing crucial tryptophan residues that is required for binding to delta-COP and essential for viability, and an evolutionarily well conserved domain at the C terminus. Most importantly, Dsl1p uses the same central acidic domain to interact not only with delta-COP but also with alpha-COP. Strong interaction with alpha-COP requires the presence of comparable amounts of epsilon-COP or beta' -COP. Thus, the binding characteristics of Dsl1p resemble those of many accessory factors of the clathrin coat. They interact with different layers of the vesicle coat by using tandemly arranged sequence motifs, some of which have dual specificity.
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Affiliation(s)
- Uwe Andag
- Department of Molecular Genetics, Max Planck Institute for Biophysical Chemistry, D-37070 Goettingen, Germany
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119
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Sato K, Nakano A. Reconstitution of coat protein complex II (COPII) vesicle formation from cargo-reconstituted proteoliposomes reveals the potential role of GTP hydrolysis by Sar1p in protein sorting. J Biol Chem 2003; 279:1330-5. [PMID: 14627716 DOI: 10.1074/jbc.c300457200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Secretory proteins are transported from the endoplasmic reticulum (ER) in vesicles coated with coat protein complex II (COPII). To investigate the molecular mechanism of protein sorting into COPII vesicles, we have developed an in vitro budding reaction comprising purified coat proteins and cargo reconstituted proteolipsomes. Emp47p, a type-I membrane protein, is specifically required for the transport of an integral membrane protein, Emp46p, from the ER. Recombinant Emp46/47p proteins and the ER resident protein Ufe1p were reconstituted into liposomes whose composition resembles yeast ER membranes. When the proteoliposomes were mixed with COPII proteins and GMP-PNP, Emp46/47p, but not Ufe1p, were concentrated into COPII vesicles. We also show here that reconstituted Emp47p accelerates the GTP hydrolysis by Sar1p as stimulated by its GTPase-activating protein, Sec23/24p, both of which are components of the COPII coat. Furthermore, this GTP hydrolysis decreases the error of cargo sorting. We suggest that GTP hydrolysis by Sar1p promotes exclusion of improper proteins from COPII vesicles.
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Affiliation(s)
- Ken Sato
- Molecular Membrane Biology Laboratory, RIKEN Discovery Research Institute, Japan.
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120
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Elsner M, Hashimoto H, Simpson JC, Cassel D, Nilsson T, Weiss M. Spatiotemporal dynamics of the COPI vesicle machinery. EMBO Rep 2003; 4:1000-4. [PMID: 14502225 PMCID: PMC1326400 DOI: 10.1038/sj.embor.embor942] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2003] [Revised: 08/19/2003] [Accepted: 08/19/2003] [Indexed: 11/09/2022] Open
Abstract
Assembly of the coat protein I (COPI) vesicle coat is controlled by the small GTPase ADP ribosylation factor 1 (ARF1) and its GTPase-activating protein, ARFGAP1. Here, we investigate the diffusional behaviours of coatomer, the main component of the coat, and also those of ARF1 and ARFGAP1. Using fluorescence-correlation spectroscopy, we found that most ARF1 and ARFGAP1 molecules are highly mobile in the cytosol (diffusion constant D approximately equal to 15 microm(2) s(-1)), whereas coatomer diffuses 5-10 times more slowly than expected (D approximately equal to 1 microm(2) s(-1)). This slow diffusion causes diffusion-limited binding kinetics to Golgi membranes, which, in FRAP (fluorescence recovery after photobleaching) experiments, translates into a twofold slower binding rate. The addition of aluminium fluoride locks coatomer onto Golgi membranes and also decreases the binding kinetics of both ARF1 and ARFGAP1, suggesting that these proteins function in concert to mediate sorting and vesicle formation.
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Affiliation(s)
- Markus Elsner
- Cell Biology and Cell Biophysics Programme, EMBL,
Meyerhofstrasse 1, D-69117 Heidelberg,
Germany
| | - Hitoshi Hashimoto
- Cell Biology and Cell Biophysics Programme, EMBL,
Meyerhofstrasse 1, D-69117 Heidelberg,
Germany
| | - Jeremy C. Simpson
- Cell Biology and Cell Biophysics Programme, EMBL,
Meyerhofstrasse 1, D-69117 Heidelberg,
Germany
| | - Dan Cassel
- Department of Biology, Technion,
Haifa 32000, Israel
| | - Tommy Nilsson
- Cell Biology and Cell Biophysics Programme, EMBL,
Meyerhofstrasse 1, D-69117 Heidelberg,
Germany
| | - Matthias Weiss
- Cell Biology and Cell Biophysics Programme, EMBL,
Meyerhofstrasse 1, D-69117 Heidelberg,
Germany
- Physics Department, MEMPHYS Center for
Biomembrane Physics, University of Southern Denmark, Campusvej 55,
DK-5230 Odense M, Denmark
- Tel: +45 6550 3686; Fax: +45 6615 8760;
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121
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van Vliet C, Thomas EC, Merino-Trigo A, Teasdale RD, Gleeson PA. Intracellular sorting and transport of proteins. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2003; 83:1-45. [PMID: 12757749 DOI: 10.1016/s0079-6107(03)00019-1] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The secretory and endocytic pathways of eukaryotic organelles consist of multiple compartments, each with a unique set of proteins and lipids. Specific transport mechanisms are required to direct molecules to defined locations and to ensure that the identity, and hence function, of individual compartments are maintained. The localisation of proteins to specific membranes is complex and involves multiple interactions. The recent dramatic advances in understanding the molecular mechanisms of membrane transport has been due to the application of a multi-disciplinary approach, integrating membrane biology, genetics, imaging, protein and lipid biochemistry and structural biology. The aim of this review is to summarise the general principles of protein sorting in the secretory and endocytic pathways and to highlight the dynamic nature of these processes. The molecular mechanisms involved in this transport along the secretory and endocytic pathways are discussed along with the signals responsible for targeting proteins to different intracellular locations.
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Affiliation(s)
- Catherine van Vliet
- The Russell Grimwade School of Biochemistry and Molecular Biology, University of Melbourne, Victoria 3010, Melbourne, Australia
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122
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Cabrera M, Muñiz M, Hidalgo J, Vega L, Martín ME, Velasco A. The retrieval function of the KDEL receptor requires PKA phosphorylation of its C-terminus. Mol Biol Cell 2003; 14:4114-25. [PMID: 14517323 PMCID: PMC207004 DOI: 10.1091/mbc.e03-04-0194] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The KDEL receptor is a Golgi/intermediate compartment-located integral membrane protein that carries out the retrieval of escaped ER proteins bearing a C-terminal KDEL sequence. This occurs throughout retrograde traffic mediated by COPI-coated transport carriers. The role of the C-terminal cytoplasmic domain of the KDEL receptor in this process has been investigated. Deletion of this domain did not affect receptor subcellular localization although cells expressing this truncated form of the receptor failed to retain KDEL ligands intracellularly. Permeabilized cells incubated with ATP and GTP exhibited tubular processes-mediated redistribution from the Golgi area to the ER of the wild-type receptor, whereas the truncated form lacking the C-terminal domain remained concentrated in the Golgi. As revealed with a peptide-binding assay, this domain did not interact with both coatomer and ARF-GAP unless serine 209 was mutated to aspartic acid. In contrast, alanine replacement of serine 209 inhibited coatomer/ARF-GAP recruitment, receptor redistribution into the ER, and intracellular retention of KDEL ligands. Serine 209 was phosphorylated by both cytosolic and recombinant protein kinase A (PKA) catalytic subunit. Inhibition of endogenous PKA activity with H89 blocked Golgi-ER transport of the native receptor but did not affect redistribution to the ER of a mutated form bearing aspartic acid at position 209. We conclude that PKA phosphorylation of serine 209 is required for the retrograde transport of the KDEL receptor from the Golgi complex to the ER from which the retrieval of proteins bearing the KDEL signal depends.
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Affiliation(s)
- Margarita Cabrera
- Department of Cell Biology, Faculty of Biology, University of Seville, 41012 Seville, Spain
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123
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Abstract
The molecular machines that drive protein transport through the secretory pathway function exert their activities on the surfaces of membrane bilayers. It is now clear that the various lipid components of these bilayers play direct and versatile roles in modulating the activity of proteins that either themselves constitute core components of the membrane trafficking machinery, or represent proteins that regulate such core components.
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Affiliation(s)
- Vytas A Bankaitis
- Department of Cell and Developmental Biology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7090, USA.
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124
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Abstract
Arf GTP-binding proteins regulate membrane traffic and actin remodeling. Similar to other GTP-binding proteins, a complex of Arf-GTP with an effector protein mediates Arf function. Arf interacts with at least three qualitatively different types of effectors. First, it interacts with structural proteins, the vesicle coat proteins. The second type of effector is lipid-metabolizing enzymes, and the third comprises those proteins that bind to Arf-GTP but whose biochemical or biological functions are not yet clearly defined. Arf interacts with two other families of proteins, the exchange factors and the GTPase-activating proteins. Recent work examining the functional relationships among the diverse Arf interactors has led to reconsideration of the prevailing paradigms for Arf action.
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Affiliation(s)
- Zhongzhen Nie
- Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, Building 37, Room 4118, Bethesda, MD 20892, USA
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125
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Shimada O, Hara-Kuge S, Yamashita K, Tosaka-Shimada H, Yanchao L, Einan L, Atsumi S, Ishikawa H. Localization of VIP36 in the post-Golgi secretory pathway also of rat parotid acinar cells. J Histochem Cytochem 2003; 51:1057-63. [PMID: 12871987 DOI: 10.1177/002215540305100809] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
VIP36 (36-kD vesicular integral membrane protein), originally purified from Madin-Darby canine kidney (MDCK) epithelial cells, belongs to a family of animal lectins and may act as a cargo receptor. To understand its role in secretory processes, we performed morphological analysis of the rat parotid gland. Immunoelectron microscopy provided evidence that endogenous VIP36 is localized in the trans-Golgi network, on immature granules, and on mature secretory granules in acinar cells. Double-staining immunofluorescence experiments confirmed that VIP36 and amylase co-localized in the apical regions of the acinar cells. This is the first study to demonstrate that endogenous VIP36 is involved in the post-Golgi secretory pathway, suggesting that VIP36 plays a role in trafficking and sorting of secretory and/or membrane proteins during granule formation.
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Affiliation(s)
- Osamu Shimada
- Department of Anatomy, Yamanashi University School of Medicine, Yamanashi, Japan.
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126
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Abstract
COP I and COP II coat proteins direct protein and membrane trafficking in between early compartments of the secretory pathway in eukaryotic cells. These coat proteins perform the dual, essential tasks of selecting appropriate cargo proteins and deforming the lipid bilayer of appropriate donor membranes into buds and vesicles. COP II proteins are required for selective export of newly synthesized proteins from the endoplasmic reticulum (ER). COP I proteins mediate a retrograde transport pathway that selectively recycles proteins from the cis-Golgi complex to the ER. Additionally, COP I coat proteins have complex functions in intra-Golgi trafficking and in maintaining the normal structure of the mammalian interphase Golgi complex.
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Affiliation(s)
- Rainer Duden
- Cambridge Institute for Medical Research, Department of Clinical Biochemistry, University of Cambridge, Hills Road, Cambridge CB2 2XY, UK.
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127
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Elsner M, Hashimoto H, Nilsson T. Cisternal maturation and vesicle transport: join the band wagon! (Review). Mol Membr Biol 2003; 20:221-9. [PMID: 12893530 DOI: 10.1080/0968768031000114024] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
'No cellular organelle has been the subject of as many, as long-lasting or as diverse polemics as the Golgi apparatus'. This statement was made by Whaley almost 30 years ago in the book The Golgi Apparatus and still holds true today, perhaps more then ever. Why is this? How come something as mundane as a series of intracellular membrane bound structures continues to fascinate and captivate a large section of the cell biology community? One simple reason (putting polemics aside) is that the secretory pathway appears deceptively simple. Once probed, however, it has a persistent habit of developing into an enigma. Is one then not closer than 30 years ago? In a sense yes, in that one has more components and a better understanding of inherent membrane dynamics, but it is still not known how newly synthesized proteins and lipids make their way from the ER to the plasma membrane. Is it by vesicles, cisternal carriers or transient tubular connections? It has also been learned that newly synthesized proteins are segregated away from the resident components throughout the pathway, but not how. Do coat proteins hold the key? It is understood that the cytoskeleton is important, but not really why. It is known that each Golgi stack is a fully functional unit, but not why stacks are connected laterally into a large ribbon (the Golgi apparatus). This review focuses on how proteins make their way through the pathway, a basic question that remains to be answered.
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Affiliation(s)
- Markus Elsner
- Cell Biology Programme, EMBL, Meyerhofstrasse 1, D-690117, Heidelberg, Germany
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128
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Feng Y, Yu S, Lasell TKR, Jadhav AP, Macia E, Chardin P, Melancon P, Roth M, Mitchison T, Kirchhausen T. Exo1: a new chemical inhibitor of the exocytic pathway. Proc Natl Acad Sci U S A 2003; 100:6469-74. [PMID: 12738886 PMCID: PMC164470 DOI: 10.1073/pnas.0631766100] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
A phenotypic screen was used to search for drug-like molecules that can interfere with specific steps in membrane traffic. 2-(4-Fluorobenzoylamino)-benzoic acid methyl ester (Exo1), identified in this screen, induces a rapid collapse of the Golgi to the endoplasmic reticulum, thus acutely inhibiting the traffic emanating from the endoplasmic reticulum. Like Brefeldin A (BFA), Exo1 induces the rapid release of ADP-ribosylation factor (ARF) 1 from Golgi membranes but has less effect on the organization of the trans-Golgi network. Our data indicate that Exo1 acts by a different mechanism from BFA. Unlike BFA, Exo1 does not induce the ADP-ribosylation of CtBP/Bars50 and does not interfere with the activity of guanine nucleotide exchange factors specific for Golgi-based ARFs. Thus, Exo1 allows the fatty acid exchange activity of Bars50 to be distinguished from ARF1 activity in the control of Golgi tubulation.
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Affiliation(s)
- Yan Feng
- Institute of Chemistry and Cell Biology, Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
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129
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Sousa VL, Brito C, Costa T, Lanoix J, Nilsson T, Costa J. Importance of Cys, Gln, and Tyr from the transmembrane domain of human alpha 3/4 fucosyltransferase III for its localization and sorting in the Golgi of baby hamster kidney cells. J Biol Chem 2003; 278:7624-9. [PMID: 12493760 DOI: 10.1074/jbc.m209325200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human fucosyltransferase III (EC ) (FT3wt) is localized in the Golgi of baby hamster kidney cells and synthesizes Lewis determinants associated with cell adhesion events. Replacement of the amino acid residues from the transmembrane domain (TM) Cys-16, Gln-23, Cys-29, and Tyr-33 by Leu (FT3np) caused a shift in enzyme localization to the plasma membrane. The mislocalization caused a dramatic decrease in the amount of biosynthetic products of FT3wt, the Lewis determinants. Determination of the expression levels on the surface with mutants of the enzyme, where one, two, or three of these residues were replaced by Leu, suggested that Cys from the TM was required for the localization of FT3 in the Golgi. Furthermore, Cys-23 and Cys-29 mediated the formation of disulfide-bonded dimers but not higher molecular weight oligomers. In vitro reconstitution of intra-Golgi transport showed that FT3wt was incorporated into coatomer protein (COP) I vesicles, contrary to FT3np. These data suggested that Cys, Gln, and Tyr residues are important for FT3wt sorting into the transport vesicles possibly due to interactions with other membrane proteins.
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Affiliation(s)
- Victor L Sousa
- Laboratory of Glycobiology, Instituto de Tecnologia Quimica e Biológica, Apartado 127, 2780 Oeiras, Portugal
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130
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Abstract
Resident proteins of the exocytic pathway are maintained at various levels through coatomer protein I (COPI)-mediated recycling. Sorting of cargo by COPI requires GTP hydrolysis by ADP-ribosylation factor 1 (ARF-1). This small GTPase recruits coatomer onto Golgi membranes and upon hydrolysis, is thought to release coatomer back into the cytosol. This step requires the activating protein, ARFGAP1. By coupling sorting to a cargo-induced sequestering of ARFGAP1, we have formulated a kinetic proof-reading model that explains how a GTP hydrolysis-driven coat release can yield an active sorting event. The sorting scheme predicts a dependency on the amount of ARFGAP1 and explains the recent experimental findings that ARF-1 and COPI detach with different time constants from the Golgi membrane in vivo.
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Affiliation(s)
- Matthias Weiss
- Cell Biology and Cell Biophysics Programme, EMBL, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
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131
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Otte S, Barlowe C. The Erv41p-Erv46p complex: multiple export signals are required in trans for COPII-dependent transport from the ER. EMBO J 2002; 21:6095-104. [PMID: 12426381 PMCID: PMC137190 DOI: 10.1093/emboj/cdf598] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Erv41p and Erv46p form an integral membrane protein complex that cycles between the endoplasmic reticulum (ER) and Golgi. Both proteins contain a large lumenal domain and short N- and C-terminal tail sequences exposed to the cytosol. The coat protein complex II (COPII) packages the Erv41p-Erv46p complex into ER-derived vesicles for delivery to the Golgi. We determined signals in the Erv41p-Erv46p complex that are required for COPII-dependent export from the ER. Mutants lacking the Erv41p or Erv46p C-terminus accumulated in the ER and were not packaged efficiently into vesicles. We identified an isoleucine-leucine sequence in the Erv41p tail that was required for COPII binding and inclusion of the complex into vesicles. This signal was sufficient for COPII binding but not for ER export. The Erv46p tail contains a phenylalanine-tyrosine sequence required together with the isoleucine-leucine signal in Erv41p for export of the complex. Surprisingly, Erv41p- Erv46p tail-swapped chimeras were not exported from the ER, indicating that signals in both the Erv41p and the Erv46p tail sequences are required in a specific orientation for efficient packaging of the Erv41p-Erv46p complex.
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Affiliation(s)
| | - Charles Barlowe
- Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755, USA
Corresponding author e-mail:
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132
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Beznoussenko GV, Mironov AA. Models of intracellular transport and evolution of the Golgi complex. THE ANATOMICAL RECORD 2002; 268:226-38. [PMID: 12382321 DOI: 10.1002/ar.10157] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We have performed a systematic analysis of models explaining the mechanisms of the intracellular biosecretory transport. The models assessed include not only those based on one mechanism (the dissociation model (and its individual case, the vesicular model), the progression model (and its individual cases, the cisterna maturation/progression and the carrier maturation models), and the lateral diffusion model (and its individual case, the bolus model), but also combined models of transport (the percolating-vesicles model and the synthetic model), including several transport mechanisms. Most of these models are not able to explain recent data on the evolution of genes involved in intracellular transport and Golgi evolution. The carrier maturation model proposing that fusion of the large cargo domain with the distal (closer to the plasmalemma) compartment precedes fission of the domain from the proximal compartment exhibits the best performance in correlation with the available information on evolution of the biosecretory pathway.
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Affiliation(s)
- Galina V Beznoussenko
- Istituto di Ricerche Farmacologiche Mario Negri, Consorzio Mario Negri Sud, Department of Cell Biology and Oncology, Santa Maria Imbaro (Chieti), Italy
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133
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Antonny B. Contrôle de l’assemblage des manteaux protéiques COP par les petites protéines G Arf et Sar. Med Sci (Paris) 2002. [DOI: 10.1051/medsci/200218101012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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134
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Yang JS, Lee SY, Gao M, Bourgoin S, Randazzo PA, Premont RT, Hsu VW. ARFGAP1 promotes the formation of COPI vesicles, suggesting function as a component of the coat. J Cell Biol 2002; 159:69-78. [PMID: 12379802 PMCID: PMC2173491 DOI: 10.1083/jcb.200206015] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The role of GTPase-activating protein (GAP) that deactivates ADP-ribosylation factor 1 (ARF1) during the formation of coat protein I (COPI) vesicles has been unclear. GAP is originally thought to antagonize vesicle formation by triggering uncoating, but later studies suggest that GAP promotes cargo sorting, a process that occurs during vesicle formation. Recent models have attempted to reconcile these seemingly contradictory roles by suggesting that cargo proteins suppress GAP activity during vesicle formation, but whether GAP truly antagonizes coat recruitment in this process has not been assessed directly. We have reconstituted the formation of COPI vesicles by incubating Golgi membrane with purified soluble components, and find that ARFGAP1 in the presence of GTP promotes vesicle formation and cargo sorting. Moreover, the presence of GTPgammaS not only blocks vesicle uncoating but also vesicle formation by preventing the proper recruitment of GAP to nascent vesicles. Elucidating how GAP functions in vesicle formation, we find that the level of GAP on the reconstituted vesicles is at least as abundant as COPI and that GAP binds directly to the dilysine motif of cargo proteins. Collectively, these findings suggest that ARFGAP1 promotes vesicle formation by functioning as a component of the COPI coat.
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Affiliation(s)
- Jia-Shu Yang
- Division of Rheumatology, Immunology, and Allergy, Brigham and Women's Hospital, and Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
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135
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Abstract
Since the first description of the Golgi in 1898, key issues regarding this organelle have remained contentious among cell biologists. Resolving these complex debates, which revolve around Golgi structure-function relationships, is prerequisite to understanding how the Golgi fulfils its role as the central organelle and sorting station of the mammalian secretory pathway.
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Affiliation(s)
- Brad J Marsh
- Boulder Laboratory for 3D EM, Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309, USA
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136
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Abstract
Understanding the biosynthetic pathways involved in cellular transport is an important issue in cell biology. More than a hundred years after the discovery of the Golgi apparatus, we still do not understand the regulation of vesicular transport to, within and from the Golgi apparatus. Recently, however, it has become clear that cargo might not simply be a passive passenger, and that ADP-ribosylation factor (ARF) GAPs are not only GTPase-activating proteins for ARF, but might play crucial roles in regulating coat protein complex I vesicle formation.
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Affiliation(s)
- Anne Spang
- Friedrich Miescher Laboratorium, Max-Planck-Gesellschaft, Spemannstrasse 39 D-72076 Tübingen, Germany.
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137
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Abstract
Does the Golgi apparatus proliferate by adding new material to a permanent template, or do Golgi structures form de novo by a process of self-organization? Recent work suggests that the Golgi is capable of forming de novo.
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138
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Abstract
Most models put forward to explain cellular processes do not stand the test of time. The 'lucky' few that are able to survive extensive experimental tests and peer critique may eventually become dogmas or paradigms. When this happens, the amount of experimental data required to overturn the paradigm is extensive. To some, such inertia may seem prohibitive to scientific progress but rather, in our opinion, this helps to maintain a degree of coherence. It is needed so that experiments and interpretations may be conducted within relatively safe boundaries. In the field of protein transport in the secretory pathway, we have enjoyed a relatively stable and productive period for quite some time (more than 30 years!). It is only very recently that the field has entered into a phase where all bets seem to be off. As in any paradigm shift, the accumulation of experimental observations inconsistent with the old dogma eventually reached a critical point. As we 'reluctantly' dispense with the long-standing paradigm of forward vesicular transport, we face a time that is bound to be trying as well as exciting.
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Affiliation(s)
- Brian Storrie
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0308, USA.
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139
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Abstract
Intracellular traffic is mediated by vesicular/tubular carriers. The carriers are formed by the activity of cytosolic coat proteins that are recruited to their target membranes and deform these membranes into buds and vesicles. Specific interactions between recruited coat subunits and short peptide sequences (transport motifs) on cargo proteins direct the incorporation of cargo into budded vesicles. Here, we focus on cargo selection reactions mediated by COPII and AP-2/clathrin vesicle coat complexes to explore common mechanisms by which coat assembly support localized and selective cargo sorting. Recent findings suggest that multiple, low-affinity interactions are employed in a cooperative manner to support coat assembly and enable cargo recognition. Thus low-binding affinities between coat subunits and transport motifs are transiently transformed into high-avidity, multivalent and selective interactions at vesicle bud sites. The temporal and regulated nature of the interactions provide the key to cargo selection.
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Affiliation(s)
- Meir Aridor
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, 3500 Terrace St., Pittsburgh, PA 15261, USA. aridor+@pitt.edu
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140
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Arvan P, Zhang BY, Feng L, Liu M, Kuliawat R. Lumenal protein multimerization in the distal secretory pathway/secretory granules. Curr Opin Cell Biol 2002; 14:448-53. [PMID: 12383795 DOI: 10.1016/s0955-0674(02)00344-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Differences in protein solubility appear to play an important role in lumenal protein trafficking through Golgi/post-Golgi compartments. Recent advances indicate that multimeric protein assembly is one of the factors regulating the efficiency of protein storage within secretory granules, by mechanisms that, with slight modification, might be considered to represent the culmination of a process of Golgi cisternal maturation.
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Affiliation(s)
- Peter Arvan
- Division of Endocrinology/Diabetes Center, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
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141
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Rein U, Andag U, Duden R, Schmitt HD, Spang A. ARF-GAP-mediated interaction between the ER-Golgi v-SNAREs and the COPI coat. J Cell Biol 2002; 157:395-404. [PMID: 11970962 PMCID: PMC2173288 DOI: 10.1083/jcb.200112092] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
In eukaryotic cells, secretion is achieved by vesicular transport. Fusion of such vesicles with the correct target compartment relies on SNARE proteins on both vesicle (v-SNARE) and the target membranes (t-SNARE). At present it is not clear how v-SNAREs are incorporated into transport vesicles. Here, we show that binding of ADP-ribosylation factor (ARF)-GTPase-activating protein (GAP) to ER-Golgi v-SNAREs is an essential step for recruitment of Arf1p and coatomer, proteins that together form the COPI coat. ARF-GAP acts catalytically to recruit COPI components. Inclusion of v-SNAREs into COPI vesicles could be mediated by direct interaction with the coat. The mechanisms by which v-SNAREs interact with COPI and COPII coat proteins seem to be different and may play a key role in determining specificity in vesicle budding.
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Affiliation(s)
- Ulrike Rein
- Friedrich Miescher Laboratory, Max Planck Society, D-72076 Tübingen, Germany
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142
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Abstract
Recent studies have questioned the idea that the Golgi complex is a stable organelle with a unique identity through which secretory cargo is transported by vesicles. Instead, it is proposed that Golgi apparatus proteins continuously recycle via the endoplasmic reticulum by vesicle transport, whereas cargo molecules remain in maturing cisternal structures. Rather than forming a rigid matrix, structural Golgi proteins might be highly dynamic and recycle via the cytoplasm. I will discuss the evidence for these claims and consider whether or not they really disprove older ideas on how the Golgi apparatus is structured and performs its function.
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143
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A maturing model. Nat Rev Mol Cell Biol 2002. [DOI: 10.1038/nrm742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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144
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Abstract
The role of vesicles in cargo transport through the Golgi apparatus has been controversial. Large forms of cargo such as protein aggregates are thought to progress through the Golgi stack by a process of cisternal maturation, balanced by a return flow of Golgi resident proteins in COPI-coated vesicles. However, whether this is the primary role of vesicles, or whether they also serve to transport small cargo molecules in a forward direction has been debated. Two papers (Martínez-Menárguez et al., 2001; Mironov et al., 2001, this issue) use sophisticated light and electron microscopy to provide evidence that the vesicular stomatitis virus membrane glycoprotein (VSV G)* is largely excluded from vesicles in vivo, and does not move between cisternae, whereas resident Golgi enzymes freely enter vesicles as predicted by the cisternal maturation model. Both papers conclude that vesicles are likely to play only a minor role in the anterograde transport of cargo through the Golgi apparatus in mammalian tissue culture cells.
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Affiliation(s)
- H R Pelham
- Laboratory of Molecular Biology, Medical Research Council, Hills Road, Cambridge CB2 2QH, UK.
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