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Dabsan S, Twito G, Biadsy S, Igbaria A. Less is better: various means to reduce protein load in the endoplasmic reticulum. FEBS J 2024. [PMID: 38865586 DOI: 10.1111/febs.17201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 04/08/2024] [Accepted: 06/05/2024] [Indexed: 06/14/2024]
Abstract
The endoplasmic reticulum (ER) is an important organelle that controls the intracellular and extracellular environments. The ER is responsible for folding almost one-third of the total protein population in the eukaryotic cell. Disruption of ER-protein folding is associated with numerous human diseases, including metabolic disorders, neurodegenerative diseases, and cancer. During ER perturbations, the cells deploy various mechanisms to increase the ER-folding capacity and reduce ER-protein load by minimizing the number of substrates entering the ER to regain homeostasis. These mechanisms include signaling pathways, degradation mechanisms, and other processes that mediate the reflux of ER content to the cytosol. In this review, we will discuss the recent discoveries of five different ER quality control mechanisms, including the unfolded protein response (UPR), ER-associated-degradation (ERAD), pre-emptive quality control, ER-phagy and ER to cytosol signaling (ERCYS). We will discuss the roles of these processes in decreasing ER-protein load and inter-mechanism crosstalk.
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Affiliation(s)
- Salam Dabsan
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Gal Twito
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Suma Biadsy
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Aeid Igbaria
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
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2
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Bravo-Plaza I, Tagua VG, Arst HN, Alonso A, Pinar M, Monterroso B, Galindo A, Peñalva MA. The Uso1 globular head interacts with SNAREs to maintain viability even in the absence of the coiled-coil domain. eLife 2023; 12:e85079. [PMID: 37249218 PMCID: PMC10275640 DOI: 10.7554/elife.85079] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 05/29/2023] [Indexed: 05/31/2023] Open
Abstract
Uso1/p115 and RAB1 tether ER-derived vesicles to the Golgi. Uso1/p115 contains a globular-head-domain (GHD), a coiled-coil (CC) mediating dimerization/tethering, and a C-terminal region (CTR) interacting with golgins. Uso1/p115 is recruited to vesicles by RAB1. Genetic studies placed Uso1 paradoxically acting upstream of, or in conjunction with RAB1 (Sapperstein et al., 1996). We selected two missense mutations in uso1 resulting in E6K and G540S in the GHD that rescued lethality of rab1-deficient Aspergillus nidulans. The mutations are phenotypically additive, their combination suppressing the complete absence of RAB1, which emphasizes the key physiological role of the GHD. In living hyphae Uso1 recurs on puncta (60 s half-life) colocalizing partially with the Golgi markers RAB1, Sed5, and GeaA/Gea1/Gea2, and totally with the retrograde cargo receptor Rer1, consistent with Uso1 dwelling in a very early Golgi compartment from which ER residents reaching the Golgi recycle back to the ER. Localization of Uso1, but not of Uso1E6K/G540S, to puncta is abolished by compromising RAB1 function, indicating that E6K/G540S creates interactions bypassing RAB1. That Uso1 delocalization correlates with a decrease in the number of Gea1 cisternae supports that Uso1-and-Rer1-containing puncta are where the protein exerts its physiological role. In S-tag-coprecipitation experiments, Uso1 is an associate of the Sed5/Bos1/Bet1/Sec22 SNARE complex zippering vesicles with the Golgi, with Uso1E6K/G540S showing a stronger association. Using purified proteins, we show that Bos1 and Bet1 bind the Uso1 GHD directly. However, Bet1 is a strong E6K/G540S-independent binder, whereas Bos1 is weaker but becomes as strong as Bet1 when the GHD carries E6K/G540S. G540S alone markedly increases GHD binding to Bos1, whereas E6K causes a weaker effect, correlating with their phenotypic contributions. AlphaFold2 predicts that G540S increases the binding of the GHD to the Bos1 Habc domain. In contrast, E6K lies in an N-terminal, potentially alpha-helical, region that sensitive genetic tests indicate as required for full Uso1 function. Remarkably, this region is at the end of the GHD basket opposite to the end predicted to interact with Bos1. We show that, unlike dimeric full-length and CTR∆ Uso1 proteins, the GHD lacking the CC/CTR dimerization domain, whether originating from bacteria or Aspergillus extracts and irrespective of whether it carries or not E6K/G540S, would appear to be monomeric. With the finding that overexpression of E6K/G540S and wild-type GHD complement uso1∆, our data indicate that the GHD monomer is capable of providing, at least partially, the essential Uso1 functions, and that long-range tethering activity is dispensable. Rather, these findings strongly suggest that the essential role of Uso1 involves the regulation of SNAREs.
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Affiliation(s)
- Ignacio Bravo-Plaza
- Department of Cellular and Molecular Biology, CSIC Centro de Investigaciones BiológicasMadridSpain
| | - Victor G Tagua
- Instituto de Tecnologías Biomédicas, Hospital Universitario Nuestra Señora de CandelariaSanta Cruz de TenerifeSpain
| | - Herbert N Arst
- Department of Infectious Diseases, Faculty of Medicine, Flowers Building, Imperial CollegeLondonUnited Kingdom
| | - Ana Alonso
- Department of Cellular and Molecular Biology, CSIC Centro de Investigaciones BiológicasMadridSpain
| | - Mario Pinar
- Department of Cellular and Molecular Biology, CSIC Centro de Investigaciones BiológicasMadridSpain
| | - Begoña Monterroso
- Department of Structural and Chemical Biology, CSIC Centro de Investigaciones BiológicasMadridSpain
| | - Antonio Galindo
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Francis Crick AvenueCambridgeUnited Kingdom
| | - Miguel A Peñalva
- Department of Cellular and Molecular Biology, CSIC Centro de Investigaciones BiológicasMadridSpain
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3
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Ishchuk OP, Frost AT, Muñiz-Paredes F, Matsumoto S, Laforge N, Eriksson NL, Martínez JL, Petranovic D. Improved production of human hemoglobin in yeast by engineering hemoglobin degradation. Metab Eng 2021; 66:259-267. [PMID: 33984513 DOI: 10.1016/j.ymben.2021.05.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 04/09/2021] [Accepted: 05/04/2021] [Indexed: 12/23/2022]
Abstract
With the increasing demand for blood transfusions, the production of human hemoglobin (Hb) from sustainable sources is increasingly studied. Microbial production is an attractive option, as it may provide a cheap, safe, and reliable source of this protein. To increase the production of human hemoglobin by the yeast Saccharomyces cerevisiae, the degradation of Hb was reduced through several approaches. The deletion of the genes HMX1 (encoding heme oxygenase), VPS10 (encoding receptor for vacuolar proteases), PEP4 (encoding vacuolar proteinase A), ROX1 (encoding heme-dependent repressor of hypoxic genes) and the overexpression of the HEM3 (encoding porphobilinogen deaminase) and the AHSP (encoding human alpha-hemoglobin-stabilizing protein) genes - these changes reduced heme and Hb degradation and improved heme and Hb production. The reduced hemoglobin degradation was validated by a bilirubin biosensor. During glucose fermentation, the engineered strains produced 18% of intracellular Hb relative to the total yeast protein, which is the highest production of human hemoglobin reported in yeast. This increased hemoglobin production was accompanied with an increased oxygen consumption rate and an increased glycerol yield, which (we speculate) is the yeast's response to rebalance its NADH levels under conditions of oxygen limitation and increased protein-production.
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Affiliation(s)
- Olena P Ishchuk
- Department of Biology and Biological Engineering, Systems and Synthetic Biology, Chalmers University of Technology, SE41296, Gothenburg, Sweden.
| | - August T Frost
- Department of Biotechnology and Biomedicine, Section for Synthetic Biology, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark
| | - Facundo Muñiz-Paredes
- Department of Biology and Biological Engineering, Systems and Synthetic Biology, Chalmers University of Technology, SE41296, Gothenburg, Sweden
| | - Saki Matsumoto
- Department of Biology and Biological Engineering, Systems and Synthetic Biology, Chalmers University of Technology, SE41296, Gothenburg, Sweden
| | - Nathalie Laforge
- Department of Biology and Biological Engineering, Systems and Synthetic Biology, Chalmers University of Technology, SE41296, Gothenburg, Sweden
| | - Nélida Leiva Eriksson
- Department of Chemistry, Division of Biotechnology, Lund University, 221 00, Lund, Sweden
| | - José L Martínez
- Department of Biology and Biological Engineering, Systems and Synthetic Biology, Chalmers University of Technology, SE41296, Gothenburg, Sweden; Department of Biotechnology and Biomedicine, Section for Synthetic Biology, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark
| | - Dina Petranovic
- Department of Biology and Biological Engineering, Systems and Synthetic Biology, Chalmers University of Technology, SE41296, Gothenburg, Sweden; Novo Nordisk Foundation Centre for Biosustainability, Chalmers University of Technology, SE41296, Gothenburg, Sweden.
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4
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The Golgi architecture and cell sensing. Biochem Soc Trans 2018; 46:1063-1072. [DOI: 10.1042/bst20180323] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 08/06/2018] [Accepted: 08/21/2018] [Indexed: 12/23/2022]
Abstract
An array of signalling molecules are located at the Golgi apparatus, including phosphoinositides, small GTPases, kinases, and phosphatases, which are linked to multiple signalling pathways. Initially considered to be associated predominantly with membrane trafficking, signalling pathways at the Golgi are now recognised to regulate a diverse range of higher-order functions. Many of these signalling pathways are influenced by the architecture of the Golgi. In vertebrate cells, the Golgi consists of individual stacks fused together into a compact ribbon structure and the function of this ribbon structure has been enigmatic. Notably, recent advances have identified a role for the Golgi ribbon in regulation of cellular processes. Fragmentation of the Golgi ribbon results in modulation of many signalling pathways. Various diseases and disorders, including cancer and neurodegeneration, are associated with the loss of the Golgi ribbon and the appearance of a dispersed fragmented Golgi. Here, we review the emerging theme of the Golgi as a cell sensor and highlight the relationship between the morphological status of the Golgi in vertebrate cells and the modulation of signalling networks.
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Labonté D, Thies E, Pechmann Y, Groffen AJ, Verhage M, Smit AB, van Kesteren RE, Kneussel M. TRIM3 regulates the motility of the kinesin motor protein KIF21B. PLoS One 2013; 8:e75603. [PMID: 24086586 PMCID: PMC3782429 DOI: 10.1371/journal.pone.0075603] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 08/15/2013] [Indexed: 01/01/2023] Open
Abstract
Kinesin superfamily proteins (KIFs) are molecular motors that transport cellular cargo along the microtubule cytoskeleton. KIF21B is a neuronal kinesin that is highly enriched in dendrites. The regulation and specificity of microtubule transport involves the binding of motors to individual cargo adapters and accessory proteins. Moreover, posttranslational modifications of either the motor protein, their cargos or tubulin regulate motility, cargo recognition and the binding or unloading of cargos. Here we show that the ubiquitin E3 ligase TRIM3, also known as BERP, interacts with KIF21B via its RBCC domain. TRIM3 is found at intracellular and Golgi-derived vesicles and co-localizes with the KIF21B motor in neurons. Trim3 gene deletion in mice and TRIM3 overexpression in cultured neurons both suggested that the E3-ligase function of TRIM3 is not involved in KIF21B degradation, however TRIM3 depletion reduces the motility of the motor. Together, our data suggest that TRIM3 is a regulator in the modulation of KIF21B motor function.
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Affiliation(s)
- Dorthe Labonté
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Edda Thies
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Yvonne Pechmann
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Alexander J. Groffen
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Matthijs Verhage
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - August B. Smit
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Ronald E. van Kesteren
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Matthias Kneussel
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- * E-mail:
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6
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van der Zand A, Gent J, Braakman I, Tabak HF. Biochemically distinct vesicles from the endoplasmic reticulum fuse to form peroxisomes. Cell 2012; 149:397-409. [PMID: 22500805 DOI: 10.1016/j.cell.2012.01.054] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Revised: 11/18/2011] [Accepted: 01/26/2012] [Indexed: 12/31/2022]
Abstract
As a rule, organelles in eukaryotic cells can derive only from pre-existing organelles. Peroxisomes are unique because they acquire their lipids and membrane proteins from the endoplasmic reticulum (ER), whereas they import their matrix proteins directly from the cytosol. We have discovered that peroxisomes are formed via heterotypic fusion of at least two biochemically distinct preperoxisomal vesicle pools that arise from the ER. These vesicles each carry half a peroxisomal translocon complex. Their fusion initiates assembly of the full peroxisomal translocon and subsequent uptake of enzymes from the cytosol. Our findings demonstrate a remarkable mechanism to maintain biochemical identity of organelles by transporting crucial components via different routes to their final destination.
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Affiliation(s)
- Adabella van der Zand
- Cellular Protein Chemistry, Faculty of Science, Utrecht University, NL-3584 CH Utrecht, The Netherlands.
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7
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Hilbi H, Haas A. Secretive bacterial pathogens and the secretory pathway. Traffic 2012; 13:1187-97. [PMID: 22340894 DOI: 10.1111/j.1600-0854.2012.01344.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 02/15/2012] [Accepted: 02/17/2012] [Indexed: 11/30/2022]
Abstract
Eukaryotic cells possess two extensive endomembrane systems, each consisting of several sub-compartments connected by vesicular trafficking. One of these systems, the endocytic pathway, serves incoming traffic, and the other system, the secretory pathway (SP), is responsible for surface-bound traffic of intracellularly formed vesicles. Compartments derived of either system can be colonized by intracellular pathogens. In this review, we discuss the interactions between the SP and prominent intracellular bacterial pathogens of the genera Legionella, Brucella, Chlamydia and Salmonella. We emphasize secreted bacterial effector proteins, which directly manipulate host components of this pathway.
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Affiliation(s)
- Hubert Hilbi
- Max von Pettenkofer Institute, Ludwig-Maximilians University, Pettenkoferstraße 9a, Munich, 80336, Germany.
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8
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Diefenbacher M, Thorsteinsdottir H, Spang A. The Dsl1 tethering complex actively participates in soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein receptor (SNARE) complex assembly at the endoplasmic reticulum in Saccharomyces cerevisiae. J Biol Chem 2011; 286:25027-38. [PMID: 21482823 DOI: 10.1074/jbc.m110.215657] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Intracellular transport is largely dependent on vesicles that bud off from one compartment and fuse with the target compartment. The first contact of an incoming vesicle with the target membrane is mediated by tethering factors. The tethering factor responsible for recruiting Golgi-derived vesicles to the ER is the Dsl1 tethering complex, which is comprised of the essential proteins Dsl1p, Dsl3p, and Tip20p. We investigated the role of the Tip20p subunit at the ER by analyzing two mutants, tip20-5 and tip20-8. Both mutants contained multiple mutations that were scattered throughout the TIP20 sequence. Individual mutations could not reproduce the temperature-sensitive phenotype of tip20-5 and tip20-8, indicating that the overall structure of Tip20p might be altered in the mutants. Using molecular dynamics simulations comparing Tip20p and Tip20-8p revealed that some regions, particularly the N-terminal domain and parts of the stalk region, were more flexible in the mutant protein, consistent with its increased susceptibility to proteolysis. Both Tip20-5p and Tip20-8p mutants prevented proper ER trans-SNARE complex assembly in vitro. Moreover, Tip20p mutant proteins disturbed the interaction between Dsl1p and the coatomer coat complex, indicating that the Dsl1p-coatomer interaction could be stabilized or regulated by Tip20p. We provide evidence for a direct role of the Dsl1 complex, in particular Tip20p, in the formation and stabilization of ER SNARE complexes.
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Affiliation(s)
- Melanie Diefenbacher
- Biozentrum, Growth & Development, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
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9
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Protein Quality Control, Retention, and Degradation at the Endoplasmic Reticulum. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2011; 292:197-280. [DOI: 10.1016/b978-0-12-386033-0.00005-0] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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10
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Lorente-Rodríguez A, Barlowe C. Requirement for Golgi-localized PI(4)P in fusion of COPII vesicles with Golgi compartments. Mol Biol Cell 2010; 22:216-29. [PMID: 21119004 PMCID: PMC3020917 DOI: 10.1091/mbc.e10-04-0317] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The role of specific membrane lipids in ER-Golgi transport is unclear. Using cell-free assays that measure stages in ER-Golgi transport, a variety of enzyme inhibitors, lipid-modifying enzymes, and lipid ligands were screened. The results indicate that PI(4)P is required for SNARE-dependent fusion of COPII vesicles with the Golgi complex. The role of specific membrane lipids in transport between endoplasmic reticulum (ER) and Golgi compartments is poorly understood. Using cell-free assays that measure stages in ER-to-Golgi transport, we screened a variety of enzyme inhibitors, lipid-modifying enzymes, and lipid ligands to investigate requirements in yeast. The pleckstrin homology (PH) domain of human Fapp1, which binds phosphatidylinositol-4-phosphate (PI(4)P) specifically, was a strong and specific inhibitor of anterograde transport. Analysis of wild type and mutant PH domain proteins in addition to recombinant versions of the Sac1p phosphoinositide-phosphatase indicated that PI(4)P was required on Golgi membranes for fusion with coat protein complex II (COPII) vesicles. PI(4)P inhibition did not prevent vesicle tethering but significantly reduced formation of soluble n-ethylmaleimide sensitive factor adaptor protein receptor (SNARE) complexes between vesicle and Golgi SNARE proteins. Moreover, semi-intact cell membranes containing elevated levels of the ER-Golgi SNARE proteins and Sly1p were less sensitive to PI(4)P inhibitors. Finally, in vivo analyses of a pik1 mutant strain showed that inhibition of PI(4)P synthesis blocked anterograde transport from the ER to early Golgi compartments. Together, the data presented here indicate that PI(4)P is required for the SNARE-dependent fusion stage of COPII vesicles with the Golgi complex.
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11
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Sevova ES, Goren MA, Schwartz KJ, Hsu FF, Turk J, Fox BG, Bangs JD. Cell-free synthesis and functional characterization of sphingolipid synthases from parasitic trypanosomatid protozoa. J Biol Chem 2010; 285:20580-7. [PMID: 20457606 PMCID: PMC2898309 DOI: 10.1074/jbc.m110.127662] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Revised: 05/03/2010] [Indexed: 11/06/2022] Open
Abstract
The Trypanosoma brucei genome has four highly similar genes encoding sphingolipid synthases (TbSLS1-4). TbSLSs are polytopic membrane proteins that are essential for viability of the pathogenic bloodstream stage of this human protozoan parasite and, consequently, can be considered as potential drug targets. TbSLS4 was shown previously to be a bifunctional sphingomyelin/ethanolamine phosphorylceramide synthase, whereas functions of the others were not characterized. Using a recently described liposome-supplemented cell-free synthesis system, which eliminates complications from background cellular activities, we now unambiguously define the enzymatic specificity of the entire gene family. TbSLS1 produces inositol phosphorylceramide, TbSLS2 produces ethanolamine phosphorylceramide, and TbSLS3 is bifunctional, like TbSLS4. These findings indicate that TbSLS1 is uniquely responsible for synthesis of inositol phosphorylceramide in insect stage parasites, in agreement with published expression array data (17). This approach also revealed that the Trypanosoma cruzi ortholog (TcSLS1) is a dedicated inositol phosphorylceramide synthase. The cell-free synthesis system allowed rapid optimization of the reaction conditions for these enzymes and site-specific mutagenesis to alter end product specificity. A single residue at position 252 (TbSLS1, Ser(252); TbSLS3, Phe(252)) strongly influences enzymatic specificity. We also have used this system to demonstrate that aureobasidin A, a potent inhibitor of fungal inositol phosphorylceramide synthases, does not significantly affect any of the TbSLS activities, consistent with the phylogenetic distance of these two clades of sphingolipid synthases. These results represent the first application of cell-free synthesis for the rapid preparation and functional annotation of integral membrane proteins and thus illustrate its utility in studying otherwise intractable enzyme systems.
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Affiliation(s)
- Elitza S. Sevova
- From the Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706
| | | | - Kevin J. Schwartz
- From the Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706
| | - Fong-Fu Hsu
- the Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - John Turk
- the Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Brian G. Fox
- the Department of Biochemistry and
- the Center for Eukaryotic Structural Genomics, College of Agriculture and Life Sciences, University of Wisconsin, Madison, Wisconsin 53706, and
| | - James D. Bangs
- From the Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706
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12
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Abstract
Estimates based on proteomic analyses indicate that a third of translated proteins in eukaryotic genomes enter the secretory pathway. After folding and assembly of nascent secretory proteins in the endoplasmic reticulum (ER), the coat protein complex II (COPII) selects folded cargo for export in membrane-bound vesicles. To accommodate the great diversity in secretory cargo, protein sorting receptors are required in a number of instances for efficient ER export. These transmembrane sorting receptors couple specific secretory cargo to COPII through interactions with both cargo and coat subunits. After incorporation into COPII transport vesicles, protein sorting receptors release bound cargo in pre-Golgi or Golgi compartments, and receptors are then recycled back to the ER for additional rounds of cargo export. Distinct types of protein sorting receptors that recognize carbohydrate and/or polypeptide signals in secretory cargo have been characterized. Our current understanding of the molecular mechanisms underlying cargo receptor function are described.
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Affiliation(s)
- Julia Dancourt
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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13
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Lorente-Rodríguez A, Heidtman M, Barlowe C. Multicopy suppressor analysis of thermosensitive YIP1 alleles implicates GOT1 in transport from the ER. J Cell Sci 2009; 122:1540-50. [PMID: 19383723 DOI: 10.1242/jcs.042457] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Yip1p belongs to a conserved family of membrane-spanning proteins that are involved in intracellular trafficking. Studies have shown that Yip1p forms a heteromeric integral membrane complex, is required for biogenesis of ER-derived COPII vesicles, and can interact with Rab GTPases. However, the role of the Yip1 complex in vesicle budding is not well understood. To gain further insight, we isolated multicopy suppressors of the thermosensitive yip1-2 allele. This screen identified GOT1, FYV8 and TSC3 as novel high-copy suppressors. The strongest suppressor, GOT1, also displayed moderate suppressor activity toward temperature-sensitive mutations in the SEC23 and SEC31 genes, which encode subunits of the COPII coat. Further characterization of Got1p revealed that this protein was efficiently packaged into COPII vesicles and cycled rapidly between the ER and Golgi compartments. Based on the findings we propose that Got1p has an unexpected role in vesicle formation from the ER by influencing membrane properties.
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14
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Harsay E, Schekman R. Avl9p, a member of a novel protein superfamily, functions in the late secretory pathway. Mol Biol Cell 2007; 18:1203-19. [PMID: 17229886 PMCID: PMC1838974 DOI: 10.1091/mbc.e06-11-1035] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The branching of exocytic transport routes in both yeast and mammalian cells has complicated studies of the late secretory pathway, and the mechanisms involved in exocytic cargo sorting and exit from the Golgi and endosomes are not well understood. Because cargo can be sorted away from a blocked route and secreted by an alternate route, mutants defective in only one route do not exhibit a strong secretory phenotype and are therefore difficult to isolate. In a genetic screen designed to isolate such mutants, we identified a novel conserved protein, Avl9p, the absence of which conferred lethality in a vps1Delta apl2Delta strain background (lacking a dynamin and an adaptor-protein complex 1 subunit). Depletion of Avl9p in this strain resulted in secretory defects as well as accumulation of Golgi-like membranes. The triple mutant also had a depolarized actin cytoskeleton and defects in polarized secretion. Overexpression of Avl9p in wild-type cells resulted in vesicle accumulation and a post-Golgi defect in secretion. Phylogenetic analysis indicated evolutionary relationships between Avl9p and regulators of membrane traffic and actin function.
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Affiliation(s)
- Edina Harsay
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA.
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15
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Welsh LM, Tong AHY, Boone C, Jensen ON, Otte S. Genetic and molecular interactions of the Erv41p-Erv46p complex involved in transport between the endoplasmic reticulum and Golgi complex. J Cell Sci 2006; 119:4730-40. [PMID: 17077122 DOI: 10.1242/jcs.03250] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Erv41p and Erv46p are integral membrane proteins conserved across species. They were originally identified as abundant constituents of COPII-coated vesicles, and form a complex which cycles between the endoplasmic reticulum and Golgi complex. Yeast strains lacking these proteins are viable but display subtle secretory phenotypes. In order to obtain information about possible biological roles of this protein complex in endoplasmic reticulum to Golgi transport, we employed the Synthetic Genetic Array approach to screen for synthetic genetic interactions with the erv46 null mutation. We identified synthetic interactions with vma12, vma21, vma22 and vps1 deletion mutations. The vma21Δ mutation exacerbates transport defects caused by the erv46Δ mutation. Unexpectedly, yeast strains lacking Vma21p fail to sort the endoplasmic reticulum to Golgi v-SNARE, Bos1p, efficiently into COPII vesicles, yet these vesicles are fully fusion competent. In addition, we set out to identify, by a biochemical approach, proteins interacting with the Erv41p-Erv46p complex. We report a strong interaction between the Erv41p-Erv46p complex and endoplasmic reticulum glucosidase II. Strains lacking a cycling Erv41p-Erv46p complex display a mild glycoprotein processing defect.
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Affiliation(s)
- Leah M Welsh
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607, USA
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16
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Yahara N, Sato K, Nakano A. The Arf1p GTPase-activating protein Glo3p executes its regulatory function through a conserved repeat motif at its C-terminus. J Cell Sci 2006; 119:2604-12. [PMID: 16735437 DOI: 10.1242/jcs.02997] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
ADP-ribosylation factors (Arfs), key regulators of intracellular membrane traffic, are known to exert multiple roles in vesicular transport. We previously isolated eight temperature-sensitive (ts) mutants of the yeast ARF1 gene, which showed allele-specific defects in protein transport, and classified them into three groups of intragenic complementation. In this study, we show that the overexpression of Glo3p, one of the GTPase-activating proteins of Arf1p (ArfGAP), suppresses the ts growth of a particular group of the arf1 mutants (arf1-16 and arf1-17). Other ArfGAPs do not show such a suppression activity. All these ArfGAPs show sequence similarity in the ArfGAP catalytic domain, but are divergent in the rest of molecules. By domain swapping analysis of Glo3p and another ArfGAP, Gcs1p, we have shown that the non-catalytic C-terminal region of Glo3p is required for the suppression of the growth defect in the arf1 ts mutants. Interestingly, Glo3p and its homologues from other eukaryotes harbor a well-conserved repeated ISSxxxFG sequence near the C-terminus, which is not found in Gcs1p and its homologues. We name this region the Glo3 motif and present evidence that the motif is required for the function of Glo3p in vivo.
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Affiliation(s)
- Natsuko Yahara
- Molecular Membrane Biology Laboratory, RIKEN Discovery Research Institute, Hirosawa, Wako, Saitama 351-0198, Japan
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17
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Trautwein M, Schindler C, Gauss R, Dengjel J, Hartmann E, Spang A. Arf1p, Chs5p and the ChAPs are required for export of specialized cargo from the Golgi. EMBO J 2006; 25:943-54. [PMID: 16498409 PMCID: PMC1409733 DOI: 10.1038/sj.emboj.7601007] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2005] [Accepted: 01/23/2006] [Indexed: 11/09/2022] Open
Abstract
In Saccharomyces cerevisiae, the synthesis of chitin is temporally and spatially regulated through the transport of Chs3p (chitin synthase III) to the plasma membrane in the bud neck region. Traffic of Chs3p from the trans-Golgi network (TGN)/early endosome to the plasma membrane requires the function of Chs5p and Chs6p. Chs6p belongs to a family of four proteins that we have named ChAPs for Chs5p-Arf1p-binding Proteins. Here, we show that all ChAPs physically interact not only with Chs5p but also with the small GTPase Arf1p. A short sequence at the C-terminus of the ChAPs is required for protein function and the ability to bind to Chs5p. Simultaneous disruption of two members, Deltabud7 and Deltabch1, phenocopies a Deltachs6 or Deltachs5 deletion with respect to Chs3p transport. Moreover, the ChAPs interact with each other and can form complexes. In addition, they are all at least partially localized to the TGN in a Chs5p-dependent manner. Most importantly, several ChAPs can interact physically with Chs3p. We propose that the ChAPs facilitate export of cargo out of the Golgi.
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Affiliation(s)
- Mark Trautwein
- Friedrich Miescher Laboratorium, Max Planck Gesellschaft, Tübingen, Germany
| | | | - Robert Gauss
- Friedrich Miescher Laboratorium, Max Planck Gesellschaft, Tübingen, Germany
| | - Jörn Dengjel
- Universität Tübingen, Interfakultäres Institut für Zellbiologie, Tübingen, Germany
| | | | - Anne Spang
- Friedrich Miescher Laboratorium, Max Planck Gesellschaft, Tübingen, Germany
- Present address: Biozentrum, Universitát Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
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18
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Abstract
Yeast Ypt1p-interacting protein (Yip1p) belongs to a conserved family of transmembrane proteins that interact with Rab GTPases. We encountered Yip1p as a constituent of ER-derived transport vesicles, leading us to hypothesize a direct role for this protein in transport through the early secretory pathway. Using a cell-free assay that recapitulates protein transport from the ER to the Golgi complex, we find that affinity-purified antibodies directed against the hydrophilic amino terminus of Yip1p potently inhibit transport. Surprisingly, inhibition is specific to the COPII-dependent budding stage. In support of this in vitro observation, strains bearing the temperature-sensitive yip1-4 allele accumulate ER membranes at a nonpermissive temperature, with no apparent accumulation of vesicle intermediates. Genetic interaction analyses of the yip1-4 mutation corroborate a function in ER budding. Finally, ordering experiments show that preincubation of ER membranes with COPII proteins decreases sensitivity to anti-Yip1p antibodies, indicating an early requirement for Yip1p in vesicle formation. We propose that Yip1p has a previously unappreciated role in COPII vesicle biogenesis.
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Affiliation(s)
- Matthew Heidtman
- Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755, USA
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19
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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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20
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Sandmann T, Herrmann JM, Dengjel J, Schwarz H, Spang A. Suppression of coatomer mutants by a new protein family with COPI and COPII binding motifs in Saccharomyces cerevisiae. Mol Biol Cell 2003; 14:3097-113. [PMID: 12925749 PMCID: PMC181553 DOI: 10.1091/mbc.e02-11-0736] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Protein trafficking is achieved by a bidirectional vesicle flow between the various compartments of the eukaryotic cell. COPII coated vesicles mediate anterograde protein transport from the endoplasmic reticulum to the Golgi apparatus, whereas retrograde Golgi-to-endoplasmic reticulum vesicles use the COPI coat. Inactivation of COPI vesicle formation in conditional sec21 (gamma-COP) mutants rapidly blocks transport of certain proteins along the early secretory pathway. We have identified the integral membrane protein Mst27p as a strong suppressor of sec21-3 and ret1-1 mutants. A C-terminal KKXX motif of Mst27p that allows direct binding to the COPI complex is crucial for its suppression ability. Mst27p and its homolog Yar033w (Mst28p) are part of the same complex. Both proteins contain cytoplasmic exposed C termini that have the ability to interact directly with COPI and COPII coat complexes. Site-specific mutations of the COPI binding domain abolished suppression of the sec21 mutants. Our results indicate that overexpression of MST27 provides an increased number of coat binding sites on membranes of the early secretory pathway and thereby promotes vesicle formation. As a consequence, the amount of cargo that can bind COPI might be important for the regulation of the vesicle flow in the early secretory pathway.
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Affiliation(s)
- Thomas Sandmann
- Friedrich Miescher Laboratorium der Max Planck Gesellschaft, D-72076 Tübingen, Germany
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21
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Siddiqi SA, Gorelick FS, Mahan JT, Mansbach CM. COPII proteins are required for Golgi fusion but not for endoplasmic reticulum budding of the pre-chylomicron transport vesicle. J Cell Sci 2003; 116:415-27. [PMID: 12482926 DOI: 10.1242/jcs.00215] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The budding of vesicles from endoplasmic reticulum (ER) that contains nascent proteins is regulated by COPII proteins. The mechanisms that regulate lipid-carrying pre-chylomicron transport vesicles (PCTVs) budding from the ER are unknown. To study the dependence of PCTV-ER budding on COPII proteins we examined protein and PCTV budding by using ER prepared from rat small intestinal mucosal cells prelabeled with (3)H-oleate or (14)C-oleate and (3)H-leucine. Budded (3)H-oleate-containing PCTVs were separated by sucrose density centrifugation and were revealed by electron microscopy as 142-500 nm vesicles. Our results showed the following: (1) Proteinase K treatment did not degrade the PCTV cargo protein, apolipoprotein B-48, unless Triton X-100 was added. (2) PCTV budding was dependent on cytosol and ATP. (3) The COPII proteins Sar1, Sec24 and Sec13/31 and the membrane proteins syntaxin 5 and rBet1 were associated with PCTVs. (4) Isolated PCTVs were able to fuse with intestinal Golgi. (5) Antibodies to Sar1 completely inhibited protein vesicle budding but increased the generation of PCTV; these changes were reversed by the addition of recombinant Sar1. (6) PCTVs formed in the absence of Sar1 did not contain the COPII proteins Sar1, Sec24 or Sec31 and did not fuse with the Golgi complex. Together, these findings suggest that COPII proteins may not be required for the exit of membrane-bound chylomicrons from the ER but that they or other proteins may be necessary for PCTV fusion with the Golgi.
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Affiliation(s)
- Shadab A Siddiqi
- Division of Gastroenterology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
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22
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Affiliation(s)
- Yuval Shimoni
- Genetech, Inc., South San Francisco, California 94080, USA
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23
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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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24
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Reilly BA, Kraynack BA, VanRheenen SM, Waters MG. Golgi-to-endoplasmic reticulum (ER) retrograde traffic in yeast requires Dsl1p, a component of the ER target site that interacts with a COPI coat subunit. Mol Biol Cell 2001; 12:3783-96. [PMID: 11739780 PMCID: PMC60755 DOI: 10.1091/mbc.12.12.3783] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
DSL1 was identified through its genetic interaction with SLY1, which encodes a t-SNARE-interacting protein that functions in endoplasmic reticulum (ER)-to-Golgi traffic. Conditional dsl1 mutants exhibit a block in ER-to-Golgi traffic at the restrictive temperature. Here, we show that dsl1 mutants are defective for retrograde Golgi-to-ER traffic, even under conditions where no anterograde transport block is evident. These results suggest that the primary function of Dsl1p may be in retrograde traffic, and that retrograde defects can lead to secondary defects in anterograde traffic. Dsl1p is an ER-localized peripheral membrane protein that can be extracted from the membrane in a multiprotein complex. Immunoisolation of the complex yielded Dsl1p and proteins of approximately 80 and approximately 55 kDa. The approximately 80-kDa protein has been identified as Tip20p, a protein that others have shown to exist in a tight complex with Sec20p, which is approximately 50 kDa. Both Sec20p and Tip20p function in retrograde Golgi-to-ER traffic, are ER-localized, and bind to the ER t-SNARE Ufe1p. These findings suggest that an ER-localized complex of Dsl1p, Sec20p, and Tip20p functions in retrograde traffic, perhaps upstream of a Sly1p/Ufe1p complex. Last, we show that Dsl1p interacts with the delta-subunit of the retrograde COPI coat, Ret2p, and discuss possible roles for this interaction.
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Affiliation(s)
- B A Reilly
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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25
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Spang A, Herrmann JM, Hamamoto S, Schekman R. The ADP ribosylation factor-nucleotide exchange factors Gea1p and Gea2p have overlapping, but not redundant functions in retrograde transport from the Golgi to the endoplasmic reticulum. Mol Biol Cell 2001; 12:1035-45. [PMID: 11294905 PMCID: PMC32285 DOI: 10.1091/mbc.12.4.1035] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The activation of the small ras-like GTPase Arf1p requires the action of guanine nucleotide exchange factors. Four Arf1p guanine nucleotide exchange factors have been identified in yeast: Sec7p, Syt1p, Gea1p, and its homologue Gea2p. We identified GEA2 as a multicopy suppressor of a sec21-3 temperature-sensitive mutant. SEC21 encodes the gamma-subunit of coatomer, a heptameric protein complex that together with Arf1p forms the COPI coat. GEA1 and GEA2 have at least partially overlapping functions, because deletion of either gene results in no obvious phenotype, whereas the double null mutant is inviable. Conditional mutants defective in both GEA1 and GEA2 accumulate endoplasmic reticulum and Golgi membranes under restrictive conditions. The two genes do not serve completely overlapping functions because a Deltagea1 Deltaarf1 mutant is not more sickly than a Deltaarf1 strain, whereas Deltagea2 Deltaarf1 is inviable. Biochemical experiments revealed similar distributions and activities for the two proteins. Gea1p and Gea2p exist both in membrane-bound and in soluble forms. The membrane-bound forms, at least one of which, Gea2p, can be visualized on Golgi structures, are both required for vesicle budding and protein transport from the Golgi to the endoplasmic reticulum. In contrast, Sec7p, which is required for protein transport within the Golgi, is not required for retrograde protein trafficking.
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Affiliation(s)
- A Spang
- Friedrich Miescher Laboratorium, Max Planck Gesellschaft, D-72076 Tübingen, Germany.
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26
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Belden WJ, Barlowe C. Deletion of yeast p24 genes activates the unfolded protein response. Mol Biol Cell 2001; 12:957-69. [PMID: 11294899 PMCID: PMC32279 DOI: 10.1091/mbc.12.4.957] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Yeast cells lacking a functional p24 complex accumulate a subset of secretory proteins in the endoplasmic reticulum (ER) and increase the extracellular secretion of HDEL-containing ER residents such as Kar2p/BiP. We report that a loss of p24 function causes activation of the unfolded protein response (UPR) and leads to increased KAR2 expression. The HDEL receptor (Erd2p) is functional and traffics in p24 deletion strains as in wild-type strains, however the capacity of the retrieval pathway is exceeded. Other conditions that activate the UPR and elevate KAR2 expression also lead to extracellular secretion of Kar2p. Using an in vitro assay that reconstitutes budding from the ER, we detect elevated levels of Kar2p in ER-derived vesicles from p24 deletion strains and from wild-type strains with an activated UPR. Silencing the UPR by IRE1 deletion diminished Kar2p secretion under these conditions. We suggest that activation of the UPR plays a major role in extracellular secretion of Kar2p.
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Affiliation(s)
- W J Belden
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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27
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Otte S, Belden WJ, Heidtman M, Liu J, Jensen ON, Barlowe C. Erv41p and Erv46p: new components of COPII vesicles involved in transport between the ER and Golgi complex. J Cell Biol 2001; 152:503-18. [PMID: 11157978 PMCID: PMC2195992 DOI: 10.1083/jcb.152.3.503] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Proteins contained on purified COPII vesicles were analyzed by matrix-assisted laser desorption ionization mass spectrometry combined with database searching. We identified four known vesicle proteins (Erv14p, Bet1p, Emp24p, and Erv25p) and an additional nine species (Yip3p, Rer1p, Erp1p, Erp2p, Erv29p, Yif1p, Erv41p, Erv46p, and Emp47p) that had not been localized to ER vesicles. Using antibodies, we demonstrate that these proteins are selectively and efficiently packaged into COPII vesicles. Three of the newly identified vesicle proteins (Erv29p, Erv41p, and Erv46p) represent uncharacterized integral membrane proteins that are conserved across species. Erv41p and Erv46p were further characterized. These proteins colocalized to ER and Golgi membranes and exist in a detergent-soluble complex that was isolated by immunoprecipitation. Yeast strains lacking Erv41p and/or Erv46p are viable but display cold sensitivity. The expression levels of Erv41p and Erv46p are interdependent such that Erv46p was reduced in an erv41Delta strain, and Erv41p was not detected in an erv46Delta strain. When the erv41Delta or ev46Delta alleles were combined with other mutations in the early secretory pathway, altered growth phenotypes were observed in some of the double mutant strains. A cell-free assay that reproduces transport between the ER and Golgi indicates that deletion of the Erv41p-Erv46p complex influences the membrane fusion stage of transport.
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Affiliation(s)
- Stefan Otte
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755
| | - William J. Belden
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755
| | - Matthew Heidtman
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755
| | - Jay Liu
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755
| | - Ole N. Jensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense University, DK-5230 Odense M, Denmark
| | - Charles Barlowe
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755
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28
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Abstract
It is currently thought that all secretory proteins travel together to the Golgi apparatus where they are sorted to different destinations. However, the specific requirements for transport of GPI-anchored proteins from the endoplasmic reticulum to the Golgi apparatus in yeast could be explained if protein sorting occurs earlier in the pathway. Using an in vitro assay that reconstitutes a single round of budding from the endoplasmic reticulum, we found that GPI-anchored proteins and other secretory proteins exit the endoplasmic reticulum in distinct vesicles. Therefore, GPI-anchored proteins are sorted from other proteins, in particular other plasma membrane proteins, at an early stage of the secretory pathway. These results have wide implications for the mechanism of protein exit from the endoplasmic reticulum.
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Affiliation(s)
- M Muñiz
- Biozentrum of the University of Basel, Klingelbergstrasse 70, CH-4056, Basel, Switzerland
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29
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Aridor M, Fish KN, Bannykh S, Weissman J, Roberts TH, Lippincott-Schwartz J, Balch WE. The Sar1 GTPase coordinates biosynthetic cargo selection with endoplasmic reticulum export site assembly. J Cell Biol 2001; 152:213-29. [PMID: 11149932 PMCID: PMC2193666 DOI: 10.1083/jcb.152.1.213] [Citation(s) in RCA: 191] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2000] [Accepted: 11/03/2000] [Indexed: 11/30/2022] Open
Abstract
Cargo selection and export from the endoplasmic reticulum is mediated by the COPII coat machinery that includes the small GTPase Sar1 and the Sec23/24 and Sec13/31 complexes. We have analyzed the sequential events regulated by purified Sar1 and COPII coat complexes during synchronized export of cargo from the ER in vitro. We find that activation of Sar1 alone, in the absence of other cytosolic components, leads to the formation of ER-derived tubular domains that resemble ER transitional elements that initiate cargo selection. These Sar1-generated tubular domains were shown to be transient, functional intermediates in ER to Golgi transport in vitro. By following cargo export in live cells, we show that ER export in vivo is also characterized by the formation of dynamic tubular structures. Our results demonstrate an unanticipated and novel role for Sar1 in linking cargo selection with ER morphogenesis through the generation of transitional tubular ER export sites.
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Affiliation(s)
- Meir Aridor
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Kenneth N. Fish
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
- The Harold L. Dorris Neurological Research Center, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - Sergei Bannykh
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Jacques Weissman
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Theresa H. Roberts
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - Jennifer Lippincott-Schwartz
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - William E. Balch
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
- The Institute of Childhood and Neglected Diseases, The Scripps Research Institute, La Jolla, California 92037
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30
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Xu D, Joglekar AP, Williams AL, Hay JC. Subunit structure of a mammalian ER/Golgi SNARE complex. J Biol Chem 2000; 275:39631-9. [PMID: 11035026 DOI: 10.1074/jbc.m007684200] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SNAP receptor (SNARE) complexes bridge opposing membranes to promote membrane fusion within the secretory and endosomal pathways. Because only the exocytic SNARE complexes have been characterized in detail, the structural features shared by SNARE complexes from different fusion steps are not known. We now describe the subunit structure, assembly, and regulation of a quaternary SNARE complex, which appears to mediate an early step in endoplasmic reticulum (ER) to Golgi transport. Purified recombinant syntaxin 5, membrin, and rbet1, three Q-SNAREs, assemble cooperatively to create a high affinity binding site for sec22b, an R-SNARE. The syntaxin 5 amino-terminal domain potently inhibits SNARE complex assembly. The ER/Golgi quaternary complex is remarkably similar to the synaptic complex, suggesting that a common pattern is followed at all transport steps, where three Q-helices assemble to form a high affinity binding site for a fourth R-helix on an opposing membrane. Interestingly, although sec22b binds to the combination of syntaxin 5, membrin, and rbet1, it can only bind if it is present while the others assemble; sec22b cannot bind to a pre-assembled ternary complex of syntaxin 5, membrin, and rbet1. Finally, we demonstrate that the quaternary complex containing sec22b is not an in vitro entity only, but is a bona fide species in living cells.
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Affiliation(s)
- D Xu
- Department of Biology and Program in Biomedical Sciences, University of Michigan, Ann Arbor, Michigan 48109-1048, USA
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31
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Todorow Z, Spang A, Carmack E, Yates J, Schekman R. Active recycling of yeast Golgi mannosyltransferase complexes through the endoplasmic reticulum. Proc Natl Acad Sci U S A 2000; 97:13643-8. [PMID: 11095735 PMCID: PMC17629 DOI: 10.1073/pnas.250472397] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mnn9p is a component of two distinct multiprotein complexes in the Saccharomyces cerevisiae cis-Golgi that have both been shown to have alpha-1,6-mannosyltransferase activity in vitro. In one of these complexes, Mnn9p associates with four other membrane proteins, Anp1p, Mnn10p, Mnn11p, and Hoc1p, whereas the other complex consists of Mnn9p and Van1p. Members of the Mnn9p-containing complexes were incorporated into COPII vesicles made in vitro from endoplasmic reticulum (ER) membranes isolated from cycloheximide-treated cells. This behavior is consistent with an active Golgi to ER recycling process. To examine this path in vivo, we monitored retrograde transport of subunits of the complex in cells blocked in anterograde transport from the ER. In this situation, specific relocation of the proteins from the Golgi to the ER was observed in the absence of new protein synthesis. Conversely, when retrograde transport was blocked in vivo, subunits of the mannosyltransferase complex accumulated in the vacuole. Packaging of Mnn9p in COPI-coated vesicles from purified Golgi membranes was also investigated using a coatomer-dependent vesicle budding assay. Gradient fractionation experiments showed that Mnn9p and the retrograde v-SNARE, Sec22p, were incorporated into COPI-coated vesicles. These observations indicate that the Mnn9p-containing mannosyltransferase complexes cycle back and forth between the ER and Golgi.
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Affiliation(s)
- Z Todorow
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA
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32
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Shimoni Y, Kurihara T, Ravazzola M, Amherdt M, Orci L, Schekman R. Lst1p and Sec24p cooperate in sorting of the plasma membrane ATPase into COPII vesicles in Saccharomyces cerevisiae. J Cell Biol 2000; 151:973-84. [PMID: 11086000 PMCID: PMC2174359 DOI: 10.1083/jcb.151.5.973] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Formation of ER-derived protein transport vesicles requires three cytosolic components, a small GTPase, Sar1p, and two heterodimeric complexes, Sec23/24p and Sec13/31p, which comprise the COPII coat. We investigated the role of Lst1p, a Sec24p homologue, in cargo recruitment into COPII vesicles in Saccharomyces cerevisiae. A tagged version of Lst1p was purified and eluted as a heterodimer complexed with Sec23p comparable to the Sec23/24p heterodimer. We found that cytosol from an lst1-null strain supported the packaging of alpha-factor precursor into COPII vesicles but was deficient in the packaging of Pma1p, the essential plasma membrane ATPase. Supplementation of mutant cytosol with purified Sec23/Lst1p restored Pma1p packaging into the vesicles. When purified COPII components were used in the vesicle budding reaction, Pma1p packaging was optimal with a mixture of Sec23/24p and Sec23/Lst1p; Sec23/Lst1p did not replace Sec23/24p. Furthermore, Pma1p coimmunoprecipitated with Lst1p and Sec24p from vesicles. Vesicles formed with a mixture of Sec23/Lst1p and Sec23/24p were similar morphologically and in their buoyant density, but larger than normal COPII vesicles (87-nm vs. 75-nm diameter). Immunoelectronmicroscopic and biochemical studies revealed both Sec23/Lst1p and Sec23/24p on the membranes of the same vesicles. These results suggest that Lst1p and Sec24p cooperate in the packaging of Pma1p and support the view that biosynthetic precursors of plasma membrane proteins must be sorted into ER-derived transport vesicles. Sec24p homologues may comprise a more complex coat whose combinatorial subunit composition serves to expand the range of cargo to be packaged into COPII vesicles. By changing the geometry of COPII coat polymerization, Lst1p may allow the transport of bulky cargo molecules, polymers, or particles.
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Affiliation(s)
- Y Shimoni
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, California 94720, USA
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33
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Abstract
Membrane fusion events that occur in yeast have been reconstituted with a minimal set of SNARE protein components. This system has been exploited to establish the syntax underlying specificity of intracellular fusion events from yeast to mammals.
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Affiliation(s)
- M J Clague
- Physiological Laboratory, University of Liverpool, UK.
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34
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Parlati F, McNew JA, Fukuda R, Miller R, Söllner TH, Rothman JE. Topological restriction of SNARE-dependent membrane fusion. Nature 2000; 407:194-8. [PMID: 11001058 DOI: 10.1038/35025076] [Citation(s) in RCA: 209] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
To fuse transport vesicles with target membranes, proteins of the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) complex must be located on both the vesicle (v-SNARE) and the target membrane (t-SNARE). In yeast, four integral membrane proteins, Sed5, Bos1, Sec22 and Bet1 (refs 2-6), each probably contribute a single helix to form the SNARE complex that is needed for transport from endoplasmic reticulum to Golgi. This generates a four-helix bundle, which ultimately mediates the actual fusion event. Here we explore how the anchoring arrangement of the four helices affects their ability to mediate fusion. We reconstituted two populations of phospholipid bilayer vesicles, with the individual SNARE proteins distributed in all possible combinations between them. Of the eight non-redundant permutations of four subunits distributed over two vesicle populations, only one results in membrane fusion. Fusion only occurs when the v-SNARE Bet1 is on one membrane and the syntaxin heavy chain Sed5 and its two light chains, Bos1 and Sec22, are on the other membrane where they form a functional t-SNARE. Thus, each SNARE protein is topologically restricted by design to function either as a v-SNARE or as part of a t-SNARE complex.
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Affiliation(s)
- F Parlati
- Cellular Biochemistry and Biophysics Program, Memorial Sloan Kettering Cancer Center, New York, New York 10021, USA
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35
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Allan BB, Moyer BD, Balch WE. Rab1 recruitment of p115 into a cis-SNARE complex: programming budding COPII vesicles for fusion. Science 2000; 289:444-8. [PMID: 10903204 DOI: 10.1126/science.289.5478.444] [Citation(s) in RCA: 407] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The guanosine triphosphatase Rab1 regulates the transport of newly synthesized proteins from the endoplasmic reticulum to the Golgi apparatus through interaction with effector molecules, but the molecular mechanisms by which this occurs are unknown. Here, the tethering factor p115 was shown to be a Rab1 effector that binds directly to activated Rab1. Rab1 recruited p115 to coat protein complex II (COPII) vesicles during budding from the endoplasmic reticulum, where it interacted with a select set of COPII vesicle-associated SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) to form a cis-SNARE complex that promotes targeting to the Golgi apparatus. We propose that Rab1-regulated assembly of functional effector-SNARE complexes defines a conserved molecular mechanism to coordinate recognition between subcellular compartments.
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Affiliation(s)
- B B Allan
- Departments of Cell and Molecular Biology, Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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36
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Higashio H, Kimata Y, Kiriyama T, Hirata A, Kohno K. Sfb2p, a yeast protein related to Sec24p, can function as a constituent of COPII coats required for vesicle budding from the endoplasmic reticulum. J Biol Chem 2000; 275:17900-8. [PMID: 10749860 DOI: 10.1074/jbc.m000751200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The COPII coat is required for vesicle budding from the endoplasmic reticulum (ER), and consists of two heterodimeric subcomplexes, Sec23p/Sec24p, Sec13p/Sec31p, and a small GTPase, Sar1p. We characterized a yeast mutant, anu1 (abnormal nuclear morphology) exhibiting proliferated ER as well as abnormal nuclear morphology at the restrictive temperature. Based on the finding that ANU1 is identical to SEC24, we confirmed a temperature-sensitive protein transport from the ER to the Golgi in anu1-1/sec24-20 cells. Overexpression of SFB2, a SEC24 homologue with 56% identity, partially suppressed not only the mutant phenotype of sec24-20 cells but also rescued the SEC24-disrupted cells. Moreover, the yeast two-hybrid assay revealed that Sfb2p, similarly to Sec24p, interacted with Sec23p. In SEC24-disrupted cells rescued by overexpression of SFB2, some cargo proteins were still retained in the ER, while most of the protein transport was restored. Together, these findings strongly suggest that Sfb2p functions as the component of COPII coats in place of Sec24p, and raise the possibility that each member of the SEC24 family of proteins participates directly and/or indirectly in cargo-recognition events with its own cargo specificity at forming ER-derived vesicles.
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Affiliation(s)
- H Higashio
- Research and Education Center for Genetic Information, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan
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37
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Abstract
Intracellular transport between the endoplasmic reticulum and Golgi compartments is mediated by coat protein complexes (COPI and COPII) that form transport vesicles and collect the desired set of cargo. Although the COPI and COPII coats are molecularly distinct, a number of mechanistic parallels appear to be emerging, most notably a general role for small guanine triphosphatases in co-ordinating coat assembly with cargo selection. A combination of morphological, biochemical, and genetic methods is revealing a very dynamic relationship between these compartments, and highlights a central role for COPs in directing traffic through the early secretory pathway. This review focuses on recent advances in molecular mechanisms underlying coated-vesicle assembly and connections with cellular structures.
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Affiliation(s)
- C Barlowe
- Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755, USA.
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38
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Cao X, Barlowe C. Asymmetric requirements for a Rab GTPase and SNARE proteins in fusion of COPII vesicles with acceptor membranes. J Cell Biol 2000; 149:55-66. [PMID: 10747087 PMCID: PMC2175085 DOI: 10.1083/jcb.149.1.55] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/1999] [Accepted: 02/24/2000] [Indexed: 11/22/2022] Open
Abstract
Soluble NSF attachment protein receptor (SNARE) proteins are essential for membrane fusion in transport between the yeast ER and Golgi compartments. Subcellular fractionation experiments demonstrate that the ER/Golgi SNAREs Bos1p, Sec22p, Bet1p, Sed5p, and the Rab protein, Ypt1p, are distributed similarly but localize primarily with Golgi membranes. All of these SNARE proteins are efficiently packaged into COPII vesicles and suggest a dynamic cycling of SNARE machinery between ER and Golgi compartments. Ypt1p is not efficiently packaged into vesicles under these conditions. To determine in which membranes protein function is required, temperature-sensitive alleles of BOS1, BET1, SED5, SLY1, and YPT1 that prevent ER/Golgi transport in vitro at restrictive temperatures were used to selectively inactivate these gene products on vesicles or on Golgi membranes. Vesicles bearing mutations in Bet1p or Bos1p inhibit fusion with wild-type acceptor membranes, but acceptor membranes containing these mutations are fully functional. In contrast, vesicles bearing mutations in Sed5p, Sly1p, or Ypt1p are functional, whereas acceptor membranes containing these mutations block fusion. Thus, this set of SNARE proteins is symmetrically distributed between vesicle and acceptor compartments, but they function asymmetrically such that Bet1p and Bos1p are required on vesicles and Sed5p activity is required on acceptor membranes. We propose the asymmetry in SNARE protein function is maintained by an asymmetric distribution and requirement for the Ypt1p GTPase in this fusion event. When a transmembrane-anchored form of Ypt1p is used to restrict this GTPase to the acceptor compartment, vesicles depleted of Ypt1p remain competent for fusion.
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Affiliation(s)
- Xiaochun Cao
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755
| | - Charles Barlowe
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755
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39
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Lau WT, Howson RW, Malkus P, Schekman R, O'Shea EK. Pho86p, an endoplasmic reticulum (ER) resident protein in Saccharomyces cerevisiae, is required for ER exit of the high-affinity phosphate transporter Pho84p. Proc Natl Acad Sci U S A 2000; 97:1107-12. [PMID: 10655492 PMCID: PMC15537 DOI: 10.1073/pnas.97.3.1107] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In the budding yeast Saccharomyces cerevisiae, PHO84 and PHO86 are among the genes that are most highly induced in response to phosphate starvation. They are essential for growth when phosphate is limiting, and they function in the high-affinity phosphate uptake system. PHO84 encodes a high-affinity phosphate transporter, and mutations in PHO86 cause many of the same phenotypes as mutations in PHO84, including a phosphate uptake defect and constitutive expression of the secreted acid phosphatase, Pho5p. Here, we show that the subcellular localization of Pho84p is regulated in response to extracellular phosphate levels; it is localized to the plasma membrane in low-phosphate medium but quickly endocytosed and transported to the vacuole upon addition of phosphate to the medium. Moreover, Pho84p is localized to the endoplasmic reticulum (ER) and fails to be targeted to the plasma membrane in the absence of Pho86p. Utilizing an in vitro vesicle budding assay, we demonstrate that Pho86p is required for packaging of Pho84p into COPII vesicles. Pho86p is an ER resident protein, which itself is not transported out of the ER. Interestingly, the requirement of Pho86p for ER exit is specific to Pho84p, because other members of the hexose transporter family to which Pho84 belongs are not mislocalized in the absence of Pho86p.
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Affiliation(s)
- W T Lau
- Program in Biophysics, University of California, San Francisco, CA 94143-0448, USA
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40
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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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41
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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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42
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Appenzeller C, Andersson H, Kappeler F, Hauri HP. The lectin ERGIC-53 is a cargo transport receptor for glycoproteins. Nat Cell Biol 1999; 1:330-4. [PMID: 10559958 DOI: 10.1038/14020] [Citation(s) in RCA: 261] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Soluble secretory proteins are transported from the endoplasmic reticulum (ER) to the ER-Golgi intermediate compartment (ERGIC) in vesicles coated with COP-II coat proteins. The sorting of secretory cargo into these vesicles is thought to involve transmembrane cargo-receptor proteins. Here we show that a cathepsin-Z-related glycoprotein binds to the recycling, mannose-specific membrane lectin ERGIC-53. Binding occurs in the ER, is carbohydrate- and calcium-ion-dependent and is affected by untrimmed glucose residues. Binding does not, however, require oligomerization of ERGIC-53, although oligomerization is required for exit of ERGIC-53 from the ER. Dissociation of ERGIC-53 occurs in the ERGIC and is delayed if ERGIC-53 is mislocalized to the ER. These results strongly indicate that ERGIC-53 may function as a receptor facilitating ER-to-ERGIC transport of soluble glycoprotein cargo.
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Affiliation(s)
- C Appenzeller
- Department of Pharmacology/Neurobiology, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
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43
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Rehling P, Darsow T, Katzmann DJ, Emr SD. Formation of AP-3 transport intermediates requires Vps41 function. Nat Cell Biol 1999; 1:346-53. [PMID: 10559961 DOI: 10.1038/14037] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Transport of a subset of membrane proteins to the yeast vacuole requires the function of the AP-3 adaptor protein complex. To define the molecular requirements of vesicular transport in this pathway, we used a biochemical approach to analyse the formation and content of the AP-3 transport intermediate. A vam3tsf (vacuolar t-SNARE) mutant blocks vesicle docking and fusion with the vacuole and causes the accumulation of 50-130-nanometre membrane vesicles, which we isolated and showed by biochemical analysis and immunocytochemistry to contain both AP-3 adaptors and alkaline phosphatase (ALP) pathway cargoes. Inactivation of AP-3 or the protein Vps41 blocks formation of this vesicular intermediate. Vps41 binds to the AP-3 delta-adaptin subunit, suggesting that they function together in the formation of ALP pathway transport intermediates at the late Golgi.
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Affiliation(s)
- P Rehling
- Division of Cellular and Molecular Medicine and Howard Hughes Medical Institute, University of California, San Diego, La Jolla, California 92093-0668, USA
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44
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Abstract
The major cytosolic and membrane proteins that represent machinery of coat protein (COP)-coated transport vesicles within the secretory pathway are characterized to date. This has allowed investigation of the molecular mechanisms that underlie the formation of these vesicles. In vitro binding studies and reconstitution experiments have provided insights at the molecular level into the biogenesis of COPII- and COPI-coated vesicles.
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Affiliation(s)
- F Wieland
- Biochemie-Zentrum Heidelberg (BZH), Ruprecht-Karls-Universität, Im Neuenheimer Feld 328, D-69120, Heidelberg, Germany.
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45
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Marzioch M, Henthorn DC, Herrmann JM, Wilson R, Thomas DY, Bergeron JJ, Solari RC, Rowley A. Erp1p and Erp2p, partners for Emp24p and Erv25p in a yeast p24 complex. Mol Biol Cell 1999; 10:1923-38. [PMID: 10359606 PMCID: PMC25390 DOI: 10.1091/mbc.10.6.1923] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Six new members of the yeast p24 family have been identified and characterized. These six genes, named ERP1-ERP6 (for Emp24p- and Erv25p-related proteins) are not essential, but deletion of ERP1 or ERP2 causes defects in the transport of Gas1p, in the retention of BiP, and deletion of ERP1 results in the suppression of a temperature-sensitive mutation in SEC13 encoding a COPII vesicle coat protein. These phenotypes are similar to those caused by deletion of EMP24 or ERV25, two previously identified genes that encode related p24 proteins. Genetic and biochemical studies demonstrate that Erp1p and Erp2p function in a heteromeric complex with Emp24p and Erv25p.
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Affiliation(s)
- M Marzioch
- Cell Biology Unit, Glaxo-Wellcome Research and Development, Stevenage, Hertfordshire, SG1 2NY, United Kingdom
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46
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Nothwehr SF, Bruinsma P, Strawn LA. Distinct domains within Vps35p mediate the retrieval of two different cargo proteins from the yeast prevacuolar/endosomal compartment. Mol Biol Cell 1999; 10:875-90. [PMID: 10198044 PMCID: PMC25208 DOI: 10.1091/mbc.10.4.875] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Resident membrane proteins of the trans-Golgi network (TGN) of Saccharomyces cerevisiae are selectively retrieved from a prevacuolar/late endosomal compartment. Proper cycling of the carboxypeptidase Y receptor Vps10p between the TGN and prevacuolar compartment depends on Vps35p, a hydrophilic peripheral membrane protein. In this study we use a temperature-sensitive vps35 allele to show that loss of Vps35p function rapidly leads to mislocalization of A-ALP, a model TGN membrane protein, to the vacuole. Vps35p is required for the prevacuolar compartment-to-TGN transport of both A-ALP and Vps10p. This was demonstrated by phenotypic analysis of vps35 mutant strains expressing A-ALP mutants lacking either the retrieval or static retention signals and by an assay for prevacuolar compartment-to-TGN transport. A novel vps35 allele was identified that was defective for retrieval of A-ALP but functional for retrieval of Vps10p. Moreover, several other vps35 alleles were identified with the opposite characteristics: they were defective for Vps10p retrieval but near normal for A-ALP localization. These data suggest a model in which distinct structural features within Vps35p are required for associating with the cytosolic domains of each cargo protein during the retrieval process.
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Affiliation(s)
- S F Nothwehr
- Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211, USA.
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47
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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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48
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Zhang T, Wong SH, Tang BL, Xu Y, Hong W. Morphological and functional association of Sec22b/ERS-24 with the pre-Golgi intermediate compartment. Mol Biol Cell 1999; 10:435-53. [PMID: 9950687 PMCID: PMC25179 DOI: 10.1091/mbc.10.2.435] [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: 11/11/2022] Open
Abstract
Yeast Sec22p participates in both anterograde and retrograde vesicular transport between the endoplasmic reticulum (ER) and the Golgi apparatus by functioning as a v-SNARE (soluble N-ethylmaleimide-sensitive factor [NSF] attachment protein receptor) of transport vesicles. Three mammalian proteins homologous to Sec22p have been identified and are referred to as Sec22a, Sec22b/ERS-24, and Sec22c, respectively. The existence of three homologous proteins in mammalian cells calls for detailed cell biological and functional examinations of each individual protein. The epitope-tagged forms of all three proteins have been shown to be primarily associated with the ER, although functional examination has not been carefully performed for any one of them. In this study, using antibodies specific for Sec22b/ERS-24, it is revealed that endogenous Sec22b/ERS-24 is associated with vesicular structures in both the perinuclear Golgi and peripheral regions. Colabeling experiments for Sec22b/ERS-24 with Golgi mannosidase II, the KDEL receptor, and the envelope glycoprotein G (VSVG) of vesicular stomatitis virus (VSV) en route from the ER to the Golgi under normal, brefeldin A, or nocodazole-treated cells suggest that Sec22b/ERS-24 is enriched in the pre-Golgi intermediate compartment (IC). In a well-established semi-intact cell system that reconstitutes transport from the ER to the Golgi, transport of VSVG is inhibited by antibodies against Sec22b/ERS-24. EGTA is known to inhibit ER-Golgi transport at a stage after vesicle/transport intermediate docking but before the actual fusion event. Antibodies against Sec22b/ERS-24 inhibit ER-Golgi transport only when they are added before the EGTA-sensitive stage. Transport of VSVG accumulated in pre-Golgi IC by incubation at 15 degreesC is also inhibited by Sec22b/ERS-24 antibodies. Morphologically, VSVG is transported from the ER to the Golgi apparatus via vesicular intermediates that scatter in the peripheral as well as the Golgi regions. In the presence of antibodies against Sec22b/ERS-24, VSVG is seen to accumulate in these intermediates, suggesting that Sec22b/ERS-24 functions at the level of the IC in ER-Golgi transport.
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Affiliation(s)
- T Zhang
- Membrane Biology Laboratory, Institute of Molecular and Cell Biology, Singapore 117609, Singapore
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49
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Poon PP, Cassel D, Spang A, Rotman M, Pick E, Singer RA, Johnston GC. Retrograde transport from the yeast Golgi is mediated by two ARF GAP proteins with overlapping function. EMBO J 1999; 18:555-64. [PMID: 9927415 PMCID: PMC1171148 DOI: 10.1093/emboj/18.3.555] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
ARF proteins, which mediate vesicular transport, have little or no intrinsic GTPase activity. They rely on the actions of GTPase-activating proteins (GAPs) for their function. The in vitro GTPase activity of the Saccharomyces cerevisiae ARF proteins Arf1 and Arf2 is stimulated by the yeast Gcs1 protein, and in vivo genetic interactions between arf and gcs1 mutations implicate Gcs1 in vesicular transport. However, the Gcs1 protein is dispensable, indicating that additional ARF GAP proteins exist. We show that the structurally related protein Glo3, which is also dispensable, also exhibits ARF GAP activity. Genetic and in vitro approaches reveal that Glo3 and Gcs1 have an overlapping essential function at the endoplasmic reticulum (ER)-Golgi stage of vesicular transport. Mutant cells deficient for both ARF GAPs cannot proliferate, undergo a dramatic accumulation of ER and are defective for protein transport between ER and Golgi. The glo3Delta and gcs1Delta single mutations each interact with a sec21 mutation that affects a component of COPI, which mediates vesicular transport within the ER-Golgi shuttle, while increased dosage of the BET1, BOS1 and SEC22 genes encoding members of a v-SNARE family that functions within the ER-Golgi alleviates the effects of a glo3Delta mutation. An in vitro assay indicates that efficient retrieval from the Golgi to the ER requires these two proteins. These findings suggest that Glo3 and Gcs1 ARF GAPs mediate retrograde vesicular transport from the Golgi to the ER.
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Affiliation(s)
- P P Poon
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7
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50
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Reggiori F, Conzelmann A. Biosynthesis of inositol phosphoceramides and remodeling of glycosylphosphatidylinositol anchors in Saccharomyces cerevisiae are mediated by different enzymes. J Biol Chem 1998; 273:30550-9. [PMID: 9804825 DOI: 10.1074/jbc.273.46.30550] [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: 11/06/2022] Open
Abstract
Metabolic labeling of cells with [3H]dihydrosphingosine ([3H]DHS) allows us to follow the incorporation of this tracer into ceramides (Cer), inositol phosphoceramides (IPCs), and mannosylated IPCs and at the same time to assess the remodeling of glycosylphosphatidylinositol proteins during which preexisting anchor lipid moieties are replaced by [3H]Cer-containing anchors. The results indicate that the remodelases in the endoplasmic reticulum and Golgi use as their substrate Cers that are not generated by the breakdown of IPCs but are newly synthesized. Aureobasidin A, an inhibitor of the IPC synthase Aur1p completely blocks IPC biosynthesis at 0.5 micrograms/ml but does not block remodeling of glycosylphosphatidylinositol anchors even at concentrations up to 10 micrograms/ml. In addition, a synthetic Cer analogue, N-hexanoyl-[3H]DHS, is used as a substrate by Aur1p but not by the remodelases. Thus, remodeling is not mediated by Aur1p although remodeling presumably proceeds by an analogous reaction. Studies with secretion mutants deficient in COPII or COPI coat proteins show that all COPII mutants are unable to introduce [3H]Cer by the Golgi remodelase at the restrictive temperature. This suggests that Cer has to be transported by a COPII-dependent way from the endoplasmic reticulum to Golgi for Golgi remodeling to occur. Golgi remodeling is also not operating in the erd2 mutant and is significantly reduced in COPI mutants, suggesting a dependence of Golgi remodeling on retrotransport.
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Affiliation(s)
- F Reggiori
- Institute of Biochemistry, University of Fribourg, Rue du Musée 5, CH-1700 Fribourg, Switzerland
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