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Arlt H, Raman B, Filali-Mouncef Y, Hu Y, Leytens A, Hardenberg R, Guimarães R, Kriegenburg F, Mari M, Smaczynska-de Rooij II, Ayscough KR, Dengjel J, Ungermann C, Reggiori F. The dynamin Vps1 mediates Atg9 transport to the sites of autophagosome formation. J Biol Chem 2023; 299:104712. [PMID: 37060997 DOI: 10.1016/j.jbc.2023.104712] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 03/14/2023] [Accepted: 04/06/2023] [Indexed: 04/17/2023] Open
Abstract
Autophagy is a key process in eukaryotes to maintain cellular homeostasis by delivering cellular components to lysosomes/vacuoles for degradation and reuse of the resulting metabolites. Membrane rearrangements and trafficking events are mediated by the core machinery of autophagy-related (Atg) proteins, which carry out a variety of functions. How Atg9, a lipid scramblase and the only conserved transmembrane protein within this core Atg machinery, is trafficked during autophagy remained largely unclear. Here, we addressed this question in yeast Saccharomyces cerevisiae and found that retromer complex and dynamin Vps1 mutants alter Atg9 subcellular distribution and severely impair the autophagic flux by affecting two separate autophagy steps. We provide evidence that Vps1 interacts with Atg9 at Atg9 reservoirs. In the absence of Vps1, Atg9 fails to reach the sites of autophagosome formation, and this results in an autophagy defect. The function of Vps1 in autophagy requires its GTPase activity. Moreover, Vps1 point mutants associated with human diseases such as microcytic anemia and Charcot-Marie-Tooth are unable to sustain autophagy and affect Atg9 trafficking. Together, our data provide novel insights on the role of dynamins in Atg9 trafficking and suggest that a defect in this autophagy step could contribute to severe human pathologies.
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Affiliation(s)
- Henning Arlt
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; University of Osnabrück, Department of Biology/Chemistry, Biochemistry section, Barbarastrasse 13, 49076 Osnabrück, Germany
| | - Babu Raman
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Yasmina Filali-Mouncef
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Yan Hu
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000 Aarhus C, Denmark
| | - Alexandre Leytens
- Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland
| | - Ralph Hardenberg
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Rodrigo Guimarães
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Franziska Kriegenburg
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Muriel Mari
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000 Aarhus C, Denmark
| | | | - Kathryn R Ayscough
- Department of Biomedical Sciences, University of Sheffield, Sheffield, S10 2TN, United Kingdom
| | - Jörn Dengjel
- Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland
| | - Christian Ungermann
- University of Osnabrück, Department of Biology/Chemistry, Biochemistry section, Barbarastrasse 13, 49076 Osnabrück, Germany
| | - Fulvio Reggiori
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000 Aarhus C, Denmark; Aarhus Institute of Advanced Studies (AIAS), Aarhus University, Høegh-Guldbergs Gade 6B, 8000 Aarhus C, Denmark.
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Menon D, Hummel D, Kaksonen M. Regulation of membrane scission in yeast endocytosisDepartment of Biochemistry and National Centre of Competence in Research, Chemical Biology, University of Geneva, Geneva, Switzerland. Mol Biol Cell 2022; 33:ar114. [PMID: 35976707 DOI: 10.1091/mbc.e21-07-0346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
During clathrin-mediated endocytosis, a flat plasma membrane is shaped into an invagination that undergoes scission to form a vesicle. In mammalian cells, the force that drives the transition from invagination to vesicle is primarily provided by the GTPase dynamin that acts in concert with crescent-shaped BAR domain proteins. In yeast cells, the mechanism of endocytic scission is unclear. The yeast BAR domain protein complex Rvs161/167 (Rvs) nevertheless plays an important role in this process: deletion of Rvs dramatically reduces scission efficiency. A mechanistic understanding of the influence of Rvs on scission however, remains incomplete. We used quantitative live-cell imaging and genetic manipulation to understand the recruitment and function of Rvs and other late-stage proteins at yeast endocytic sites. We found that arrival of Rvs at endocytic sites is timed by interaction of its BAR domain with specific membrane curvature. A second domain of Rvs167 - the SH3 domain - affects localization efficiency of Rvs. We show that Myo3, one of the two type-I myosins in Saccharomyces cerevisiae, has a role in recruiting Rvs167 via the SH3 domain. Removal of the SH3 domain also affects assembly and disassembly of actin and impedes membrane invagination. Our results indicate that both BAR and SH3 domains are important for the role of Rvs as a regulator of scission. We tested other proteins implicated in vesicle formation in Saccharomyces cerevisiae, and found that neither synaptojanins nor dynamin contribute directly to membrane scission. We propose that recruitment of Rvs BAR domains delays scission and allows invaginations to grow by stabilizing them. We also propose that vesicle formation is dependent on the force exerted by the actin network.
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Affiliation(s)
- Deepikaa Menon
- Department of Biochemistry and National Centre of Competence in Research, Chemical Biology, University of Geneva, Geneva, Switzerland
| | - Daniel Hummel
- Department of Biochemistry and National Centre of Competence in Research, Chemical Biology, University of Geneva, Geneva, Switzerland
| | - Marko Kaksonen
- Department of Biochemistry and National Centre of Competence in Research, Chemical Biology, University of Geneva, Geneva, Switzerland
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Kruasuwan W, Puseenam A, Phithakrotchanakoon C, Tanapongpipat S, Roongsawang N. Modulation of heterologous protein secretion in the thermotolerant methylotrophic yeast Ogataea thermomethanolica TBRC 656 by CRISPR-Cas9 system. PLoS One 2021; 16:e0258005. [PMID: 34582499 PMCID: PMC8478189 DOI: 10.1371/journal.pone.0258005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 09/16/2021] [Indexed: 11/18/2022] Open
Abstract
The thermotolerant methylotrophic yeast Ogataea thermomethanolica TBRC 656 is a potential host strain for industrial protein production. Heterologous proteins are often retained intracellularly in yeast resulting in endoplasmic reticulum (ER) stress and poor secretion, and despite efforts to engineer protein secretory pathways, heterologous protein production is often lower than expected. We hypothesized that activation of genes involved in the secretory pathway could mitigate ER stress. In this study, we created mutants defective in protein secretory-related functions using clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) tools. Secretion of the model protein xylanase was significantly decreased in loss of function mutants for oxidative stress (sod1Δ) and vacuolar and protein sorting (vps1Δ and ypt7Δ) genes. However, xylanase secretion was unaffected in an autophagy related atg12Δ mutant. Then, we developed a system for sequence-specific activation of target gene expression (CRISPRa) in O. thermomethanolica and used it to activate SOD1, VPS1 and YPT7 genes. Production of both non-glycosylated xylanase and glycosylated phytase was enhanced in the gene activated mutants, demonstrating that CRISPR-Cas9 systems can be used as tools for understanding O. thermomethanolica genes involved in protein secretion, which could be applied for increasing heterologous protein secretion in this yeast.
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Affiliation(s)
- Worarat Kruasuwan
- Microbial Cell Factory Research Team, Microbial Biotechnology and Biochemicals Research Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Khlong Nueng, Khlong Luang, Pathum Thani, Thailand
| | - Aekkachai Puseenam
- Microbial Cell Factory Research Team, Microbial Biotechnology and Biochemicals Research Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Khlong Nueng, Khlong Luang, Pathum Thani, Thailand
| | - Chitwadee Phithakrotchanakoon
- Microbial Systems and Computational Biology Research Team, Thailand Bioresource Research Center, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Khlong Nueng, Khlong Luang, Pathum Thani, Thailand
| | - Sutipa Tanapongpipat
- Microbial Cell Factory Research Team, Microbial Biotechnology and Biochemicals Research Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Khlong Nueng, Khlong Luang, Pathum Thani, Thailand
| | - Niran Roongsawang
- Microbial Cell Factory Research Team, Microbial Biotechnology and Biochemicals Research Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Khlong Nueng, Khlong Luang, Pathum Thani, Thailand
- * E-mail:
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Igoshin OA, Chen J, Xing J, Liu J, Elston TC, Grabe M, Kim KS, Nirody JA, Rangamani P, Sun SX, Wang H, Wolgemuth C. Biophysics at the coffee shop: lessons learned working with George Oster. Mol Biol Cell 2019; 30:1882-1889. [PMID: 31322997 PMCID: PMC6727762 DOI: 10.1091/mbc.e19-02-0107] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Over the past 50 years, the use of mathematical models, derived from physical reasoning, to describe molecular and cellular systems has evolved from an art of the few to a cornerstone of biological inquiry. George Oster stood out as a pioneer of this paradigm shift from descriptive to quantitative biology not only through his numerous research accomplishments, but also through the many students and postdocs he mentored over his long career. Those of us fortunate enough to have worked with George agree that his sharp intellect, physical intuition, and passion for scientific inquiry not only inspired us as scientists but also greatly influenced the way we conduct research. We would like to share a few important lessons we learned from George in honor of his memory and with the hope that they may inspire future generations of scientists.
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Affiliation(s)
- Oleg A Igoshin
- Departments of Bioengineering, Biosciences, and Chemistry and Center for Theoretical Biological Physics, Rice University, Houston, TX 77005
| | - Jing Chen
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061
| | - Jianhua Xing
- Department of Computational and Systems Biology and UPMC-Hillman Cancer Center, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261
| | - Jian Liu
- Department of Cell Biology and Center for Cell Dynamics, School of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Timothy C Elston
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Michael Grabe
- Cardiovascular Research Institute, School of Pharmacy, University of California, San Francisco, San Francisco, CA 94158
| | - Kenneth S Kim
- Lawrence Livermore National Laboratory, Livermore, CA 94550
| | - Jasmine A Nirody
- Center for Studies in Physics and Biology, Rockefeller University, New York, NY 10065
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA 92093
| | - Sean X Sun
- Department of Mechanical Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, MD 21218
| | - Hongyun Wang
- Department of Applied Mathematics and Statistics, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Charles Wolgemuth
- Department of Physics and Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721
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Yeast dynamin associates with the GARP tethering complex for endosome-to-Golgi traffic. Eur J Cell Biol 2017; 96:612-621. [DOI: 10.1016/j.ejcb.2017.04.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 03/24/2017] [Accepted: 04/18/2017] [Indexed: 11/21/2022] Open
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Goud Gadila SK, Williams M, Saimani U, Delgado Cruz M, Makaraci P, Woodman S, Short JC, McDermott H, Kim K. Yeast dynamin Vps1 associates with clathrin to facilitate vesicular trafficking and controls Golgi homeostasis. Eur J Cell Biol 2017; 96:182-197. [DOI: 10.1016/j.ejcb.2017.02.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 01/11/2017] [Accepted: 02/16/2017] [Indexed: 10/20/2022] Open
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Williams M, Kim K. From membranes to organelles: emerging roles for dynamin-like proteins in diverse cellular processes. Eur J Cell Biol 2014; 93:267-77. [PMID: 24954468 DOI: 10.1016/j.ejcb.2014.05.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 05/12/2014] [Accepted: 05/14/2014] [Indexed: 11/18/2022] Open
Abstract
Dynamin is a GTPase mechanoenzyme most noted for its role in vesicle scission during endocytosis, and belongs to the dynamin family proteins. The dynamin family consists of classical dynamins and dynamin-like proteins (DLPs). Due to structural and functional similarities DLPs are thought to carry out membrane tubulation and scission in a similar manner to dynamin. Here, we discuss the newly emerging roles for DLPs, which include vacuole fission and fusion, peroxisome maintenance, endocytosis and intracellular trafficking. Specific focus is given to the role of DLPs in the budding yeast Saccharomyces cerevisiae because the diverse function of DLPs has been well characterized in this organism. Recent insights into DLPs may provide a better understanding of mammalian dynamin and its associated diseases.
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Affiliation(s)
- Michelle Williams
- Department of Biology, Missouri State University, 901 South National, Springfield, MO 65897, United States
| | - Kyoungtae Kim
- Department of Biology, Missouri State University, 901 South National, Springfield, MO 65897, United States.
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Lukehart J, Highfill C, Kim K. Vps1, a recycling factor for the traffic from early endosome to the late Golgi. Biochem Cell Biol 2013; 91:455-65. [DOI: 10.1139/bcb-2013-0044] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recycling of cellular membranes and their constituents plays a role for cell survival and growth. In the budding yeast, there are recycling traffics from early and late endosomal compartments to the late Golgi. Here, we examined a possible role for Vps1, a large GTPase, in the recycling traffic of GFP-Snc1 from early endosomes to the late Golgi. In the absence of Vps1 we observed an aberrant accumulation of GFP-Snc1 puncta in the cytoplasm that we identified as early endosomes. The N-terminal GTPase and the C-terminal GED domains of Vps1 are essential for Vps1’s function in Snc1 recycling. Our finding of genetic interactions of VPS1 with genes involved in early endosome-to-Golgi traffic further suggests Vps1 functions as a recycling factor in the membrane traffic. Finally, we provide evidence that the severe accumulation of GFP-Snc1 cytoplasmic puncta in vps1Δ cells is attributed to a mild defect in the retention of the GARP component Vps51 at the late Golgi, as well as a severe disruption of actin cables.
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Affiliation(s)
- Joshua Lukehart
- Department of Biology, Missouri State University, Springfield, MO 65897, USA
| | - Chad Highfill
- Department of molecular bioscience, University of Kansas, Lawrence, KS 66045, USA
| | - Kyoungtae Kim
- Department of Biology, Missouri State University, Springfield, MO 65897, USA
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10
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Hayden J, Williams M, Granich A, Ahn H, Tenay B, Lukehart J, Highfill C, Dobard S, Kim K. Vps1 in the late endosome-to-vacuole traffic. J Biosci 2013; 38:73-83. [PMID: 23385815 DOI: 10.1007/s12038-012-9295-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Vacuolar protein sorting 1 (Vps1), the yeast homolog to human dynamin, is a GTP hydrolyzing protein, which plays an important role in protein sorting and targeting between the Golgi and late endosomal compartments. In this study, we assessed the functional significance of Vps1 in the membrane traffic towards the vacuole. We show here that vps1 delta cells accumulated FM4-64 to a greater extent than wild-type (WT))cells, suggesting slower endocytic degradation traffic toward the vacuole. In addition, we observed that two endosome-to-vacuole traffic markers, DsRed-FYVE and Ste2-GFP, were highly accumulated in Vps1-deficient cells, further supporting Vps1's implication in efficient trafficking of endocytosed materials to the vacuole. Noteworthy, a simultaneous imaging analysis in conjunction with FM4-64 pulse-chase experiment further revealed that Vps1 plays a role in late endosome to the vacuole transport. Consistently, our subcellular localization analysis showed that Vps1 is present at the late endosome. The hyperaccumulation of endosomal intermediates in the vps1 mutant cells appears to be caused by the disruption of integrity of HOPS tethering complexes, manifested by mislocalization of Vps39 to the cytoplasm. Finally, we postulate that Vps1 functions together with the Endosomal Sorting Complex Required for Transport (ESCRT) complex at the late endosomal compartments, based on the observation that the double mutants, in which VPS1 along with singular ESCRT I, II and III genes have been disrupted, exhibited synthetic lethality. Together, we propose that Vps1 is required for correct and efficient trafficking from the late endosomal compartments to the vacuole.
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Affiliation(s)
- Jacob Hayden
- Department of Biology, Missouri State University, 901 S National, Springfield, Missouri 65807, USA
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Gossing M, Chidambaram S, Fischer von Mollard G. Importance of the N-terminal domain of the Qb-SNARE Vti1p for different membrane transport steps in the yeast endosomal system. PLoS One 2013; 8:e66304. [PMID: 23776654 PMCID: PMC3680383 DOI: 10.1371/journal.pone.0066304] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 05/04/2013] [Indexed: 01/11/2023] Open
Abstract
SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) on transport vesicles and target membranes are crucial for vesicle targeting and fusion. They form SNARE complexes, which contain four α-helical SNARE motifs contributed by three or four different SNAREs. Most SNAREs function only in a single transport step. The yeast SNARE Vti1p participates in four distinct SNARE complexes in transport from the trans Golgi network to late endosomes, in transport to the vacuole, in retrograde transport from endosomes to the trans Golgi network and in retrograde transport within the Golgi. So far, all vti1 mutants investigated had mutations within the SNARE motif. Little is known about the function of the N-terminal domain of Vti1p, which forms a three helix bundle called Habc domain. Here we generated a temperature-sensitive mutant of this domain to study the effects on different transport steps. The secondary structure of wild type and vti1-3 Habc domain was analyzed by circular dichroism spectroscopy. The amino acid exchanges identified in the temperature-sensitive vti1-3 mutant caused unfolding of the Habc domain. Transport pathways were investigated by immunoprecipitation of newly synthesized proteins after pulse-chase labeling and by fluorescence microscopy of a GFP-tagged protein cycling between plasma membrane, early endosomes and Golgi. In vti1-3 cells transport to the late endosome and assembly of the late endosomal SNARE complex was blocked at 37°C. Retrograde transport to the trans Golgi network was affected while fusion with the vacuole was possible but slower. Steady state levels of SNARE complexes mediating these steps were less affected than that of the late endosomal SNARE complex. As different transport steps were affected our data demonstrate the importance of a folded Vti1p Habc domain for transport.
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Affiliation(s)
- Michael Gossing
- Biochemie III, Fakultät für Chemie, Universität Bielefeld, Bielefeld, Germany
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Sasaki T, Takagi H. Phosphorylation of a conserved Thr357 in yeast Nedd4-like ubiquitin ligase Rsp5 is involved in down-regulation of the general amino acid permease Gap1. Genes Cells 2013; 18:459-75. [DOI: 10.1111/gtc.12049] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Accepted: 02/18/2013] [Indexed: 11/27/2022]
Affiliation(s)
- Toshiya Sasaki
- Graduate School of Biological Sciences; Nara Institute of Science and Technology; 8916-5 Takayama; Ikoma; Nara; 630-0192; Japan
| | - Hiroshi Takagi
- Graduate School of Biological Sciences; Nara Institute of Science and Technology; 8916-5 Takayama; Ikoma; Nara; 630-0192; Japan
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Hachiro T, Yamamoto T, Nakano K, Tanaka K. Phospholipid flippases Lem3p-Dnf1p and Lem3p-Dnf2p are involved in the sorting of the tryptophan permease Tat2p in yeast. J Biol Chem 2012; 288:3594-608. [PMID: 23250744 DOI: 10.1074/jbc.m112.416263] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The type 4 P-type ATPases are flippases that generate phospholipid asymmetry in membranes. In budding yeast, heteromeric flippases, including Lem3p-Dnf1p and Lem3p-Dnf2p, translocate phospholipids to the cytoplasmic leaflet of membranes. Here, we report that Lem3p-Dnf1/2p are involved in transport of the tryptophan permease Tat2p to the plasma membrane. The lem3Δ mutant exhibited a tryptophan requirement due to the mislocalization of Tat2p to intracellular membranes. Tat2p was relocalized to the plasma membrane when trans-Golgi network (TGN)-to-endosome transport was inhibited. Inhibition of ubiquitination by mutations in ubiquitination machinery also rerouted Tat2p to the plasma membrane. Lem3p-Dnf1/2p are localized to endosomal/TGN membranes in addition to the plasma membrane. Endocytosis mutants, in which Lem3p-Dnf1/2p are sequestered to the plasma membrane, also exhibited the ubiquitination-dependent missorting of Tat2p. These results suggest that Tat2p is ubiquitinated at the TGN and missorted to the vacuolar pathway in the lem3Δ mutant. The NH(2)-terminal cytoplasmic region of Tat2p containing ubiquitination acceptor lysines interacted with liposomes containing acidic phospholipids, including phosphatidylserine. This interaction was abrogated by alanine substitution mutations in the basic amino acids downstream of the ubiquitination sites. Interestingly, a mutant Tat2p containing these substitutions was missorted in a ubiquitination-dependent manner. We propose the following model based on these results; Tat2p is not ubiquitinated when the NH(2)-terminal region is bound to membrane phospholipids, but if it dissociates from the membrane due to a low level of phosphatidylserine caused by perturbation of phospholipid asymmetry in the lem3Δ mutant, Tat2p is ubiquitinated and then transported from the TGN to the vacuole.
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Affiliation(s)
- Takeru Hachiro
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, N15 W7, Kita-ku, Sapporo 060-0815, Japan
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Shanks SG, Carpp LN, Struthers MS, McCann RK, Bryant NJ. The Sec1/Munc18 protein Vps45 regulates cellular levels of its SNARE binding partners Tlg2 and Snc2 in Saccharomyces cerevisiae. PLoS One 2012; 7:e49628. [PMID: 23166732 PMCID: PMC3498219 DOI: 10.1371/journal.pone.0049628] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Accepted: 10/11/2012] [Indexed: 12/29/2022] Open
Abstract
Intracellular membrane trafficking pathways must be tightly regulated to ensure proper functioning of all eukaryotic cells. Central to membrane trafficking is the formation of specific SNARE (soluble N-ethylmeleimide-sensitive factor attachment protein receptor) complexes between proteins on opposing lipid bilayers. The Sec1/Munc18 (SM) family of proteins play an essential role in SNARE-mediated membrane fusion, and like the SNAREs are conserved through evolution from yeast to humans. The SM protein Vps45 is required for the formation of yeast endosomal SNARE complexes and is thus essential for traffic through the endosomal system. Here we report that, in addition to its role in regulating SNARE complex assembly, Vps45 regulates cellular levels of its SNARE binding partners: the syntaxin Tlg2 and the v-SNARE Snc2: Cells lacking Vps45 have reduced cellular levels of Tlg2 and Snc2; and elevation of Vps45 levels results in concomitant increases in the levels of both Tlg2 and Snc2. As well as regulating traffic through the endosomal system, the Snc v-SNAREs are also required for exocytosis. Unlike most vps mutants, cells lacking Vps45 display multiple growth phenotypes. Here we report that these can be reversed by selectively restoring Snc2 levels in vps45 mutant cells. Our data indicate that as well as functioning as part of the machinery that controls SNARE complex assembly, Vps45 also plays a key role in determining the levels of its cognate SNARE proteins; another key factor in regulation of membrane traffic.
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Affiliation(s)
- Scott G. Shanks
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell & Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Lindsay N. Carpp
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell & Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Marion S. Struthers
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell & Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Rebecca K. McCann
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell & Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Nia J. Bryant
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell & Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- * E-mail:
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Abstract
Clathrin-mediated endocytosis (CME) is the major pathway for internalization of membrane proteins from the cell surface. Half a century of studies have uncovered tremendous insights into how a clathrin-coated vesicle is formed. More recently, the advent of live-cell imaging has provided a dynamic view of this process. As CME is highly conserved from yeast to humans, budding yeast provides an evolutionary template for this process and has been a valuable system for dissecting the underlying molecular mechanisms. In this review we trace the formation of a clathrin-coated vesicle from initiation to uncoating, focusing on key findings from the yeast system.
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Finnigan GC, Hanson-Smith V, Houser BD, Park HJ, Stevens TH. The reconstructed ancestral subunit a functions as both V-ATPase isoforms Vph1p and Stv1p in Saccharomyces cerevisiae. Mol Biol Cell 2011; 22:3176-91. [PMID: 21737673 PMCID: PMC3164464 DOI: 10.1091/mbc.e11-03-0244] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The vacuolar ATPase complex in yeast contains two isoforms of subunit a that dictate the subcellular localization of the V-ATPase enzyme. The most recent common ancestor of subunit a (Anc.a) is reconstructed, and its function and localization in modern Saccharomyces cerevisiae are characterized. Anc.a is able to replace both subunit a isoforms. The vacuolar-type, proton-translocating ATPase (V-ATPase) is a multisubunit enzyme responsible for organelle acidification in eukaryotic cells. Many organisms have evolved V-ATPase subunit isoforms that allow for increased specialization of this critical enzyme. Differential targeting of the V-ATPase to specific subcellular organelles occurs in eukaryotes from humans to budding yeast. In Saccharomyces cerevisiae, the two subunit a isoforms are the only difference between the two V-ATPase populations. Incorporation of Vph1p or Stv1p into the V-ATPase dictates the localization of the V-ATPase to the vacuole or late Golgi/endosome, respectively. A duplication event within fungi gave rise to two subunit a genes. We used ancestral gene reconstruction to generate the most recent common ancestor of Vph1p and Stv1p (Anc.a) and tested its function in yeast. Anc.a localized to both the Golgi/endosomal network and vacuolar membrane and acidified these compartments as part of a hybrid V-ATPase complex. Trafficking of Anc.a did not require retrograde transport from the late endosome to the Golgi that has evolved for retrieval of the Stv1p isoform. Rather, Anc.a localized to both structures through slowed anterograde transport en route to the vacuole. Our results suggest an evolutionary model that describes the differential localization of the two yeast V-ATPase isoforms.
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Affiliation(s)
- Gregory C Finnigan
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
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17
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Orlando K, Sun X, Zhang J, Lu T, Yokomizo L, Wang P, Guo W. Exo-endocytic trafficking and the septin-based diffusion barrier are required for the maintenance of Cdc42p polarization during budding yeast asymmetric growth. Mol Biol Cell 2011; 22:624-33. [PMID: 21209323 PMCID: PMC3046059 DOI: 10.1091/mbc.e10-06-0484] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Revised: 11/16/2010] [Accepted: 12/22/2010] [Indexed: 12/24/2022] Open
Abstract
Cdc42p plays a central role in asymmetric cell growth in yeast by controlling actin organization and vesicular trafficking. However, how Cdc42p is maintained specifically at the daughter cell plasma membrane during asymmetric cell growth is unclear. We have analyzed Cdc42p localization in yeast mutants defective in various stages of membrane trafficking by fluorescence microscopy and biochemical fractionation. We found that two separate exocytic pathways mediate Cdc42p delivery to the daughter cell. Defects in one of these pathways result in Cdc42p being rerouted through the other. In particular, the pathway involving trafficking through endosomes may couple Cdc42p endocytosis from, and subsequent redelivery to, the plasma membrane to maintain Cdc42p polarization at the daughter cell. Although the endo-exocytotic coupling is necessary for Cdc42p polarization, it is not sufficient to prevent the lateral diffusion of Cdc42p along the cell cortex. A barrier function conferred by septins is required to counteract the dispersal of Cdc42p and maintain its localization in the daughter cell but has no effect on the initial polarization of Cdc42p at the presumptive budding site before symmetry breaking. Collectively, membrane trafficking and septins function synergistically to maintain the dynamic polarization of Cdc42p during asymmetric growth in yeast.
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Affiliation(s)
- Kelly Orlando
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19096
| | - Xiaoli Sun
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19096
| | - Jian Zhang
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19096
| | - Tu Lu
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19096
| | - Lauren Yokomizo
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19096
| | - Puyue Wang
- College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Wei Guo
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19096
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18
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Lamb CA, McCann RK, Stöckli J, James DE, Bryant NJ. Insulin-regulated trafficking of GLUT4 requires ubiquitination. Traffic 2010; 11:1445-54. [PMID: 20854370 PMCID: PMC3152195 DOI: 10.1111/j.1600-0854.2010.01113.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A major consequence of insulin binding its receptor on fat and muscle cells is translocation of the facilitative glucose transporter GLUT4 from an intracellular store to the cell surface where it serves to clear glucose from the bloodstream. Sorting of GLUT4 into its insulin-sensitive store requires the GGA [Golgi-localized, γ-ear-containing, ADP ribosylation factor (ARF)-binding] adaptor proteins, but the signal on GLUT4 to direct this sorting step is unknown. Here, we have identified a role for ubiquitination of GLUT4 in this process. We demonstrate that GLUT4 is ubiquitinated in 3T3-L1 adipocytes, and that a ubiquitin-resistant version fails to translocate to the cell surface of these cells in response to insulin. Our data support a model in which ubiquitination acts as a signal for the trafficking of GLUT4 from the endosomal/trans-Golgi network (TGN) system into its intracellular storage compartment, from where it is mobilized to the cell surface in response to insulin.
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Affiliation(s)
- Christopher A Lamb
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell & Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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19
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Smaczynska-de Rooij II, Allwood EG, Aghamohammadzadeh S, Hettema EH, Goldberg MW, Ayscough KR. A role for the dynamin-like protein Vps1 during endocytosis in yeast. J Cell Sci 2010; 123:3496-506. [PMID: 20841380 DOI: 10.1242/jcs.070508] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Dynamins are a conserved family of proteins involved in membrane fusion and fission. Although mammalian dynamins are known to be involved in several membrane-trafficking events, the role of dynamin-1 in endocytosis is the best-characterised role of this protein family. Despite many similarities between endocytosis in yeast and mammalian cells, a comparable role for dynamins in yeast has not previously been demonstrated. The reported lack of involvement of dynamins in yeast endocytosis has raised questions over the general applicability of the current yeast model of endocytosis, and has also precluded studies using well-developed methods in yeast, to further our understanding of the mechanism of dynamin function during endocytosis. Here, we investigate the yeast dynamin-like protein Vps1 and demonstrate a transient burst of localisation to sites of endocytosis. Using live-cell imaging of endocytic reporters in strains lacking vps1, and also electron microscopy and biochemical approaches, we demonstrate a role for Vps1 in facilitating endocytic invagination. Vps1 mutants were generated, and analysis in several assays reveals a role for the C-terminal self-assembly domain in endocytosis but not in other membrane fission events with which Vps1 has previously been associated.
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Affiliation(s)
- Iwona I Smaczynska-de Rooij
- Department of Molecular Biology and Biotechnology, Firth Court, University of Sheffield, Sheffield S102TN, UK
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20
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Lin AEJ, Guttman JA. Hijacking the endocytic machinery by microbial pathogens. PROTOPLASMA 2010; 244:75-90. [PMID: 20574860 DOI: 10.1007/s00709-010-0164-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Accepted: 05/19/2010] [Indexed: 05/24/2023]
Abstract
Understanding the mechanisms that microbes exploit to invade host cells and cause disease is crucial if we are to eliminate their threat. Although pathogens use a variety of microbial factors to trigger entry into non-phagocytic cells, their targeting of the host cell process of endocytosis has emerged as a common theme. To accomplish this, microbes often rewire the normal course of particle internalization, frequently usurping theoretical maximal sizes to permit entry and reconfiguring molecular components that were once thought to be required for vesicle formation. Here, we discuss recent advances in our understanding of how toxins, viruses, bacteria, and fungi manipulate the host cell endocytic machinery to generate diseases. Additionally, we will reveal the advantages of using these organisms to expand our general knowledge of endocytic mechanisms in eukaryotic cells.
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Affiliation(s)
- Ann En-Ju Lin
- Department of Biological Sciences, Shrum Science Centre, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada
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21
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A chemical genetic screen for modulators of exocytic transport identifies inhibitors of a transport mechanism linked to GTR2 function. EUKARYOTIC CELL 2009; 9:116-26. [PMID: 19897736 DOI: 10.1128/ec.00184-09] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Membrane and protein traffic to the cell surface is mediated by partially redundant pathways that are difficult to perturb in ways that yield a strong phenotype. Such robustness is expected in a fine-tuned process, regulated by environmental cues, that is required for controlled cell surface growth and cell proliferation. Synthetic genetic interaction screens are especially valuable for investigating complex processes involving partially redundant pathways or mechanisms. In a previous study, we used a triple-synthetic-lethal yeast mutant screen to identify a novel component of the late exocytic transport machinery, Avl9. In a chemical-genetic version of the successful mutant screen, we have now identified small molecules that cause a rapid (within 15 min) accumulation of secretory cargo and abnormal Golgi compartment-like membranes at low concentration (<2 muM), indicating that the compounds likely target the exocytic transport machinery at the Golgi. We screened for genes that, when overexpressed, suppress the drug effects, and found that the Ras-like small GTPase, Gtr2, but not its homolog and binding partner, Gtr1, efficiently suppresses the toxic effects of the compounds. Furthermore, assays for suppression of the secretory defect caused by the compounds suggest that Gtr proteins can regulate a pathway that is perturbed by the compounds. Because avl9Delta and gtr mutants share some phenotypes, our results indicate that the small molecules identified by our chemical-genetic strategy are promising tools for understanding Avl9 function and the mechanisms that control late exocytic transport.
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22
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Angers CG, Merz AJ. HOPS interacts with Apl5 at the vacuole membrane and is required for consumption of AP-3 transport vesicles. Mol Biol Cell 2009; 20:4563-74. [PMID: 19741093 DOI: 10.1091/mbc.e09-04-0272] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Adaptor protein complexes (APs) are evolutionarily conserved heterotetramers that couple cargo selection to the formation of highly curved membranes during vesicle budding. In Saccharomyces cerevisiae, AP-3 mediates vesicle traffic from the late Golgi to the vacuolar lysosome. The HOPS subunit Vps41 is one of the few proteins reported to have a specific role in AP-3 traffic, yet its function remains undefined. We now show that although the AP-3 delta subunit, Apl5, binds Vps41 directly, this interaction occurs preferentially within the context of the HOPS docking complex. Fluorescence microscopy indicates that Vps41 and other HOPS subunits do not detectably colocalize with AP-3 at the late Golgi or on post-Golgi (Sec7-negative) vesicles. Vps41 and HOPS do, however, transiently colocalize with AP-3 vesicles when these vesicles dock at the vacuole membrane. In cells with mutations in HOPS subunits or the vacuole SNARE Vam3, AP-3 shifts from the cytosol to a membrane fraction. Fluorescence microscopy suggests that this fraction consists of post-Golgi AP-3 vesicles that have failed to dock or fuse at the vacuole membrane. We propose that AP-3 remains associated with budded vesicles, interacts with Vps41 and HOPS upon vesicle docking at the vacuole, and finally dissociates during docking or fusion.
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Affiliation(s)
- Cortney G Angers
- Department of Biochemistry, University of Washington, Seattle, WA 98195-3750, USA
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23
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Röthlisberger S, Jourdain I, Johnson C, Takegawa K, Hyams JS. The dynamin-related protein Vps1 regulates vacuole fission, fusion and tubulation in the fission yeast, Schizosaccharomyces pombe. Fungal Genet Biol 2009; 46:927-35. [PMID: 19643199 DOI: 10.1016/j.fgb.2009.07.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Revised: 07/13/2009] [Accepted: 07/19/2009] [Indexed: 01/07/2023]
Abstract
Fission yeast cells lacking the dynamin-related protein (DRP) Vps1 had smaller vacuoles with reduced capacity for both fusion and fission in response to hypotonic and hypertonic conditions respectively. vps1Delta cells showed normal vacuolar protein sorting, actin organisation and endocytosis. Over-expression of vps1 transformed vacuoles from spherical to tubular. Tubule formation was enhanced in fission conditions and required the Rab protein Ypt7. Vacuole tubulation by Vps1 was more extensive in the absence of a second DRP, Dnm1. Both dnm1Delta and the double mutant vps1Delta dnm1Delta showed vacuole fission defects similar to that of vps1Delta. Over-expression of vps1 in dnm1Delta, or of dnm1 in vps1Delta failed to rescue this phenotype. Over-expression of dnm1 in wild-type cells, on the other hand, induced vacuole fission. Our results are consistent with a model of vacuole fission in which Vps1 creates a tubule of an appropriate diameter for subsequent scission by Dnm1.
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Affiliation(s)
- Sarah Röthlisberger
- Institute of Molecular Biosciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
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24
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TVP23 interacts genetically with the yeast SNARE VTI1 and functions in retrograde transport from the early endosome to the late Golgi. Biochem J 2009; 419:229-36. [DOI: 10.1042/bj20081973] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
SNARE (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor) proteins contribute to specific recognition between transport vesicles and target membranes and are required for fusion of membranes. The SNARE Vti1p is required for several transport steps between late Golgi, endosomes and the vacuole in the yeast Saccharomyces cerevisiae. Here, we identified the late Golgi membrane protein TVP23 as a multicopy suppressor of the growth defect in vti1-2 cells. By contrast, the growth defect in vti1-11 cells was not suppressed by TVP23 overexpression. Deletion of TVP23 aggravated the growth defect in vti1-2 cells. Genetic interactions between TVP23 and vti1-2 were not found in transport from the late Golgi via the late endosome to the vacuole or in transport from the Golgi directly to the vacuole. These results suggest that Tvp23p is not involved in forward transport from the late Golgi. Therefore retrograde traffic to the late Golgi was analysed. vti1-2 cells accumulated GFP (green fluorescent protein)–Snc1p within the cell, indicating that retrograde transport from the early endosome to the late Golgi was defective in these cells. Deletion of TVP23 in vti1-2 cells resulted in a synthetic defect in GFP–Snc1p recycling, whereas tvp23Δ cells had a slight defect. These results indicate that Tvp23p performs a partially redundant function in retrograde transport from the early endosome to the late Golgi. This transport step was unaffected in vti1-11 cells, providing an explanation for the allele-specific multicopy suppression by TVP23.
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25
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Dunkel M, Latz A, Schumacher K, Müller T, Becker D, Hedrich R. Targeting of vacuolar membrane localized members of the TPK channel family. MOLECULAR PLANT 2008; 1:938-49. [PMID: 19825594 DOI: 10.1093/mp/ssn064] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Four members of the tandem-pore potassium channel family of Arabidopsis thaliana (TPK1, 2, 3, and 5) reside in the vacuolar membrane, whereas TPK4 is a plasma membrane K(+)-channel. By constructing chimeras between TPK1 and TPK4, we attempted to identify channel domains involved in the trafficking process and found that the TPK1 cytoplasmic C-terminal domain (CT) is critical for the ER- as well as Golgi-sorting steps. Following site-directed mutagenesis, we identified a diacidic motif (DLE) required for ER-export of TPK1. However, this diacidic motif in the C-terminus is not conserved among other members of the TPK family, and TPK3 sorting is independent of its CT. Moreover, the 14-3-3 binding site of TPK1, essential for channel activation, is not involved in channel sorting.
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Affiliation(s)
- Marcel Dunkel
- University of Würzburg, Julius-von-Sachs-Platz 2, 97082 Würzburg, Germany
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26
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Disrupting vesicular trafficking at the endosome attenuates transcriptional activation by Gcn4. Mol Cell Biol 2008; 28:6796-818. [PMID: 18794364 DOI: 10.1128/mcb.00800-08] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The late endosome (MVB) plays a key role in coordinating vesicular transport of proteins between the Golgi complex, vacuole/lysosome, and plasma membrane. We found that deleting multiple genes involved in vesicle fusion at the MVB (class C/D vps mutations) impairs transcriptional activation by Gcn4, a global regulator of amino acid biosynthetic genes, by decreasing the ability of chromatin-bound Gcn4 to stimulate preinitiation complex assembly at the promoter. The functions of hybrid activators with Gal4 or VP16 activation domains are diminished in class D mutants as well, suggesting a broader defect in activation. Class E vps mutations, which impair protein sorting at the MVB, also decrease activation by Gcn4, provided they elicit rapid proteolysis of MVB cargo proteins in the aberrant late endosome. By contrast, specifically impairing endocytic trafficking from the plasma membrane, or vesicular transport to the vacuole, has a smaller effect on Gcn4 function. Thus, it appears that decreasing cargo proteins in the MVB through impaired delivery or enhanced degradation, and not merely the failure to transport cargo properly to the vacuole or downregulate plasma membrane proteins by endocytosis, is required to attenuate substantially transcriptional activation by Gcn4.
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27
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Flannery AR, Stevens TH. Functional characterization of the N-terminal domain of subunit H (Vma13p) of the yeast vacuolar ATPase. J Biol Chem 2008; 283:29099-108. [PMID: 18708638 DOI: 10.1074/jbc.m803280200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The yeast Saccharomyces cerevisiae vacuolar H(+)-ATPase (V-ATPase) is a multisubunit complex responsible for acidifying intracellular organelles and is highly regulated. One of the regulatory subunits, subunit H, is encoded by the VMA13 gene in yeast and is composed of two domains, the N-terminal domain (amino acids (aa) 1-352) and the C-terminal domain (aa 353-478). The N-terminal domain is required for the activation of the complex, whereas the C-terminal domain is required for coupling ATP hydrolysis to proton translocation (Liu, M., Tarsio, M., Charsky, C. M., and Kane, P. M. (2005) J. Biol. Chem. 280, 36978-36985). Experiments with epitope-tagged copies of Vma13p revealed that there is only one copy of Vma13p/subunit H per V-ATPase complex. Analysis of the N-terminal domain shows that the first 179 amino acids are not required for the activation and full function of the V-ATPase complex and that the minimal region of Vma13p/subunit H capable of activating the V-ATPase is aa 180-353 of the N-terminal domain. Subunit H is expressed as two splice variants in mammals, and deletion of 18 amino acids in yeast Vma13p corresponding to the mammalian subunit H beta isoform results in reduced V-ATPase activity and significantly lower coupling of ATPase hydrolysis to proton translocation. Intriguingly, the yeast Vma13p mimicking the mammalian subunit H beta isoform is functionally equivalent to Vma13p lacking the entire C-terminal domain. These results suggest that the mammalian V-ATPase complexes with subunit H splice variant SFD-alpha or SFD-beta are likely to have different activities and may perform distinct cellular functions.
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Affiliation(s)
- Andrew R Flannery
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut 06536-0812, USA
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28
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Gustavsson M, Barmark G, Larsson J, Murén E, Ronne H. Functional genomics of monensin sensitivity in yeast: implications for post-Golgi traffic and vacuolar H+-ATPase function. Mol Genet Genomics 2008; 280:233-48. [PMID: 18612650 DOI: 10.1007/s00438-008-0359-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Accepted: 06/13/2008] [Indexed: 11/24/2022]
Abstract
We have screened a complete collection of yeast knockout mutants for sensitivity to monensin, an ionophore that interferes with intracellular transport. A total of 63 sensitive strains were found. Most of the strains were deleted for genes involved in post-Golgi traffic, with an emphasis on vacuolar biogenesis. A high correlation was thus seen with VPS and VAM genes, but there were also significant differences between the three sets of genes. A weaker correlation was seen with sensitivity to NaCl, in particular rate of growth effects. Interestingly, all 14 genes encoding subunits of the vacuolar H(+)-ATPase (V-ATPase) were absent in our screen, even though they appeared in the VPS or VAM screens. All monensin-sensitive mutants that could be tested interact synthetically with a deletion of the A subunit of the V-ATPase, Vma1. Synthetic lethality was limited to mutations affecting endocytosis or retrograde transport to Golgi. In addition, vma1 was epistatic over the monensin sensitivity of vacuolar transport mutants, but not endocytosis mutants. Deletions of the two isoforms of the V-ATPase a subunit, Vph1 and Stv1 had opposite effects on the monensin sensitivity of a ypt7 mutant. These findings are consistent with a model where monensin inhibits growth by interfering with the maintenance of an acidic pH in the late secretory pathway. The synthetic lethality of vma1 with mutations affecting retrograde transport to the Golgi further suggests that it is in the late Golgi that a low pH must be maintained.
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Affiliation(s)
- Marie Gustavsson
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
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29
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Chidambaram S, Zimmermann J, von Mollard GF. ENTH domain proteins are cargo adaptors for multiple SNARE proteins at the TGN endosome. J Cell Sci 2008; 121:329-38. [DOI: 10.1242/jcs.012708] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
ENTH and ANTH domain proteins are involved in budding of clathrin-coated vesicles. SNAREs are fusogenic proteins that function in the targeting and fusion of transport vesicles. In mammalian and yeast cells, ENTH domain proteins (epsinR and Ent3p) interact with SNAREs of the vti1 family (Vti1b or Vti1p). This interaction indicates that ENTH proteins could function in cargo sorting, which prompted us to search for additional SNAREs as potential cargo for Ent3p and epsinR. We carried out specific yeast two-hybrid assays, which identified interactions between epsinR and the mammalian late endosomal SNAREs syntaxin 7 and syntaxin 8 as well as between Ent3p and the endosomal SNAREs Pep12p and Syn8p from yeast. Lack of Ent3p affected the trafficking of Pep12p. Ent3p binding to Pep12p required the FSD late endosomal sorting signal in Pep12p. Inactivation of the sorting signal had a similar effect to removal of Ent3p on Pep12p stability indicating that Ent3p acts as a cargo adaptor for Pep12p by binding to the sorting signal. As Vti1p, Pep12p and Syn8p participate in a SNARE complex whereas Vti1b, syntaxin 7 and syntaxin 8 are mammalian SNARE partners, we propose that ENTH domain proteins at the TGN-endosome are cargo adaptors for these endosomal SNAREs.
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Affiliation(s)
- Subbulakshmi Chidambaram
- Biochemie III, Fakultät für Chemie, Universitätstrasse 25, Universität Bielefeld, 33615 Bielefeld, Germany
| | - Jana Zimmermann
- Biochemie III, Fakultät für Chemie, Universitätstrasse 25, Universität Bielefeld, 33615 Bielefeld, Germany
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30
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Bernardo SM, Khalique Z, Kot J, Jones JK, Lee SA. Candida albicans VPS1 contributes to protease secretion, filamentation, and biofilm formation. Fungal Genet Biol 2008; 45:861-77. [PMID: 18296085 DOI: 10.1016/j.fgb.2008.01.001] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Revised: 01/14/2008] [Accepted: 01/15/2008] [Indexed: 01/12/2023]
Abstract
To investigate the pre-vacuolar secretory pathway in Candida albicans, we cloned and analyzed the C. albicans homolog of the Saccharomyces cerevisiae vacuolar protein sorting gene VPS1. C. albicans VPS1 encodes a predicted 694-aa dynamin-like GTPase that is 73.3% similar to S. cerevisiae Vps1p. Plasmids bearing C. albicans VPS1 complemented the temperature-sensitive growth, abnormal class F vacuolar morphology, and carboxypeptidase missorting of a S. cerevisiae vps1 null mutant. To study VPS1 function in C. albicans, a conditional mutant strain (tetR-VPS1) was generated by deleting the first allele of VPS1 and placing the second allele under control of a tetracycline-regulatable promoter. With doxycycline, the tetR-VPS1 mutant was hyper-susceptible to sub-inhibitory concentrations of fluconazole, but not amphotericin B, 5-fluorocytosine, or non-specific osmotic stresses. The repressed tetR-VPS1 mutant was defective in filamentation and secreted less extracellular protease activity. Biofilm production and filamentation within the biofilm were markedly reduced. These results suggest that C. albicans VPS1 has a key role in several important virulence-related phenotypes.
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Affiliation(s)
- Stella M Bernardo
- Division of Infectious Diseases, New Mexico Veterans Healthcare System, University of New Mexico Health Science Center, Albuquerque, NM 87108, USA
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31
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Restrepo R, Zhao X, Peter H, Zhang BY, Arvan P, Nothwehr SF. Structural features of vps35p involved in interaction with other subunits of the retromer complex. Traffic 2007; 8:1841-1853. [PMID: 17892535 PMCID: PMC2504507 DOI: 10.1111/j.1600-0854.2007.00659.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The penta-subunit retromer complex of yeast mediates selective retrieval of membrane proteins from the prevacuolar endosome to the trans Golgi network. In this study, we set out to generate a panel of vps35 dominant-negative mutants that disrupt retromer-mediated cargo sorting. Mapping of the mutations revealed two types of alterations leading to dominant-negative behavior of the 944-amino acid protein: (i) mutations at or near the R(98) residue or (ii) C-terminal truncations exemplified by a nonsense mutation at codon 733. Both could be suppressed by overexpression of wild-type Vps35p, suggesting that these dominant-negative mutants compete for interactions with other retromer subunits. Interestingly, Vps35-R(98)W expression destabilized Vps26p while having no effect on Vps29p stability, while Vps35-Q(733)* expression affected Vps29p stability but had no effect on Vps26p. Measurement of Vps35/Vps26 and Vps35/Vps29 pairwise associations by coimmunoprecipitation in the presence or absence of other retromer subunits indicated that the R(98) residue, which is part of a conserved PRLYL motif, is critical for Vps35p binding to Vps26p, while both R(98) and residues 733-944 are needed for efficient binding to Vps29p.
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Affiliation(s)
- Ricardo Restrepo
- Division of Biological Sciences, 401 Tucker Hall, University of Missouri, Columbia, MO 65211, USA
| | - Xiang Zhao
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, 5560 MSRB2, 1150 W. Medical Center Drive, Ann Arbor, MI 48109, USA
| | - Harald Peter
- Institute of Technical Biochemistry, University of Stuttgart, Allmandring 31, D-70569 Stuttgart, Germany
| | - Bao-yan Zhang
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, 5560 MSRB2, 1150 W. Medical Center Drive, Ann Arbor, MI 48109, USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, 5560 MSRB2, 1150 W. Medical Center Drive, Ann Arbor, MI 48109, USA
| | - Steven F. Nothwehr
- Division of Biological Sciences, 401 Tucker Hall, University of Missouri, Columbia, MO 65211, USA
- *Corresponding author: Steven F. Nothwehr,
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Zhao X, Nothwehr S, Lara-Lemus R, Zhang BY, Peter H, Arvan P. Dominant-negative behavior of mammalian Vps35 in yeast requires a conserved PRLYL motif involved in retromer assembly. Traffic 2007; 8:1829-1840. [PMID: 17916227 DOI: 10.1111/j.1600-0854.2007.00658.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The retromer protein complex assists in recycling selected integral membrane proteins from endosomes to the trans Golgi network. One protein subcomplex (Vps35p, Vps26p and Vps29p) combines with a second (Vps17p and Vps5p) to form a coat involved in sorting and budding of endosomal vesicles. Yeast Vps35p (yVps35) exhibits similarity to human Vps35 (hVps35), especially in a completely conserved PRLYL motif contained within an amino-terminal domain. Companion studies indicate that an R(98)W mutation in yVps35 causes defective retromer assembly in Saccharomyces cerevisiae. Herein, we find that the expression of hVps35 in yeast confers dominant-negative vacuolar proenzyme secretion and defective secretory proprotein processing. The mutant phenotype appears to be driven by hVps35 competing with endogenous yVps35, becoming incorporated into defective retromer complexes and causing proteasomal degradation of endogenous Vps26 and Vps29. Increased expression of yVps35 displaces some hVps35 to a 100 000 x g supernatant and suppresses the dominant-negative phenotype. Remarkably, mutation of the conserved R(107)W of hVps35 displaces some of the protein to the 100 000 x g supernatant, slows protein turnover and restores stability of Vps26p and Vps29p and completely abrogates dominant-negative trafficking behavior. We show that hVps35 coprecipitates Vps26, whereas the R(107)W mutant does not. In pancreatic beta cells, the R(107)W mutant shifts hVps35 from peripheral endosomes to a juxtanuclear compartment, affecting both mannose phosphate receptors and insulin. These data underscore importance of the Vps35 PRLYL motif in retromer subcomplex interactions and function.
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Affiliation(s)
- Xiang Zhao
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, 5560 MSRB2, 1150 W. Medical Center Drive, Ann Arbor, MI 48109, USA
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Daicho K, Maruyama H, Suzuki A, Ueno M, Uritani M, Ushimaru T. The ergosterol biosynthesis inhibitor zaragozic acid promotes vacuolar degradation of the tryptophan permease Tat2p in yeast. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:1681-90. [PMID: 17531951 DOI: 10.1016/j.bbamem.2007.03.022] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2005] [Revised: 03/13/2007] [Accepted: 03/15/2007] [Indexed: 11/29/2022]
Abstract
Ergosterol is the yeast functional equivalent of cholesterol in mammalian cells. Deletion of the ERG6 gene, which encodes an enzyme catalyzing a late step of ergosterol biosynthesis, impedes targeting of the tryptophan permease Tat2p to the plasma membrane, but does not promote vacuolar degradation. It is unknown whether similar features appear when other steps of ergosterol biogenesis are inhibited. We show herein that the ergosterol biosynthesis inhibitor zaragozic acid (ZA) evoked massive vacuolar degradation of Tat2p, accompanied by a decrease in tryptophan uptake. ZA inhibits squalene synthetase (SQS, EC 2.5.1.21), which catalyzes the first committed step in the formation of cholesterol/ergosterol. The degradation of Tat2p was dependent on the Rsp5p-mediated ubiquitination of Tat2p and was not suppressed by deletions of VPS1, VPS27, VPS45 or PEP12. We will discuss ZA-mediated Tat2p degradation in the context of lipid rafts.
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Affiliation(s)
- Katsue Daicho
- Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan
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34
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He B, Xi F, Zhang J, TerBush D, Zhang X, Guo W. Exo70p mediates the secretion of specific exocytic vesicles at early stages of the cell cycle for polarized cell growth. ACTA ACUST UNITED AC 2007; 176:771-7. [PMID: 17339375 PMCID: PMC2064051 DOI: 10.1083/jcb.200606134] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In budding yeast, two classes of post-Golgi secretory vesicles carrying different sets of cargoes typified by Bgl2p and invertase are delivered to the plasma membrane for secretion. The exocyst is implicated in tethering these vesicles to the daughter cell membrane for exocytosis. In this study, we report that mutations in the exocyst component Exo70p predominantly block secretion of the Bgl2p vesicles. Furthermore, a defect in invertase vesicle trafficking caused by vps1Δ or pep12Δ in the exo70 mutant background is detrimental to the cell. The secretion defect in exo70 mutants was most pronounced during the early budding stage, which affected daughter cell growth. The selective secretion block does not occur at the vesicle formation or sorting stage because the exocytic vesicles are properly generated and protein processing is normal in the exo70 mutants. Our study suggests that Exo70p functions primarily at early stages of the cell cycle in Bgl2p vesicle secretion, which is critical for polarized cell growth.
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Affiliation(s)
- Bing He
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
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35
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Charneau S, Bastos IMD, Mouray E, Ribeiro BM, Santana JM, Grellier P, Florent I. Characterization of PfDYN2, a dynamin-like protein of Plasmodium falciparum expressed in schizonts. Microbes Infect 2007; 9:797-805. [PMID: 17533148 DOI: 10.1016/j.micinf.2007.02.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2006] [Revised: 02/14/2007] [Accepted: 02/21/2007] [Indexed: 10/23/2022]
Abstract
Dynamin superfamily members are large GTPases conserved through evolution mainly described as mechanochemical enzymes involved in membrane scission events. The Plasmodium falciparum dynamin-2 (Pfdyn2) gene was cloned from the FcB1 strain. PfDYN2 belongs to the dynamin-like protein subgroup of the dynamin superfamily since it possesses a large GTPase domain together with the conserved dynamin_M and GED domains. Recombinant PfDYN2 was able to bind GTP, to hydrolyze GTP into GDP and to self-associate in low-salt conditions. PfDYN2 expression was restricted to schizonts where it localized in punctuate structures within the parasite cytoplasm. PfDYN2 partly co-localized with markers of the parasite endoplasmic reticulum, Golgi apparatus and apicoplast, suggesting it could be implicated in vesicular trafficking and/or organelle fission events known to occur during the last hours of the parasite development in erythrocytes. PfDYN2 and the previously described PfDYN1 are the only two dynamin superfamily members identified in the P. falciparum genome and the available data suggest that this situation is conserved in the Apicomplexa phylum.
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Affiliation(s)
- Sébastien Charneau
- USM504-EA3335, RDDM, Muséum National d'Histoire Naturelle, 61, rue Buffon, CP52, 75231 Paris cedex 05, France
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36
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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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37
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Kaksonen M, Toret CP, Drubin DG. Harnessing actin dynamics for clathrin-mediated endocytosis. Nat Rev Mol Cell Biol 2006; 7:404-14. [PMID: 16723976 DOI: 10.1038/nrm1940] [Citation(s) in RCA: 548] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Actin polymerization often occurs at the plasma membrane to drive the protrusion of lamellipodia and filopodia at the leading edge of migrating cells. A role for actin polymerization in another cellular process that involves the reshaping of the plasma membrane--namely endocytosis--has recently been established. Live-cell imaging studies are shedding light on the order and timing of the molecular events and mechanisms of actin function during endocytosis.
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Affiliation(s)
- Marko Kaksonen
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202, USA
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38
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Liu J, Kaksonen M, Drubin DG, Oster G. Endocytic vesicle scission by lipid phase boundary forces. Proc Natl Acad Sci U S A 2006; 103:10277-10282. [PMID: 16801551 PMCID: PMC1502448 DOI: 10.1073/pnas.0601045103] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Endocytosis in budding yeast is thought to occur in several phases. First, the membrane invaginates and then elongates into a tube. A vesicle forms at the end of the tube, eventually pinching off to form a "free" vesicle. Experiments show that actin polymerization is an active participant in the endocytic process, along with a number of membrane-associated proteins. Here we investigate the possible roles of these components in driving vesiculation by constructing a quantitative model of the process beginning at the stage where the membrane invagination has elongated into a tube encased in a sheath of membrane-associated protein. This protein sheath brings about the scission step where the vesicle separates from the tube. When the protein sheath is dynamin, it is commonly assumed that scission is brought about by the constriction of the sheath. Here, we show that an alternative scenario can work as well: The protein sheath acts as a "filter" to effect a phase separation of lipid species. The resulting line tension tends to minimize the interface between the tube region and the vesicle region. Interestingly, large vesicle size can further facilitate the reduction of the interfacial diameter down to a few nanometers, small enough so that thermal fluctuations can fuse the membrane and pinch off the vesicle. To deform the membrane into the tubular vesicle shape, the membrane elastic resistance forces must be balanced by some additional forces that we show can be generated by actin polymerization and/or myosin I. These active forces are shown to be important in successful scission processes as well.
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Affiliation(s)
| | - Marko Kaksonen
- Molecular and Cellular Biology, University of California, Berkeley, CA 94720
| | - David G Drubin
- Molecular and Cellular Biology, University of California, Berkeley, CA 94720
| | - George Oster
- Molecular and Cellular Biology, University of California, Berkeley, CA 94720
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39
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Foote C, Nothwehr SF. The clathrin adaptor complex 1 directly binds to a sorting signal in Ste13p to reduce the rate of its trafficking to the late endosome of yeast. ACTA ACUST UNITED AC 2006; 173:615-26. [PMID: 16702232 PMCID: PMC2063869 DOI: 10.1083/jcb.200510161] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Yeast trans-Golgi network (TGN) membrane proteins maintain steady-state localization by constantly cycling to and from endosomes. In this study, we examined the trafficking itinerary and molecular requirements for delivery of a model TGN protein A(F-->A)-alkaline phosphatase (ALP) to the prevacuolar/endosomal compartment (PVC). A(F-->A)-ALP was found to reach the PVC via early endosomes (EEs) with a half-time of approximately 60 min. Delivery of A(F-->A)-ALP to the PVC was not dependent on either the GGA or adaptor protein 1 (AP-1) type of clathrin adaptors, which are thought to function in TGN to PVC and TGN to EE transport, respectively. Surprisingly, in cells lacking the function of both GGA and AP-1 adaptors, A(F-->A)-ALP transport to the PVC was dramatically accelerated. A 12-residue cytosolic domain motif of A(F-->A)-ALP was found to mediate direct binding to AP-1 and was sufficient to slow TGN-->EE-->PVC trafficking. These results suggest a model in which this novel sorting signal targets A(F-->A)-ALP into clathrin/AP-1 vesicles at the EE for retrieval back to the TGN.
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Affiliation(s)
- Christopher Foote
- Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA
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40
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Kirkham M, Parton RG. Clathrin-independent endocytosis: new insights into caveolae and non-caveolar lipid raft carriers. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1745:273-86. [PMID: 16046009 DOI: 10.1016/j.bbamcr.2005.06.002] [Citation(s) in RCA: 191] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 03/24/2005] [Revised: 06/06/2005] [Accepted: 06/06/2005] [Indexed: 01/06/2023]
Abstract
A number of recent studies have provided new insights into the complexity of the endocytic pathways originating at the plasma membrane of mammalian cells. Many of the molecules involved in clathrin coated pit internalization are now well understood but other pathways are less well defined. Caveolae appear to represent a low capacity but highly regulated pathway in a restricted set of tissues in vivo. A third pathway, which is both clathrin- and caveolae-independent, may constitute a specialized high capacity endocytic pathway for lipids and fluid. The relationship of this pathway, if any, to macropinocytosis or to the endocytic pathways of lower eukaryotes remains an interesting open question. Our understanding of the regulatory mechanisms and molecular components involved in this pathway are at a relatively primitive stage. In this review, we will consider some of the characteristics of different endocytic pathways in high and lower eukaryotes and consider some of the common themes in endocytosis. One theme which becomes apparent from comparison of these pathways is that apparently different pathways can share common molecular machinery and that pathways considered to be distinct actually represent similar basic pathways to which additional levels of regulatory complexity have been added.
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Affiliation(s)
- Matthew Kirkham
- Institute for Molecular Bioscience, University of Queensland, Queensland 4072, Australia
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41
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Ren G, Vajjhala P, Lee JS, Winsor B, Munn AL. The BAR domain proteins: molding membranes in fission, fusion, and phagy. Microbiol Mol Biol Rev 2006; 70:37-120. [PMID: 16524918 PMCID: PMC1393252 DOI: 10.1128/mmbr.70.1.37-120.2006] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The Bin1/amphiphysin/Rvs167 (BAR) domain proteins are a ubiquitous protein family. Genes encoding members of this family have not yet been found in the genomes of prokaryotes, but within eukaryotes, BAR domain proteins are found universally from unicellular eukaryotes such as yeast through to plants, insects, and vertebrates. BAR domain proteins share an N-terminal BAR domain with a high propensity to adopt alpha-helical structure and engage in coiled-coil interactions with other proteins. BAR domain proteins are implicated in processes as fundamental and diverse as fission of synaptic vesicles, cell polarity, endocytosis, regulation of the actin cytoskeleton, transcriptional repression, cell-cell fusion, signal transduction, apoptosis, secretory vesicle fusion, excitation-contraction coupling, learning and memory, tissue differentiation, ion flux across membranes, and tumor suppression. What has been lacking is a molecular understanding of the role of the BAR domain protein in each process. The three-dimensional structure of the BAR domain has now been determined and valuable insight has been gained in understanding the interactions of BAR domains with membranes. The cellular roles of BAR domain proteins, characterized over the past decade in cells as distinct as yeasts, neurons, and myocytes, can now be understood in terms of a fundamental molecular function of all BAR domain proteins: to sense membrane curvature, to bind GTPases, and to mold a diversity of cellular membranes.
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Affiliation(s)
- Gang Ren
- Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland 4072, Australia
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42
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Kirkham M, Parton RG. Clathrin-independent endocytosis: new insights into caveolae and non-caveolar lipid raft carriers. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1746:349-63. [PMID: 16440447 DOI: 10.1016/j.bbamcr.2005.11.007] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A number of recent studies have provided new insights into the complexity of the endocytic pathways originating at the plasma membrane of mammalian cells. Many of the molecules involved in clathrin coated pit internalization are now well understood but other pathways are less well defined. Caveolae appear to represent a low capacity but highly regulated pathway in a restricted set of tissues in vivo. A third pathway, which is both clathrin- and caveolae-independent, may constitute a specialized high capacity endocytic pathway for lipids and fluid. The relationship of this pathway, if any, to macropinocytosis or to the endocytic pathways of lower eukaryotes remains an interesting open question. Our understanding of the regulatory mechanisms and molecular components involved in this pathway are at a relatively primitive stage. In this review, we will consider some of the characteristics of different endocytic pathways in high and lower eukaryotes and consider some of the common themes in endocytosis. One theme which becomes apparent from comparison of these pathways is that apparently different pathways can share common molecular machinery and that pathways considered to be distinct actually represent similar basic pathways to which additional levels of regulatory complexity have been added.
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Affiliation(s)
- Matthew Kirkham
- Institute for Molecular Bioscience, University of Queensland, 4072, Australia
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43
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Meiling-Wesse K, Epple UD, Krick R, Barth H, Appelles A, Voss C, Eskelinen EL, Thumm M. Trs85 (Gsg1), a Component of the TRAPP Complexes, Is Required for the Organization of the Preautophagosomal Structure during Selective Autophagy via the Cvt Pathway. J Biol Chem 2005; 280:33669-78. [PMID: 16079147 DOI: 10.1074/jbc.m501701200] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Autophagosomes and Cvt vesicles are limited by two membrane layers. The biogenesis of these unconventional vesicles and the origin of their membranes are hardly understood. Here we identify in Saccharomyces cerevisiae Trs85, a nonessential component of the TRAPP complexes, to be required for the biogenesis of Cvt vesicles. The TRAPP complexes function in endoplasmic reticulum-to-Golgi and Golgi trafficking. Growing trs85delta cells show a defect in the organization of the preautophagosomal structure. Although proaminopeptidase I is normally recruited to the preautophagosomal structure, the recruitment of green fluorescent protein-Atg8 depends on Trs85. Autophagy proceeds in the absence of Trs85, albeit at a reduced rate. Our electron microscopic analysis demonstrated that the reduced autophagic rate of trs85delta cells does not result from a reduced size of the autophagosomes. Growing and starved cells lacking Trs85 did not show defects in vacuolar biogenesis; mature vacuolar proteinase B and carboxypeptidase Y were present. Also vacuolar acidification was normal in these cells. It is known that mutations impairing the integrity of the ER or Golgi block both autophagy and the Cvt pathway. But the phenotypes of trs85delta cells show striking differences to those seen in mutants with defects in the early secretory pathway. This suggests that Trs85 might play a direct role in the Cvt pathway and autophagy.
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Affiliation(s)
- Khuyen Meiling-Wesse
- Center of Biochemistry and Molecular Cell Biology, Georg-August-University, Heinrich-Dueker-Weg 12, D-37073 Goettingen, Germany
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44
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Bowers K, Stevens TH. Protein transport from the late Golgi to the vacuole in the yeast Saccharomyces cerevisiae. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1744:438-54. [PMID: 15913810 DOI: 10.1016/j.bbamcr.2005.04.004] [Citation(s) in RCA: 210] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2005] [Revised: 04/15/2005] [Accepted: 04/19/2005] [Indexed: 10/25/2022]
Abstract
The late Golgi compartment is a major protein sorting station in the cell. Secreted proteins, cell surface proteins, and proteins destined for endosomes or lysosomes must be sorted from one another at this compartment and targeted to their correct destinations. The molecular details of protein trafficking pathways from the late Golgi to the endosomal system are becoming increasingly well understood due in part to information obtained by genetic analysis of yeast. It is now clear that proteins identified in yeast have functional homologues (orthologues) in higher organisms. We will review the molecular mechanisms of protein targeting from the late Golgi to endosomes and to the vacuole (the equivalent of the mammalian lysosome) of the budding yeast Saccharomyces cerevisiae.
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Affiliation(s)
- Katherine Bowers
- Cambridge Institute for Medical Research and Department of Clinical, Biochemistry, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2XY, UK
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45
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Dubouloz F, Deloche O, Wanke V, Cameroni E, De Virgilio C. The TOR and EGO Protein Complexes Orchestrate Microautophagy in Yeast. Mol Cell 2005; 19:15-26. [PMID: 15989961 DOI: 10.1016/j.molcel.2005.05.020] [Citation(s) in RCA: 258] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2005] [Revised: 04/18/2005] [Accepted: 05/19/2005] [Indexed: 11/20/2022]
Abstract
The rapamycin-sensitive TOR signaling pathway in Saccharomyces cerevisiae positively controls cell growth in response to nutrient availability. Accordingly, TOR depletion or rapamycin treatment causes regulated entry of cells into a quiescent growth phase. Although this process has been elucidated in considerable detail, the transition from quiescence back to proliferation is poorly understood. Here, we describe the identification of a conserved member of the RagA subfamily of Ras-related GTPases, Gtr2, which acts in a vacuolar membrane-associated protein complex together with Ego1 and Ego3 to ensure proper exit from rapamycin-induced growth arrest. We demonstrate that the EGO complex, in conjunction with TOR, positively regulates microautophagy, thus counterbalancing the massive rapamycin-induced, macroautophagy-mediated membrane influx toward the vacuolar membrane. Moreover, large-scale genetic analyses of the EGO complex confirm the existence of a growth control mechanism originating at the vacuolar membrane and pinpoint the amino acid glutamine as a key metabolite in TOR signaling.
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Affiliation(s)
- Frédérique Dubouloz
- Department of Microbiology and Molecular Medicine, University of Geneva Medical School, 1211 Geneva 4, Switzerland
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46
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Marchais V, Kempf M, Licznar P, Lefrançois C, Bouchara JP, Robert R, Cottin J. DNA array analysis ofCandida albicansgene expression in response to adherence to polystyrene. FEMS Microbiol Lett 2005; 245:25-32. [PMID: 15796975 DOI: 10.1016/j.femsle.2005.02.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2004] [Revised: 01/20/2005] [Accepted: 02/08/2005] [Indexed: 11/24/2022] Open
Abstract
Candidiasis is often initiated by the colonization of inert surfaces. In order to elucidate the mechanisms involved in this adherence process, DNA macroarrays were used to analyze the transcriptome of Candida albicans, the main causative agent of this mycoses, in a simple adherence model using germ tubes produced in polystyrene Petri dishes. Non-adherent germ tubes produced on glass surface were used as a control. Analysis of gene expression displayed 77 genes identified as statistically overexpressed in adherent germ tubes. Among these genes, some encoded enzymes participating in metabolism of lipids (such as LIP6), of proteins (such as SAP1) or of carbohydrates (like PGI1, PMI40 and PSA1. Some of these genes have already been reported as playing a role in pathogenesis of C. albicans. However, functions were unknown for a large part (45.5%) of the overexpressed genes which will be analyzed further in order to define their relationship with adherence.
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Affiliation(s)
- Véronique Marchais
- Groupe d'Etude des Interactions Hôte-Parasite, UPRES EA 3142, UFR des Sciences Pharmaceutiques et d'Ingénierie de la Santé, 16 Bd Daviers, 49045 Angers Cedex, France.
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47
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Johnston HD, Foote C, Santeford A, Nothwehr SF. Golgi-to-late endosome trafficking of the yeast pheromone processing enzyme Ste13p is regulated by a phosphorylation site in its cytosolic domain. Mol Biol Cell 2005; 16:1456-68. [PMID: 15647379 PMCID: PMC551507 DOI: 10.1091/mbc.e04-07-0642] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
This study addressed whether phosphorylation regulates trafficking of yeast membrane proteins that cycle between the trans-Golgi network (TGN) and endosomal system. The TGN membrane proteins A-ALP, a model protein containing the Ste13p cytosolic domain fused to alkaline phosphatase (ALP), and Kex2p were found to be phosphorylated in vivo. Mutation of the S13 residue on the cytosolic domain of A-ALP to Ala was found to block trafficking to the prevacuolar compartment (PVC), whereas a S13D mutation generated to mimic phosphorylation accelerated trafficking into the PVC. The S13 residue was shown by mass spectrometry to be phosphorylated. The rate of endoplasmic reticulum-to-Golgi transport of newly synthesized A(S13A)-ALP was indistinguishable from wild-type, indicating that the lack of transport of A(S13A)-ALP to the PVC was instead due to differences in Golgi/endosomal trafficking. The A(S13A)-ALP protein exhibited a TGN-like localization similar to that of wild-type A-ALP. Similarly, the S13A mutation in endogenous Ste13p did not reduce the extent of or longevity of its localization to the TGN as shown by alpha-factor processing assays. These results indicate that S13 phosphorylation is required for TGN-to-PVC trafficking of A-ALP and imply that phosphorylation of S13 may regulate recognition of A-ALP by vesicular trafficking machinery.
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Affiliation(s)
- Holly D Johnston
- Division of Biological Sciences, University of Missouri, Columbia, MO 65211
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Chen SH, Chen S, Tokarev AA, Liu F, Jedd G, Segev N. Ypt31/32 GTPases and their novel F-box effector protein Rcy1 regulate protein recycling. Mol Biol Cell 2005; 16:178-92. [PMID: 15537705 PMCID: PMC539162 DOI: 10.1091/mbc.e04-03-0258] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2004] [Revised: 10/07/2004] [Accepted: 10/26/2004] [Indexed: 11/11/2022] Open
Abstract
Ypt/Rab GTPases control various aspects of vesicle formation and targeting via their diverse effectors. We report a new role for these GTPases in protein recycling through a novel effector. The F-box protein Rcy1, which mediates plasma membrane recycling, is identified here as a downstream effector of the Ypt31/32 GTPase pair because it binds active GTP-bound Ypt31/32 and colocalizes with these GTPases on late Golgi and endosomes. Furthermore, Ypt31/32 regulates the polarized localization and half-life of Rcy1. This suggests that Ypt/Rabs can regulate the protein level of their effectors, in addition to the established ways by which they control their effectors. We show that like Rcy1, Ypt31/32 regulate the coupled phosphorylation and recycling of the plasma membrane v-SNARE Snc1. Moreover, Ypt31/32 and Rcy1 regulate the recycling of the furin-homolog Kex2 to the Golgi. Therefore, Ypt31/32 and Rcy1 mediate endosome-to-Golgi transport, because this is the only step shared by Snc1 and Kex2. Finally, we show that Rcy1 physically interacts with Snc1. Based on this result and because F-box proteins serve as adaptors between specific substrates and ubiquitin ligases, we propose that Ypt31/32 GTPases regulate the function of Rcy1 in the phosphorylation and/or ubiquitination of proteins that recycle through the Golgi.
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Affiliation(s)
- Shu Hui Chen
- Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, Chicago, IL 60612, USA
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Abazeed ME, Blanchette JM, Fuller RS. Cell-free transport from the trans-golgi network to late endosome requires factors involved in formation and consumption of clathrin-coated vesicles. J Biol Chem 2004; 280:4442-50. [PMID: 15572353 DOI: 10.1074/jbc.m412553200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Transport between the trans-Golgi network (TGN) and late endosome represents a conserved, clathrin-dependent sorting event that separates lysosomal from secretory cargo molecules and is also required for localization of integral membrane proteins to the TGN. Previously, we reported a cell-free reaction that reconstitutes transport from the yeast TGN to the late endosome/prevacuolar compartment (PVC) and requires the PVC t-SNARE Pep12p. Here, we report that factors required both for formation of clathrin-coated vesicles at the TGN (the Chc1p clathrin heavy chain and the Vps1p dynamin homolog) and for vesicle fusion at the PVC (the Vps21p rab protein and Vps45p SM (Sec1/Munc18) protein) are required for cell-free transport. The marker for TGN-PVC transport, Kex2p, is initially present in a clathrin-containing membrane compartment that is competent for delivery of Kex2p to the PVC. A Kex2p chimera containing the cytosolic tail (C-tail) of the vacuolar protein sorting receptor, Vps10p, is also efficiently transported to the PVC. Antibodies against the Kex2p and Vps10p C-tails selectively block transport of Kex2p and the Kex2-Vps10p chimera. The requirements for factors involved in vesicle formation and fusion, the identification of the donor compartment as a clathrin-containing membrane, and the need for accessibility of C-tail sequences argue that the TGN-PVC transport reaction involves selective incorporation of TGN cargo molecules into clathrin-coated vesicle intermediates. Further biochemical dissection of this reaction should help elucidate the molecular requirements and hierarchy of events in TGN-to-PVC sorting and transport.
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Affiliation(s)
- Mohamed E Abazeed
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
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Peters C, Baars TL, Bühler S, Mayer A. Mutual Control of Membrane Fission and Fusion Proteins. Cell 2004; 119:667-78. [PMID: 15550248 DOI: 10.1016/j.cell.2004.11.023] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2004] [Revised: 09/27/2004] [Accepted: 10/20/2004] [Indexed: 11/24/2022]
Abstract
Membrane fusion and fission are antagonistic reactions controlled by different proteins. Dynamins promote membrane fission by GTP-driven changes of conformation and polymerization state, while SNAREs fuse membranes by forming complexes between t- and v-SNAREs from apposed vesicles. Here, we describe a role of the dynamin-like GTPase Vps1p in fusion of yeast vacuoles. Vps1p forms polymers that couple several t-SNAREs together. At the onset of fusion, the SNARE-activating ATPase Sec18p/NSF and the t-SNARE depolymerize Vps1p and release it from the membrane. This activity is independent of the SNARE coactivator Sec17p/alpha-SNAP and of the v-SNARE. Vps1p release liberates the t-SNAREs for initiating fusion and at the same time disrupts fission activity. We propose that reciprocal control between fusion and fission components exists, which may prevent futile cycles of fission and fusion.
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Affiliation(s)
- Christopher Peters
- Département de Biochimie, Université de Lausanne, Chemin des Boveresses 155, 1066 Epalinges, Switzerland.
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