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Srivastava VK, Kaushik S, Jyoti A. A comparative in silico analysis of Rab5 proteins from pathogenic species to find its role in the pathogenesis. J Mol Recognit 2019; 32:e2808. [PMID: 31432591 DOI: 10.1002/jmr.2808] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 07/09/2019] [Accepted: 07/10/2019] [Indexed: 12/14/2022]
Abstract
The enteric protozoan parasite, Entamoeba histolytica (Eh), is the causative agent of amoebic dysentery and liver abscess in humans. It infects around 50 million people worldwide, which is a third general cause of death from parasitic diseases after malaria and schistosomiasis. The other prevalent form of the disease is Visceral leishmaniasis caused by Leishmania donovani which is a human blood parasite. On the other hand, the Toxoplasma gondii is an obligate intracellular protozoan parasite; it causes serious opportunistic infections in HIV-positive persons. The biological processes in all living organisms are mostly mediated by the proteins, and recognizing new target proteins and finding their function in pathogenesis will help in choosing better diagnostic markers. In eukaryotes, Rab protein plays a major role in pathogenesis. Rabs represent the largest branch in the Ras superfamily of GTPases. Among them, the Rab5 is important in the endocytosis and thus involved in pathogenesis. In this paper, we discussed the physiochemical profiling, modelling, and docking of the Rab5 protein from pathogenic species that is Entamoeba histolytica, Leishmania donovani, and Toxoplasma gondii. The modeled structures from this study and the key residues identified would give a better understanding of the three-dimensional structure and functional insights into these proteins and help in developing new drug targets.
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Affiliation(s)
- Vijay Kumar Srivastava
- Amity Institute of Biotechnology, Amity University Rajasthan, Kant Kalwar, Jaipur, India
| | - Sanket Kaushik
- Amity Institute of Biotechnology, Amity University Rajasthan, Kant Kalwar, Jaipur, India
| | - Anupam Jyoti
- Amity Institute of Biotechnology, Amity University Rajasthan, Kant Kalwar, Jaipur, India
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2
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Locke MN, Thorner J. Regulation of TORC2 function and localization by Rab5 GTPases in Saccharomyces cerevisiae. Cell Cycle 2019; 18:1084-1094. [PMID: 31068077 DOI: 10.1080/15384101.2019.1616999] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The evolutionarily conserved Target of Rapamycin (TOR) complex-2 (TORC2) is an essential regulator of plasma membrane homeostasis in budding yeast (Saccharomyces cerevisiae). In this yeast, TORC2 phosphorylates and activates the effector protein kinase Ypk1 and its paralog Ypk2. These protein kinases, in turn, carry out all the crucial functions of TORC2 by phosphorylating and thereby controlling the activity of at least a dozen downstream substrates. A previously uncharacterized interplay between the Rab5 GTPases and TORC2 signaling was uncovered through analysis of a newly suspected Ypk1 target. Muk1, one of two guanine nucleotide exchange factors for the Rab5 GTPases, was found to be a physiologically relevant Ypk1 substrate; and, genetic analysis indicates that Ypk1-mediated phosphorylation activates the guanine nucleotide exchange activity of Muk1. Second, it was demonstrated both in vivo and in vitro that the GTP-bound state of the Rab5 GTPase Vps21/Ypt51 physically associates with TORC2 and acts as a direct positive effector required for full TORC2 activity. These interrelationships provide a self-reinforcing control circuit for sustained up-regulation of TORC2-Ypk1 signaling. In this overview, we summarize the experimental basis of these findings, their implications, and speculate as to the molecular basis for Rab5-mediated TORC2 activation.
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Affiliation(s)
- Melissa N Locke
- a Division of Biochemistry, Biophysics & Structural Biology, and Division of Cell & Developmental Biology, Department of Molecular and Cell Biology , University of California at Berkeley , Berkeley , CA , USA
| | - Jeremy Thorner
- a Division of Biochemistry, Biophysics & Structural Biology, and Division of Cell & Developmental Biology, Department of Molecular and Cell Biology , University of California at Berkeley , Berkeley , CA , USA
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3
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Li W, Wu Z, Liang Y. Vrl1 relies on its VPS9-domain to play a role in autophagy in Saccharomyces cerevisiae. Cell Biol Int 2019; 43:875-889. [PMID: 31038239 DOI: 10.1002/cbin.11156] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 04/28/2019] [Indexed: 11/10/2022]
Abstract
Autophagy is an intracellular degradation process involving many Atg proteins, which are recruited hierarchically to regulate this process. Rab/Ypt GTPases and their activators, guanine nucleotide exchange factors (GEFs), which are critical for regulating vesicle trafficking, are also involved in autophagy. Previously, we reported that yeast Vps21 and its GEF Vps9 are required for autophagy. Later, a third yeast VPS9-domain-containing protein, VARP-like 1 (Vrl1), which was identified as a mutant in major laboratory strains, had partially overlapping functions with Vps9 in trafficking. In this study, we showed that Vrl1 performed roles in autophagy, and its VPS9-domain was crucial for its role in autophagy. We found that localization of Vrl1 differed from the other two VPS9-domain-containing proteins, Vps9 and Muk1, and only Vrl1 changed from multipoint to diffusion after starvation. Like Vps9, Vrl1 suppressed autophagic defects caused by the VPS9 deletion. We further showed that these VPS9-domain-containing proteins, Vps9, Muk1, and Vrl1, all co-localized with Atg8 on autophagosomes in cells blocked in any late step of starvation-induced autophagy, with Vrl1 most often co-localizing with Atg8. A small portion (<25%) of these VPS9-domain-containing proteins were degraded through autophagy. However, a large portion (>60%) of Vrl1 decreased independently of autophagy. We propose that Vrl1 may regulate autophagy in a similar way as Vps9, and the level of Vrl1 partly decreases through both autophagy-dependent and -independent routes.
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Affiliation(s)
- Wenjing Li
- Key Laboratory of Agricultural Environmental Microbiology of Ministry of Agriculture and Rural Affairs, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Zulin Wu
- Key Laboratory of Agricultural Environmental Microbiology of Ministry of Agriculture and Rural Affairs, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Yongheng Liang
- Key Laboratory of Agricultural Environmental Microbiology of Ministry of Agriculture and Rural Affairs, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
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4
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Locke MN, Thorner J. Rab5 GTPases are required for optimal TORC2 function. J Cell Biol 2018; 218:961-976. [PMID: 30578283 PMCID: PMC6400565 DOI: 10.1083/jcb.201807154] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2018] [Revised: 11/16/2018] [Accepted: 12/11/2018] [Indexed: 12/19/2022] Open
Abstract
This study reveals a previously unappreciated interplay between Rab5 GTPases and TORC2 function in yeast. TORC2 signaling stimulates the Rab5-specific guanine nucleotide exchange factor Muk1, and, in turn, activated Rab5 GTPases, especially Vps21, act as positive effectors to stimulate TORC2 activity. Target of rapamycin complex-2 (TORC2), a conserved protein kinase complex, is an indispensable regulator of plasma membrane homeostasis. In budding yeast (Saccharomyces cerevisiae), the essential downstream effector of TORC2 is protein kinase Ypk1 and its paralog Ypk2. Muk1, a Rab5-specific guanine nucleotide exchange factor (GEF), was identified in our prior global screen for candidate Ypk1 targets. We confirm here that Muk1 is a substrate of Ypk1 and demonstrate that Ypk1-mediated phosphorylation stimulates Muk1 function in vivo. Strikingly, yeast lacking its two Rab5 GEFs (Muk1 and Vps9) or its three Rab5 paralogs (Vps21/Ypt51, Ypt52, and Ypt53) or overexpressing Msb3, a Rab5-directed GTPase-activating protein, all exhibit pronounced reduction in TORC2-mediated phosphorylation and activation of Ypk1. Vps21 coimmunoprecipitates with TORC2, and immuno-enriched TORC2 is less active in vitro in the absence of Rab5 GTPases. Thus, TORC2-dependent and Ypk1-mediated activation of Muk1 provides a control circuit for positive (self-reinforcing) up-regulation to sustain TORC2-Ypk1 signaling.
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Affiliation(s)
- Melissa N Locke
- Division of Biochemistry, Biophysics, and Structural Biology and Division of Cell and Developmental Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics, and Structural Biology and Division of Cell and Developmental Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA
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5
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Schmidt O, Weyer Y, Fink MJ, Müller M, Weys S, Bindreither M, Teis D. Regulation of Rab5 isoforms by transcriptional and post-transcriptional mechanisms in yeast. FEBS Lett 2017; 591:2803-2815. [PMID: 28792590 PMCID: PMC5637908 DOI: 10.1002/1873-3468.12785] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 07/26/2017] [Accepted: 07/31/2017] [Indexed: 12/15/2022]
Abstract
Rab5 GTPases are master regulators of early endosome biogenesis and transport. The genome of Saccharomyces cerevisiae encodes three Rab5 proteins: Vps21, the major isoform, Ypt52 and Ypt53. Here, we show that Vps21 is the most abundant Rab5 protein and Ypt53 is the least abundant. In stressed cells, Ypt53 levels increase but never exceed that of Vps21. Its induction requires the transcription factors Crz1 and Gis1. In growing cells, the expression of Ypt53 is suppressed by post-transcriptional mechanisms mediated by the untranslated regions of the YPT53 mRNA. Based on genetic experiments, these sequences appear to stimulate deadenylation, Pat1-activated decapping and Xrn1-mediated mRNA degradation. Once this regulation is bypassed, Ypt53 protein levels surpass Vps21, and Ypt53 is sufficient to maintain endosomal function and cell growth.
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Affiliation(s)
- Oliver Schmidt
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Austria
| | - Yannick Weyer
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Austria
| | - Matthias J Fink
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Austria
| | - Martin Müller
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Austria
| | - Sabine Weys
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Austria
| | | | - David Teis
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Austria
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6
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Morse D, Webster W, Kalanon M, Langsley G, McFadden GI. Plasmodium falciparum Rab1A Localizes to Rhoptries in Schizonts. PLoS One 2016; 11:e0158174. [PMID: 27348424 PMCID: PMC4922565 DOI: 10.1371/journal.pone.0158174] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 06/11/2016] [Indexed: 12/17/2022] Open
Abstract
Over-expression of a GFP-PfRab1A fusion protein in Plasmodium falciparum schizonts produces a punctate pattern of fluorescence typical of rhoptries, secretory organelles involved in host cell invasion. The GFP-positive bodies were purified by a combination of differential and density gradient centrifugation and their protein content determined by MS/MS sequencing. Consistent with the GFP rhoptry-like pattern of transgenic parasites, four of the 19 proteins identified have been previously described to be rhoptry-associated and another four are ER or ER-associated proteins. Confirmation that GFP-PfRab1A decorates rhoptries was obtained by its co-localization with Rap1 and Ron4 in late phase schizonts. We conclude that PfRab1A potentially regulates vesicular traffic from the endoplasmic reticulum to the rhoptries in Apicomplexa parasites.
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Affiliation(s)
- David Morse
- School of BioSciences, University of Melbourne, Melbourne, VIC, 3010, Australia
- * E-mail:
| | - Wesley Webster
- School of BioSciences, University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Ming Kalanon
- School of BioSciences, University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Gordon Langsley
- Laboratoire de Biologie Cellulaire Comparative des Apicomplexes, Institut Cochin, INSERM U1016, CNRS UMR 8104, Université Paris Descartes, 75014, Paris, France
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7
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Ebine K, Hirai M, Sakaguchi M, Yahata K, Kaneko O, Saito-Nakano Y. Plasmodium Rab5b is secreted to the cytoplasmic face of the tubovesicular network in infected red blood cells together with N-acylated adenylate kinase 2. Malar J 2016; 15:323. [PMID: 27316546 PMCID: PMC4912828 DOI: 10.1186/s12936-016-1377-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Accepted: 06/08/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Rab5 GTPase regulates membrane trafficking between the plasma membrane and endosomes and harbours a conserved C-terminal isoprenyl modification that is necessary for membrane recruitment. Plasmodium falciparum encodes three Rab5 isotypes, and one of these, Rab5b (PfRab5b), lacks the C-terminal modification but possesses the N-terminal myristoylation motif. PfRab5b was reported to localize to the parasite periphery. However, the trafficking pathway regulated by PfRab5b is unknown. METHODS A complementation analysis of Rab5 isotypes was performed in Plasmodium berghei. A constitutively active PfRab5b mutant was expressed under the regulation of a ligand-dependent destabilization domain (DD)-tag system in P. falciparum. The localization of PfRab5b was evaluated after removing the ligand followed by selective permeabilization of the membrane with different detergents. Furthermore, P. falciparum N-terminally myristoylated adenylate kinase 2 (PfAK2) was co-expressed with PfRab5b, and trafficking of PfAK2 to the parasitophorous vacuole membrane was examined by confocal microscopy. RESULTS PfRab5b complemented the function of PbRab5b, however, the conventional C-terminally isoprenylated Rab5, PbRab5a or PbRab5c, did not. The constitutively active PfRab5b mutant localized to the cytosol of the parasite and the tubovesicular network (TVN), a region that extends from the parasitophorous vacuole membrane (PVM) in infected red blood cells (iRBCs). By removing the DD-ligand, parasite cytosolic PfRab5b signal disappeared and a punctate structure adjacent to the endoplasmic reticulum (ER) and parasite periphery accumulated. The peripheral PfRab5b was sensitive to extracellular proteolysis after treatment with streptolysin O, which selectively permeabilizes the red blood cell plasma membrane, indicating that PfRab5b localized on the iRBC cytoplasmic face of the TVN. Transport of PfAK2 to the PVM was abrogated by overexpression of PfRab5b, and PfAK2 accumulated in the punctate structure together with PfRab5b. CONCLUSION N-myristoylated Plasmodium Rab5b plays a role that is distinct from that of conventional mammalian Rab5 isotypes. PfRab5b localizes to a compartment close to the ER, translocated to the lumen of the organelle, and co-localizes with PfAK2. PfRab5b and PfAK2 are then transported to the TVN, and PfRab5b localizes on the iRBC cytoplasmic face of TVN. These data demonstrate that PfRab5b is transported from the parasite cytosol to TVN together with N-myristoylated PfAK2 via an uncharacterized membrane-trafficking pathway.
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Affiliation(s)
- Kazuo Ebine
- Department of Parasitology, National Institute of Infectious Diseases, Shinjuku-Ku, Tokyo, Japan. .,Division of Cellular Dynamics, National Institute for Basic Biology, Okazaki, Aichi, Japan.
| | - Makoto Hirai
- Department of Molecular and Cellular Parasitology, Graduate School of Medicine, Juntendo University, Bunkyo-Ku, Tokyo, Japan.,Department of Parasitology, Graduate School of Medicine, Gunma University, Gunma, Japan
| | - Miako Sakaguchi
- Central Laboratory, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Nagasaki, Japan
| | - Kazuhide Yahata
- Department of Protozoology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Nagasaki, Japan
| | - Osamu Kaneko
- Department of Protozoology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Nagasaki, Japan
| | - Yumiko Saito-Nakano
- Department of Parasitology, National Institute of Infectious Diseases, Shinjuku-Ku, Tokyo, Japan.
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8
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Zheng H, Zheng W, Wu C, Yang J, Xi Y, Xie Q, Zhao X, Deng X, Lu G, Li G, Ebbole D, Zhou J, Wang Z. Rab GTPases are essential for membrane trafficking-dependent growth and pathogenicity in Fusarium graminearum. Environ Microbiol 2015; 17:4580-99. [PMID: 26177389 DOI: 10.1111/1462-2920.12982] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2015] [Revised: 07/06/2015] [Accepted: 07/07/2015] [Indexed: 12/12/2022]
Abstract
Rab GTPases represent the largest subfamily of Ras-related small GTPases and regulate membrane trafficking. Vesicular transport is a general mechanism that governs intracellular membrane trafficking along the endocytic and exocytic pathways in all eukaryotic cells. Fusarium graminearum is a filamentous fungus and causes the devastating and economically important head blight of wheat and related species. The mechanism of vesicular transport is not well understood, and little is known about Rab GTPases in F. graminearum. In this study, we systematically characterized all eleven FgRabs by live cell imaging and genetic analysis. We find that FgRab51 and FgRab52 are important for the endocytosis, FgRab7 localizes to the vacuolar membrane and regulates the fusion of vacuoles and autophagosomes, and FgRab8 and FgRab11 are important for polarized growth and/or exocytosis. Furthermore, both endocytic and exocytic FgRabs are required for vegetative growth, conidiogenesis, sexual reproduction, as well as pathogenesis and deoxynivalenol metabolism in F. graminearum. Thus, we conclude that Rab GTPases are essential for membrane trafficking-dependent growth and pathogenicity in F. graminearum.
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Affiliation(s)
- Huawei Zheng
- Fujian Province Key Laboratory of Pathogenic Fungi and Mycotoxins, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China.,Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Wenhui Zheng
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Congxian Wu
- Fujian Province Key Laboratory of Pathogenic Fungi and Mycotoxins, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Jie Yang
- Institute of Forestry Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yang Xi
- Fujian Province Key Laboratory of Pathogenic Fungi and Mycotoxins, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Qiurong Xie
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xu Zhao
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xiaolong Deng
- Fujian Province Key Laboratory of Pathogenic Fungi and Mycotoxins, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Guodong Lu
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Guangpu Li
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China.,Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Daniel Ebbole
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China.,Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, USA
| | - Jie Zhou
- Fujian Province Key Laboratory of Pathogenic Fungi and Mycotoxins, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China.,Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zonghua Wang
- Fujian Province Key Laboratory of Pathogenic Fungi and Mycotoxins, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China.,Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
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9
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Lipatova Z, Hain AU, Nazarko VY, Segev N. Ypt/Rab GTPases: principles learned from yeast. Crit Rev Biochem Mol Biol 2015; 50:203-11. [PMID: 25702751 DOI: 10.3109/10409238.2015.1014023] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Ypt/Rab GTPases are key regulators of all membrane trafficking events in eukaryotic cells. They act as molecular switches that attach to membranes via lipid tails to recruit their multiple downstream effectors, which mediate vesicular transport. Originally discovered in yeast as Ypts, they were later shown to be conserved from yeast to humans, where Rabs are relevant to a wide array of diseases. Major principles learned from our past studies in yeast are currently accepted in the Ypt/Rab field including: (i) Ypt/Rabs are not transport-step specific, but are rather compartment specific, (ii) stimulation by nucleotide exchangers, GEFs, is critical to their function, whereas GTP hydrolysis plays a role in their cycling between membranes and the cytoplasm for multiple rounds of action, (iii) they mediate diverse functions ranging from vesicle formation to vesicle fusion and (iv) they act in GTPase cascades to regulate intracellular trafficking pathways. Our recent studies on Ypt1 and Ypt31/Ypt32 and their modular GEF complex TRAPP raise three exciting novel paradigms for Ypt/Rab function: (a) coordination of vesicular transport substeps, (b) integration of individual transport steps into pathways and (c) coordination of different transport pathways. In addition to its amenability to genetic analysis, yeast provides a superior model system for future studies on the role of Ypt/Rabs in traffic coordination due to the smaller proteome that results in a simpler traffic grid. We propose that different types of coordination are important also in human cells for fine-tuning of intracellular trafficking, and that coordination defects could result in disease.
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Affiliation(s)
- Zhanna Lipatova
- a Department of Biochemistry and Molecular Genetics , University of Illinois at Chicago , Chicago , IL , USA
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10
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POT1b regulates phagocytosis and NO production by modulating activity of the small GTPase Rab5. Biochem Biophys Res Commun 2013; 439:413-7. [DOI: 10.1016/j.bbrc.2013.08.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 08/07/2013] [Indexed: 01/08/2023]
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11
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Jia T, Gao C, Cui Y, Wang J, Ding Y, Cai Y, Ueda T, Nakano A, Jiang L. ARA7(Q69L) expression in transgenic Arabidopsis cells induces the formation of enlarged multivesicular bodies. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:2817-29. [PMID: 23682115 PMCID: PMC3697957 DOI: 10.1093/jxb/ert125] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Arabidopsis thaliana ARA7 (AtRabF2b), a member of the plant Rab5 small GTPases functioning in the vacuolar transport pathway, localizes to pre-vacuolar compartments (PVCs), known as multivesicular bodies (MVBs) in plant cells. Overexpression of the constitutively active GTP-bound mutant of ARA7, ARA7(Q69L), induces the formation of large ring-like structures (1-2 µm in diameter). To better understand the biology of these ARA7(Q69L)-induced ring-like structures, transgenic Arabidopsis cell lines expressing ARA7(Q69L) tagged with green fluorescent protein (GFP) under the control of a heat shock-inducible promoter were generated. In these transgenic cells, robust ring-like structures were formed after 4 h of heat shock induction. Transient co-expression, confocal imaging, and immunogold electron microscopy (immunogold-EM) experiments demonstrated that these GFP-ARA7(Q69L)-labelled ring-like structures were distinct from the Golgi apparatus and trans-Golgi network, but were labelled with an antibody against an MVB marker protein. In addition, live cell imaging and detailed EM analysis showed that the GFP-ARA7(Q69L)-induced spherical structures originated from the homotypic fusion of MVBs. In summary, it was demonstrated that GFP-ARA7(Q69L) expression is an efficient tool for studying PVC/MVB-mediated protein trafficking and vacuolar degradation in plant cells.
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Affiliation(s)
- Tianran Jia
- School of Life Sciences, Centre for Cell and Developmental Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Caiji Gao
- School of Life Sciences, Centre for Cell and Developmental Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yong Cui
- School of Life Sciences, Centre for Cell and Developmental Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Junqi Wang
- School of Life Sciences, Centre for Cell and Developmental Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yu Ding
- School of Life Sciences, Centre for Cell and Developmental Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yi Cai
- School of Life Sciences, Centre for Cell and Developmental Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Takashi Ueda
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Akihiko Nakano
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
- Molecular Membrane Biology Laboratory, RIKEN Advanced Science Institute, Wako, Saitama 351-0198, Japan
| | - Liwen Jiang
- School of Life Sciences, Centre for Cell and Developmental Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
- *To whom correspondence should be addressed. E-mail:
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12
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Paulsel AL, Merz AJ, Nickerson DP. Vps9 family protein Muk1 is the second Rab5 guanosine nucleotide exchange factor in budding yeast. J Biol Chem 2013; 288:18162-71. [PMID: 23612966 DOI: 10.1074/jbc.m113.457069] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
VPS9 domains can act as guanosine nucleotide exchange factors (GEFs) against small G proteins of the Rab5 family. Saccharomyces cerevisiae vps9Δ mutants have trafficking defects considerably less severe than multiple deletions of the three cognate Rab5 paralogs (Vps21, Ypt52, and Ypt53). Here, we show that Muk1, which also contains a VPS9 domain, acts as a second GEF against Vps21, Ypt52, and Ypt53. Muk1 is partially redundant with Vps9 in vivo, with vps9Δ muk1Δ double mutant cells displaying hypersensitivity to temperature and ionic stress, as well as profound impairments in endocytic and Golgi endosome trafficking, including defects in sorting through the multivesicular body. Cells lacking both Vps9 and Muk1 closely phenocopy double and triple knock-out strains lacking Rab5 paralogs. Microscopy and overexpression experiments demonstrate that Vps9 and Muk1 have distinct localization determinants. These experiments establish Muk1 as the second Rab5 GEF in budding yeast.
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Affiliation(s)
- Andrew L Paulsel
- Department of Biochemistry, University of Washington, Seattle, Washington 98195-7350, USA
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13
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Russell MRG, Shideler T, Nickerson DP, West M, Odorizzi G. Class E compartments form in response to ESCRT dysfunction in yeast due to hyperactivity of the Vps21 Rab GTPase. J Cell Sci 2012; 125:5208-20. [PMID: 22899724 DOI: 10.1242/jcs.111310] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The endosomal sorting complexes required for transport (ESCRTs) mediate the budding of intralumenal vesicles (ILVs) at late endosomes. ESCRT dysfunction causes drastic changes in endosome morphology, which are manifested in Saccharomyces cerevisiae by the formation of aberrant endosomes known as class E compartments. Except for the absence of ILVs, the mechanistic basis for class E compartment biogenesis is unknown. We used electron microscopy to examine endosomal morphology in response to transient ESCRT inactivation and recovery in yeast expressing the temperature-sensitive mutant vps4(ts) allele. Our results show class E compartments accumulate fourfold the amount of membrane normally present at multivesicular bodies and that multivesicular bodies can form directly from class E compartments upon recovery of ESCRT function. We found class E compartment formation requires Vps21, which is orthologous to the Rab5A GTPase in metazoans that promotes fusion of endocytic vesicles with early endosomes and homotypic fusion of early endosomes with one another. We also determined that class E compartments accumulate GTP-bound Vps21 and its effector, the class C core vacuole/endosome tethering (CORVET). Ypt7, the yeast ortholog of Rab7 that in metazoans promotes fusion of late endosomes with lysosomes, also accumulates at class E compartments but without its effector, the homotypic fusion and protein sorting (HOPS), signifying that Ypt7 at class E compartments is dysfunctional. These results suggest that failure to complete Rab5-Rab7 conversion is a consequence of ESCRT dysfunction, which results in Vps21 hyperactivity that drives the class E compartment morphology. Indeed, genetic disruption of Rab conversion without ESCRT dysfunction autonomously drives the class E compartment morphology without blocking ILV budding.
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Affiliation(s)
- Matthew R G Russell
- Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder, Campus Box 347, Boulder, CO 80309, USA
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Nickerson DP, Russell MRG, Lo SY, Chapin HC, Milnes J, Merz AJ. Termination of isoform-selective Vps21/Rab5 signaling at endolysosomal organelles by Msb3/Gyp3. Traffic 2012; 13:1411-1428. [PMID: 22748138 DOI: 10.1111/j.1600-0854.2012.01390.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Revised: 06/26/2012] [Accepted: 07/02/2012] [Indexed: 12/11/2022]
Abstract
Traffic through endosomes and lysosomes is controlled by small G-proteins of the Rab5 and Rab7 families. Like humans, Saccharomyces cerevisiae has three Rab5s (Vps21, Ypt52 and Ypt53) and one Rab7 (Ypt7). Here, we elucidate the functional roles and regulation of the yeast Rab5s. Using GFP-tagged cargoes, a novel quantitative multivesicular body (MVB) sorting assay, and electron microscopy, we show that MVB biogenesis and thus MVB cargo sorting is severely impaired in vps21Δ ypt52Δ double mutants. Ypt53, the third Rab5 paralog, is hardly expressed during normal growth but its transcription is strongly induced by cellular stress through the calcineurin-Crz1 pathway. The requirement for Rab5 activity in stress tolerance facilitated identification of Msb3/Gyp3 as the principal Rab5 GAP (GTPase accelerating protein). In vitro GAP assays verified that Vps21 is a preferred Gyp3 target. Moreover, we demonstrate that Gyp3 spatially restricts active Vps21 to intermediate endosomal compartments by preventing Vps21 accumulation on lysosomal vacuoles. Gyp3, therefore, operates as a compartmental insulator that helps to define the spatial domain of Vps21 signaling in the endolysosomal pathway.
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Affiliation(s)
- Daniel P Nickerson
- Department of Biochemistry University of Washington School of Medicine, Seattle WA 98195-3750
| | - Matthew R G Russell
- Department of Molecular, Cell and Developmental Biology University of Colorado, Boulder CO 80309-0347
| | - Shing-Yeng Lo
- Department of Biochemistry University of Washington School of Medicine, Seattle WA 98195-3750
| | - Hannah C Chapin
- Department of Biochemistry University of Washington School of Medicine, Seattle WA 98195-3750
| | - Joshua Milnes
- Department of Biochemistry University of Washington School of Medicine, Seattle WA 98195-3750
| | - Alexey J Merz
- Department of Biochemistry University of Washington School of Medicine, Seattle WA 98195-3750
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Wang Y, Ren Y, Liu X, Jiang L, Chen L, Han X, Jin M, Liu S, Liu F, Lv J, Zhou K, Su N, Bao Y, Wan J. OsRab5a regulates endomembrane organization and storage protein trafficking in rice endosperm cells. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 64:812-24. [PMID: 21105928 DOI: 10.1111/j.1365-313x.2010.04370.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Rice glutelins are synthesized at the endoplasmic reticulum (ER) as precursors (pro-glutelins), and are transported to protein storage vacuoles, where they are processed into mature proteins. The molecular basis of this process is largely unknown. Here, we report the isolation of a rice mutant, gpa1, that accumulates 57 kDa pro-glutelins in seeds and whose endosperm has a floury appearance. Transmission electron microscopy analysis showed that the gpa1 endosperm cells have an enlarged ER lumen and a smaller protein body II (PBII), and accumulated three types of newly generated subcellular structures. Moreover, a proportion of glutelins in the gpa1 endosperm cells were not delivered to PBII, and instead were mis-targeted to two of the newly generated structures or secreted. The gene corresponding to the gpa1 mutation was found to be OsRab5a, which encodes a small GTPase. In Arabidopsis protoplasts, OsRab5a protein was found to co-localize predominantly with AtVSR2, a molecular marker for the pre-vacuolar compartments (PVC). We conclude that OsRab5a plays an essential role in trafficking of storage protein to PBII, possibly as part of its function in organizing the endomembrane system in developing endosperm cells of rice.
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Affiliation(s)
- Yihua Wang
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing 210095, China
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16
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Barbosa S, Pratte D, Schwarz H, Pipkorn R, Singer-Krüger B. Oligomeric Dop1p is Part of the Endosomal Neo1p-Ysl2p-Arl1p Membrane Remodeling Complex. Traffic 2010; 11:1092-106. [DOI: 10.1111/j.1600-0854.2010.01079.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abenza JF, Pantazopoulou A, Rodríguez JM, Galindo A, Peñalva MA. Long-Distance Movement of Aspergillus nidulans Early Endosomes on Microtubule Tracks. Traffic 2008; 10:57-75. [DOI: 10.1111/j.1600-0854.2008.00848.x] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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18
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González-Agüero M, Pavez L, Ibáñez F, Pacheco I, Campos-Vargas R, Meisel LA, Orellana A, Retamales J, Silva H, González M, Cambiazo V. Identification of woolliness response genes in peach fruit after post-harvest treatments. JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:1973-86. [PMID: 18453640 PMCID: PMC2413281 DOI: 10.1093/jxb/ern069] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Revised: 01/28/2008] [Accepted: 01/31/2008] [Indexed: 05/21/2023]
Abstract
Woolliness is a physiological disorder of peaches and nectarines that becomes apparent when fruit are ripened after prolonged periods of cold storage. This disorder is of commercial importance since shipping of peaches to distant markets and storage before selling require low temperature. However, knowledge about the molecular basis of peach woolliness is still incomplete. To address this issue, a nylon macroarray containing 847 non-redundant expressed sequence tags (ESTs) from a ripe peach fruit cDNA library was developed and used. Gene expression changes of peach fruit (Prunus persica cv. O'Henry) ripened for 7 d at 21 degrees C (juicy fruit) were compared with those of fruit stored for 15 d at 4 degrees C and then ripened for 7 d at 21 degrees C (woolly fruit). A total of 106 genes were found to be differentially expressed between juicy and woolly fruit. Data analysis indicated that the activity of most of these genes (>90%) was repressed in the woolly fruit. In cold-stored peaches (cv. O'Henry), the expression level of selected genes (cobra, endopolygalacturonase, cinnamoyl-CoA-reductase, and rab11) was lower than in the juicy fruit, and it remained low in woolly peaches after ripening, a pattern that was conserved in woolly fruit from two other commercial cultivars (cv. Flamekist and cv. Elegant Lady). In addition, the results of this study indicate that molecular changes during fruit woolliness involve changes in the expression of genes associated with cell wall metabolism and endomembrane trafficking. Overall, the results reported here provide an initial characterization of the transcriptome activity of peach fruit under different post-harvest treatments.
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Affiliation(s)
- Mauricio González-Agüero
- Laboratorio de Bioinformática y Expresión Génica, INTA-Universidad de Chile, Millennium Nucleus Center for Genomics of the Cell (CGC), Santiago, Chile
| | - Leonardo Pavez
- Laboratorio de Bioinformática y Expresión Génica, INTA-Universidad de Chile, Millennium Nucleus Center for Genomics of the Cell (CGC), Santiago, Chile
| | - Freddy Ibáñez
- Laboratorio de Bioinformática y Expresión Génica, INTA-Universidad de Chile, Millennium Nucleus Center for Genomics of the Cell (CGC), Santiago, Chile
| | - Igor Pacheco
- Laboratorio de Bioinformática y Expresión Génica, INTA-Universidad de Chile, Millennium Nucleus Center for Genomics of the Cell (CGC), Santiago, Chile
| | | | - Lee A. Meisel
- Millennium Nucleus in Plant Cell Biology and Plant Biotechnology Center, Andres Bello University, Santiago, Chile
| | - Ariel Orellana
- Millennium Nucleus in Plant Cell Biology and Plant Biotechnology Center, Andres Bello University, Santiago, Chile
| | - Julio Retamales
- Faculty of Agricultural Sciences, Universidad de Chile, Santiago, Chile
| | - Herman Silva
- Millennium Nucleus in Plant Cell Biology and Plant Biotechnology Center, Andres Bello University, Santiago, Chile
| | - Mauricio González
- Laboratorio de Bioinformática y Expresión Génica, INTA-Universidad de Chile, Millennium Nucleus Center for Genomics of the Cell (CGC), Santiago, Chile
| | - Verónica Cambiazo
- Laboratorio de Bioinformática y Expresión Génica, INTA-Universidad de Chile, Millennium Nucleus Center for Genomics of the Cell (CGC), Santiago, Chile
- To whom correspondence should be addressed. E-mail:
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Pal A, Severin F, Höpfner S, Zerial M. Regulation of endosome dynamics by Rab5 and Huntingtin-HAP40 effector complex in physiological versus pathological conditions. Methods Enzymol 2008; 438:239-57. [PMID: 18413253 DOI: 10.1016/s0076-6879(07)38017-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Vesicular transport of signaling molecules, specifically neurotrophins, in neurons is essential for their differentiation, survival, and plasticity. Neurotrophins such as neuron growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are internalized by receptor-mediated endocytosis at synaptic terminals and loaded into endosomes for microtubule-based transport along axons to the cell body where they exert their signaling function in the nucleus. The molecular mechanisms underlying this intracellular transport are not only relevant from a basic knowledge viewpoint, but have also important implications for neurodegenerative diseases. Defects in trafficking are increasingly implicated in the pathology of Huntington's disease (HD) and other neurodegenerative disorders. The small GTPases Rab5 and Rab7 play important roles in the endocytic trafficking of neurotrophins. We have recently identified Huntingtin (Htt) and Huntingtin associated protein of 40 kDa (HAP40) as a novel Rab5 effector complex that regulates endosome motility. In HD, we detected higher HAP40 protein levels compared with normal cells. Such increase causes an augmented recruitment of Htt onto Rab5-positive early endosomes that drastically reduces their motility by "switching" these organelles from microtubules to F-actin. These findings suggest a mechanism by which impaired Rab5-mediated trafficking of neurotrophic factors may be a key event of the pathogenetic process leading to neurodegeneration in HD. To dissect the mechanisms by which Htt, HAP40, and Rab5 function in early endosome interactions with the cytoskeleton, we developed assays to investigate endosome-cytoskeleton interactions that can be applied to normal and pathological conditions. We provide here detailed protocols for, first, an assay that measures binding of early endosomes to microtubules and F-actin. Second, we describe an improved protocol for a cell-free assay that recapitulates the motility of early endosomes along microtubules in vitro. These assays provide mechanistic insights into the dysfunction of endosome motility occurring in HD as well as other neurodegenerative disorders.
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Affiliation(s)
- Arun Pal
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
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Zhao X, Chang AY, Toh-e A, Arvan P. A role for Lte1p (a low temperature essential protein involved in mitosis) in proprotein processing in the yeast secretory pathway. J Biol Chem 2006; 282:1670-8. [PMID: 17121813 PMCID: PMC2533109 DOI: 10.1074/jbc.m610500200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We previously identified six single gene disruptions in Saccharomyces cerevisiae that allow enhanced immunoreactive insulin secretion primarily because of defective Kex2p-mediated endoproteolytic processing. Five eis mutants disrupted established VPS (vacuolar protein sorting) genes, The sixth, LTE1, is a Low Temperature (<15 degrees C) Essential gene encoding a large protein with potential guanine nucleotide exchange (GEF) domains. Lte1p functions as a positive regulator of the mitotic GTPase Tem1p, and overexpression of Tem1p suppresses the low temperature mitotic defect of lte1. By sequence analysis, Tem1p has highest similarity to Vps21p (yeast homolog of mammalian Rab5). Unlike TEM1, LTE1 is not restricted to mitosis but is expressed throughout the cell cycle. Lte1p function in interphase cells is largely unknown. Here we confirm the eis phenotype of lte1 mutant cells and demonstrate a defect in proalpha factor processing that is rescued by expression of full-length Lte1p but not a C-terminally truncated Lte1p lacking its GEF homology domain. Neither overexpression of Tem1p nor 13 other structurally related GTPases can suppress the secretory proprotein processing defect. However, overexpression of Vps21p selectively restores proprotein processing in a manner dependent upon the active GTP-bound form of the GTPase. By contrast, a vps21 mutant produces a synthetic defect with lte1 in proprotein processing, as well as a synthetic growth defect. Together, the data underscore a link between the mitotic regulator, Lte1p, and protein processing and trafficking in the secretory/endosomal system.
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Affiliation(s)
- Xiang Zhao
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48109
- Sue Golding Graduate Division, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Amy Y. Chang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109
| | - Akio Toh-e
- Department of Biological Science, University of Tokyo, Hongo 7-3-1, Tokyo 113-0033, Japan
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48109
- To whom correspondence should be addressed: Division of Metabolism, Endocrinology & Diabetes, 5560 MSRB2, University of Michigan, 1500 E. Medical Ctr Dr., Ann Arbor MI 48109. Tel.: 734-936-5505; Fax: 734-936-6684; E-mail:
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Buvelot Frei S, Rahl PB, Nussbaum M, Briggs BJ, Calero M, Janeczko S, Regan AD, Chen CZ, Barral Y, Whittaker GR, Collins RN. Bioinformatic and comparative localization of Rab proteins reveals functional insights into the uncharacterized GTPases Ypt10p and Ypt11p. Mol Cell Biol 2006; 26:7299-317. [PMID: 16980630 PMCID: PMC1592887 DOI: 10.1128/mcb.02405-05] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A striking characteristic of a Rab protein is its steady-state localization to the cytosolic surface of a particular subcellular membrane. In this study, we have undertaken a combined bioinformatic and experimental approach to examine the evolutionary conservation of Rab protein localization. A comprehensive primary sequence classification shows that 10 out of the 11 Rab proteins identified in the yeast (Saccharomyces cerevisiae) genome can be grouped within a major subclass, each comprising multiple Rab orthologs from diverse species. We compared the locations of individual yeast Rab proteins with their localizations following ectopic expression in mammalian cells. Our results suggest that green fluorescent protein-tagged Rab proteins maintain localizations across large evolutionary distances and that the major known player in the Rab localization pathway, mammalian Rab-GDI, is able to function in yeast. These findings enable us to provide insight into novel gene functions and classify the uncharacterized Rab proteins Ypt10p (YBR264C) as being involved in endocytic function and Ypt11p (YNL304W) as being localized to the endoplasmic reticulum, where we demonstrate it is required for organelle inheritance.
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Affiliation(s)
- Stéphanie Buvelot Frei
- Institut für Biochemie, Swiss Federal Institute of Technology (ETH), CH-8093 Zürich, Switzerland
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Abstract
To maintain cellular homeostasis, the levels of transmembrane receptors found on the plasma membrane must be tightly regulated. Endocytosis of activated receptors and the eventual degradation of these transmembrane proteins in the lysosome serve a vital role in maintaining the plasma membrane receptor levels as well as attenuating the downstream signaling pathways. Two processes that regulate this receptor trafficking are the covalent modification of the receptor with ubiquitin (ubiquitylation) and the activation of the Rab5 family of small GTPases. Activation of Rab5 family proteins has been shown to be critical for early steps of the endocytic pathway including delivery of activated receptors to the early endosome, while ubiquitylation of activated receptors has been shown to be involved in receptor internalization, delivery to the endosome, and sorting into the multivesiclar body. In yeast, the guanine nucleotide exchange factor Vps9p serves to integrate the activation of a Rab5 protein (Vps21p) via the Vps9 domain with ubiquitin binding via the CUE domain to facilitate the delivery of ubiquitylated receptors to the endosome. Here we provide detailed protocols for the study of Vps9p in vivo and in vitro with regard to Vps21p activation, ubiquitin binding, and Vps9p ubiquitylation.
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Sirokmány G, Szidonya L, Káldi K, Gáborik Z, Ligeti E, Geiszt M. Sec14 Homology Domain Targets p50RhoGAP to Endosomes and Provides a Link between Rab and Rho GTPases. J Biol Chem 2006; 281:6096-105. [PMID: 16380373 DOI: 10.1074/jbc.m510619200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sec14 protein was first identified in Saccharomyces cerevisiae, where it serves as a phosphatidylinositol transfer protein that is essential for the transport of secretory proteins from the Golgi complex. A protein domain homologous to Sec14 was identified in several mammalian proteins that regulates Rho GTPases, including exchange factors and GTPase activating proteins. P50RhoGAP, the first identified GTPase activating protein for Rho GTPases, is composed of a Sec14-like domain and a Rho-GTPase activating protein (GAP) domain. The biological function of its Sec14-like domain is still unknown. Here we show that p50RhoGAP is present on endosomal membranes, where it colocalizes with internalized transferrin receptor. We demonstrate that the Sec14-like domain of P50RhoGAP is responsible for the endosomal targeting of the protein. We also show that overexpression of p50RhoGAP or its Sec14-like domain inhibits transferrin uptake. Furthermore, both P50RhoGAP and its Sec14-like domain show colocalization with small GTPases Rab11 and Rab5. We measured bioluminescence resonance energy transfer between p50RhoGAP and Rab11, indicating that these proteins form molecular complex in vivo on endosomal membranes. The interaction was mediated by the Sec 14-like domain of p50RhoGAP. Our results indicate that Sec14-like domain, which was previously considered as a phospholipid binding module, may have a role in the mediation of protein-protein interactions. We suggest that p50RhoGAP provides a link between Rab and Rho GTPases in the regulation of receptor-mediated endocytosis.
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Affiliation(s)
- Gábor Sirokmány
- Department of Physiology, Semmelweis University, P. O. Box 259, 1444 Budapest, Hungary
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Kail M, Hollinshead M, Kaufmann M, Boettcher J, Vaux D, Barnekow A. Yeast Ypt11 is targeted to recycling endosomes in mammalian cells. Biol Cell 2005; 97:651-8. [PMID: 15850457 DOI: 10.1042/bc20040139] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND INFORMATION In yeast, Ypt11 or Ypt32 along with the highly homologous Ypt8 or Ypt31 has been reported to be an essential component of intra-Golgi trafficking and has been implicated in the budding of vesicles from the most distal Golgi compartment. RESULTS AND CONCLUSIONS In the present study, we show that, in human cells, after heterologous expression of GFP-Ypt11 (where GFP stands for green fluorescent protein), the protein is targeted to transferrin-positive recycling endosomes. This compartment has been shown to form extensive tubular networks on applying the drug Brefeldin A. We also show, by confocal fluorescent microscopy, that these networks also contain Rab11 in cells expressing CFP-Rab11a (where CFP stands for cyan fluorescent protein) fusion protein and that these structures are identical with those targeted by GFP-Ypt11.
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Affiliation(s)
- Mark Kail
- Department of Experimental Tumorbiology, University Muenster, Badestr. 9, 48149 Muenster, Germany.
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Talarek N, Balguerie A, Aigle M, Durrens P. A novel link between a rab GTPase and Rvs proteins: the yeast amphiphysin homologues. Cell Biochem Funct 2005; 23:253-66. [PMID: 15473003 DOI: 10.1002/cbf.1146] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The BAR proteins are a well-conserved family of proteins including Rvsp in yeast, amphiphysins and Bin proteins in mammals. In yeast, as in mammals, BAR proteins are known to be implicated in vesicular traffic. The Gyp5p (Ypl249p) and Ymr192p proteins interact in two-hybrid tests with both Rvs161p and Rvs167p. Gyp5p is a Ypt/Rab-specific GAP and Ymr192p is highly similar to Gyp5p. To specify the interaction between Rvsp and Gyp5p, we used two-hybrid tests to determine the domains necessary for these interactions. The specific SH3 domain of Rvs167p interacted with the N-terminal domain of Gyp5p. Moreover, Gyp5p could form a homodimer. Fus2 protein is a specific partner of Rvs161p in two-hybrid tests. To characterize the functional relationships between these five proteins, we have studied cellular phenotypes in single, double and triple mutant strains for which rvs mutants present defects, such as polarity, cell fusion and meiosis. Phenotypic analysis showed that Gyp5p, Ymr192p and Fus2p were involved in bipolar budding pattern and in meiosis. Specific epistasis or suppressive phenomena were found between the five mutations. Finally, The Gyp5p-GFP fusion protein was localized at the bud tip during apical growth and at the mother-bud neck during cytokinesis. Moreover, Rvs167p and Rvs161p were shown to be essential for the correct localization of Gyp5p. Altogether, these data support the hypothesis that both Rvsp proteins act in vesicular traffic through physical and functional interactions with Ypt/Rab regulators.
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Ali BR, Wasmeier C, Lamoreux L, Strom M, Seabra MC. Multiple regions contribute to membrane targeting of Rab GTPases. J Cell Sci 2004; 117:6401-12. [PMID: 15561774 DOI: 10.1242/jcs.01542] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Small GTPases of the Rab family are key regulators of membrane trafficking. Each Rab shows a characteristic subcellular distribution, and may serve as an important determinant of organelle identity. The molecular mechanisms responsible for targeting Rabs to specific intracellular compartments, however, remain poorly understood. The divergent C-terminal hypervariable region was postulated to contain Rab targeting information. We generated a series of hybrid Rab proteins by exchanging the hypervariable domains of Rab1a, Rab2a, Rab5a, Rab7 and Rab27a, and analysed their subcellular localisations. We found that the various hybrid proteins retained their targeting to the parent organelle and were functionally active. We conclude that the hypervariable region does not contain a general Rab targeting signal. Furthermore, we identified other regions within the RabF and RabSF motifs that are required for specific targeting of Rab27a to secretory granules or melanosomes, and Rab5a to endosomes. We observed only partial overlap between targeting-determining regions in the Rab proteins examined, suggesting that Rab recruitment may be complex and at least partially Rab-specific. Mutations in these targeting-determining regions induced localisation to the ER, an observation that further strengthens our previous finding that ER/Golgi membranes serve as the default location for Rabs that have lost targeting information.
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Affiliation(s)
- Bassam R Ali
- Cell and Molecular Biology, Division of Biomedical Sciences, Faculty of Medicine, Imperial College London, London, SW7 2AZ, UK
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Saito-Nakano Y, Yasuda T, Nakada-Tsukui K, Leippe M, Nozaki T. Rab5-associated Vacuoles Play a Unique Role in Phagocytosis of the Enteric Protozoan Parasite Entamoeba histolytica. J Biol Chem 2004; 279:49497-507. [PMID: 15347665 DOI: 10.1074/jbc.m403987200] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In mammals, Rab5 and Rab7 play a specific and coordinated role in a sequential process during phagosome maturation. Here, we report that Rab5 and Rab7 in the enteric protozoan parasite Entamoeba histolytica, EhRab5 and EhRab7A, are involved in steps that are distinct from those known for mammals. EhRab5 and EhRab7A were localized to independent small vesicular structures at steady state. Priming with red blood cells induced the formation of large vacuoles associated with both EhRab5 and EhRab7A ("prephagosomal vacuoles (PPV)") in the amoeba within an incubation period of 5-10 min. PPV emerged de novo physically and distinct from phagosomes. PPV were gradually acidified and matured by fusion with lysosomes containing a digestive hydrolase, cysteine proteinase, and a membrane-permeabilizing peptide amoebapore. After EhRab5 dissociated from PPV, 5-10 min later, the EhRab7A-PPV fused with phagosomes, and EhRab7A finally dissociated from the phagosomes. Immunoelectron and light micrographs showed that PPV contained small vesicle-like structures containing fluid-phase markers and amoebapores, which were not evenly distributed within PPV, suggesting that the mechanism was similar to multivesicular body formation in PPV generation. In contrast to Rab5 from other organisms, EhRab5 was involved exclusively in phagocytosis, but not in endocytosis. Overexpression of wild-type EhRab5 enhanced phagocytosis and the transport of amoebapore to phagosomes. Conversely, expression of an EhRab5Q67L GTP form mutant impaired the formation of PPV and phagocytosis. Altogether, we propose that the amoebic Rab5 plays an important role in the formation of unique vacuoles, which is essential for engulfment of erythrocytes and important for packaging of lysosomal hydrolases, prior to the targeting to phagosomes.
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Affiliation(s)
- Yumiko Saito-Nakano
- Department of Parasitology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
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Wicky S, Schwarz H, Singer-Krüger B. Molecular interactions of yeast Neo1p, an essential member of the Drs2 family of aminophospholipid translocases, and its role in membrane trafficking within the endomembrane system. Mol Cell Biol 2004; 24:7402-18. [PMID: 15314152 PMCID: PMC507011 DOI: 10.1128/mcb.24.17.7402-7418.2004] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neo1p is an essential yeast member of the highly conserved Drs2 family of P-type ATPases with proposed aminophospholipid translocase activity. Here we present evidence that Neo1p localizes to endosomes and Golgi elements. In agreement with that finding, the temperature-sensitive neo1-37 and neo1-69 mutants exhibit defects in receptor-mediated endocytosis, vacuole biogenesis, and vacuolar protein sorting. Furthermore, neo1 mutants accumulate aberrantly shaped membranous structures most likely derived from vacuoles and the endosomal/Golgi system. At permissive temperatures, HA-Neo1-69p, like wild-type Neo1p, is stable and associates with endosomes. In contrast, HA-Neo1-37p is rapidly degraded and is predominantly retained within the endoplasmic reticulum (ER). Thus, the two neo1 alleles affect the stability and localization of the mutant polypeptides in different ways. A C-terminally truncated and a C-terminally epitope-tagged version of Neo1p are nonfunctional and also mislocalize to the ER. In agreement with a role within the endomembrane system, Neo1p exhibits genetic and physical interactions with Ysl2p, a potential guanine nucleotide exchange factor for Arl1p. Interestingly, deletion of ARL1 rescues the temperature sensitivity of neo1-37 and neo1-69. We demonstrate that Arl1p in its myristoylated and GTP-bound form is responsible for the inhibitory effect. Thus, Neo1p, Ysl2p, and Arl1p represent three proteins that collaborate in membrane trafficking within the endosomal/Golgi system.
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Affiliation(s)
- Sidonie Wicky
- Institute for Biochemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
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29
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Abstract
The vacuole/lysosome of the budding yeast Saccharomyces cerevisiae is actively divided between mother and daughter cells. Vacuole inheritance initiates early in the cell cycle and ends in G2, just prior to nuclear migration. The process begins with a portion of the vacuole extending into the emerging bud. This tubular-vesicular entity, the segregation structure, enables continued exchange of vacuole contents between mother and daughter vacuoles. Genetic, biochemical, and cytological analyses of vacuole inheritance have provided insight into the molecular basis of membrane movement, the spatial and temporal control of organelle transport, and the molecular basis of membrane fusion and fission.
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Affiliation(s)
- Lois S Weisman
- Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242, USA.
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Enouf V, Chwetzoff S, Trugnan G, Cohen J. Interactions of rotavirus VP4 spike protein with the endosomal protein Rab5 and the prenylated Rab acceptor PRA1. J Virol 2003; 77:7041-7. [PMID: 12768023 PMCID: PMC156175 DOI: 10.1128/jvi.77.12.7041-7047.2003] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rotavirus spike protein VP4 is implicated in several important functions, such as cell attachment, penetration, hemagglutination, neutralization, virulence, and host range. It is present at the plasma membrane and colocalizes with the cytoskeleton in infected cells. We looked for cellular partners responsible for the localization of VP4 by two-hybrid screening of a monkey CV1 cell cDNA library. In the screen we isolated repeatedly three cDNAs encoding either two isoforms (a and c) of Rab5 protein or the prenylated Rab acceptor (PRA1). The small GTPase Rab5 is a molecule regulating the vesicular traffic and the motility of early endosomes along microtubules. Rab5 interacts with a large number of effectors, in particular with PRA1. Interactions of VP4 with both partners, Rab5 and PRA1, were confirmed by coimmunoprecipitation from infected- or transfected-cell lysates. Interaction of Rab5 and PRA1 was restricted to free VP4, since neither triple-layered particles nor NSP4-VP4-VP7 heterotrimeric complexes could be coprecipitated. Site-directed and deletion mutants of VP4 were used to map a VP4 domain(s) interacting with Rab5 or PRA1. Of the 10 mutants tested, 2 interacted exclusively with a single partner. In contrast, the domain extending from amino acids 560 to 722 of VP4 is essential for both interactions. These results suggest that Rab5 and PRA1 may be involved in the localization and trafficking of VP4 in infected cells.
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Affiliation(s)
- Vincent Enouf
- Virologie Moléculaire et Structurale, UMR CNRS-INRA 2472, F-91190 Gif-sur-Yvette, France
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31
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Calero M, Chen CZ, Zhu W, Winand N, Havas KA, Gilbert PM, Burd CG, Collins RN. Dual prenylation is required for Rab protein localization and function. Mol Biol Cell 2003; 14:1852-67. [PMID: 12802060 PMCID: PMC165082 DOI: 10.1091/mbc.e02-11-0707] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2002] [Revised: 01/01/2003] [Accepted: 01/13/2003] [Indexed: 12/14/2022] Open
Abstract
The majority of Rab proteins are posttranslationally modified with two geranylgeranyl lipid moieties that enable their stable association with membranes. In this study, we present evidence to demonstrate that there is a specific lipid requirement for Rab protein localization and function. Substitution of different prenyl anchors on Rab GTPases does not lead to correct function. In the case of YPT1 and SEC4, two essential Rab genes in Saccharomyces cerevisiae, alternative lipid tails cannot support life when present as the sole source of YPT1 and SEC4. Furthermore, our data suggest that double geranyl-geranyl groups are required for Rab proteins to correctly localize to their characteristic organelle membrane. We have identified a factor, Yip1p that specifically binds the di-geranylgeranylated Rab and does not interact with mono-prenylated Rab proteins. This is the first demonstration that the double prenylation modification of Rab proteins is an important feature in the function of this small GTPase family and adds specific prenylation to the already known determinants of Rab localization.
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Affiliation(s)
- Monica Calero
- Department of Molecular Medicine, Cornell University, Ithaca, New York 14853-6401, USA
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32
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Vernoud V, Horton AC, Yang Z, Nielsen E. Analysis of the small GTPase gene superfamily of Arabidopsis. PLANT PHYSIOLOGY 2003; 131:1191-208. [PMID: 12644670 PMCID: PMC166880 DOI: 10.1104/pp.013052] [Citation(s) in RCA: 427] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Small GTP-binding proteins regulate diverse processes in eukaryotic cells such as signal transduction, cell proliferation, cytoskeletal organization, and intracellular membrane trafficking. These proteins function as molecular switches that cycle between "active" and "inactive" states, and this cycle is linked to the binding and hydrolysis of GTP. The Arabidopsis genome contains 93 genes that encode small GTP-binding protein homologs. Phylogenetic analysis of these genes shows that plants contain Rab, Rho, Arf, and Ran GTPases, but no Ras GTPases. We have assembled complete lists of these small GTPases families, as well as accessory proteins that control their activity, and review what is known of the functions of individual members of these families in Arabidopsis. We also discuss the possible roles of these GTPases in relation to their similarity to orthologs with known functions and localizations in yeast and/or animal systems.
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Affiliation(s)
- Vanessa Vernoud
- Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA
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33
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Wicky S, Frischmuth S, Singer-Krüger B. Bsp1p/Ypr171p is an adapter that directly links some synaptojanin family members to the cortical actin cytoskeleton in yeast. FEBS Lett 2003; 537:35-41. [PMID: 12606027 DOI: 10.1016/s0014-5793(03)00067-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In this study we identified a novel protein, Bsp1p, that interacts directly with two yeast synaptojanins, Sjl2p and Sjl3p, but not with Sjl1p. The interaction takes place via the Sac1/polyphosphoinositide phosphatase domain, whose conserved C-terminal region is important for binding. Subcellular localization and genetic interactions revealed a function of Bsp1p in the cortical actin cytoskeleton. A fraction of Bsp1p was found to be membrane-associated. Studies with mutants of phosphatidylinositol 4-kinase, PIK1, suggested that the interaction with membranes is facilitated by phosphoinositides. We propose that Bsp1p is an adapter that links Sjl2p and Sjl3p to the cortical actin cytoskeleton.
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Affiliation(s)
- Sidonie Wicky
- Institute for Biochemistry, University of Stuttgart, Pfaffenwaldring 55, Germany
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34
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Misu K, Fujimura-Kamada K, Ueda T, Nakano A, Katoh H, Tanaka K. Cdc50p, a conserved endosomal membrane protein, controls polarized growth in Saccharomyces cerevisiae. Mol Biol Cell 2003; 14:730-47. [PMID: 12589066 PMCID: PMC150004 DOI: 10.1091/mbc.e02-06-0314] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
During the cell cycle of the yeast Saccharomyces cerevisiae, the actin cytoskeleton and the growth of cell surface are polarized, mediating bud emergence, bud growth, and cytokinesis. We identified CDC50 as a multicopy suppressor of the myo3 myo5-360 temperature-sensitive mutant, which is defective in organization of cortical actin patches. The cdc50 null mutant showed cold-sensitive cell cycle arrest with a small bud as reported previously. Cortical actin patches and Myo5p, which are normally localized to polarization sites, were depolarized in the cdc50 mutant. Furthermore, actin cables disappeared, and Bni1p and Gic1p, effectors of the Cdc42p small GTPase, were mislocalized in the cdc50 mutant. As predicted by its amino acid sequence, Cdc50p appears to be a transmembrane protein because it was solubilized from the membranes by detergent treatment. Cdc50p colocalized with Vps21p in endosomal compartments and was also localized to the class E compartment in the vps27 mutant. The cdc50 mutant showed defects in a late stage of endocytosis but not in the internalization step. It showed, however, only modest defects in vacuolar protein sorting. Our results indicate that Cdc50p is a novel endosomal protein that regulates polarized cell growth.
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Affiliation(s)
- Kenjiro Misu
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-ku, Sapporo, 060-0815, Japan
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35
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Jochum A, Jackson D, Schwarz H, Pipkorn R, Singer-Krüger B. Yeast Ysl2p, homologous to Sec7 domain guanine nucleotide exchange factors, functions in endocytosis and maintenance of vacuole integrity and interacts with the Arf-Like small GTPase Arl1p. Mol Cell Biol 2002; 22:4914-28. [PMID: 12052896 PMCID: PMC133889 DOI: 10.1128/mcb.22.13.4914-4928.2002] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We previously described the isolation of ysl2-1 due to its genetic interaction with Delta ypt51/vps21, a mutant with a deletion of the coding sequence for the yeast Rab5 homolog, which regulates endocytic traffic between early and late endosomes. Here we report that Ysl2p is a novel 186.8-kDa peripheral membrane protein homologous to members of the Sec7 family. We provide multiple genetic and biochemical evidence for an interaction between Ysl12p and the Arf-like protein Arl1p, consistent with a potential function as an Arf guanine nucleotide exchange factor (GEF). The temperature-sensitive alleles ysl2-307 and ysl2-316 are specifically defective in ligand-induced degradation of Ste2p and alpha-factor and exhibit vacuole fragmentation directly upon a shift to 37 degrees C. In living cells, green fluorescent protein (GFP)-Ysl2p colocalizes with endocytic elements that accumulate FM4-64. The GFP-Ysl2p staining is sensitive to a mutation in VPS27 resulting in the formation of an aberrant class E compartment, but it is not affected by a sec7 mutation. Consistent with the idea that Ysl2p and Arl1p have closely related functions, Delta arl1 cells are defective in endocytic transport and in vacuolar protein sorting.
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Affiliation(s)
- Alexandra Jochum
- Institute for Biochemistry, University of Stuttgart, D-70569 Stuttgart, Germany
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36
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Robibaro B, Stedman TT, Coppens I, Ngô HM, Pypaert M, Bivona T, Nam HW, Joiner KA. Toxoplasma gondii Rab5 enhances cholesterol acquisition from host cells. Cell Microbiol 2002; 4:139-52. [PMID: 11906451 DOI: 10.1046/j.1462-5822.2002.00178.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The role of endocytosis in nutrient uptake by Toxoplasma gondii is unknown. To explore this issue, we characterized an endosomal compartment by identifying a T. gondii Rab5 homologue, a molecular marker for early endosomes in eukaryotic cells. The deduced amino acid sequence of the T. gondii Rab5 gene encodes a protein of 240 amino acids, which we termed TgRab51. TgRab51 was epitope-tagged at the N-terminus, expressed in the parasite, and localized by immunofluorescence and immunoelectron microscopy to tubulovesicular structures anterior to the parasite nucleus and adjacent to, but distinct from the Golgi. By immunofluorescence analysis, TgRab51wt-HA staining partially overlapped with Golgi/TGN markers, but not with the T. gondii secretory organelles. A dominant positive mutant, TgRab51Q103L-HA, enhanced uptake of exogenous cholesterol analogues in intracellular parasites, augmented formation of lipid droplets and accelerated parasite growth. Brefeldin A disrupted the TgRab51 compartment, and altered the distribution of fluorescent exogenous cholesterol in cells expressing TgRab51Q103L-HA. These results suggest that TgRab51 facilitates sterol uptake, possibly through a Golgi-dependent pathway.
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Affiliation(s)
- Bruno Robibaro
- Department of Medicine, Yale University School of Medicine, New Haven, CT 06520-8022, USA
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37
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Abstract
We have characterized the morphology of the yeast endocytic pathway leading from the plasma membrane to the vacuole by following the trafficking of positively charged nanogold in combination with compartment identification using immunolocalization of t-SNARE proteins. The first endocytic compartment, termed the early/recycling endosome, contains the t-SNARE, Tlg1p. The next compartment, the prevacuolar compartment, contains Pep12p. After transport to the prevacuolar compartment, where vacuolar enzymes are seen on their way to the vacuole, endocytic content is delivered to the late endosome and on to the vacuole, both of which are devoid of Pep12p immunolabel. Traffic to the prevacuolar compartment is reduced in strains mutant for the Rab5 homologs, Vps21p, Ypt52p, and Ypt53p and in vps27 mutant cells. On the other hand, traffic to the early recycling endosome is less dependent on Rab5 homologs and does not require Vps27p.
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38
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39
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Segev N. Ypt/rab gtpases: regulators of protein trafficking. SCIENCE'S STKE : SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT 2001; 2001:re11. [PMID: 11579231 DOI: 10.1126/stke.2001.100.re11] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Ypt/Rab guanosine triphosphatases (GTPases) have emerged in the last decade as key regulators of protein transport in all eukaryotic cells. They seem to be involved in all aspects of vesicle trafficking: vesicle formation, motility, and docking, and membrane remodeling and fusion. The functions of Ypt/Rabs are themselves controlled by upstream regulators that stimulate both their nucleotide cycling and their cycling between membranes. Ypt/Rabs transmit signals to downstream effectors in a guanosine triphosphate (GTP)-dependent manner. The identity of upstream regulators and downstream effectors is known for a number of Ypt/Rabs, and models for their mechanisms of action are emerging. In at least two cases, Ypt/Rab upstream regulators and downstream effectors are found together in a single complex. In agreement with the idea that Ypt/Rabs function in all aspects of vesicular transport, their diverse effectors have recently been shown to function in all identified aspects of vesicle transport. Activators and effectors for individual Ypt/Rabs share no similarity, but are conserved between yeast and mammalian cells. Finally, cross talk demonstrated among the various Ypt/Rabs, and between Ypt/Rabs and other signaling factors, suggests possible coordination among secretory steps, as well as between protein transport and other cellular processes.
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Affiliation(s)
- N Segev
- Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, MBRB 4120, 900 South Ashland Avenue, Chicago, IL 60607, USA.
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40
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Calero M, Whittaker GR, Collins RN. Yop1p, the yeast homolog of the polyposis locus protein 1, interacts with Yip1p and negatively regulates cell growth. J Biol Chem 2001; 276:12100-12. [PMID: 11278413 DOI: 10.1074/jbc.m008439200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rab proteins are small GTPases that are essential elements of the protein transport machinery of eukaryotic cells. Each round of membrane transport requires a cycle of Rab protein nucleotide binding and hydrolysis. We have recently characterized a protein, Yip1p, which appears to play a role in Rab-mediated membrane transport in Saccharomyces cerevisiae. In this study, we report the identification of a Yip1p-associated protein, Yop1p. Yop1p is a membrane protein with a hydrophilic region at its N terminus through which it interacts specifically with the cytosolic domain of Yip1p. Yop1p could also be coprecipitated with Rab proteins from total cellular lysates. The TB2 gene is the human homolog of Yop1p (Kinzler, K. W., Nilbert, M. C., Su, L.-K., Vogelstein, B., Bryan, T. M., Levey, D. B., Smith, K. J., Preisinger, A. C., Hedge, P., McKechnie, D., Finniear, R., Markham, A., Groffen, J., Boguski, M. S., Altschul, S. F., Horii, A., Ando, H. M., Y., Miki, Y., Nishisho, I., and Nakamura, Y. (1991) Science 253, 661-665). Our data demonstrate that Yop1p negatively regulates cell growth. Disruption of YOP1 has no apparent effect on cell viability, while overexpression results in cell death, accumulation of internal cell membranes, and a block in membrane traffic. These results suggest that Yop1p acts in conjunction with Yip1p to mediate a common step in membrane traffic.
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Affiliation(s)
- M Calero
- Department of Molecular Medicine, and Microbiology and Immunology, Cornell University, Ithaca, New York 14830, USA
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41
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Abstract
Genetic and biochemical studies in yeast and animal cells have led to the identification of many components required for endocytosis. In this review, we summarize our understanding of the endocytic machinery with an emphasis on the proteins regulating the internalization step of endocytosis and endosome fusion. Even though the overall endocytic machinery appears to be conserved between yeast and animals, clear differences exist. We also discuss the roles of phosphoinositides, sterols, and sphingolipid precursors in endocytosis, because in addition to proteins, these lipids have emerged as important determinants in the spatial and most likely temporal specificity of endocytic membrane trafficking events.
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Affiliation(s)
- K D'Hondt
- Biozentrum-University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
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42
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Rak A, Fedorov R, Alexandrov K, Albert S, Goody RS, Gallwitz D, Scheidig AJ. Crystal structure of the GAP domain of Gyp1p: first insights into interaction with Ypt/Rab proteins. EMBO J 2000; 19:5105-13. [PMID: 11013213 PMCID: PMC302102 DOI: 10.1093/emboj/19.19.5105] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We present the 1.9 A resolution crystal structure of the catalytic domain of Gyp1p, a specific GTPase activating protein (GAP) for Ypt proteins, the yeast homologues of Rab proteins, which are involved in vesicular transport. Gyp1p is a member of a large family of eukaryotic proteins with shared sequence motifs. Previously, no structural information was available for any member of this class of proteins. The GAP domain of Gyp1p was found to be fully alpha-helical. However, the observed fold does not superimpose with other alpha-helical GAPs (e.g. Ras- and Cdc42/Rho-GAP). The conserved and catalytically crucial arginine residue, identified by mutational analysis, is in a comparable position to the arginine finger in the Ras- and Cdc42-GAPs, suggesting that Gyp1p utilizes an arginine finger in the GAP reaction, in analogy to Ras- and Cdc42-GAPs. A model for the interaction between Gyp1p and the Ypt protein satisfying biochemical data is given.
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Affiliation(s)
- A Rak
- Max-Planck-Institute for Molecular Physiology, Department of Physical Biochemistry, Otto-Hahn-Strasse 11, D-44227 Dortmund, Germany
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43
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Götte M, Lazar T, Yoo JS, Scheglmann D, Gallwitz D. The full complement of yeast Ypt/Rab-GTPases and their involvement in exo- and endocytic trafficking. Subcell Biochem 2000; 34:133-73. [PMID: 10808333 DOI: 10.1007/0-306-46824-7_4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- M Götte
- Department of Molecular Genetics, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
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44
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Luo WJ, Chang A. An endosome-to-plasma membrane pathway involved in trafficking of a mutant plasma membrane ATPase in yeast. Mol Biol Cell 2000; 11:579-92. [PMID: 10679016 PMCID: PMC14795 DOI: 10.1091/mbc.11.2.579] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The plasma membrane ATPase, encoded by PMA1, is delivered to the cell surface via the secretory pathway. Previously, we characterized a temperature-sensitive pma1 mutant in which newly synthesized Pma1-7 is not delivered to the plasma membrane but is mislocalized instead to the vacuole at 37 degrees C. Several vps mutants, which are defective in vacuolar protein sorting, suppress targeting-defective pma1 by allowing mutant Pma1 to move once again to the plasma membrane. In this study, we have analyzed trafficking in the endosomal system by monitoring the movement of Pma1-7 in vps36, vps1, and vps8 mutants. Upon induction of expression, mutant Pma1 accumulates in the prevacuolar compartment in vps36 cells. After chase, a fraction of newly synthesized Pma1-7 is delivered to the plasma membrane. In both vps1 and vps8 cells, newly synthesized mutant Pma1 appears in small punctate structures before arrival at the cell surface. Nevertheless, biosynthetic membrane traffic appears to follow different routes in vps8 and vps1: the vacuolar protein-sorting receptor Vps10p is stable in vps8 but not in vps1. Furthermore, a defect in endocytic delivery to the vacuole was revealed in vps8 (and vps36) but not vps1 by endocytosis of the bulk membrane marker FM 4-64. Moreover, in vps8 cells, there is defective down-regulation from the cell surface of the mating receptor Ste3, consistent with persistent receptor recycling from an endosomal compartment to the plasma membrane. These data support a model in which mutant Pma1 is diverted from the Golgi to the surface in vps1 cells. We hypothesize that in vps8 and vps36, in contrast to vps1, mutant Pma1 moves to the surface via endosomal intermediates, implicating an endosome-to-surface traffic pathway.
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Affiliation(s)
- W j Luo
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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45
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Gerrard SR, Bryant NJ, Stevens TH. VPS21 controls entry of endocytosed and biosynthetic proteins into the yeast prevacuolar compartment. Mol Biol Cell 2000; 11:613-26. [PMID: 10679018 PMCID: PMC14797 DOI: 10.1091/mbc.11.2.613] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Mutations in the VPS (vacuolar protein sorting) genes of Saccharomyces cerevisiae have been used to define the trafficking steps that soluble vacuolar hydrolases take en route from the late Golgi to the vacuole. The class D VPS genes include VPS21, PEP12, and VPS45, which appear to encode components of a membrane fusion complex involved in Golgi-to-endosome transport. Vps21p is a member of the Rab family of small Ras-like GTPases and shows strong homology to the mammalian Rab5 protein, which is involved in endocytosis and the homotypic fusion of early endosomes. Although Rab5 and Vps21p appear homologous at the sequence level, it has not been clear if the functions of these two Rabs are similar. We find that Vps21p is an endosomal protein that is involved in the delivery of vacuolar and endocytosed proteins to the vacuole. Vacuolar and endocytosed proteins accumulate in distinct transport intermediates in cells that lack Vps21p function. Therefore, it appears that Vps21p is involved in two trafficking steps into the prevacuolar/late endosomal compartment.
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Affiliation(s)
- S R Gerrard
- Institute of Molecular Biology, Department of Chemistry, University of Oregon, Eugene, Oregon 97403-1229, USA
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46
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Gerrard SR, Mecklem AB, Stevens TH. The yeast endosomal t-SNARE, Pep12p, functions in the absence of its transmembrane domain. Traffic 2000; 1:45-55. [PMID: 11208059 DOI: 10.1034/j.1600-0854.2000.010108.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Delivery of proteins to the vacuole of the yeast Saccharomyces cerevisiae requires the function of two distinct SNARE complexes. Pep12p and Vam3p are both t-SNAREs of the syntaxin family that are components of these SNARE complexes. We have used a genetic approach to address the role of Pep12p in vacuolar protein transport. Our screen for temperature-sensitive pep12 mutants yielded six alleles that were rapidly inactivated upon exposure to the non-permissive temperature. Surprisingly, the proteins encoded by these alleles were all truncated immediately prior to the transmembrane domain. Here we demonstrate that Pep12p requires its transmembrane domain for proper localization, but not for its role in vesicle fusion. In addition, we show that although Pep12p can replace Vam3p in the vacuolar SNARE complex, its transmembrane domain is required to function at this step. Therefore, the transmembrane domain of Pep12p performs different roles in the prevacuolar and vacuolar SNARE complexes.
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Affiliation(s)
- S R Gerrard
- Institute of Molecular Biology, Department of Chemistry, University of Oregon, Eugene, OR 97403-1229, USA
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47
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Chiariello M, Bruni CB, Bucci C. The small GTPases Rab5a, Rab5b and Rab5c are differentially phosphorylated in vitro. FEBS Lett 1999; 453:20-4. [PMID: 10403367 DOI: 10.1016/s0014-5793(99)00686-9] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Rab GTPases play a fundamental role in the regulation of membrane traffic. Three different Rab5 isoforms have been reported but no differences in their function in endocytosis have been discovered. As the Rab5 isoforms show a conserved consensus site for Ser/Thr phosphorylation, we investigated whether this site was phosphorylated. Here, we report that the three Rab5 proteins are differentially recognized by different kinases. Rab5a is efficiently phosphorylated by extracellular-regulated kinase 1 but not by extracellular-regulated kinase 2, while cdc2 kinase preferentially phosphorylates Ser-123 of Rab5b. These findings strongly suggest that phosphorylation could be important to differentially regulate the function of the Rab5 isoforms.
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Affiliation(s)
- M Chiariello
- Dipartimento di Biologia e Patologia Cellulare e Molecolare L. Califano and Centro di Endocrinologia ed Oncologia Sperimentale G. Salvatore del Consiglio Nazionale delle Ricerche, Napoli, Italy
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48
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Li Y, Kane T, Tipper C, Spatrick P, Jenness DD. Yeast mutants affecting possible quality control of plasma membrane proteins. Mol Cell Biol 1999; 19:3588-99. [PMID: 10207082 PMCID: PMC84152 DOI: 10.1128/mcb.19.5.3588] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/1998] [Accepted: 01/30/1999] [Indexed: 11/20/2022] Open
Abstract
Mutations gef1, stp22, STP26, and STP27 in Saccharomyces cerevisiae were identified as suppressors of the temperature-sensitive alpha-factor receptor (mutation ste2-3) and arginine permease (mutation can1(ts)). These suppressors inhibited the elimination of misfolded receptors (synthesized at 34 degrees C) as well as damaged surface receptors (shifted from 22 to 34 degrees C). The stp22 mutation (allelic to vps23 [M. Babst and S. Emr, personal communication] and the STP26 mutation also caused missorting of carboxypeptidase Y, and ste2-3 was suppressed by mutations vps1, vps8, vps10, and vps28 but not by mutation vps3. In the stp22 mutant, both the mutant and the wild-type receptors (tagged with green fluorescent protein [GFP]) accumulated within an endosome-like compartment and were excluded from the vacuole. GFP-tagged Stp22p also accumulated in this compartment. Upon reaching the vacuole, cytoplasmic domains of both mutant and wild-type receptors appeared within the vacuolar lumen. Stp22p and Gef1p are similar to tumor susceptibility protein TSG101 and voltage-gated chloride channel, respectively. These results identify potential elements of plasma membrane quality control and indicate that cytoplasmic domains of membrane proteins are translocated into the vacuolar lumen.
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Affiliation(s)
- Y Li
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655-0122, USA
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49
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Alvarez-Dominguez C, Stahl PD. Increased expression of Rab5a correlates directly with accelerated maturation of Listeria monocytogenes phagosomes. J Biol Chem 1999; 274:11459-62. [PMID: 10206948 DOI: 10.1074/jbc.274.17.11459] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previous studies have shown that Listeria monocytogenes (LM) modulates phagocytic membrane traffic. Here we explore whether Rab5a, a GTPase associated with phagosome-endosome fusion, is related to phagosome maturation and to the intracellular survival of LM. Stable transfection of Rab5a cDNA into macrophages accelerates intracellular degradation of LM. Morphological studies confirmed that phagosome maturation and phagosome-lysosome fusion is enhanced by overexpression of Rab5a. Down-regulation experiments using antisense oligonucleotides targeted to the Rab5a mRNA efficiently reduced Rab5a synthesis, reduced phagosome-endosome traffic, blocked phagosome-lysosome fusion, and extended intraphagosomal survival of LM. Down-regulation of Rab5a had no effect on LM internalization. Down-regulation of Rab5c had no effect on phagosome maturation and phagosome-lysosome fusion. The results indicate that Rab5a controls early phagosome-endosome interactions and governs the maturation of the early phagosome leading to phagosome-lysosome fusion.
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Affiliation(s)
- C Alvarez-Dominguez
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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50
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Mulholland J, Konopka J, Singer-Kruger B, Zerial M, Botstein D. Visualization of receptor-mediated endocytosis in yeast. Mol Biol Cell 1999; 10:799-817. [PMID: 10069819 PMCID: PMC25203 DOI: 10.1091/mbc.10.3.799] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We studied the ligand-induced endocytosis of the yeast alpha-factor receptor Ste2p by immuno-electron microscopy. We observed and quantitated time-dependent loss of Ste2p from the plasma membrane of cells exposed to alpha-factor. This ligand-induced internalization of Ste2p was blocked in the well-characterized endocytosis-deficient mutant sac6Delta. We provide evidence that implicates furrow-like invaginations of the plasma membrane as the site of receptor internalization. These invaginations are distinct from the finger-like plasma membrane invaginations within actin cortical patches. Consistent with this, we show that Ste2p is not located within the cortical actin patch before and during receptor-mediated endocytosis. In wild-type cells exposed to alpha-factor we also observed and quantitated a time-dependent accumulation of Ste2p in intracellular, membrane-bound compartments. These compartments have a characteristic electron density but variable shape and size and are often located adjacent to the vacuole. In immuno-electron microscopy experiments these compartments labeled with antibodies directed against the rab5 homologue Ypt51p (Vps21p), the resident vacuolar protease carboxypeptidase Y, and the vacuolar H+-ATPase Vph1p. Using a new double-labeling technique we have colocalized antibodies against Ste2p and carboxypeptidase Y to this compartment, thereby identifying these compartments as prevacuolar late endosomes.
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Affiliation(s)
- J Mulholland
- Department of Genetics, Stanford University School of Medicine, Stanford, California 94305-5120, USA
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