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Chen Q, Zhou S, Qu M, Yang Y, Chen Q, Meng X, Fan H. Cucumber (Cucumis sativus L.) translationally controlled tumor protein interacts with CsRab11A and promotes activation of target of rapamycin in response to Podosphaera xanthii. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2024; 119:332-347. [PMID: 38700955 DOI: 10.1111/tpj.16766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 03/12/2024] [Accepted: 03/26/2024] [Indexed: 05/05/2024]
Abstract
The target of rapamycin (TOR) kinase serves as a central regulator that integrates nutrient and energy signals to orchestrate cellular and organismal physiology in both animals and plants. Despite significant advancements having been made in understanding the molecular and cellular functions of plant TOR kinases, the upstream regulators that modulate TOR activity are not yet fully elucidated. In animals, the translationally controlled tumor protein (TCTP) is recognized as a key player in TOR signaling. This study reveals that two TCTP isoforms from Cucumis sativus, when introduced into Arabidopsis, are instrumental in balancing growth and defense mechanisms against the fungal pathogen Golovinomyces cichoracearum. We hypothesize that plant TCTPs act as upstream regulators of TOR in response to powdery mildew caused by Podosphaera xanthii in Cucumis. Our research further uncovers a stable interaction between CsTCTP and a small GTPase, CsRab11A. Transient transformation assays indicate that CsRab11A is involved in the defense against P. xanthii and promotes the activation of TOR signaling through CsTCTP. Moreover, our findings demonstrate that the critical role of TOR in plant disease resistance is contingent upon its regulated activity; pretreatment with a TOR inhibitor (AZD-8055) enhances cucumber plant resistance to P. xanthii, while pretreatment with a TOR activator (MHY-1485) increases susceptibility. These results suggest a sophisticated adaptive response mechanism in which upstream regulators, CsTCTP and CsRab11A, coordinate to modulate TOR function in response to P. xanthii, highlighting a novel aspect of plant-pathogen interactions.
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Affiliation(s)
- Qiumin Chen
- College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, China
| | - Shuang Zhou
- College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, China
| | - Mengqi Qu
- College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, China
| | - Yun Yang
- College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, China
| | - Qinglei Chen
- College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, China
| | - Xiangnan Meng
- College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, China
- Key Laboratory of Agricultural Biotechnology of Liaoning Province, Shenyang Agricultural University, Shenyang, China
| | - Haiyan Fan
- College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, China
- Key Laboratory of Protected Horticulture of Ministry of Education, Shenyang Agricultural University, Shenyang, China
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2
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Füllbrunn N, Nicastro R, Mari M, Griffith J, Herrmann E, Rasche R, Borchers AC, Auffarth K, Kümmel D, Reggiori F, De Virgilio C, Langemeyer L, Ungermann C. The GTPase activating protein Gyp7 regulates Rab7/Ypt7 activity on late endosomes. J Cell Biol 2024; 223:e202305038. [PMID: 38536036 PMCID: PMC10978497 DOI: 10.1083/jcb.202305038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 01/22/2024] [Accepted: 03/08/2024] [Indexed: 04/01/2024] Open
Abstract
Organelles of the endomembrane system contain Rab GTPases as identity markers. Their localization is determined by guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs). It remains largely unclear how these regulators are specifically targeted to organelles and how their activity is regulated. Here, we focus on the GAP Gyp7, which acts on the Rab7-like Ypt7 protein in yeast, and surprisingly observe the protein exclusively in puncta proximal to the vacuole. Mistargeting of Gyp7 to the vacuole strongly affects vacuole morphology, suggesting that endosomal localization is needed for function. In agreement, efficient endolysosomal transport requires Gyp7. In vitro assays reveal that Gyp7 requires a distinct lipid environment for membrane binding and activity. Overexpression of Gyp7 concentrates Ypt7 in late endosomes and results in resistance to rapamycin, an inhibitor of the target of rapamycin complex 1 (TORC1), suggesting that these late endosomes are signaling endosomes. We postulate that Gyp7 is part of regulatory machinery involved in late endosome function.
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Affiliation(s)
- Nadia Füllbrunn
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany
- Center of Cellular Nanoanalytics, Osnabrück University, Osnabrück, Germany
| | - Raffaele Nicastro
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Muriel Mari
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Janice Griffith
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, Netherlands
| | - Eric Herrmann
- Institute of Biochemistry, University of Münster, Münster, Germany
| | - René Rasche
- Institute of Biochemistry, University of Münster, Münster, Germany
| | - Ann-Christin Borchers
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany
| | - Kathrin Auffarth
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany
| | - Daniel Kümmel
- Institute of Biochemistry, University of Münster, Münster, Germany
| | - Fulvio Reggiori
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, Netherlands
| | | | - Lars Langemeyer
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany
- Center of Cellular Nanoanalytics, Osnabrück University, Osnabrück, Germany
| | - Christian Ungermann
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany
- Center of Cellular Nanoanalytics, Osnabrück University, Osnabrück, Germany
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3
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Feathers JR, Vignogna RC, Fromme JC. Structural basis for Rab6 activation by the Ric1-Rgp1 complex. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.06.592747. [PMID: 38766083 PMCID: PMC11100747 DOI: 10.1101/2024.05.06.592747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Rab GTPases act as molecular switches to regulate organelle homeostasis and membrane trafficking. Rab6 plays a central role in regulating cargo flux through the Golgi and is activated via nucleotide exchange by the Ric1-Rgp1 protein complex. Ric1-Rgp1 is conserved throughout eukaryotes but the structural and mechanistic basis for its function has not been established. Here we report the cryoEM structure of a Ric1-Rgp1-Rab6 complex representing a key intermediate of the nucleotide exchange reaction. This structure reveals the overall architecture of the complex and enabled us to identify interactions critical for proper recognition and activation of Rab6 on the Golgi membrane surface. Ric1-Rgp1 interacts with the nucleotide-binding domain of Rab6 using an uncharacterized helical domain, which we establish as a novel RabGEF domain by identifying residues required for Rab6 nucleotide exchange. Unexpectedly, the complex uses an arrestin fold to interact with the Rab6 hypervariable domain, indicating that interactions with the unstructured C-terminal regions of Rab GTPases may be a common specificity mechanism used by their activators. Collectively, our findings provide a detailed mechanistic understanding of regulated Rab6 activation at the Golgi.
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Affiliation(s)
- J. Ryan Feathers
- Department of Molecular Biology & Genetics and Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14850 USA
- Current address: 201 Schultz Laboratory, Princeton University, Princeton, NJ 08544 USA
| | - Ryan C. Vignogna
- Department of Molecular Biology & Genetics and Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14850 USA
| | - J. Christopher Fromme
- Department of Molecular Biology & Genetics and Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14850 USA
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4
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Kumar R, Francis V, Ioannou MS, Aguila A, Khan M, Banks E, Kulasekaran G, McPherson PS. DENND2B activates Rab35 at the intercellular bridge, regulating cytokinetic abscission and tetraploidy. Cell Rep 2023; 42:112795. [PMID: 37454296 DOI: 10.1016/j.celrep.2023.112795] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 05/05/2023] [Accepted: 06/26/2023] [Indexed: 07/18/2023] Open
Abstract
Cytokinesis relies on membrane trafficking pathways regulated by Rabs and guanine nucleotide exchange factors (GEFs). During cytokinesis, the intercellular cytokinetic bridge (ICB) connecting daughter cells undergoes abscission, which requires actin depolymerization. Rab35 recruits MICAL1 to oxidize and depolymerize actin filaments. We show that DENND2B, a protein linked to cancer and congenital disorders, functions as a Rab35 GEF, recruiting and activating Rab35 at the ICB. DENND2B's N-terminal region also interacts with an active form of Rab35, suggesting that DENND2B is both a Rab35 GEF and effector. Knockdown of DENND2B delays abscission, leading to multinucleated cells and filamentous actin (F-actin) accumulation at the ICB, impairing recruitment of ESCRT-III at the abscission site. Additionally, F-actin accumulation triggers the formation of a chromatin bridge, activating the NoCut/abscission checkpoint, and DENND2B knockdown activates Aurora B kinase, a hallmark of checkpoint activation. Thus, our study identifies DENND2B as a crucial player in cytokinetic abscission.
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Affiliation(s)
- Rahul Kumar
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada.
| | - Vincent Francis
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Maria S Ioannou
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Adriana Aguila
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Maleeha Khan
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Emily Banks
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Gopinath Kulasekaran
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Peter S McPherson
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada.
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Li X, Liu D, Griffis E, Novick P. Exploring the consequences of redirecting an exocytic Rab onto endocytic vesicles. Mol Biol Cell 2023; 34:ar38. [PMID: 36857153 PMCID: PMC10162416 DOI: 10.1091/mbc.e23-01-0037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 02/22/2023] [Indexed: 03/02/2023] Open
Abstract
Bidirectional vesicular traffic links compartments along the exocytic and endocytic pathways. Rab GTPases have been implicated in specifying the direction of vesicular transport. To explore this possibility, we sought to redirect an exocytic Rab, Sec4, onto endocytic vesicles by fusing the catalytic domain of the Sec4 GEF, Sec2, onto the CUE localization domain of Vps9, a GEF for the endocytic Rab Ypt51. The Sec2GEF-GFP-CUE construct localized to bright puncta predominantly near sites of polarized growth, and this localization was dependent on the ability of the CUE domain to bind to the ubiquitin moieties added to the cytoplasmic tails of proteins destined for endocytic internalization. Sec4 and Sec4 effectors were recruited to these puncta with various efficiencies. Cells expressing Sec2GEF-GFP-CUE grew surprisingly well and secreted protein at near-normal efficiency, implying that Golgi-derived secretory vesicles were delivered to polarized sites of cell growth despite the misdirection of Sec4 and its effectors. A low efficiency mechanism for localization of Sec2 to secretory vesicles that is independent of known cues might be responsible. In total, the results suggest that while Rabs may play a critical role in specifying the direction of vesicular transport, cells are remarkably tolerant of Rab misdirection.
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Affiliation(s)
- Xia Li
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093-0644
| | - Dongmei Liu
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093-0644
| | - Eric Griffis
- Nikon Imaging Center, University of California, San Diego, La Jolla, CA 92093-0694
| | - Peter Novick
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093-0644
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6
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Li X, Liu D, Griffis E, Novick P. Exploring the consequences of redirecting an exocytic Rab onto endocytic vesicles. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.09.527811. [PMID: 36798320 PMCID: PMC9934678 DOI: 10.1101/2023.02.09.527811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Bidirectional vesicular traffic links compartments along the exocytic and endocytic pathways. Rab GTPases have been implicated in specifying the direction of vesicular transport because anterograde vesicles are marked with a different Rab than retrograde vesicles. To explore this proposal, we sought to redirect an exocytic Rab, Sec4, onto endocytic vesicles by fusing the catalytic domain of the Sec4 GEF, Sec2, onto the CUE localization domain of Vps9, a GEF for the endocytic Rab, Ypt51. The Sec2GEF-GFP-CUE construct was found to localize to bright puncta predominantly near sites of polarized growth and this localization was strongly dependent upon the ability of the CUE domain to bind to the ubiquitin moieties added to the cytoplasmic tails of proteins destined for endocytic internalization. Sec4 and Sec4 effectors were recruited to these puncta with varying efficiency. The puncta appeared to consist of clusters of 80 nm vesicles and although the puncta are largely static, FRAP analysis suggests that traffic into and out of these clusters continues. Cells expressing Sec2GEF-GFP-CUE grew surprisingly well and secreted protein at near normal efficiency, implying that Golgi derived secretory vesicles were delivered to polarized sites of cell growth, where they tethered and fused with the plasma membrane despite the misdirection of Sec4 and its effectors. In total, the results suggest that while Rabs play a critical role in regulating vesicular transport, cells are remarkably tolerant of Rab misdirection.
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Affiliation(s)
- Xia Li
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California, United States
| | - Dongmei Liu
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California, United States
| | - Eric Griffis
- Nikon Imaging Center, University of California at San Diego, La Jolla, California, United States
| | - Peter Novick
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California, United States
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7
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Sung HJ, Jeong SH, Kang JY, Kim C, Nam YJ, Kim JY, Choi JY, Lee HJ, Lee YS, Kim EY, Baek YW, Lee H, Lee JH. Hematotoxic Effect of Respiratory Exposure to PHMG-p and Its Integrated Genetic Analysis. TOXICS 2022; 10:694. [PMID: 36422902 PMCID: PMC9693004 DOI: 10.3390/toxics10110694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 11/14/2022] [Accepted: 11/15/2022] [Indexed: 06/16/2023]
Abstract
Polyhexamethylene guanidine phosphate (PHMG-p), the main ingredient of humidifier disinfectants, circulates systemically through the lungs; however, its toxicological assessment has been primarily limited to pulmonary disease. Herein, we investigated the possible abnormalities in hematopoietic function 20 weeks after intratracheal instillation of PHMG-p in a rat model. Notable abnormalities were found out in the peripheral blood cell count and bone marrow (BM) biopsy, while RNA sequencing of BM tissue revealed markedly altered gene expression. Furthermore, signaling involved in hematopoietic dysfunction was predicted by analyzing candidate genes through Ingenuity Pathway Analysis (IPA) program. Respiratory PHMG-p exposure significantly decreased monocyte and platelet (PLT) counts and total protein, while significantly increasing hemoglobin and hematocrit levels in peripheral blood. Histopathological analysis of the BM revealed a reduced number of megakaryocytes, with no significant differences in spleen and liver weight to body weight. Moreover, PHMG-p exposure significantly activated estrogen receptor signaling and RHOA signaling, and inhibited RHOGDI signaling. In IPA analysis, candidate genes were found to be strongly related to 'hematological system development and function' and 'hematological disease.' Accordingly, our results suggest that PHMG-p could affect hematopoiesis, which participates in monocyte differentiation and PLT production, and may induce hematologic diseases via the respiratory tract.
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Affiliation(s)
- Hwa Jung Sung
- Department of Oncology and Hematology, Ansan Hospital, Korea University College of Medicine, Ansan-si 15355, Gyeonggi, Republic of Korea
| | - Sang Hoon Jeong
- Medical Science Research Center, Ansan Hospital, Korea University College of Medicine, Ansan-si 15355, Gyeonggi, Republic of Korea
| | - Ja Young Kang
- Medical Science Research Center, Ansan Hospital, Korea University College of Medicine, Ansan-si 15355, Gyeonggi, Republic of Korea
| | - Cherry Kim
- Department of Radiology, Ansan Hospital, Korea University College of Medicine, Ansan-si 15355, Gyeonggi, Republic of Korea
| | - Yoon Jeong Nam
- Medical Science Research Center, Ansan Hospital, Korea University College of Medicine, Ansan-si 15355, Gyeonggi, Republic of Korea
| | - Jae Young Kim
- Medical Science Research Center, Ansan Hospital, Korea University College of Medicine, Ansan-si 15355, Gyeonggi, Republic of Korea
| | - Jin Young Choi
- Medical Science Research Center, Ansan Hospital, Korea University College of Medicine, Ansan-si 15355, Gyeonggi, Republic of Korea
| | - Hye Jin Lee
- Medical Science Research Center, Ansan Hospital, Korea University College of Medicine, Ansan-si 15355, Gyeonggi, Republic of Korea
| | - Yu Seon Lee
- Medical Science Research Center, Ansan Hospital, Korea University College of Medicine, Ansan-si 15355, Gyeonggi, Republic of Korea
| | - Eun Yeob Kim
- Medical Science Research Center, Ansan Hospital, Korea University College of Medicine, Ansan-si 15355, Gyeonggi, Republic of Korea
| | - Yong Wook Baek
- Humidifier Disinfectant Health Center, Environmental Health Research Department, National Institute of Environmental Research, Incheon 22689, Republic of Korea
| | - Hong Lee
- Medical Science Research Center, Ansan Hospital, Korea University College of Medicine, Ansan-si 15355, Gyeonggi, Republic of Korea
| | - Ju Han Lee
- Department of Pathology, Ansan Hospital, Korea University College of Medicine, Ansan-si 15355, Gyeonggi, Republic of Korea
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8
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Bean BDM, Whiteway M, Martin VJJ. The MyLO CRISPR-Cas9 toolkit: a markerless yeast localization and overexpression CRISPR-Cas9 toolkit. G3 (BETHESDA, MD.) 2022; 12:jkac154. [PMID: 35708612 PMCID: PMC9339301 DOI: 10.1093/g3journal/jkac154] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 06/13/2022] [Indexed: 12/28/2022]
Abstract
The genetic tractability of the yeast Saccharomyces cerevisiae has made it a key model organism for basic research and a target for metabolic engineering. To streamline the introduction of tagged genes and compartmental markers with powerful Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) - CRISPR-associated protein 9 (Cas9)-based genome editing tools, we constructed a Markerless Yeast Localization and Overexpression (MyLO) CRISPR-Cas9 toolkit with 3 components: (1) a set of optimized Streptococcus pyogenes Cas9-guide RNA expression vectors with 5 selectable markers and the option to either preclone or cotransform the gRNAs; (2) vectors for the one-step construction of integration cassettes expressing an untagged or green fluorescent protein/red fluorescent protein/hemagglutinin-tagged gene of interest at one of 3 levels, supporting localization and overexpression studies; and (3) integration cassettes containing moderately expressed green fluorescent protein- or red fluorescent protein-tagged compartmental markers for colocalization experiments. These components allow rapid, high-efficiency genomic integrations and modifications with only transient selection for the Cas9 vector, resulting in markerless transformations. To demonstrate the ease of use, we applied our complete set of compartmental markers to colabel all target subcellular compartments with green fluorescent protein and red fluorescent protein. Thus, the MyLO toolkit packages CRISPR-Cas9 technology into a flexible, optimized bundle that allows the stable genomic integration of DNA with the ease of use approaching that of transforming plasmids.
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Affiliation(s)
- Björn D M Bean
- Department of Biology, Centre for Applied Synthetic Biology, Concordia University, Montréal, QC H4B1R6, Canada
| | - Malcolm Whiteway
- Department of Biology, Centre for Applied Synthetic Biology, Concordia University, Montréal, QC H4B1R6, Canada
| | - Vincent J J Martin
- Department of Biology, Centre for Applied Synthetic Biology, Concordia University, Montréal, QC H4B1R6, Canada
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9
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Matsumoto N, Sekiya M, Sun-Wada GH, Wada Y, Nakanishi-Matsui M. The lysosomal V-ATPase a3 subunit is involved in localization of Mon1-Ccz1, the GEF for Rab7, to secretory lysosomes in osteoclasts. Sci Rep 2022; 12:8455. [PMID: 35589873 PMCID: PMC9120031 DOI: 10.1038/s41598-022-12397-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Accepted: 05/10/2022] [Indexed: 11/16/2022] Open
Abstract
We have shown previously that the lysosomal a3 isoform of the a subunit of vacuolar-type ATPase (V-ATPase) interacts with inactive (GDP-bound form) Rab7, a small GTPase that regulates late endosome/lysosome trafficking, and that a3 recruits Rab7 to secretory lysosomes in mouse osteoclasts. This is essential for outward trafficking of secretory lysosomes and thus for bone resorption. However, the molecular mechanism underlying the recruitment of Rab7 by a3 remains to be fully elucidated. Here, we showed that a3 interacts with the Mon1A-Ccz1 complex, a guanine nucleotide exchange factor (GEF) for Rab7, using HEK293T cells. The interaction was mediated by the amino-terminal half domain of a3 and the longin motifs of Mon1A and Ccz1. Exogenous expression of the GEF promoted the interaction between a3 and Rab7. Mon1A mutants that interact inefficiently with Rab7 interacted with a3 at a similar level to wild-type Mon1A. Lysosomal localization of endogenous Ccz1 was abolished in osteoclasts lacking a3. These results suggest that the lysosomal a3 isoform of V-ATPase interacts with Mon1A-Ccz1, and that a3 is important for Mon1A-Ccz1 localization to secretory lysosomes, which mediates Rab7 recruitment to the organelle.
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Affiliation(s)
- Naomi Matsumoto
- Division of Biochemistry, School of Pharmacy, Iwate Medical University, Idaidori 1-1-1, Shiwa, Yahaba, Iwate, 028-3694, Japan
| | - Mizuki Sekiya
- Division of Biochemistry, School of Pharmacy, Iwate Medical University, Idaidori 1-1-1, Shiwa, Yahaba, Iwate, 028-3694, Japan
| | - Ge-Hong Sun-Wada
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Doshisha Women's College, Kyotanabe, Kyoto, 610-0395, Japan
| | - Yoh Wada
- Division of Biological Sciences, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, 567-0047, Japan
| | - Mayumi Nakanishi-Matsui
- Division of Biochemistry, School of Pharmacy, Iwate Medical University, Idaidori 1-1-1, Shiwa, Yahaba, Iwate, 028-3694, Japan.
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10
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Duarte PV, Hardenberg R, Mari M, Walter S, Reggiori F, Fröhlich F, Montoro AG, Ungermann C. The yeast LYST homolog Bph1 is a Rab5 effector and prevents Atg8 lipidation at endosomes. J Cell Sci 2022; 135:274866. [PMID: 35343566 DOI: 10.1242/jcs.259421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 03/18/2022] [Indexed: 01/18/2023] Open
Abstract
Lysosomes mediate degradation of macromolecules to their precursors for their cellular recycling. Additionally, lysosome-related organelles mediate cell type-specific functions. The Chédiak-Higashi syndrome is an autosomal, recessive disease, in which loss of the protein LYST causes defects in lysosomes and lysosome-related organelles. The molecular function of LYST, however, is largely unknown. Here, we dissected the function of the yeast LYST homolog, Bph1. We show that Bph1 is an endosomal protein, and an effector of the minor Rab5 isoform Ypt52. Strikingly, the bph1▵ mutant has lipidated Atg8 on their endosomes, which is sorted via late endosomes into the vacuole lumen under non-autophagy inducing conditions. In agreement, proteomics of bph1▵ vacuoles reveal an accumulation of Atg8, reduced flux via selective autophagy, and defective endocytosis. Additionally, bph1▵ cells have reduced autophagic flux under starvation conditions. Our observations suggest that Bph1 is a novel Rab5 effector that maintains endosomal functioning. When lost, Atg8 is lipidated at endosomes even during normal growth and ends up in the vacuole lumen. Thus, our results contribute to the understanding of the role of LYST-related proteins and associated diseases.
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Affiliation(s)
- Prado Vargas Duarte
- Osnabrück University, Department of Biology/Chemistry, Biochemistry section, Barbarastrasse 13, 49076 Osnabrück, Germany
| | - Ralph Hardenberg
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Muriel Mari
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Stefan Walter
- Osnabrück University, Center of Cellular Nanoanalytic Osnabrück (CellNanOs), Barbarastrasse 11, 49076 Osnabrück, Germany
| | - Fulvio Reggiori
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Florian Fröhlich
- Osnabrück University, Center of Cellular Nanoanalytic Osnabrück (CellNanOs), Barbarastrasse 11, 49076 Osnabrück, Germany.,Osnabrück University, Department of Biology/Chemistry, Molecular Membrane Biology section, Barbarastrasse 13, 49076 Osnabrück, Germany
| | - Ayelén González Montoro
- Osnabrück University, Center of Cellular Nanoanalytic Osnabrück (CellNanOs), Barbarastrasse 11, 49076 Osnabrück, Germany.,Osnabrück University, Department of Biology/Chemistry, Cellular Communication Laboratory, Barbarastrasse 13, 49076 Osnabrück, Germany
| | - Christian Ungermann
- Osnabrück University, Department of Biology/Chemistry, Biochemistry section, Barbarastrasse 13, 49076 Osnabrück, Germany.,Osnabrück University, Center of Cellular Nanoanalytic Osnabrück (CellNanOs), Barbarastrasse 11, 49076 Osnabrück, Germany
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11
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Kumar R, Francis V, Kulasekaran G, Khan M, Armstrong GAB, McPherson PS. A cell-based GEF assay reveals new substrates for DENN domains and a role for DENND2B in primary ciliogenesis. SCIENCE ADVANCES 2022; 8:eabk3088. [PMID: 35196081 PMCID: PMC8865772 DOI: 10.1126/sciadv.abk3088] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 12/30/2021] [Indexed: 06/14/2023]
Abstract
Primary cilia are sensory antennae crucial for cell and organism development, and defects in their biogenesis cause ciliopathies. Ciliogenesis involves membrane trafficking mediated by small guanosine triphosphatases (GTPases) including Rabs, molecular switches activated by guanine nucleotide exchange factors (GEFs). The largest family of Rab GEFs is the DENN domain-bearing proteins. Here, we screen all 60 Rabs against two major DENN domain families using a cellular GEF assay, uncovering 19 novel DENN/Rab pairs. The screen reveals Rab10 as a substrate for DENND2B, a protein previously implicated in cancer and severe mental retardation. Through activation of Rab10, DENND2B represses the formation of primary cilia. Through a second pathway, DENND2B functions as a GEF for RhoA to control the length of primary cilia. This work thus identifies an unexpected diversity in DENN domain-mediated activation of Rabs, a previously unidentified non-Rab substrate for a DENN domain, and a new regulatory protein in primary ciliogenesis.
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12
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Borchers AC, Langemeyer L, Ungermann C. Who's in control? Principles of Rab GTPase activation in endolysosomal membrane trafficking and beyond. J Cell Biol 2021; 220:212549. [PMID: 34383013 PMCID: PMC8366711 DOI: 10.1083/jcb.202105120] [Citation(s) in RCA: 68] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 07/08/2021] [Accepted: 07/08/2021] [Indexed: 12/12/2022] Open
Abstract
The eukaryotic endomembrane system consists of multiple interconnected organelles. Rab GTPases are organelle-specific markers that give identity to these membranes by recruiting transport and trafficking proteins. During transport processes or along organelle maturation, one Rab is replaced by another, a process termed Rab cascade, which requires at its center a Rab-specific guanine nucleotide exchange factor (GEF). The endolysosomal system serves here as a prime example for a Rab cascade. Along with endosomal maturation, the endosomal Rab5 recruits and activates the Rab7-specific GEF Mon1-Ccz1, resulting in Rab7 activation on endosomes and subsequent fusion of endosomes with lysosomes. In this review, we focus on the current idea of Mon1-Ccz1 recruitment and activation in the endolysosomal and autophagic pathway. We compare identified principles to other GTPase cascades on endomembranes, highlight the importance of regulation, and evaluate in this context the strength and relevance of recent developments in in vitro analyses to understand the underlying foundation of organelle biogenesis and maturation.
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Affiliation(s)
- Ann-Christin Borchers
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany
| | - Lars Langemeyer
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany
| | - Christian Ungermann
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany.,Center of Cellular Nanoanalytics Osnabrück (CellNanOs), Osnabrück University, Osnabrück, Germany
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13
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Prasai B, Haber GJ, Strub MP, Ahn R, Ciemniecki JA, Sochacki KA, Taraska JW. The nanoscale molecular morphology of docked exocytic dense-core vesicles in neuroendocrine cells. Nat Commun 2021; 12:3970. [PMID: 34172739 PMCID: PMC8233335 DOI: 10.1038/s41467-021-24167-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 06/04/2021] [Indexed: 12/31/2022] Open
Abstract
Rab-GTPases and their interacting partners are key regulators of secretory vesicle trafficking, docking, and fusion to the plasma membrane in neurons and neuroendocrine cells. Where and how these proteins are positioned and organized with respect to the vesicle and plasma membrane are unknown. Here, we use correlative super-resolution light and platinum replica electron microscopy to map Rab-GTPases (Rab27a and Rab3a) and their effectors (Granuphilin-a, Rabphilin3a, and Rim2) at the nanoscale in 2D. Next, we apply a targetable genetically-encoded electron microscopy labeling method that uses histidine based affinity-tags and metal-binding gold-nanoparticles to determine the 3D axial location of these exocytic proteins and two SNARE proteins (Syntaxin1A and SNAP25) using electron tomography. Rab proteins are distributed across the entire surface and t-SNARE proteins at the base of docked vesicles. We propose that the circumferential distribution of Rabs and Rab-effectors could aid in the efficient transport, capture, docking, and rapid fusion of calcium-triggered exocytic vesicles in excitable cells.
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Affiliation(s)
- Bijeta Prasai
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Gideon J Haber
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Marie-Paule Strub
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Regina Ahn
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - John A Ciemniecki
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Kem A Sochacki
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Justin W Taraska
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
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14
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Thomas LL, Highland CM, Fromme JC. Arf1 orchestrates Rab GTPase conversion at the trans-Golgi network. Mol Biol Cell 2021; 32:1104-1120. [PMID: 33788577 PMCID: PMC8351538 DOI: 10.1091/mbc.e20-10-0664] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Rab family GTPases are key organizers of membrane trafficking and function as markers of organelle identity. Accordingly, Rab GTPases often occupy specific membrane domains, and mechanisms exist to prevent the inappropriate mixing of distinct Rab domains. The yeast Golgi complex can be divided into two broad Rab domains: Ypt1 (Rab1) and Ypt6 (Rab6) are present at the early/medial Golgi and sharply transition to Ypt31/32 (Rab11) at the late Golgi/trans-Golgi network (TGN). This Rab conversion has been attributed to GTPase-activating protein (GAP) cascades in which Ypt31/32 recruits the Rab-GAPs Gyp1 and Gyp6 to inactivate Ypt1 and Ypt6, respectively. Here we report that Rab transition at the TGN involves additional layers of regulation. We provide new evidence confirming the TRAPPII complex as an important regulator of Ypt6 inactivation and uncover an unexpected role of the Arf1 GTPase in recruiting Gyp1 to drive Ypt1 inactivation at the TGN. Given its established role in directly recruiting TRAPPII to the TGN, Arf1 is therefore a master regulator of Rab conversion on maturing Golgi compartments.
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Affiliation(s)
- Laura L Thomas
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
| | - Carolyn M Highland
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
| | - J Christopher Fromme
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
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15
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Role of calcineurin biosignaling in cell secretion and the possible regulatory mechanisms. Saudi J Biol Sci 2021; 28:116-124. [PMID: 33424288 PMCID: PMC7783665 DOI: 10.1016/j.sjbs.2020.08.042] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Revised: 08/02/2020] [Accepted: 08/30/2020] [Indexed: 11/22/2022] Open
Abstract
Cyclic adenosine monophosphate (cAMP) and calcium ions (Ca2+) are two chemical molecules that play a central role in the stimulus-dependent secretion processes within cells. Ca2+ acts as the basal signaling molecule responsible to initiate cell secretion. cAMP primarily acts as an intracellular second messenger in a myriad of cellular processes by activating cAMP-dependent protein kinases through association with such kinases in order to mediate post-translational phosphorylation of those protein targets. Put succinctly, both Ca2+ and cAMP act by associating or activating other proteins to ensure successful secretion. Calcineurin is one such protein regulated by Ca2+; its action depends on the intracellular levels of Ca2+. Being a phosphatase, calcineurin dephosphorylate and other proteins, as is the case with most other phosphatases, such as protein phosphatase 2A (PP2A), PP2C, and protein phosphatase-1 (PP1), will likely be activated by phosphorylation. Via this process, calcineurin is able to affect different intracellular signaling with clinical importance, some of which has been the basis for development of different calcineurin inhibitors. In this review, the cAMP-dependent calcineurin bio-signaling, protein-protein interactions and their physiological implications as well as regulatory signaling within the context of cellular secretion are explored.
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16
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Yuan H, Novick P. Testing the Phenotypic Effects of a Rab Chimera that Resolves Exchange Factor Specificity from Effector Specificity. Methods Mol Biol 2021; 2293:57-67. [PMID: 34453710 DOI: 10.1007/978-1-0716-1346-7_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Rab GTPases play key roles in defining the identity of the various compartments that comprise the secretory and endocytic pathways. Recruitment of a Rab to a specific compartment requires its localized activation by a guanine nucleotide exchange factor (GEF). This in turn results in the recruitment of a distinct set of Rab effectors that directs the recognition of the appropriate target compartment by a carrier vesicle and their subsequent fusion. A chimeric Rab protein, Ypt1-SW1Sec4, was found to separate GEF specificity from effector specificity (Grosshans BL, et al. Proc Natl Acad Sci U S A 103(32):11821-11827, 2006), but early studies did not observe strong effects of this allele on growth or membrane traffic (Brennwald P, Novick P. Nature 362(6420):560-563, 1993). To resolve this apparent conundrum, yeast strains expressing the chimeric Rab were subjected to a more extensive battery of phenotypic tests. These tests demonstrated that changing the specificity of the GEF interaction does lead to a change in Rab localization and can lead to the ectopic recruitment of an effector, creating trafficking defects that are dependent upon the level of expression (Grosshans BL, et al. Proc Natl Acad Sci U S A 103(32):11821-11827, 2006). Here we describe the methods used in this analysis. Specifically we describe the following: 1. An assay used to quantify the efficiency of export of a cell wall protein Bgl2, 2. The use of thin section electron microscopy to address the morphology of the secretory machinery, 3. The use of a fluorescently tagged vesicle SNARE protein, GFP-Snc1, to follow plasma membrane recycling and. 4. The use of fluorescently tagged Ypt1 effectors, Cog3-GFP, Uso1-GFP, and Sec7-GFP to follow their recruitment by Ypt1-SW1Sec4.
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Affiliation(s)
- Hua Yuan
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA, USA
| | - Peter Novick
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA, USA.
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17
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Abu Irqeba A, Ogilvie JM. Di-arginine and FFAT-like motifs retain a subpopulation of PRA1 at ER-mitochondria membrane contact sites. PLoS One 2020; 15:e0243075. [PMID: 33259547 PMCID: PMC7707580 DOI: 10.1371/journal.pone.0243075] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Accepted: 11/14/2020] [Indexed: 11/19/2022] Open
Abstract
Prenylated Rab Acceptor 1 (PRA1/Rabac1) is a four-pass transmembrane protein that has been found to localize to the Golgi and promiscuously associate with a diverse array of Rab GTPases. We have previously identified PRA1 to be among the earliest significantly down-regulated genes in the rd1 mouse model of retinitis pigmentosa, a retinal degenerative disease. Here, we show that an endogenous subpopulation of PRA1 resides within the endoplasmic reticulum (ER) at ER-mitochondria membrane contact sites in cultured mammalian cells. We also demonstrate that PRA1 contains two previously unidentified ER retention/retrieval amino acid sequences on its cytosolic N-terminal region: a membrane distal di-arginine motif and a novel membrane proximal FFAT-like motif. Using a truncation construct that lacks complete Golgi targeting information, we show that mutation of either motif leads to an increase in cell surface localization, while mutation of both motifs exhibits an additive effect. We also present evidence that illustrates that N- or C- terminal addition of a tag to full-length PRA1 leads to differential localization to either the Golgi or reticular ER, phenotypes that do not completely mirror endogenous protein localization. The presence of multiple ER retention motifs on the PRA1 N-terminal region further suggests that it has a functional role within the ER.
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Affiliation(s)
- Ameair Abu Irqeba
- Department of Biology, Saint Louis University, St. Louis, Missouri, United States of America
- * E-mail: (AAI); (JMO)
| | - Judith Mosinger Ogilvie
- Department of Biology, Saint Louis University, St. Louis, Missouri, United States of America
- * E-mail: (AAI); (JMO)
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18
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Kawai K, Egami Y, Nishigaki A, Araki N. Rab35 Targeting to the Plasma Membrane Is Dependent on the C-terminal Polybasic Cluster. Acta Histochem Cytochem 2020; 53:93-97. [PMID: 32873993 PMCID: PMC7450177 DOI: 10.1267/ahc.20-00006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 06/20/2020] [Indexed: 12/14/2022] Open
Abstract
Rab35, a member of the Rab GTPase family, has been implicated in various cellular processes including cell motility and membrane trafficking. Although Rab35 is localized to the plasma membrane, Rab proteins that are identified to have high sequence homology with Rab35 exhibit distinct subcellular localization patterns. Comparing the amino acid sequences between Rab35 and its family members revealed a significant variation in an approximate 30-amino acid region of the C-terminus. This suggests that this region determines the subcellular localization of individual Rab proteins. To confirm this hypothesis, we constructed Rab35–Rab10 chimera proteins by exchanging their C-terminal domains with one another. Confocal microscopy of RAW264 cells expressing EGFP-fused Rab35–Rab10 chimeras has indicated that the C-terminal region of Rab35 is critical for its plasma membrane localization. Furthermore, we were able to determine that a basic amino acid cluster exists in the C-terminal region of Rab35 and that Rab35 localization shifts to the Golgi membrane when the number of basic amino acids in this region is reduced. Thus, it is likely that the approximate 30-amino acid C-terminal region containing basic clusters is responsible for Rab35 plasma membrane localization and that its preferential localization depends on the number of basic amino acids.
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Affiliation(s)
- Katsuhisa Kawai
- Department of Histology and Cell Biology, School of Medicine, Kagawa University
| | - Youhei Egami
- Department of Histology and Cell Biology, School of Medicine, Kagawa University
| | - Arata Nishigaki
- Department of Histology and Cell Biology, School of Medicine, Kagawa University
| | - Nobukazu Araki
- Department of Histology and Cell Biology, School of Medicine, Kagawa University
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19
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Elliott L, Moore I, Kirchhelle C. Spatio-temporal control of post-Golgi exocytic trafficking in plants. J Cell Sci 2020; 133:133/4/jcs237065. [PMID: 32102937 DOI: 10.1242/jcs.237065] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
A complex and dynamic endomembrane system is a hallmark of eukaryotic cells and underpins the evolution of specialised cell types in multicellular organisms. Endomembrane system function critically depends on the ability of the cell to (1) define compartment and pathway identity, and (2) organise compartments and pathways dynamically in space and time. Eukaryotes possess a complex molecular machinery to control these processes, including small GTPases and their regulators, SNAREs, tethering factors, motor proteins, and cytoskeletal elements. Whereas many of the core components of the eukaryotic endomembrane system are broadly conserved, there have been substantial diversifications within different lineages, possibly reflecting lineage-specific requirements of endomembrane trafficking. This Review focusses on the spatio-temporal regulation of post-Golgi exocytic transport in plants. It highlights recent advances in our understanding of the elaborate network of pathways transporting different cargoes to different domains of the cell surface, and the molecular machinery underpinning them (with a focus on Rab GTPases, their interactors and the cytoskeleton). We primarily focus on transport in the context of growth, but also highlight how these pathways are co-opted during plant immunity responses and at the plant-pathogen interface.
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Affiliation(s)
- Liam Elliott
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | - Ian Moore
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | - Charlotte Kirchhelle
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
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20
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Kalde M, Elliott L, Ravikumar R, Rybak K, Altmann M, Klaeger S, Wiese C, Abele M, Al B, Kalbfuß N, Qi X, Steiner A, Meng C, Zheng H, Kuster B, Falter-Braun P, Ludwig C, Moore I, Assaad FF. Interactions between Transport Protein Particle (TRAPP) complexes and Rab GTPases in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2019; 100:279-297. [PMID: 31264742 DOI: 10.1111/tpj.14442] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 05/15/2019] [Accepted: 06/11/2019] [Indexed: 05/23/2023]
Abstract
Transport Protein Particle II (TRAPPII) is essential for exocytosis, endocytosis, protein sorting and cytokinesis. In spite of a considerable understanding of its biological role, little information is known about Arabidopsis TRAPPII complex topology and molecular function. In this study, independent proteomic approaches initiated with TRAPP components or Rab-A GTPase variants converge on the TRAPPII complex. We show that the Arabidopsis genome encodes the full complement of 13 TRAPPC subunits, including four previously unidentified components. A dimerization model is proposed to account for binary interactions between TRAPPII subunits. Preferential binding to dominant negative (GDP-bound) versus wild-type or constitutively active (GTP-bound) RAB-A2a variants discriminates between TRAPPII and TRAPPIII subunits and shows that Arabidopsis complexes differ from yeast but resemble metazoan TRAPP complexes. Analyzes of Rab-A mutant variants in trappii backgrounds provide genetic evidence that TRAPPII functions upstream of RAB-A2a, allowing us to propose that TRAPPII is likely to behave as a guanine nucleotide exchange factor (GEF) for the RAB-A2a GTPase. GEFs catalyze exchange of GDP for GTP; the GTP-bound, activated, Rab then recruits a diverse local network of Rab effectors to specify membrane identity in subsequent vesicle fusion events. Understanding GEF-Rab interactions will be crucial to unravel the co-ordination of plant membrane traffic.
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Affiliation(s)
- Monika Kalde
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - Liam Elliott
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - Raksha Ravikumar
- Plant Science Department, Botany, Technische Universität München, Freising, 85354, Germany
| | - Katarzyna Rybak
- Plant Science Department, Botany, Technische Universität München, Freising, 85354, Germany
| | - Melina Altmann
- Institute of Network Biology (INET), Helmholtz Zentrum München, Deutsches Forschungszentrum für Gesundheit und Umwelt (GmbH), Neuherberg, 85764, Germany
| | - Susan Klaeger
- Chair of Proteomics and Bioanalytics, Technische Universität München, Freising, 85354, Germany
| | - Christian Wiese
- Plant Science Department, Botany, Technische Universität München, Freising, 85354, Germany
| | - Miriam Abele
- Plant Science Department, Botany, Technische Universität München, Freising, 85354, Germany
| | - Benjamin Al
- Plant Science Department, Botany, Technische Universität München, Freising, 85354, Germany
| | - Nils Kalbfuß
- Plant Science Department, Botany, Technische Universität München, Freising, 85354, Germany
| | - Xingyun Qi
- Department of Biology, McGill University, Montreal, H3B 1A1, Canada
| | - Alexander Steiner
- Plant Science Department, Botany, Technische Universität München, Freising, 85354, Germany
| | - Chen Meng
- BayBioMS, Bavarian Center for Biomolecular Mass Spectrometry, Technische Universität München, Freising, 85354, Germany
| | - Huanquan Zheng
- Department of Biology, McGill University, Montreal, H3B 1A1, Canada
| | - Bernhard Kuster
- Chair of Proteomics and Bioanalytics, Technische Universität München, Freising, 85354, Germany
| | - Pascal Falter-Braun
- Institute of Network Biology (INET), Helmholtz Zentrum München, Deutsches Forschungszentrum für Gesundheit und Umwelt (GmbH), Neuherberg, 85764, Germany
- Faculty of Biology, Microbe-Host-Interactions, Ludwig-Maximilians-Universität (LMU) München, Planegg-Martinsried, 82152, Germany
| | - Christina Ludwig
- BayBioMS, Bavarian Center for Biomolecular Mass Spectrometry, Technische Universität München, Freising, 85354, Germany
| | - Ian Moore
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - Farhah F Assaad
- Plant Science Department, Botany, Technische Universität München, Freising, 85354, Germany
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21
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Otsuka Y, Satoh T, Nakayama N, Inaba R, Yamashita H, Satoh AK. Parcas is the predominant Rab11-GEF for rhodopsin transport in Drosophila photoreceptors. J Cell Sci 2019; 132:jcs.231431. [PMID: 31296556 DOI: 10.1242/jcs.231431] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 07/05/2019] [Indexed: 12/11/2022] Open
Abstract
Rab11 is essential for polarized post-Golgi vesicle trafficking to photosensitive membrane rhabdomeres in Drosophila photoreceptors. Here, we found that Parcas (Pcs), recently shown to have guanine nucleotide exchange (GEF) activity toward Rab11, co-localizes with Rab11 on the trans-side of Golgi units and post-Golgi vesicles at the base of the rhabdomeres in pupal photoreceptors. Pcs fused with the electron micrography tag APEX2 localizes on 150-300 nm vesicles at the trans-side of Golgi units, which are presumably fly recycling endosomes. Loss of Pcs impairs Rab11 localization on the trans-side of Golgi units and induces the cytoplasmic accumulation of post-Golgi vesicles bearing rhabdomere proteins, as observed in Rab11 deficiency. In contrast, loss of Rab11-specific subunits of the TRAPPII complex, another known Rab11-GEF, does not cause any defects in eye development nor the transport of rhabdomere proteins; however, simultaneous loss of TRAPPII and Pcs results in severe defects in eye development. These results indicate that both TRAPPII and Pcs are required for eye development, but Pcs functions as the predominant Rab11-GEF for post-Golgi transport to photosensitive membrane rhabdomeres.
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Affiliation(s)
- Yuna Otsuka
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Takunori Satoh
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Nozomi Nakayama
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Ryota Inaba
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Hitomi Yamashita
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Akiko K Satoh
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
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22
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Duan J, Lambright DG. TRAPPing a Rab GTPase by the Tail. Dev Cell 2019; 48:9-11. [PMID: 30620905 DOI: 10.1016/j.devcel.2018.12.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
GEFs play a key role in activation and membrane targeting of Rab GTPases. In this issue of Developmental Cell, Thomas et al. (2018) demonstrate how two TRAPP complexes with a common GEF core select distinct Rab substrates through a steric gating mechanism involving their hypervariable tails.
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Affiliation(s)
- Jianjun Duan
- Program in Molecular Medicine and Department of Biochemistry & Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - David G Lambright
- Program in Molecular Medicine and Department of Biochemistry & Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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23
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Sanzà P, Evans RD, Briggs DA, Cantero M, Montoliu L, Patel S, Sviderskaya EV, Itzen A, Figueiredo AC, Seabra MC, Hume AN. Nucleotide exchange factor Rab3GEP requires DENN and non-DENN elements for activation and targeting of Rab27a. J Cell Sci 2019; 132:jcs.212035. [PMID: 30898842 PMCID: PMC6526710 DOI: 10.1242/jcs.212035] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 03/11/2019] [Indexed: 02/04/2023] Open
Abstract
Rab GTPases are compartment-specific molecular switches that regulate intracellular vesicular transport in eukaryotes. GDP/GTP exchange factors (GEFs) control Rab activation, and current models propose that localised and regulated GEF activity is important in targeting Rabs to specific membranes. Here, we investigated the mechanism of GEF function using the Rab27a GEF, Rab3GEP (also known as MADD), in melanocytes as a model. We show that Rab3GEP-deficient melanocytes (melan-R3GKO) manifest partial disruption of melanosome dispersion, a read-out of Rab27a activation and targeting. Using rescue of melanosome dispersion in melan-R3GKO cells and effector pull-down approaches we show that the DENN domain of Rab3GEP (conserved among RabGEFs) is necessary, but insufficient, for its cellular function and GEF activity. Finally, using a mitochondrial re-targeting strategy, we show that Rab3GEP can target Rab27a to specific membranes in a GEF-dependent manner. We conclude that Rab3GEP facilitates the activation and targeting of Rab27a to specific membranes, but that it differs from other DENN-containing RabGEFs in requiring DENN and non-DENN elements for both of these activities and by lacking compartment-specific localisation.
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Affiliation(s)
- Paolo Sanzà
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
| | - Richard D Evans
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
| | - Deborah A Briggs
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
| | - Marta Cantero
- Centro Nacional de Biotecnologia (CNB-CSIC), Madrid 28049, Spain.,CIBERER-ISCIII, Madrid 28029, Spain
| | - Lluis Montoliu
- Centro Nacional de Biotecnologia (CNB-CSIC), Madrid 28049, Spain.,CIBERER-ISCIII, Madrid 28029, Spain
| | - Shyamal Patel
- Cell Biology and Genetics Research Centre, Molecular and Clinical Sciences Research Institute, St. George's, University of London, London SW17 0RE, UK
| | - Elena V Sviderskaya
- Cell Biology and Genetics Research Centre, Molecular and Clinical Sciences Research Institute, St. George's, University of London, London SW17 0RE, UK
| | - Aymelt Itzen
- Center for Integrated Protein Science Munich (CIPSM), Department of Chemistry, Technische Universität München, Garching 85748, Germany
| | - Ana C Figueiredo
- Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto 4200-135, Portugal.,i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto 4200-135, Portugal
| | - Miguel C Seabra
- CEDOC Faculdade de Ciencias Medicas, Universidade Nova de Lisboa, Lisbon 1169-056, Portugal
| | - Alistair N Hume
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
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24
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Lamber EP, Siedenburg AC, Barr FA. Rab regulation by GEFs and GAPs during membrane traffic. Curr Opin Cell Biol 2019; 59:34-39. [PMID: 30981180 DOI: 10.1016/j.ceb.2019.03.004] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Accepted: 03/06/2019] [Indexed: 01/05/2023]
Abstract
Rab GTPases and their regulatory proteins play a crucial role in vesicle-mediated membrane trafficking. During vesicle membrane tethering Rab GTPases are activated by GEFs (guanine nucleotide exchange factors) and then inactivated by GAPs (GTPase activating proteins). Recent evidence shows that in addition to activating and inactivating Rab GTPases, both Rab GEFs and GAPs directly contribute to membrane tethering events during vesicle traffic. Other studies have extended the range of processes, in which Rabs function, and revealed roles for Rabs and their GAPs in the regulation of autophagy. Here, we will discuss these advances and the emerging relationship between the domain architectures of Rab GEFs and vesicle coat protein complexes linked with GTPases of the Sar, ARF and Arl families in animal cells.
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Affiliation(s)
- Ekaterina P Lamber
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | | | - Francis A Barr
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
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25
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Abu Irqeba A, Ogilvie JM. Novel binding partners for Prenylated Rab Acceptor 1 identified by a split-ubiquitin yeast two-hybrid screen. BMC Res Notes 2019; 12:188. [PMID: 30925931 PMCID: PMC6441142 DOI: 10.1186/s13104-019-4219-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 03/25/2019] [Indexed: 01/17/2023] Open
Abstract
OBJECTIVE Prenylated Rab Acceptor 1 (PRA1) is a transmembrane protein localized to the early secretory pathway. It has been found to interact with an array of Rab GTPases, leading to its hypothesized function in the recycling of Rab GTPases. However, all previous strategies used to screen for novel interacting partners have utilized a classic yeast two-hybrid approach that requires both bait and its potential binding partners to be cytosolic proteins. In the split-ubiquitin yeast two-hybrid screen, a protein interaction leads to the re-constitution of ubiquitin, which is followed by proteolytic release of a transcription activator that migrates to the nucleus alone. This allows for bait and/or prey to be integral membrane protein(s). To better understand the in vivo function of PRA1, we took an unbiased approach that screened PRA1 against a normalized mouse neuronal cDNA library using this variant of the classic screening strategy. RESULTS We report 41 previously unidentified potential PRA1 binding partners revealed by this screen and validate the screen by confirming three of these interactions using a bi-molecular fluorescence complementation assay in mammalian cells. The identified proteins reside throughout the secretory pathway and are both membrane-bound and cytosolic in their identity, suggesting alternative functions for PRA1.
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Affiliation(s)
- Ameair Abu Irqeba
- Biology Department, Saint Louis University, Macelwane Hall, 3507 Laclede Ave, St. Louis, MO 63103 USA
| | - Judith Mosinger Ogilvie
- Biology Department, Saint Louis University, Macelwane Hall, 3507 Laclede Ave, St. Louis, MO 63103 USA
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26
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Kriegenburg F, Bas L, Gao J, Ungermann C, Kraft C. The multi-functional SNARE protein Ykt6 in autophagosomal fusion processes. Cell Cycle 2019; 18:639-651. [PMID: 30836834 PMCID: PMC6464585 DOI: 10.1080/15384101.2019.1580488] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 01/06/2019] [Accepted: 01/29/2019] [Indexed: 01/01/2023] Open
Abstract
Autophagy is a degradative pathway in which cytosolic material is enwrapped within double membrane vesicles, so-called autophagosomes, and delivered to lytic organelles. SNARE (Soluble N-ethylmaleimide sensitive factor attachment protein receptor) proteins are key to drive membrane fusion of the autophagosome and the lytic organelles, called lysosomes in higher eukaryotes or vacuoles in plants and yeast. Therefore, the identification of functional SNARE complexes is central for understanding fusion processes and their regulation. The SNARE proteins Syntaxin 17, SNAP29 and Vamp7/VAMP8 are responsible for the fusion of autophagosomes with lysosomes in higher eukaryotes. Recent studies reported that the R-SNARE Ykt6 is an additional SNARE protein involved in autophagosome-lytic organelle fusion in yeast, Drosophila, and mammals. These current findings point to an evolutionarily conserved role of Ykt6 in autophagosome-related fusion events. Here, we briefly summarize the principal mechanisms of autophagosome-lytic organelle fusion, with a special focus on Ykt6 to highlight some intrinsic features of this unusual SNARE protein.
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Affiliation(s)
- Franziska Kriegenburg
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Levent Bas
- Max F. Perutz Laboratories, Vienna Biocenter, University of Vienna, Vienna, Austria
| | - Jieqiong Gao
- Biochemistry Section, Department of Biology/Chemistry, University of Osnabrück, Osnabrück, Germany
- Center of Cellular Nanoanalytics Osnabrück (CellNanOs), University of Osnabrück, Osnabrück, Germany
| | - Christian Ungermann
- Biochemistry Section, Department of Biology/Chemistry, University of Osnabrück, Osnabrück, Germany
- Center of Cellular Nanoanalytics Osnabrück (CellNanOs), University of Osnabrück, Osnabrück, Germany
| | - Claudine Kraft
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Max F. Perutz Laboratories, Vienna Biocenter, University of Vienna, Vienna, Austria
- CIBSS - Centre for Integrative Biological Signalling Studies, University of Freiburg
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27
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Rab5-independent activation and function of yeast Rab7-like protein, Ypt7p, in the AP-3 pathway. PLoS One 2019; 14:e0210223. [PMID: 30682048 PMCID: PMC6347229 DOI: 10.1371/journal.pone.0210223] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 12/18/2018] [Indexed: 11/19/2022] Open
Abstract
The small GTPases, Rab5 and Rab7, are key regulators at multiple stages of the endocytic/endolysosomal pathway, including fusion and maturation of endosomes. In yeast, Vps21p (Rab5 homolog) recruits a GEF for Rab7 and activates the downstream Ypt7p (Rab7 homolog) on endosomal membrane. Although the model of this sequential activation from Vps21p to Ypt7p in the endocytic pathway has been established, activation mechanism of Ypt7p in the Vps21p-independent pathway has not been completely clarified. Here we show that Ypt7p is activated and mediates vacuolar fusion in cells lacking all yeast Rab5 genes, VPS21, YPT52, and YPT53. We also demonstrate that deletion of both VPS21 and YPT7 genes cause severe defect in the AP-3 pathway as well as the CPY pathway although the AP-3 pathway is mostly intact in each vps21Δ or ypt7Δ mutant. Interestingly, in vps21Δ ypt7Δ mutant cargos trafficked via the VPS or endocytic pathway accumulate beside nucleus whereas cargo trafficked via the AP-3 pathway disperse in the cytosol. These findings suggest that Ypt7p is activated and plays a Rab5-independent role in the AP-3-mediated pathway.
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28
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Voss S, Li F, Rätz A, Röger M, Wu YW. Spatial Cycling of Rab GTPase, Driven by the GTPase Cycle, Controls Rab's Subcellular Distribution. Biochemistry 2019; 58:276-285. [PMID: 30605611 DOI: 10.1021/acs.biochem.8b00932] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Rab GTPases (>60 members in humans) function as master regulators of intracellular membrane trafficking. Correct and specific localization of Rab proteins is required for their function. How the distinct spatial distribution of Rab GTPases in the cell is regulated remains elusive. To globally assess the subcellular localization of Rab1, we determined kinetic parameters of two pathways that control the spatial cycles of Rab1, i.e., vesicular transport and GDP dissociation inhibitor (GDI)-mediated recycling. We demonstrate that the switching between GTP and GDP binding states, which is governed by guanine nucleotide exchange factors (GEFs), GTPase-activating proteins (GAPs), GDI, and GDI displacement factor (GDF), is a major determinant of Rab1's ability to effectively cycle between cellular compartments and eventually its subcellular distribution. In silico perturbations of vesicular transport, GEFs, GAPs, GDI, and GDF using a mathematical model with simplified cellular geometries showed that these regulators play an important role in the subcellular distribution and activity of Rab1.
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Affiliation(s)
- Stephanie Voss
- Chemical Genomics Centre of the Max Planck Society , Otto-Hahn-Strasse 15 , 44227 Dortmund , Germany.,Max-Planck-Institute of Molecular Physiology , Otto-Hahn-Strasse 11 , 44227 Dortmund , Germany
| | - Fu Li
- Chemical Genomics Centre of the Max Planck Society , Otto-Hahn-Strasse 15 , 44227 Dortmund , Germany.,Max-Planck-Institute of Molecular Physiology , Otto-Hahn-Strasse 11 , 44227 Dortmund , Germany.,Department of Chemistry, Umeå Centre for Microbial Research , Umeå University , 90187 Umeå , Sweden
| | - Andreas Rätz
- TU Dortmund University , Faculty of Mathematics , Vogelpothsweg 87 , 44227 Dortmund , Germany
| | - Matthias Röger
- TU Dortmund University , Faculty of Mathematics , Vogelpothsweg 87 , 44227 Dortmund , Germany
| | - Yao-Wen Wu
- Chemical Genomics Centre of the Max Planck Society , Otto-Hahn-Strasse 15 , 44227 Dortmund , Germany.,Max-Planck-Institute of Molecular Physiology , Otto-Hahn-Strasse 11 , 44227 Dortmund , Germany.,Department of Chemistry, Umeå Centre for Microbial Research , Umeå University , 90187 Umeå , Sweden
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29
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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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30
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Thomas LL, van der Vegt SA, Fromme JC. A Steric Gating Mechanism Dictates the Substrate Specificity of a Rab-GEF. Dev Cell 2018; 48:100-114.e9. [PMID: 30528786 DOI: 10.1016/j.devcel.2018.11.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 10/23/2018] [Accepted: 11/07/2018] [Indexed: 10/27/2022]
Abstract
Correct localization of Rab GTPases in cells is critical for proper function in membrane trafficking, yet the mechanisms that target Rabs to specific subcellular compartments remain controversial. Guanine nucleotide exchange factors (GEFs) activate and consequently stabilize Rab substrates on membranes, thus implicating GEFs as the primary determinants of Rab localization. A competing hypothesis is that the Rab C-terminal hypervariable domain (HVD) serves as a subcellular targeting signal. In this study, we present a unifying mechanism in which the HVD controls targeting of certain Rabs by mediating interaction with their GEFs. We demonstrate that the TRAPP complexes, two related GEFs that use the same catalytic site to activate distinct Rabs, distinguish between Ypt1 (Rab1) and Ypt31/32 (Rab11) via their divergent HVDs. Remarkably, we find that HVD length gates Rab access to the TRAPPII complex by constraining the distance between the nucleotide-binding domain and the membrane surface.
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Affiliation(s)
- Laura L Thomas
- Department of Molecular Biology and Genetics/Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA
| | - Solveig A van der Vegt
- Department of Molecular Biology and Genetics/Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA
| | - J Christopher Fromme
- Department of Molecular Biology and Genetics/Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA.
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31
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Morris C, Foster OK, Handa S, Peloza K, Voss L, Somhegyi H, Jian Y, Vo MV, Harp M, Rambo FM, Yang C, Hermann GJ. Function and regulation of the Caenorhabditis elegans Rab32 family member GLO-1 in lysosome-related organelle biogenesis. PLoS Genet 2018; 14:e1007772. [PMID: 30419011 PMCID: PMC6268011 DOI: 10.1371/journal.pgen.1007772] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 11/30/2018] [Accepted: 10/17/2018] [Indexed: 02/07/2023] Open
Abstract
Cell type-specific modifications of conventional endosomal trafficking pathways lead to the formation of lysosome-related organelles (LROs). C. elegans gut granules are intestinally restricted LROs that coexist with conventional degradative lysosomes. The formation of gut granules requires the Rab32 family member GLO-1. We show that the loss of glo-1 leads to the mistrafficking of gut granule proteins but does not significantly alter conventional endolysosome biogenesis. GLO-3 directly binds to CCZ-1 and they both function to promote the gut granule association of GLO-1, strongly suggesting that together, GLO-3 and CCZ-1 activate GLO-1. We found that a point mutation in GLO-1 predicted to spontaneously activate, and function independently of it guanine nucleotide exchange factor (GEF), localizes to gut granules and partially restores gut granule protein localization in ccz-1(-) and glo-3(-) mutants. CCZ-1 forms a heterodimeric complex with SAND-1(MON1), which does not function in gut granule formation, to activate RAB-7 in trafficking pathways to conventional lysosomes. Therefore, our data suggest a model whereby the function of a Rab GEF can be altered by subunit exchange. glo-3(-) mutants, which retain low levels of GLO-3 activity, generate gut granules that lack GLO-1 and improperly accumulate RAB-7 in a SAND-1 dependent process. We show that GLO-1 and GLO-3 restrict the distribution of RAB-7 to conventional endolysosomes, providing insights into the segregation of pathways leading to conventional lysosomes and LROs.
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Affiliation(s)
- Caitlin Morris
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Olivia K. Foster
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Simran Handa
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Kimberly Peloza
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Laura Voss
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Hannah Somhegyi
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Youli Jian
- State Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - My Van Vo
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Marie Harp
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Fiona M. Rambo
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
| | - Chonglin Yang
- State Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Greg J. Hermann
- Department of Biology, Lewis & Clark College, Portland, Oregon, United States of America
- * E-mail:
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32
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Son YE, Jung WH, Oh SH, Kwak JH, Cardenas ME, Park HS. Mon1 Is Essential for Fungal Virulence and Stress Survival in Cryptococcus neoformans. MYCOBIOLOGY 2018; 46:114-121. [PMID: 29963312 PMCID: PMC6023253 DOI: 10.1080/12298093.2018.1468053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 04/03/2018] [Accepted: 04/04/2018] [Indexed: 06/08/2023]
Abstract
Mon1 is a guanine nucleotide exchange factor subunit that activates the Ypt7 Rab GTPase and is essential for vacuole trafficking and autophagy in eukaryotic organisms. Here, we identified and characterized the function of Mon1, an ortholog of Saccharomyces cerevisiae Mon1, in a human fungal pathogen, Cryptococcus neoformans. Mutation in mon1 resulted in hypersensitivity to thermal stress. The mon1 deletion mutant exhibited increased sensitivity to cell wall and endoplasmic reticulum stress. However, the mon1 deletion mutant showed more resistance to the antifungal agent fluconazole. In vivo studies demonstrated that compared to the wild-type strain, the mon1 deletion mutant attenuated virulence in the Galleria mellonella insect model. Moreover, the mon1 deletion mutant was avirulent in the murine inhalation model. These results demonstrate that Mon1 plays a crucial role in stress survival and pathogenicity in C. neoformans.
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Affiliation(s)
- Ye-Eun Son
- School of Food Science and Biotechnology, Institute of Agricultural Science and Technology, Kyungpook National University, Daegu, Republic of Korea
| | - Won-Hee Jung
- School of Food Science and Biotechnology, Institute of Agricultural Science and Technology, Kyungpook National University, Daegu, Republic of Korea
| | - Sang-Hun Oh
- School of Life Science, Handong Global University, Pohang, Republic of Korea
| | - Jin-Hwan Kwak
- School of Life Science, Handong Global University, Pohang, Republic of Korea
| | - Maria E. Cardenas
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA
| | - Hee-Soo Park
- School of Food Science and Biotechnology, Institute of Agricultural Science and Technology, Kyungpook National University, Daegu, Republic of Korea
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33
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Endocytic Trafficking of the Notch Receptor. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1066:99-122. [DOI: 10.1007/978-3-319-89512-3_6] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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34
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Systematic Analysis of Human Cells Lacking ATG8 Proteins Uncovers Roles for GABARAPs and the CCZ1/MON1 Regulator C18orf8/RMC1 in Macroautophagic and Selective Autophagic Flux. Mol Cell Biol 2017; 38:MCB.00392-17. [PMID: 29038162 DOI: 10.1128/mcb.00392-17] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 10/04/2017] [Indexed: 12/26/2022] Open
Abstract
Selective autophagy and macroautophagy sequester specific organelles/substrates or bulk cytoplasm, respectively, inside autophagosomes as cargo for delivery to lysosomes. The mammalian ATG8 orthologues (MAP1LC3A/B/C and GABARAP/L1/L2) are ubiquitin (UB)-like proteins conjugated to the autophagosome membrane and are thought to facilitate cargo receptor recruitment, vesicle maturation, and lysosomal fusion. To elucidate the molecular functions of the ATG8 proteins, we engineered cells lacking genes for each subfamily as well as all six mammalian ATG8s. Loss of GABARAPs alone attenuates autophagic flux basally and in response to macroautophagic or selective autophagic stimuli, including parkin-dependent mitophagy, and cells lacking all ATG8 proteins accumulate cytoplasmic UB aggregates, which are resolved following ectopic expression of individual GABARAPs. Autophagosomes from cells lacking GABARAPs had reduced lysosomal content by quantitative proteomics, consistent with fusion defects, but accumulated regulators of late endosome (LE)/autophagosome maturation. Through interaction proteomics of proteins accumulating in GABARAP/L1/L2-deficient cells, we identified C18orf8/RMC1 as a new subunit of the CCZ1-MON1 RAB7 guanine exchange factor (GEF) that positively regulates RAB7 recruitment to LE/autophagosomes. This work defines unique roles for GABARAP and LC3 subfamilies in macroautophagy and selective autophagy and demonstrates how analysis of autophagic machinery in the absence of flux can identify new regulatory circuits.
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35
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Mima J. Reconstitution of membrane tethering mediated by Rab-family small GTPases. Biophys Rev 2017; 10:543-549. [PMID: 29204879 DOI: 10.1007/s12551-017-0358-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 11/16/2017] [Indexed: 12/18/2022] Open
Abstract
Membrane tethering is one of the most critical steps to determine the spatiotemporal specificity of membrane trafficking, which is the process to selectively transport proteins, lipids, and other biological molecules to the appropriate locations in eukaryotic cells, such as subcellular organelles, the plasma membrane, and the extracellular space. Based on genetic, cell biological, biochemical, and structural studies, Rab-family small GTPases and a number of Rab-interacting proteins (termed Rab effectors), including coiled-coil tethering proteins and multisubunit tethering complexes, have been proposed to be key protein components for membrane tethering. Nevertheless, indeed whether and how Rab GTPases and their specific Rab effectors directly act upon and catalyze membrane tethering still remains enigmatic. By chemically defined reconstitution of membrane tethering from purified Rab-family GTPase proteins and synthetic liposomal membranes, recent studies have revealed the intrinsic potency of Rab-family GTPases to physically and specifically tether two distinct lipid bilayers of liposomal membranes. Experimental evidence from these reconstitution studies support the novel working model in which Rab-family small GTPases act as a bona fide membrane tether for mediating membrane tethering events in eukaryotic membrane trafficking.
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Affiliation(s)
- Joji Mima
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan.
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36
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Abstract
Fission yeast Ypt2, an orthologue of the mammalian small GTPase Rab8, is responsible for post-Golgi membrane trafficking. During meiosis, Ypt2 localizes at the spindle pole body (SPB), where it regulates de novo biogenesis of the spore plasma membrane. Recruitment of Ypt2 to the SPB is dependent on its meiosis-specific GDP/GTP exchange factor (GEF), the SPB-resident protein Spo13. Here we have examined the SPB recruitment of Ypt2 by Spo13. The GEF activity of Spo13 was required, but not essential for recruitment. Furthermore, Ypt2 recruitment was regulated in a meiosis-specific manner and partially regulated by the nuclear Dbf2-related (NDR) kinase Sid2, indicating the existence of a novel regulatory mechanism for localization of Rab GTPases during meiosis.
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Affiliation(s)
- Kazuki Imada
- Department of Biology, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Japan.,Department of Chemistry and Biochemistry, National Institute of Technology, Suzuka College, Suzuka, Mie, Japan
| | - Taro Nakamura
- Department of Biology, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Japan
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37
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Rewiring a Rab regulatory network reveals a possible inhibitory role for the vesicle tether, Uso1. Proc Natl Acad Sci U S A 2017; 114:E8637-E8645. [PMID: 28973856 DOI: 10.1073/pnas.1708394114] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ypt1 and Sec4 are essential Rab GTPases that control the early and late stages of the yeast secretory pathway, respectively. A chimera consisting of Ypt1 with the switch I domain of Sec4, Ypt1-SW1Sec4, is efficiently activated in vitro by the Sec4 exchange factor, Sec2. This should lead to its ectopic activation in vivo and thereby disrupt membrane traffic. Nonetheless early studies found that yeast expressing Ypt1-SW1Sec4 as the sole copy of YPT1 exhibit no growth defect. To resolve this conundrum, we have analyzed yeast expressing various levels of Ypt1-SW1Sec4 We show that even normal expression of Ypt1-SW1Sec4 leads to kinetic transport defects at a late stage of the pathway, with secretory vesicles accumulating near exocytic sites. Higher levels are toxic. Toxicity is suppressed by truncation of Uso1, a vesicle tether required for endoplasmic reticulum-Golgi traffic. The globular head of Uso1 binds to Ypt1 and its coiled-coil tail binds to the Golgi-associated SNARE, Sed5. We propose that when Uso1 is inappropriately recruited to secretory vesicles by Ypt1-SW1Sec4, the extended coiled-coil tail blocks docking to the plasma membrane. This putative inhibitory function could serve to increase the fidelity of vesicle docking.
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38
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Inoshita M, Mima J. Human Rab small GTPase- and class V myosin-mediated membrane tethering in a chemically defined reconstitution system. J Biol Chem 2017; 292:18500-18517. [PMID: 28939769 DOI: 10.1074/jbc.m117.811356] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 09/21/2017] [Indexed: 12/13/2022] Open
Abstract
Membrane tethering is a fundamental process essential for the compartmental specificity of intracellular membrane trafficking in eukaryotic cells. Rab-family small GTPases and specific sets of Rab-interacting effector proteins, including coiled-coil tethering proteins and multisubunit tethering complexes, are reported to be responsible for membrane tethering. However, whether and how these key components directly and specifically tether subcellular membranes remains enigmatic. Using chemically defined proteoliposomal systems reconstituted with purified human Rab proteins and synthetic liposomal membranes to study the molecular basis of membrane tethering, we established here that Rab-family GTPases have a highly conserved function to directly mediate membrane tethering, even in the absence of any types of Rab effectors such as the so-called tethering proteins. Moreover, we demonstrate that membrane tethering mediated by endosomal Rab11a is drastically and selectively stimulated by its cognate Rab effectors, class V myosins (Myo5A and Myo5B), in a GTP-dependent manner. Of note, Myo5A and Myo5B exclusively recognized and cooperated with the membrane-anchored form of their cognate Rab11a to support membrane tethering mediated by trans-Rab assemblies on opposing membranes. Our findings support the novel concept that Rab-family proteins provide a bona fide membrane tether to physically and specifically link two distinct lipid bilayers of subcellular membranes. They further indicate that Rab-interacting effector proteins, including class V myosins, can regulate these Rab-mediated membrane-tethering reactions.
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Affiliation(s)
- Motoki Inoshita
- From the Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Joji Mima
- From the Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
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Pfeffer SR. Rab GTPases: master regulators that establish the secretory and endocytic pathways. Mol Biol Cell 2017; 28:712-715. [PMID: 28292916 PMCID: PMC5349778 DOI: 10.1091/mbc.e16-10-0737] [Citation(s) in RCA: 200] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 01/11/2017] [Accepted: 01/12/2017] [Indexed: 11/22/2022] Open
Abstract
Several of the most important discoveries in the field of membrane traffic have come from studies of Rab GTPases by Marino Zerial and Peter Novick and their colleagues. Zerial was the first to discover that Rab GTPases represent identity markers for different membrane-bound compartments, and each Rab organizes a collection of specific effectors into function-specifying membrane microdomains to carry out receptor trafficking. Novick discovered that the order (and thus polarity) of Rab GTPases along the secretory and endocytic pathways are established by their specific, cognate guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs), which partner with one Rab to regulate the subsequent- and prior-acting Rabs. Such so-called Rab cascades have evolved to establish domains that contain unique Rab proteins and their cognate effectors, which drive all steps of membrane trafficking. These findings deserve much broader recognition by the biomedical research community and are highlighted here, along with open questions that require serious attention for full understanding of the molecular basis of Rab GTPase-regulated membrane trafficking in eukaryotic cells.
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Affiliation(s)
- Suzanne R Pfeffer
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305-5307
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40
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Chichger H, Braza J, Duong H, Boni G, Harrington EO. Select Rab GTPases Regulate the Pulmonary Endothelium via Endosomal Trafficking of Vascular Endothelial-Cadherin. Am J Respir Cell Mol Biol 2017; 54:769-81. [PMID: 26551054 DOI: 10.1165/rcmb.2015-0286oc] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Pulmonary edema occurs in settings of acute lung injury, in diseases, such as pneumonia, and in acute respiratory distress syndrome. The lung interendothelial junctions are maintained in part by vascular endothelial (VE)-cadherin, an adherens junction protein, and its surface expression is regulated by endocytic trafficking. The Rab family of small GTPases are regulators of endocytic trafficking. The key trafficking pathways are regulated by Rab4, -7, and -9. Rab4 regulates the recycling of endosomes to the cell surface through a rapid-shuttle process, whereas Rab7 and -9 regulate trafficking to the late endosome/lysosome for degradation or from the trans-Golgi network to the late endosome, respectively. We recently demonstrated a role for the endosomal adaptor protein, p18, in regulation of the pulmonary endothelium through enhanced recycling of VE-cadherin to adherens junction. Thus, we hypothesized that Rab4, -7, and -9 regulate pulmonary endothelial barrier function through modulating trafficking of VE-cadherin-positive endosomes. We used Rab mutants with varying activities and associations to the endosome to study endothelial barrier function in vitro and in vivo. Our study demonstrates a key role for Rab4 activation and Rab9 inhibition in regulation of vascular permeability through enhanced VE-cadherin expression at the interendothelial junction. We further showed that endothelial barrier function mediated through Rab4 is dependent on extracellular signal-regulated kinase phosphorylation and activity. Thus, we demonstrate that Rab4 and -9 regulate VE-cadherin levels at the cell surface to modulate the pulmonary endothelium through extracellular signal-regulated kinase-dependent and -independent pathways, respectively. We propose that regulating select Rab GTPases represents novel therapeutic strategies for patients suffering with acute respiratory distress syndrome.
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Affiliation(s)
- Havovi Chichger
- Vascular Research Laboratory, Providence Veterans Affairs Medical Center, Providence, Rhode Island; and Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Julie Braza
- Vascular Research Laboratory, Providence Veterans Affairs Medical Center, Providence, Rhode Island; and Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Huetran Duong
- Vascular Research Laboratory, Providence Veterans Affairs Medical Center, Providence, Rhode Island; and Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Geraldine Boni
- Vascular Research Laboratory, Providence Veterans Affairs Medical Center, Providence, Rhode Island; and Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island
| | - Elizabeth O Harrington
- Vascular Research Laboratory, Providence Veterans Affairs Medical Center, Providence, Rhode Island; and Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island
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41
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Yin J, Huang Y, Guo P, Hu S, Yoshina S, Xuan N, Gan Q, Mitani S, Yang C, Wang X. GOP-1 promotes apoptotic cell degradation by activating the small GTPase Rab2 in C. elegans. J Cell Biol 2017; 216:1775-1794. [PMID: 28424218 PMCID: PMC5461019 DOI: 10.1083/jcb.201610001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Revised: 02/10/2017] [Accepted: 03/03/2017] [Indexed: 12/17/2022] Open
Abstract
Rab2 regulates multiple membrane traffic processes, but how it is recruited to and activated on the target membrane remains unclear. Here, Yin et al. identify a conserved protein, GOP-1, that activates UNC-108/Rab2 to promote phagosome, endosome, and DCV maturation. Apoptotic cells generated by programmed cell death are engulfed by phagocytes and enclosed within plasma membrane–derived phagosomes. Maturation of phagosomes involves a series of membrane-remodeling events that are governed by the sequential actions of Rab GTPases and lead to formation of phagolysosomes, where cell corpses are degraded. Here we identified gop-1 as a novel regulator of apoptotic cell clearance in Caenorhabditis elegans. Loss of gop-1 affects phagosome maturation through the RAB-5–positive stage, causing defects in phagosome acidification and phagolysosome formation, phenotypes identical to and unaffected by loss of unc-108, the C. elegans Rab2. GOP-1 transiently associates with cell corpse–containing phagosomes, and loss of its function abrogates phagosomal association of UNC-108. GOP-1 interacts with GDP-bound and nucleotide-free UNC-108/Rab2, disrupts GDI-UNC-108 complexes, and promotes activation and membrane recruitment of UNC-108/Rab2 in vitro. Loss of gop-1 also abolishes association of UNC-108 with endosomes, causing defects in endosome and dense core vesicle maturation. Thus, GOP-1 is an activator of UNC-108/Rab2 in multiple processes.
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Affiliation(s)
- Jianhua Yin
- National Institute of Biological Sciences, Beijing 102206, China.,Graduate Program in Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China.,National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Yaling Huang
- National Institute of Biological Sciences, Beijing 102206, China
| | - Pengfei Guo
- National Institute of Biological Sciences, Beijing 102206, China
| | - Siqi Hu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Sawako Yoshina
- Deparment of Physiology, School of Medicine and Institute for Integrated Medical Sciences, Tokyo Women's Medical University, Tokyo 162-8666, Japan
| | - Nan Xuan
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Qiwen Gan
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Shohei Mitani
- Deparment of Physiology, School of Medicine and Institute for Integrated Medical Sciences, Tokyo Women's Medical University, Tokyo 162-8666, Japan
| | - Chonglin Yang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Xiaochen Wang
- National Institute of Biological Sciences, Beijing 102206, China .,Graduate Program in Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China.,National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
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42
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Imada K, Nakamura T. The exocytic Rabs Ypt3 and Ypt2 regulate the early step of biogenesis of the spore plasma membrane in fission yeast. Mol Biol Cell 2016; 27:3317-3328. [PMID: 27630265 PMCID: PMC5170864 DOI: 10.1091/mbc.e16-03-0162] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 09/07/2016] [Indexed: 11/24/2022] Open
Abstract
Two Rabs, Ypt3 and Ypt2, regulating the trafficking of Golgi-derived secretory vesicles have key roles in biogenesis of the spore plasma membrane in fission yeast. During sporulation, the Rabs and secretory vesicles relocalize at the meiotic spindle pole body, where spore plasma membrane formation subsequently initiates. During fission yeast sporulation, a membrane compartment called the forespore membrane (FSM) is newly formed on the spindle pole body (SPB). The FSM expands by membrane vesicle fusion, encapsulates the daughter nucleus resulting from meiosis, and eventually matures into the plasma membrane of the spore. Although many of the genes involved in FSM formation have been identified, its molecular mechanism is not fully understood. Here a genetic screen for sporulation-deficient mutations identified Ypt3, a Rab-family small GTPase known to function in the exocytic pathway. The ypt3-ki8 mutant showed defects in both the initiation of FSM biogenesis and FSM expansion. We also show that a mutation in Ypt2, another Rab protein that may function in the same pathway as Ypt3, compromises the initiation of FSM formation. As meiosis proceeds, both GFP-Ypt3 and GFP-Ypt2 are observed at the SPB and then relocalize to the FSM. Their localizations at the SPB precede FSM formation and depend on the meiotic SPB component Spo13, a putative GDP/GTP exchange factor for Ypt2. Given that Spo13 is essential for initiating FSM formation, these results suggest that two exocytic Rabs, Ypt3 and Ypt2, regulate the initiation of FSM formation on the SPB in concert with Spo13.
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Affiliation(s)
- Kazuki Imada
- Department of Biology, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Taro Nakamura
- Department of Biology, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
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43
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Sakaguchi A, Sato M, Sato K. REI-1, a Novel Rab11 GEF with a SH3BP5 domain. Commun Integr Biol 2016; 9:e1208325. [PMID: 28003861 PMCID: PMC5154356 DOI: 10.1080/19420889.2016.1208325] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 06/27/2016] [Indexed: 11/10/2022] Open
Abstract
The small GTPase Rab proteins are key regulators of membrane trafficking. Rab11 is one of the best-characterized molecules among the Rab family proteins and it plays multiple roles in endocytic recycling, exocytosis, and cytokinesis. However, it remains unclear how Rab11 is activated at a precise timing and location and regulates its diverse functions. Specifically, our knowledge of the upstream regulatory factors that activate Rab11 is limited. In this regard, we have identified the RAB-11-interacting protein-1 (REI-1) as a novel guanine nucleotide exchange factor (GEF) for RAB-11 in Caenorhabditis elegans (C. elegans). REI-1 family proteins are conserved among metazoans, and its human homolog, SH3BP5, also exhibits strong GEF activity toward human Rab11. In C. elegans, REI-1 is expressed in the germline and co-localizes with RAB-11 on late-Golgi membranes. The loss of REI-1 impaired the targeting of RAB-11 to the late-Golgi compartment, as well as the recycling endosomes in embryos and further reduced the recruitment of RAB-11 to the cleavage furrow, resulting in the delay of cytokinesis. We suggest that REI-1 is the GEF responsible for regulating RAB-11 localization and function in early embryos.
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Affiliation(s)
- Aisa Sakaguchi
- Laboratory of Molecular Traffic, Institute for
Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma,
Japan
| | - Miyuki Sato
- Laboratory of Molecular Membrane Biology,
Institute for Molecular and Cellular Regulation, Gunma University,
Maebashi, Gunma, Japan
| | - Ken Sato
- Laboratory of Molecular Traffic, Institute for
Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma,
Japan
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44
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Ishida M, E Oguchi M, Fukuda M. Multiple Types of Guanine Nucleotide Exchange Factors (GEFs) for Rab Small GTPases. Cell Struct Funct 2016; 41:61-79. [PMID: 27246931 DOI: 10.1247/csf.16008] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Rab small GTPases are highly conserved master regulators of membrane traffic in all eukaryotes. The same as the activation and inactivation of other small GTPases, the activation and inactivation of Rabs are tightly controlled by specific GEFs (guanine nucleotide exchange factors) and GAPs (GTPase-activating proteins), respectively. Although almost all Rab-GAPs reported thus far have a TBC (Tre-2/Bub2/Cdc16)/Rab-GAP domain in common, recent accumulating evidence has indicated the existence of a number of structurally unrelated types of Rab-GEFs, including DENN proteins, VPS9 proteins, Sec2 proteins, TRAPP complexes, heterodimer GEFs (Mon1-Ccz1, HPS1-HPS4 (BLOC-3 complex), Ric1-Rgp1 and Rab3GAP1/2), and other GEFs (e.g., REI-1 and RPGR). In this review article we provide an up-to-date overview of the structures and functions of all putative Rab-GEFs in mammals, with a special focus on their substrate Rabs, interacting proteins, associations with genetic diseases, and intracellular localizations.
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Affiliation(s)
- Morié Ishida
- Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University
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45
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Brunet S, Saint-Dic D, Milev MP, Nilsson T, Sacher M. The TRAPP Subunit Trs130p Interacts with the GAP Gyp6p to Mediate Ypt6p Dynamics at the Late Golgi. Front Cell Dev Biol 2016; 4:48. [PMID: 27252941 PMCID: PMC4877375 DOI: 10.3389/fcell.2016.00048] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 05/09/2016] [Indexed: 01/05/2023] Open
Abstract
Small GTPases of the Rab superfamily participate in virtually all vesicle-mediated trafficking events. Cycling between an active GTP-bound form and an inactive GDP-bound form is accomplished in conjunction with guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs), respectively. Rab cascades have been described in which an effector of an activated Rab is a GEF for a downstream Rab, thus ensuring activation of a pathway in an ordered fashion. Much less is known concerning crosstalk between GEFs and GAPs although regulation between these factors could also contribute to the overall physiology of a cell. Here we demonstrate that a subunit of the TRAPP II multisubunit tethering factor, a Rab GEF, participates in the recruitment of Gyp6p, a GAP for the GTPase Ypt6p, to Golgi membranes. The extreme carboxy-terminal portion of the TRAPP II subunit Trs130p is required for the interaction between TRAPP II and Gyp6p. We further demonstrate that TRAPP II mutants, but not a TRAPP III mutant, display a defect in Gyp6p interaction. A consequence of this defective interaction is the enhanced localization of Ypt6p at late Golgi membranes. Although a ypt31/32 mutant also resulted in an enhanced localization of Gyp6p at the late Golgi, the effect was not as dramatic as that seen for TRAPP II mutants, nor was Ypt31/32 detected in the same TRAPP II purification that detected Gyp6p. We propose that the interaction between TRAPP II and Gyp6p represents a parallel mechanism in addition to that mediated by Ypt31/32 for the recruitment of a GAP to the appropriate membrane, and is a novel example of crosstalk between a Rab GAP and GEF.
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Affiliation(s)
- Stephanie Brunet
- Department of Biology, Concordia University Montreal, QC, Canada
| | | | - Miroslav P Milev
- Department of Biology, Concordia University Montreal, QC, Canada
| | - Tommy Nilsson
- Department of Medicine, McGill University Montreal, QC, Canada
| | - Michael Sacher
- Department of Biology, Concordia UniversityMontreal, QC, Canada; Department of Anatomy and Cell Biology, McGill UniversityMontreal, QC, Canada
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46
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Sakaguchi A, Sato M, Sato K, Gengyo-Ando K, Yorimitsu T, Nakai J, Hara T, Sato K, Sato K. REI-1 Is a Guanine Nucleotide Exchange Factor Regulating RAB-11 Localization and Function in C. elegans Embryos. Dev Cell 2016; 35:211-21. [PMID: 26506309 DOI: 10.1016/j.devcel.2015.09.013] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 08/18/2015] [Accepted: 09/18/2015] [Indexed: 11/29/2022]
Abstract
The small GTPase Rab11 dynamically changes its location to regulate various cellular processes such as endocytic recycling, secretion, and cytokinesis. However, our knowledge of its upstream regulators is still limited. Here, we identify the RAB-11-interacting protein-1 (REI-1) as a unique family of guanine nucleotide exchange factors (GEFs) for RAB-11 in Caenorhabditis elegans. Although REI-1 and its human homolog SH3-binding protein 5 do not contain any known Rab-GEF domains, they exhibited strong GEF activity toward Rab11 in vitro. In C. elegans, REI-1 is expressed in the germline and co-localizes with RAB-11 on the late-Golgi membranes. The loss of REI-1 specifically impaired the targeting of RAB-11 to the late-Golgi compartment and the recycling endosomes in embryos and further reduced the RAB-11 distribution to the cleavage furrow, which resulted in cytokinesis delay. These results suggest that REI-1 is a GEF specifically regulating the RAB-11 localization and functions in early embryos.
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Affiliation(s)
- Aisa Sakaguchi
- Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | - Miyuki Sato
- Laboratory of Molecular Membrane Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | - Katsuya Sato
- Laboratory of Molecular Membrane Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | - Keiko Gengyo-Ando
- Brain Science Institute, Saitama University, Saitama, Saitama 338-8570, Japan
| | - Tomohiro Yorimitsu
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Junichi Nakai
- Brain Science Institute, Saitama University, Saitama, Saitama 338-8570, Japan
| | - Taichi Hara
- Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | - Ken Sato
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Ken Sato
- Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan.
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47
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Dong Y, Yu Q, Chen Y, Xu N, Zhao Q, Jia C, Zhang B, Zhang K, Zhang B, Xing L, Li M. The Ccz1 mediates the autophagic clearance of damaged mitochondria in response to oxidative stress in Candida albicans. Int J Biochem Cell Biol 2015; 69:41-51. [PMID: 26471407 DOI: 10.1016/j.biocel.2015.10.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 08/28/2015] [Accepted: 10/07/2015] [Indexed: 10/25/2022]
Abstract
Autophagy plays a critical role in response to numerous cellular stresses, such as nutrient deprivation, hypoxia, starvation and organelle damage. The disruption of autophagy pathway affects multiple aspects of cellular stress response. Here we for the first time identified Ccz1 as an essential component for autophagy in Candida albicans. Our experiments demonstrated that loss of CCZ1 gene led to vacuolar fragmentation and disruption of the autophagy pathway. Our results also suggested that Ccz1 functioned in oxidative stress. In the ccz1Δ/Δ mutant, the levels of reactive oxidative species (ROS) sharply increased under H2O2 treatment. Further studies demonstrated that breakdown of the autophagic clearance pathway led to the accumulation of oxidative stress-damaged mitochondria, and consequently elevated cellular ROS levels in the ccz1Δ/Δ mutant. Furthermore, deletion of CCZ1 led to a significant defect in filamentous development at both 30°C and 37°C. The disruption of CCZ1 gene led to decreased capacity of macrophage killing and increased sensitivity to the macrophages. In addition, the ccz1Δ/Δ mutant exhibited attenuated virulence and decreased fungal burdens in the mouse systemic infection model, indicating that CCZ1 might provide a promising target for antifungal drugs development. In summary, our findings provide new insights into the understanding of autophagy-related gene in C. albicans.
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Affiliation(s)
- Yijie Dong
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, PR China.
| | - Qilin Yu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, PR China.
| | - Yulu Chen
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, PR China.
| | - Ning Xu
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, PR China.
| | - Qiang Zhao
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, PR China.
| | - Chang Jia
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, PR China.
| | - Bing Zhang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, PR China.
| | - Kai Zhang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, PR China.
| | - Biao Zhang
- Tianjin University of Traditional Chinese Medicine, Tianjin, PR China.
| | - Laijun Xing
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, PR China.
| | - Mingchun Li
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, PR China.
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48
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Dunst S, Kazimiers T, von Zadow F, Jambor H, Sagner A, Brankatschk B, Mahmoud A, Spannl S, Tomancak P, Eaton S, Brankatschk M. Endogenously tagged rab proteins: a resource to study membrane trafficking in Drosophila. Dev Cell 2015; 33:351-65. [PMID: 25942626 PMCID: PMC4431667 DOI: 10.1016/j.devcel.2015.03.022] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 01/21/2015] [Accepted: 03/29/2015] [Indexed: 11/25/2022]
Abstract
Membrane trafficking is key to the cell biological mechanisms underlying development. Rab GTPases control specific membrane compartments, from core secretory and endocytic machinery to less-well-understood compartments. We tagged all 27 Drosophila Rabs with YFP(MYC) at their endogenous chromosomal loci, determined their expression and subcellular localization in six tissues comprising 23 cell types, and provide this data in an annotated, searchable image database. We demonstrate the utility of these lines for controlled knockdown and show that similar subcellular localization can predict redundant functions. We exploit this comprehensive resource to ask whether a common Rab compartment architecture underlies epithelial polarity. Strikingly, no single arrangement of Rabs characterizes the five epithelia we examine. Rather, epithelia flexibly polarize Rab distribution, producing membrane trafficking architectures that are tissue- and stage-specific. Thus, the core machinery responsible for epithelial polarization is unlikely to rely on polarized positioning of specific Rab compartments.
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Affiliation(s)
- Sebastian Dunst
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany
| | - Tom Kazimiers
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany; HHMI Janelia Research Campus, Ashburn, VA 20147, USA
| | - Felix von Zadow
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany
| | - Helena Jambor
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany
| | - Andreas Sagner
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany; MRC National Institute for Medical Research, London NW7 1AA, UK
| | - Beate Brankatschk
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany; Paul Langerhans Institute, Dresden 01307, Germany
| | - Ali Mahmoud
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany
| | - Stephanie Spannl
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany
| | - Pavel Tomancak
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany.
| | - Suzanne Eaton
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany.
| | - Marko Brankatschk
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany.
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49
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Abstract
Rab GTPases control intracellular membrane traffic by recruiting specific effector proteins to restricted membranes in a GTP-dependent manner. In this Cell Science at a Glance and the accompanying poster, we highlight the regulation of Rab GTPases by proteins that control their membrane association and activation state, and provide an overview of the cellular processes that are regulated by Rab GTPases and their effectors, including protein sorting, vesicle motility and vesicle tethering. We also discuss the physiological importance of Rab GTPases and provide examples of diseases caused by their dysfunctions.
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Affiliation(s)
- Yan Zhen
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo N-0379, Norway Department for Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo N-0379, Norway
| | - Harald Stenmark
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo N-0379, Norway Department for Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo N-0379, Norway
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Cabrera M, Engelbrecht-Vandré S, Ungermann C. Function of the Mon1-Ccz1 complex on endosomes. Small GTPases 2015; 5:1-3. [PMID: 25483304 DOI: 10.4161/sgtp.29040] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Rabs exist in two forms: the inactive GDP- and the active GTP-bound form. GEF proteins mediate the exchange of GDP for GTP and thereby activate Rabs. Although GEFs share a common action, which involves the opening of the Rab nucleotide binding site, they do not contain a conserved catalytic domain. Longin domains have been either found in several GEFs (TRAPP, DENN) or predicted by sequence analyses (Mon1-Ccz1, BLOC-3). At least in TRAPP, they serve as a platform for interaction with a GTPase. We recently generated a model of the predicted longin domains of the Mon1-Ccz1 complex based upon the structure of the respective TRAPP subunits. This allowed us to identify activity-related important regions of the complex. Moreover, we analyzed the GEF activity of Mon1-Ccz1 in the presence of membranes and uncovered that certain acidic phospholipids support the recruitment of the GEF complex. In this commentary, we will discuss our findings in a broader context.
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Affiliation(s)
- Margarita Cabrera
- a Biochemistry Section; Department of Biology/Chemistry , University of Osnabrück , Osnabrück , Germany
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