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Feng H, Cheng H, Hsiao T, Lin T, Hsu J, Huang L, Yu C. ArfGAP1 acts as a GTPase‐activating protein for human ADP‐ribosylation factor‐like 1 protein. FASEB J 2021; 35:e21337. [DOI: 10.1096/fj.202000818rr] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 12/13/2020] [Accepted: 12/17/2020] [Indexed: 01/08/2023]
Affiliation(s)
- Hsiang‐Pu Feng
- Graduate Institute of Biomedical Sciences, College of Medicine Chang Gung University Taoyuan Taiwan
| | - Hsiao‐Yun Cheng
- Department of Cell and Molecular Biology, College of Medicine Chang Gung University Taoyuan Taiwan
| | - Ting‐Feng Hsiao
- Graduate Institute of Biomedical Sciences, College of Medicine Chang Gung University Taoyuan Taiwan
| | - Tai‐Wei Lin
- Graduate Institute of Biomedical Sciences, College of Medicine Chang Gung University Taoyuan Taiwan
| | - Jia‐Wei Hsu
- Institute of Molecular Medicine, College of Medicine National Taiwan University Taipei Taiwan
- Institute of Biochemical Sciences, College of Life Science National Taiwan University Taipei Taiwan
| | - Lien‐Hung Huang
- Graduate Institute of Biomedical Sciences, College of Medicine Chang Gung University Taoyuan Taiwan
- Department of Neurosurgery Kaohsiung Chang Gung Memorial Hospital Kaohsiung Taiwan
| | - Chia‐Jung Yu
- Graduate Institute of Biomedical Sciences, College of Medicine Chang Gung University Taoyuan Taiwan
- Department of Cell and Molecular Biology, College of Medicine Chang Gung University Taoyuan Taiwan
- Department of Thoracic Medicine Chang Gung Memorial Hospital Taoyuan Taiwan
- Molecular Medicine Research Center Chang Gung University Taoyuan Taiwan
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2
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The ADP-ribosylation factor-like small GTPase FgArl1 participates in growth, pathogenicity and DON production in Fusarium graminearum. Fungal Biol 2020; 124:969-980. [PMID: 33059848 DOI: 10.1016/j.funbio.2020.08.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 08/08/2020] [Accepted: 08/20/2020] [Indexed: 01/04/2023]
Abstract
Fusarium graminearum is the main pathogen of Fusarium head blight (FHB) in wheat and related species, which causes serious production decreases and economic losses and produces toxins such as deoxynivalenol (DON), which endangers the health of humans and livestock. Vesicle transport is a basic physiological process required for cell survival in eukaryotes. Many regulators of vesicle transport are reported to be involved in the pathogenicity of fungi. In yeast and mammalian cells, the ADP-ribosylation factor-like small GTPase Arl1 and its orthologs are involved in regulating vesicular trafficking, cytoskeletal reorganization and other significant biological processes. However, the role of Arl1 in F. graminearum is not well understood. In this study, we characterized the Arl1-homologous protein FgArl1 in F. graminearum and showed that FgArl1 is located in the trans-Golgi apparatus. The deletion of FgARL1 resulted in a significant decrease in vegetative growth and pathogenicity. Further analyses of the ΔFgarl1 mutant revealed defects in the production of DON. Taken together, these results indicate that FgArl1 is important in the development and pathogenicity of F. graminearum.
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3
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Sztul E, Chen PW, Casanova JE, Cherfils J, Dacks JB, Lambright DG, Lee FJS, Randazzo PA, Santy LC, Schürmann A, Wilhelmi I, Yohe ME, Kahn RA. ARF GTPases and their GEFs and GAPs: concepts and challenges. Mol Biol Cell 2019; 30:1249-1271. [PMID: 31084567 PMCID: PMC6724607 DOI: 10.1091/mbc.e18-12-0820] [Citation(s) in RCA: 149] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 02/26/2019] [Accepted: 03/11/2019] [Indexed: 12/12/2022] Open
Abstract
Detailed structural, biochemical, cell biological, and genetic studies of any gene/protein are required to develop models of its actions in cells. Studying a protein family in the aggregate yields additional information, as one can include analyses of their coevolution, acquisition or loss of functionalities, structural pliability, and the emergence of shared or variations in molecular mechanisms. An even richer understanding of cell biology can be achieved through evaluating functionally linked protein families. In this review, we summarize current knowledge of three protein families: the ARF GTPases, the guanine nucleotide exchange factors (ARF GEFs) that activate them, and the GTPase-activating proteins (ARF GAPs) that have the ability to both propagate and terminate signaling. However, despite decades of scrutiny, our understanding of how these essential proteins function in cells remains fragmentary. We believe that the inherent complexity of ARF signaling and its regulation by GEFs and GAPs will require the concerted effort of many laboratories working together, ideally within a consortium to optimally pool information and resources. The collaborative study of these three functionally connected families (≥70 mammalian genes) will yield transformative insights into regulation of cell signaling.
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Affiliation(s)
- Elizabeth Sztul
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Pei-Wen Chen
- Department of Biology, Williams College, Williamstown, MA 01267
| | - James E. Casanova
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908
| | - Jacqueline Cherfils
- Laboratoire de Biologie et Pharmacologie Appliquée, CNRS and Ecole Normale Supérieure Paris-Saclay, 94235 Cachan, France
| | - Joel B. Dacks
- Division of Infectious Disease, Department of Medicine, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - David G. Lambright
- Program in Molecular Medicine and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Amherst, MA 01605
| | - Fang-Jen S. Lee
- Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei 10002, Taiwan
| | | | - Lorraine C. Santy
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802
| | - Annette Schürmann
- German Institute of Human Nutrition, 85764 Potsdam-Rehbrücke, Germany
| | - Ilka Wilhelmi
- German Institute of Human Nutrition, 85764 Potsdam-Rehbrücke, Germany
| | - Marielle E. Yohe
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892
| | - Richard A. Kahn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322-3050
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4
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Chang SJ, Jin SC, Jiao X, Galán JE. Unique features in the intracellular transport of typhoid toxin revealed by a genome-wide screen. PLoS Pathog 2019; 15:e1007704. [PMID: 30951565 PMCID: PMC6469816 DOI: 10.1371/journal.ppat.1007704] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 04/17/2019] [Accepted: 03/13/2019] [Indexed: 12/29/2022] Open
Abstract
Typhoid toxin is a virulence factor for Salmonella Typhi and Paratyphi, the cause of typhoid fever in humans. This toxin has a unique architecture in that its pentameric B subunit, made of PltB, is linked to two enzymatic A subunits, the ADP ribosyl transferase PltA and the deoxyribonuclease CdtB. Typhoid toxin is uniquely adapted to humans, recognizing surface glycoprotein sialoglycans terminated in acetyl neuraminic acid, which are preferentially expressed by human cells. The transport pathway to its cellular targets followed by typhoid toxin after receptor binding is currently unknown. Through a genome-wide CRISPR/Cas9-mediated screen we have characterized the mechanisms by which typhoid toxin is transported within human cells. We found that typhoid toxin hijacks specific elements of the retrograde transport and endoplasmic reticulum-associated degradation machineries to reach its subcellular destination within target cells. Our study reveals unique and common features in the transport mechanisms of bacterial toxins that could serve as the bases for the development of novel anti-toxin therapeutic strategies.
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Affiliation(s)
- Shu-Jung Chang
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Sheng Chih Jin
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Xuyao Jiao
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Jorge E Galán
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
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5
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Abstract
ADP-ribosylation factors (Arfs) and ADP-ribosylation factor-like proteins (Arls) are highly conserved small GTPases that function as main regulators of vesicular trafficking and cytoskeletal reorganization. Arl1, the first identified member of the large Arl family, is an important regulator of Golgi complex structure and function in organisms ranging from yeast to mammals. Together with its effectors, Arl1 has been shown to be involved in several cellular processes, including endosomal trans-Golgi network and secretory trafficking, lipid droplet and salivary granule formation, innate immunity and neuronal development, stress tolerance, as well as the response of the unfolded protein. In this Commentary, we provide a comprehensive summary of the Arl1-dependent cellular functions and a detailed characterization of several Arl1 effectors. We propose that involvement of Arl1 in these diverse cellular functions reflects the fact that Arl1 is activated at several late-Golgi sites, corresponding to specific molecular complexes that respond to and integrate multiple signals. We also provide insight into how the GTP-GDP cycle of Arl1 is regulated, and highlight a newly discovered mechanism that controls the sophisticated regulation of Arl1 activity at the Golgi complex.
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Affiliation(s)
- Chia-Jung Yu
- Department of Cell and Molecular Biology, College of Medicine, Chang Gung University, Linkou, Tao-Yuan 33302, Taiwan.,Department of Thoracic Medicine, Chang Gung Memorial Hospital, Linkou, Tao-Yuan 33305, Taiwan
| | - Fang-Jen S Lee
- Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei 10002, Taiwan .,Department of Medical Research, National Taiwan University Hospital, Taipei 10002, Taiwan
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6
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Abstract
Macroautophagy, a highly conserved process in eukaryotic cells, is initiated in response to stress, especially nutrient starvation. Macroautophagy helps cells survive by engulfing proteins and organelles into an unusual double-membraned structure called the autophagosome, which then fuses with the lysosome. Upon degradation of the engulfed contents, the building blocks are recycled for synthesis of new macromolecules. Recent work has demonstrated that construction of the autophagosome requires a variety of small GTPases in variations of their normal roles in membrane traffic. In this Commentary, we review our own recent findings with respect to 2 different GTPases, Arl1, a member of the Arf/Arl/Sar family, and Ypt6, a member of the Rab family, in the yeast S. cerevisiae in light of other information from the literature and discuss future directions for further discerning the roles of small GTPases in autophagy.
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Affiliation(s)
- Shu Yang
- a Department of Biology , Georgetown University , Washington, DC , USA
| | - Anne Rosenwald
- a Department of Biology , Georgetown University , Washington, DC , USA
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7
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Eiseler T, Wille C, Koehler C, Illing A, Seufferlein T. Protein Kinase D2 Assembles a Multiprotein Complex at the Trans-Golgi Network to Regulate Matrix Metalloproteinase Secretion. J Biol Chem 2015; 291:462-77. [PMID: 26507660 DOI: 10.1074/jbc.m115.673582] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Indexed: 11/06/2022] Open
Abstract
Vesicle formation and fission are tightly regulated at the trans-Golgi network (TGN) during constitutive secretion. Two major protein families regulate these processes: members of the adenosyl-ribosylation factor family of small G-proteins (ARFs) and the protein kinase D (PKD) family of serine/threonine kinases. The functional relationship between these two key regulators of protein transport from the TGN so far is elusive. We here demonstrate the assembly of a novel functional protein complex at the TGN and its key members: cytosolic PKD2 binds ARF-like GTPase (ARL1) and shuttles ARL1 to the TGN. ARL1, in turn, localizes Arfaptin2 to the TGN. At the TGN, where PKD2 interacts with active ARF1, PKD2, and ARL1 are required for the assembly of a complex comprising of ARF1 and Arfaptin2 leading to secretion of matrix metalloproteinase-2 and -7. In conclusion, our data indicate that PKD2 is a core factor in the formation of this multiprotein complex at the TGN that controls constitutive secretion of matrix metalloproteinase cargo.
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Affiliation(s)
- Tim Eiseler
- From the Department of Internal Medicine I, Ulm University, Albert Einstein Allee 23, D-89081 Ulm, Germany and
| | - Christoph Wille
- From the Department of Internal Medicine I, Ulm University, Albert Einstein Allee 23, D-89081 Ulm, Germany and
| | - Conny Koehler
- the Department of Internal Medicine I, Martin-Luther University Halle-Wittenberg, Ernst-Grube, Strasse 40, D-06120 Halle (Saale), Germany
| | - Anett Illing
- From the Department of Internal Medicine I, Ulm University, Albert Einstein Allee 23, D-89081 Ulm, Germany and
| | - Thomas Seufferlein
- From the Department of Internal Medicine I, Ulm University, Albert Einstein Allee 23, D-89081 Ulm, Germany and
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8
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Torres IL, Rosa-Ferreira C, Munro S. The Arf family G protein Arl1 is required for secretory granule biogenesis in Drosophila. J Cell Sci 2014; 127:2151-60. [PMID: 24610947 DOI: 10.1242/jcs.122028] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The small G protein Arf like 1 (Arl1) is found at the Golgi complex, and its GTP-bound form recruits several effectors to the Golgi including GRIP-domain-containing coiled-coil proteins, and the Arf1 exchange factors Big1 and Big2. To investigate the role of Arl1, we have characterised a loss-of-function mutant of the Drosophila Arl1 orthologue. The gene is essential, and examination of clones of cells lacking Arl1 shows that it is required for recruitment of three of the four GRIP domain golgins to the Golgi, with Drosophila GCC185 being less dependent on Arl1. At a functional level, Arl1 is essential for formation of secretory granules in the larval salivary gland. When Arl1 is missing, Golgi are still present but there is a dispersal of adaptor protein 1 (AP-1), a clathrin adaptor that requires Arf1 for its membrane recruitment and which is known to be required for secretory granule biogenesis. Arl1 does not appear to be required for AP-1 recruitment in all tissues, suggesting that it is crucially required to enhance Arf1 activation at the trans-Golgi in particular tissues.
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Affiliation(s)
- Isabel L Torres
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | | | - Sean Munro
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
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9
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Abstract
The ARF-like (ARL) proteins, within the ARF family, are a collection of functionally diverse GTPases that share extensive (>40 %) identity with the ARFs and each other and are assumed to share basic mechanisms of regulation and a very incompletely documented degree of overlapping regulators. At least four ARLs were already present in the last eukaryotic common ancestor, along with one ARF, and these have been expanded to >20 members in mammals. We know little about the majority of these proteins so our review will focus on those about which the most is known, including ARL1, ARL2, ARL3, ARL4s, ARL6, ARL13s, and ARFRP1. From this fragmentary information we extract some generalizations and conclusions regarding the sources and extent of specificity and functions of the ARLs.
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Affiliation(s)
- Alfred Wittinghofer
- Max-Planck-Institute of Molecular Physiology, Dortmund, Nordrhein-Westfalen Germany
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10
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Chang L, Kreko T, Davison H, Cusmano T, Wu Y, Rothenfluh A, Eaton BA. Normal dynactin complex function during synapse growth in Drosophila requires membrane binding by Arfaptin. Mol Biol Cell 2013; 24:1749-64, S1-5. [PMID: 23596322 PMCID: PMC3667727 DOI: 10.1091/mbc.e12-09-0697] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 04/04/2013] [Accepted: 04/08/2013] [Indexed: 01/11/2023] Open
Abstract
Mutations in DCTN1, a component of the dynactin complex, are linked to neurodegenerative diseases characterized by a broad collection of neuropathologies. Because of the pleiotropic nature of dynactin complex function within the neuron, defining the causes of neuropathology in DCTN1 mutants has been difficult. We combined a genetic screen with cellular assays of dynactin complex function to identify genes that are critical for dynactin complex function in the nervous system. This approach identified the Drosophila homologue of Arfaptin, a multifunctional protein that has been implicated in membrane trafficking. We find that Arfaptin and the Drosophila DCTN1 homologue, Glued, function in the same pathway during synapse growth but not during axonal transport or synapse stabilization. Arfaptin physically associates with Glued and other dynactin complex components in the nervous system of both flies and mice and colocalizes with Glued at the Golgi in motor neurons. Mechanistically, membrane binding by Arfaptin mediates membrane association of the dynactin complex in motor neurons and is required for normal synapse growth. Arfaptin represents a novel dynactin complex-binding protein that specifies dynactin complex function during synapse growth.
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Affiliation(s)
- Leo Chang
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Tabita Kreko
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Holly Davison
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Tim Cusmano
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Yimin Wu
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Adrian Rothenfluh
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Benjamin A. Eaton
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
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11
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Romero N, Dumur CI, Martinez H, García IA, Monetta P, Slavin I, Sampieri L, Koritschoner N, Mironov AA, De Matteis MA, Alvarez C. Rab1b overexpression modifies Golgi size and gene expression in HeLa cells and modulates the thyrotrophin response in thyroid cells in culture. Mol Biol Cell 2013; 24:617-32. [PMID: 23325787 PMCID: PMC3583665 DOI: 10.1091/mbc.e12-07-0530] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
An increase in Rab1b levels induces changes in Golgi size and in gene expression. These Rab1b-dependent changes require the activity of p38 mitogen-activated protein kinase and the cAMP-responsive element binding protein consensus binding. The results show a Rab1b increase in secretory cells after stimulation and suggest that this increase is required to elicit a secretory response. Rab1b belongs to the Rab-GTPase family that regulates membrane trafficking and signal transduction systems able to control diverse cellular activities, including gene expression. Rab1b is essential for endoplasmic reticulum–Golgi transport. Although it is ubiquitously expressed, its mRNA levels vary among different tissues. This work aims to characterize the role of the high Rab1b levels detected in some secretory tissues. We report that, in HeLa cells, an increase in Rab1b levels induces changes in Golgi size and gene expression. Significantly, analyses applied to selected genes, KDELR3, GM130 (involved in membrane transport), and the proto-oncogene JUN, indicate that the Rab1b increase acts as a molecular switch to control the expression of these genes at the transcriptional level, resulting in changes at the protein level. These Rab1b-dependent changes require the activity of p38 mitogen-activated protein kinase and the cAMP-responsive element-binding protein consensus binding site in those target promoter regions. Moreover, our results reveal that, in a secretory thyroid cell line (FRTL5), Rab1b expression increases in response to thyroid-stimulating hormone (TSH). Additionally, changes in Rab1b expression in FRTL5 cells modify the specific TSH response. Our results show, for the first time, that changes in Rab1b levels modulate gene transcription and strongly suggest that a Rab1b increase is required to elicit a secretory response.
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Affiliation(s)
- Nahuel Romero
- Centro de Investigaciones en Bioquímica Clínica e Inmunología, Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba 5000, Argentina
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12
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Nelson DR, Goldstone JV, Stegeman JJ. The cytochrome P450 genesis locus: the origin and evolution of animal cytochrome P450s. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120474. [PMID: 23297357 DOI: 10.1098/rstb.2012.0474] [Citation(s) in RCA: 135] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The neighbourhoods of cytochrome P450 (CYP) genes in deuterostome genomes, as well as those of the cnidarians Nematostella vectensis and Acropora digitifera and the placozoan Trichoplax adhaerens were examined to find clues concerning the evolution of CYP genes in animals. CYP genes created by the 2R whole genome duplications in chordates have been identified. Both microsynteny and macrosynteny were used to identify genes that coexisted near CYP genes in the animal ancestor. We show that all 11 CYP clans began in a common gene environment. The evidence implies the existence of a single locus, which we term the 'cytochrome P450 genesis locus', where one progenitor CYP gene duplicated to create a tandem set of genes that were precursors of the 11 animal CYP clans: CYP Clans 2, 3, 4, 7, 19, 20, 26, 46, 51, 74 and mitochondrial. These early CYP genes existed side by side before the origin of cnidarians, possibly with a few additional genes interspersed. The Hox gene cluster, WNT genes, an NK gene cluster and at least one ARF gene were close neighbours to this original CYP locus. According to this evolutionary scenario, the CYP74 clan originated from animals and not from land plants nor from a common ancestor of plants and animals. The CYP7 and CYP19 families that are chordate-specific belong to CYP clans that seem to have originated in the CYP genesis locus as well, even though this requires many gene losses to explain their current distribution. The approach to uncovering the CYP genesis locus overcomes confounding effects because of gene conversion, sequence divergence, gene birth and death, and opens the way to understanding the biodiversity of CYP genes, families and subfamilies, which in animals has been obscured by more than 600 Myr of evolution.
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Affiliation(s)
- David R Nelson
- Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center, 858 Madison Avenue Suite G01, Memphis, TN 38163, USA.
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13
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Mahfouz H, Ragnini-Wilson A, Venditti R, De Matteis MA, Wilson C. Mutational analysis of the yeast TRAPP subunit Trs20p identifies roles in endocytic recycling and sporulation. PLoS One 2012; 7:e41408. [PMID: 23049729 PMCID: PMC3458868 DOI: 10.1371/journal.pone.0041408] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 06/22/2012] [Indexed: 11/20/2022] Open
Abstract
Trs20p is a subunit of the evolutionarily conserved TRAPP (TRAnsport Protein Particle) complex that mediates various aspects of membrane trafficking. Three TRAPP complexes have been identified in yeast with roles in ER-to-Golgi trafficking, post-Golgi and endosomal-to-Golgi transport and in autophagy. The role of Trs20p, which is essential for viability and a component of all three complexes, and how it might function within each TRAPP complex, has not been clarified to date. To begin to address the role of Trs20p we generated different mutants by random mutagenesis but, surprisingly, no defects were observed in diverse anterograde transport pathways or general secretion in Trs20 temperature-sensitive mutants. Instead, mutation of Trs20 led to defects in endocytic recycling and a block in sporulation/meiosis. The phenotypes of different mutants appear to be separable suggesting that the mutations affect the function of Trs20 in different TRAPP complexes.
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Affiliation(s)
- Hichem Mahfouz
- Consorzio Mario Negri Sud, Santa Maria Imbaro, Chieti, Italy
| | - Antonella Ragnini-Wilson
- Department of Biology, University of Rome “Tor Vergata”, Rome, Italy
- Consorzio Mario Negri Sud, Santa Maria Imbaro, Chieti, Italy
| | | | | | - Cathal Wilson
- Telethon Institute of Genetics and Medicine, Naples, Italy
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14
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Jaime MDLA, Lopez-Llorca LV, Conesa A, Lee AY, Proctor M, Heisler LE, Gebbia M, Giaever G, Westwood JT, Nislow C. Identification of yeast genes that confer resistance to chitosan oligosaccharide (COS) using chemogenomics. BMC Genomics 2012; 13:267. [PMID: 22727066 PMCID: PMC3505485 DOI: 10.1186/1471-2164-13-267] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Accepted: 04/25/2012] [Indexed: 12/30/2022] Open
Abstract
Background Chitosan oligosaccharide (COS), a deacetylated derivative of chitin, is an abundant, and renewable natural polymer. COS has higher antimicrobial properties than chitosan and is presumed to act by disrupting/permeabilizing the cell membranes of bacteria, yeast and fungi. COS is relatively non-toxic to mammals. By identifying the molecular and genetic targets of COS, we hope to gain a better understanding of the antifungal mode of action of COS. Results Three different chemogenomic fitness assays, haploinsufficiency (HIP), homozygous deletion (HOP), and multicopy suppression (MSP) profiling were combined with a transcriptomic analysis to gain insight in to the mode of action and mechanisms of resistance to chitosan oligosaccharides. The fitness assays identified 39 yeast deletion strains sensitive to COS and 21 suppressors of COS sensitivity. The genes identified are involved in processes such as RNA biology (transcription, translation and regulatory mechanisms), membrane functions (e.g. signalling, transport and targeting), membrane structural components, cell division, and proteasome processes. The transcriptomes of control wild type and 5 suppressor strains overexpressing ARL1, BCK2, ERG24, MSG5, or RBA50, were analyzed in the presence and absence of COS. Some of the up-regulated transcripts in the suppressor overexpressing strains exposed to COS included genes involved in transcription, cell cycle, stress response and the Ras signal transduction pathway. Down-regulated transcripts included those encoding protein folding components and respiratory chain proteins. The COS-induced transcriptional response is distinct from previously described environmental stress responses (i.e. thermal, salt, osmotic and oxidative stress) and pre-treatment with these well characterized environmental stressors provided little or any resistance to COS. Conclusions Overexpression of the ARL1 gene, a member of the Ras superfamily that regulates membrane trafficking, provides protection against COS-induced cell membrane permeability and damage. We found that the ARL1 COS-resistant over-expression strain was as sensitive to Amphotericin B, Fluconazole and Terbinafine as the wild type cells and that when COS and Fluconazole are used in combination they act in a synergistic fashion. The gene targets of COS identified in this study indicate that COS’s mechanism of action is different from other commonly studied fungicides that target membranes, suggesting that COS may be an effective fungicide for drug-resistant fungal pathogens.
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Affiliation(s)
- Maria D L A Jaime
- Department of Cell and Systems Biology, University of Toronto, Mississauga, Ontario, Canada
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15
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Manlandro CMA, Palanivel VR, Schorr EB, Mihatov N, Antony AA, Rosenwald AG. Mon2 is a negative regulator of the monomeric G protein, Arl1. FEMS Yeast Res 2012; 12:637-50. [PMID: 22594927 DOI: 10.1111/j.1567-1364.2012.00814.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Revised: 04/27/2012] [Accepted: 05/11/2012] [Indexed: 11/30/2022] Open
Abstract
Using site-directed mutants of ARL1 predicted to alter nucleotide binding, we examined phenotypes associated with the loss of ARL1 , including effects on membrane traffic and K (+) homeostasis. The GTP-restricted allele, ARL[Q72L] , complemented the membrane traffic phenotype (CPY secretion), but not the K (+) homeostasis phenotypes (sensitivity to hygromycin B, steady-state levels of K (+) , and accumulation of (86) Rb (+) ), while the XTP-restricted mutant, ARL1[D130N] , complemented the ion phenotypes, but not the membrane traffic phenotype. A GDP-restricted allele, ARL1[T32N] , did not effectively complement either phenotype. These results are consistent with a model in which Arl1 has three different conformations in vivo. We also explored the relationship between ARL1 and MON2 using the synthetic lethal phenotype exhibited by these two genes and demonstrated that MON2 is a negative regulator of the GTP-restricted allele of ARL1 , ARL1[Q72L] . Finally, we constructed several new alleles predicted to alter binding of Arl1 to the sole GRIP domain containing protein in yeast, Imh1, and found that ARL1[F52G] and ARL1[Y82G] were unable to complement the loss of ARL1 with respect to either the membrane traffic or K (+) homeostasis phenotypes. Our study expands understanding of the roles of Arl1 in vivo.
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16
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Rojas AM, Fuentes G, Rausell A, Valencia A. The Ras protein superfamily: evolutionary tree and role of conserved amino acids. ACTA ACUST UNITED AC 2012; 196:189-201. [PMID: 22270915 PMCID: PMC3265948 DOI: 10.1083/jcb.201103008] [Citation(s) in RCA: 274] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The Ras superfamily is a fascinating example of functional diversification in the context of a preserved structural framework and a prototypic GTP binding site. Thanks to the availability of complete genome sequences of species representing important evolutionary branch points, we have analyzed the composition and organization of this superfamily at a greater level than was previously possible. Phylogenetic analysis of gene families at the organism and sequence level revealed complex relationships between the evolution of this protein superfamily sequence and the acquisition of distinct cellular functions. Together with advances in computational methods and structural studies, the sequence information has helped to identify features important for the recognition of molecular partners and the functional specialization of different members of the Ras superfamily.
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Affiliation(s)
- Ana Maria Rojas
- Computational Cell Biology Group, Institute for Predictive and Personalized Medicine of Cancer, 08916 Badalona, Barcelona, Spain.
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17
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Abstract
Members of the Rab or ARF/Sar branches of the Ras GTPase superfamily regulate almost every step of intracellular membrane traffic. A rapidly growing body of evidence indicates that these GTPases do not act as lone agents but are networked to one another through a variety of mechanisms to coordinate the individual events of one stage of transport and to link together the different stages of an entire transport pathway. These mechanisms include guanine nucleotide exchange factor (GEF) cascades, GTPase-activating protein (GAP) cascades, effectors that bind to multiple GTPases, and positive-feedback loops generated by exchange factor-effector interactions. Together these mechanisms can lead to an ordered series of transitions from one GTPase to the next. As each GTPase recruits a unique set of effectors, these transitions help to define changes in the functionality of the membrane compartments with which they are associated.
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Affiliation(s)
- Emi Mizuno-Yamasaki
- Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371-8512, Japan.
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18
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Garg S, Sharma M, Ung C, Tuli A, Barral DC, Hava DL, Veerapen N, Besra GS, Hacohen N, Brenner MB. Lysosomal trafficking, antigen presentation, and microbial killing are controlled by the Arf-like GTPase Arl8b. Immunity 2011; 35:182-93. [PMID: 21802320 PMCID: PMC3584282 DOI: 10.1016/j.immuni.2011.06.009] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Revised: 02/17/2011] [Accepted: 06/24/2011] [Indexed: 01/01/2023]
Abstract
Antigen presentation and microbial killing are critical arms of host defense that depend upon cargo trafficking into lysosomes. Yet, the molecular regulators of traffic into lysosomes are only partly understood. Here, using a lysosome-dependent immunological screen of a trafficking shRNA library, we identified the Arf-like GTPase Arl8b as a critical regulator of cargo delivery to lysosomes. Homotypic fusion and vacuole protein sorting (HOPS) complex members were identified as effectors of Arl8b and were dependent on Arl8b for recruitment to lysosomes, suggesting that Arl8b-HOPS plays a general role in directing traffic to lysosomes. Moreover, the formation of CD1 antigen-presenting complexes in lysosomes, their delivery to the plasma membrane, and phagosome-lysosome fusion were all markedly impaired in Arl8b silenced cells resulting in corresponding defects in T cell activation and microbial killing. Together, these results define Arl8b as a key regulator of lysosomal cellular and immunological functions.
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Affiliation(s)
- Salil Garg
- Harvard Division of Medical Sciences, Graduate Program in Immunology and Harvard-MIT MD PhD Program, Boston, MA 02115, USA
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19
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Lee J, Lee J, Ju BG. Drosophila arf72A acts as an essential regulator of endoplasmic reticulum quality control and suppresses autosomal-dominant retinopathy. Int J Biochem Cell Biol 2011; 43:1392-401. [PMID: 21693198 DOI: 10.1016/j.biocel.2011.06.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Revised: 05/25/2011] [Accepted: 06/06/2011] [Indexed: 11/27/2022]
Abstract
The eukaryotic endoplasmic reticulum operates multiple quality control mechanisms to ensure that only properly folded proteins are exported to their final destinations via the secretory pathway and those that are not are destroyed via the degradation pathway. However, molecular mechanisms underlying such regulated exportation to these distinct routes are unknown. In this article, we report the role of Drosophila arf72A--the fly homologue of the mammalian Arl1 - in the quality checks of proteins and in the autosomal-dominant retinopathy. ARF72A localizes to the Golgi membranes of Drosophila photoreceptor cells, consistent with mammalian Arl1 localization in cell culture systems. A loss of arf72A function changes the membrane character of the endoplasmic reticulum and shifts the membrane balance between the endoplasmic reticulum and the Golgi complex toward the Golgi complex, resulting in over-proliferated Golgi complexes and accelerated protein secretion. Interestingly, our study indicated that more ARF72A localized on the endoplasmic reticulum in the ninaE(D1) photoreceptor cell, a Drosophila model of autosomal-dominant retinitis pigmentosa, compared to that in the wild-type. In addition, arf72A loss was shown to rescue the ninaE(D1)-related membrane accumulation and the rhodopsin maturation defect, and suppress ninaE(D1)-triggered retinal degeneration, indicating that rhodopsin accumulated in the endoplasmic reticulum bypasses the quality checks. While previous studies of ARF small GTPases have focused on their roles in vesicular budding and transport between the specific organelles, our findings establish an additional function of arf72A in the quality check machinery of the endoplasmic reticulum distinguishing the cargoes for secretion from those for degradation.
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Affiliation(s)
- Jongwoo Lee
- Department of Biological Science, University of Notre Dame, Notre Dame, IN 46556, USA.
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20
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Identification of yeast genes involved in k homeostasis: loss of membrane traffic genes affects k uptake. G3-GENES GENOMES GENETICS 2011; 1:43-56. [PMID: 22384317 PMCID: PMC3276120 DOI: 10.1534/g3.111.000166] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Accepted: 03/24/2011] [Indexed: 11/18/2022]
Abstract
Using the homozygous diploid Saccharomyces deletion collection, we searched for strains with defects in K(+) homeostasis. We identified 156 (of 4653 total) strains unable to grow in the presence of hygromycin B, a phenotype previously shown to be indicative of ion defects. The most abundant group was that with deletions of genes known to encode membrane traffic regulators. Nearly 80% of these membrane traffic defective strains showed defects in uptake of the K(+) homolog, (86)Rb(+). Since Trk1, a plasma membrane protein localized to lipid microdomains, is the major K(+) influx transporter, we examined the subcellular localization and Triton-X 100 insolubility of Trk1 in 29 of the traffic mutants. However, few of these showed defects in the steady state levels of Trk1, the localization of Trk1 to the plasma membrane, or the localization of Trk1 to lipid microdomains, and most defects were mild compared to wild-type. Three inositol kinase mutants were also identified, and in contrast, loss of these genes negatively affected Trk1 protein levels. In summary, this work reveals a nexus between K(+) homeostasis and membrane traffic, which does not involve traffic of the major influx transporter, Trk1.
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21
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Benjamin JJR, Poon PP, Drysdale JD, Wang X, Singer RA, Johnston GC. Dysregulated Arl1, a regulator of post-Golgi vesicle tethering, can inhibit endosomal transport and cell proliferation in yeast. Mol Biol Cell 2011; 22:2337-47. [PMID: 21562219 PMCID: PMC3128535 DOI: 10.1091/mbc.e10-09-0765] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Small monomeric G proteins regulated in part by GTPase-activating proteins (GAPs) are molecular switches for several aspects of vesicular transport. The yeast Gcs1 protein is a dual-specificity GAP for ADP-ribosylation factor (Arf) and Arf-like (Arl)1 G proteins, and also has GAP-independent activities. The absence of Gcs1 imposes cold sensitivity for growth and endosomal transport; here we present evidence that dysregulated Arl1 may cause these impairments. We show that gene deletions affecting the Arl1 or Ypt6 vesicle-tethering pathways prevent Arl1 activation and membrane localization, and restore growth and trafficking in the absence of Gcs1. A mutant version of Gcs1 deficient for both ArfGAP and Arl1GAP activity in vitro still allows growth and endosomal transport, suggesting that the function of Gcs1 that is required for these processes is independent of GAP activity. We propose that, in the absence of this GAP-independent regulation by Gcs1, the resulting dysregulated Arl1 prevents growth and impairs endosomal transport at low temperatures. In cells with dysregulated Arl1, an increased abundance of the Arl1 effector Imh1 restores growth and trafficking, and does so through Arl1 binding. Protein sequestration at the trans-Golgi membrane by dysregulated, active Arl1 may therefore be the mechanism of inhibition.
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Affiliation(s)
- Jeremy J R Benjamin
- Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 1X5
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22
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Yang YK, Qu H, Gao D, Di W, Chen HW, Guo X, Zhai ZH, Chen DY. ARF-like protein 16 (ARL16) inhibits RIG-I by binding with its C-terminal domain in a GTP-dependent manner. J Biol Chem 2011; 286:10568-80. [PMID: 21233210 PMCID: PMC3060509 DOI: 10.1074/jbc.m110.206896] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 01/11/2011] [Indexed: 12/25/2022] Open
Abstract
Retinoic acid-inducible gene I (RIG-I) recognizes RNA virus-derived nucleic acids, which leads to the production of type I interferon (IFN) in most cell types. Tight regulation of RIG-I activity is important to prevent ultra-immune responses. In this study, we identified an ARF-like (ARL) family member, ARL16, as a protein that interacts with RIG-I. Overexpression of ARL16, but not its homologous proteins ARL1 and ARF1, inhibited RIG-I-mediated downstream signaling and antiviral activity. Knockdown of endogenous ARL16 by RNAi potentiated Sendai virus-induced IFN-β expression and vesicular stomatitis virus replication. ARL16 interacted with the C-terminal domain (CTD) of RIG-I to suppress the association between RIG-I and RNA. ARL16 (T37N) and ARL16Δ45-54, which were restricted to the GTP-disassociated form, did not interact with RIG-I and also lost the inhibitory function. Furthermore, we suggest that endogenous ARL16 changes to GTP binding status upon viral infection and binds with the RIG-I CTD to negatively control its signaling activity. These findings suggested a novel innate immune function for an ARL family member, and a GTP-dependent model in which RIG-I is regulated.
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Affiliation(s)
- Yong-Kang Yang
- From the Key Laboratory of Cell Proliferation and Differentiation of Ministry of Education, College of Life Sciences, Peking University, Beijing 100871, China and
| | - Hong Qu
- From the Key Laboratory of Cell Proliferation and Differentiation of Ministry of Education, College of Life Sciences, Peking University, Beijing 100871, China and
| | - Dong Gao
- From the Key Laboratory of Cell Proliferation and Differentiation of Ministry of Education, College of Life Sciences, Peking University, Beijing 100871, China and
| | - Wei Di
- From the Key Laboratory of Cell Proliferation and Differentiation of Ministry of Education, College of Life Sciences, Peking University, Beijing 100871, China and
| | - Hai-Wei Chen
- From the Key Laboratory of Cell Proliferation and Differentiation of Ministry of Education, College of Life Sciences, Peking University, Beijing 100871, China and
| | - Xin Guo
- the Key Laboratory of Zoonosis of Ministry of Agriculture, China Agriculture University, Beijing 100083, China
| | - Zhong-He Zhai
- From the Key Laboratory of Cell Proliferation and Differentiation of Ministry of Education, College of Life Sciences, Peking University, Beijing 100871, China and
| | - Dan-Ying Chen
- From the Key Laboratory of Cell Proliferation and Differentiation of Ministry of Education, College of Life Sciences, Peking University, Beijing 100871, China and
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23
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Abstract
The trans-Golgi network (TGN) receives a select set of proteins from the endocytic pathway-about 5% of total plasma membrane glycoproteins (Duncan and Kornfeld 1988). Proteins that are delivered include mannose 6-phosphate receptors (MPRs), TGN46, sortilin, and various toxins that hitchhike a ride backward through the secretory pathway to intoxicate cells after they exit into the cytoplasm from the endoplasmic reticulum (ER). This article will review work on the molecular players that drive protein transport from the endocytic pathway to the TGN. Distinct requirements have revealed multiple routes for retrograde transport; in addition, the existence of multiple, potential coat proteins and/or cargo adaptors imply that multiple vesicular transfers are likely involved. Several comprehensive reviews have appeared recently and should be sought for additional details (Bonifacino and Rojas 2006; Johannes and Popoff 2008).
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Affiliation(s)
- Suzanne R Pfeffer
- Department of Biochemistry, Stanford University School of Medicine, California 94305-5307, USA.
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24
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Man Z, Kondo Y, Koga H, Umino H, Nakayama K, Shin HW. Arfaptins are localized to the trans-Golgi by interaction with Arl1, but not Arfs. J Biol Chem 2011; 286:11569-78. [PMID: 21239483 DOI: 10.1074/jbc.m110.201442] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Arfaptins (arfaptin-1 and arfaptin-2/POR1) were originally identified as binding partners of the Arf small GTPases. Both proteins contain a BAR (Bin/Amphiphysin/Rvs) domain, which participates in membrane deformation. Here we show that arfaptins associate with trans-Golgi membranes. Unexpectedly, Arl1 (Arf-like 1), but not Arfs, determines the trans-Golgi association of arfaptins. We also demonstrate that arfaptins interact with Arl1 through their BAR domain-containing region and compete for Arl1 binding with golgin-97 and golgin-245/p230, both of which also bind to Arl1 through their GRIP (golgin-97/RanBP2/Imh1p/p230) domains. However, arfaptins and these golgins show only limited colocalization at the trans-Golgi. Time-lapse imaging of cells overexpressing fluorescent protein-tagged arfaptins and golgin-97 reveals that arfaptins, but not golgin-97, are included in vesicular and tubular structures emanating from the Golgi region. These observations indicate that arfaptins are recruited onto trans-Golgi membranes by interacting with Arl1, and capable of inducing membrane deformation via their BAR domains.
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Affiliation(s)
- Zhiqiu Man
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, Japan
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25
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Vinogradova T, Miller PM, Kaverina I. Microtubule network asymmetry in motile cells: role of Golgi-derived array. Cell Cycle 2009; 8:2168-74. [PMID: 19556895 DOI: 10.4161/cc.8.14.9074] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Cell migration requires polarization of the cell into the leading edge and the trailing edge. Microtubules (MTs) are indispensable for polarized cell migration in the majority of cell types. To support cell polarity, MT network has to be functionally and structurally asymmetric. How is this asymmetry achieved? In interphase cells, MTs form a dynamic system radiating from a centrosome-based MT-organizing center (MTOC) to the cell edges. Symmetry of this radial array can be broken according to four general principles. Asymmetry occurs due to differential modulation of MT dynamics, relocation of existing MTs within a cell, adding an asymmetric nucleation site, and/or repositioning of a symmetric nucleation site to one side of a cell. Combinations of these asymmetry regulation principles result in a variety of asymmetric MT networks typical for diverse motile cell types. Importantly, an asymmetric MT array is formed at a non-conventional MT nucleation site, the Golgi. Here, we emphasize the contribution of this array to the asymmetry of MT network.
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Affiliation(s)
- Tatiana Vinogradova
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN, USA
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26
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Bailey LK, Campbell LJ, Evetts KA, Littlefield K, Rajendra E, Nietlispach D, Owen D, Mott HR. The structure of binder of Arl2 (BART) reveals a novel G protein binding domain: implications for function. J Biol Chem 2008; 284:992-9. [PMID: 18981177 DOI: 10.1074/jbc.m806167200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ADP-ribosylation factor-like (Arl) family of small G proteins are involved in the regulation of diverse cellular processes. Arl2 does not appear to be membrane localized and has been implicated as a regulator of microtubule dynamics. The downstream effector for Arl2, Binder of Arl 2 (BART) has no known function but, together with Arl2, can enter mitochondria and bind the adenine nucleotide transporter. We have solved the solution structure of BART and show that it forms a novel fold composed of six alpha-helices that form three interlocking "L" shapes. Analysis of the backbone dynamics reveals that the protein is highly anisotropic and that the loops between the central helices are dynamic. The regions involved in the binding of Arl2 were mapped onto the surface of BART and are found to localize to these loop regions. BART has faces of differing charge and structural elements, which may explain how it can interact with other proteins.
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Affiliation(s)
- Laura K Bailey
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
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27
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Yuksel B, Memon AR. Comparative phylogenetic analysis of small GTP-binding genes of model legume plants and assessment of their roles in root nodules. JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:3831-44. [PMID: 18849296 PMCID: PMC2576638 DOI: 10.1093/jxb/ern223] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2008] [Revised: 07/17/2008] [Accepted: 08/06/2008] [Indexed: 05/03/2023]
Abstract
Small GTP-binding genes play an essential regulatory role in a multitude of cellular processes such as vesicle-mediated intracellular trafficking, signal transduction, cytoskeletal organization, and cell division in plants and animals. Medicago truncatula and Lotus japonicus are important model plants for studying legume-specific biological processes such as nodulation. The publicly available online resources for these plants from websites such as http://www.ncbi.nih.gov, http://www.medicago.org, http://www.tigr.org, and related sites were searched to collect nucleotide sequences that encode GTP-binding protein homologues. A total of 460 small GTPase sequences from several legume species including Medicago and Lotus, Arabidopsis, human, and yeast were phyletically analysed to shed light on the evolution and functional characteristics of legume-specific homologues. One of the main emphases of this study was the elucidation of the possible involvement of some members of small GTPase homologues in the establishment and maintenance of symbiotic associations in root nodules of legumes. A high frequency of vesicle-mediated trafficking in nodules led to the idea of a probable subfunctionalization of some members of this family in legumes. As a result of the analyses, a group of 10 small GTPases that are likely to be mainly expressed in nodules was determined. The sequences determined as a result of this study could be used in more detailed molecular genetic analyses such as creation of RNA interference silencing mutants for further clarification of the role of GTPases in nodulation. This study will also assist in furthering our understanding of the evolutionary history of small GTPases in legume species.
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Affiliation(s)
- Bayram Yuksel
- Plant Molecular Biology Laboratory, Genetic Engineering and Biotechnology Institute, Marmara Research Center, TUBITAK, PO Box 21, 41400, Gebze, Kocaeli, Turkey.
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28
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Yeast and human Ysl2p/hMon2 interact with Gga adaptors and mediate their subcellular distribution. EMBO J 2008; 27:1423-35. [PMID: 18418388 DOI: 10.1038/emboj.2008.75] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Accepted: 03/19/2008] [Indexed: 11/09/2022] Open
Abstract
The Gga proteins represent a family of ubiquitously expressed clathrin adaptors engaged in vesicle budding at the tubular endosomal network/trans Golgi network. Their membrane recruitment is commonly thought to involve interactions with Arf and signals in cargo through the so-called VHS domain. For yeast Gga proteins, however, partners binding to its VHS domain have remained elusive and Gga localization does not absolutely depend on Arf. Here, we demonstrate that yeast Gga recruitment relies on a network of interactions between the scaffold Ysl2p/Mon2p, the small GTPase Arl1p, and the flippase Neo1p. Deletion of either YSL2 or ARL1 causes mislocalization of Gga2p, whereas a neo1-69 mutant accumulates Gga2p on aberrant structures. Remarkably, Ysl2p directly interacts with human and yeast Ggas through the VHS domain, and binding to Gga proteins is also found for the human Ysl2p orthologue hMon2. Thus, Ysl2p represents an essential, evolutionarily conserved member of a network controlling direct binding and membrane docking of Ggas. Because activated Arl1p is part of the network that binds Gga2p, Arf and Arf-like GTPases may interact in a regulatory cascade.
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29
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Ramirez IBR, de Graffenried CL, Ebersberger I, Yelinek J, He CY, Price A, Warren G. TbG63, a golgin involved in Golgi architecture in Trypanosoma brucei. J Cell Sci 2008; 121:1538-46. [PMID: 18411253 DOI: 10.1242/jcs.014324] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Golgins are coiled-coil proteins that have been implicated in the structure and function of the Golgi complex. Here, we identify and characterize a trypanosomal golgin, TbG63, showing that it has a C-terminal membrane anchor and an N-terminus that projects into the cytoplasm. TbG63 in procyclic parasites is localized to the Golgi and interacts with the active, GTP-form of TbRab1A. Overexpression of TbG63 has dramatic effects on Golgi architecture -- effects that require the N-terminus -- whereas depletion has little, if any, effect on the growth rate. By contrast, in the bloodstream form of the parasite, depletion of TbG63 slows growth, although it has no obvious effect on the transport of a variant surface glycoprotein (VSG) or on Golgi structure. TbG63 might be a useful tool to study the structure and functioning of the Golgi complex.
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30
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Pérez-Victoria FJ, Mardones GA, Bonifacino JS. Requirement of the human GARP complex for mannose 6-phosphate-receptor-dependent sorting of cathepsin D to lysosomes. Mol Biol Cell 2008; 19:2350-62. [PMID: 18367545 DOI: 10.1091/mbc.e07-11-1189] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The biosynthetic sorting of acid hydrolases to lysosomes relies on transmembrane, mannose 6-phosphate receptors (MPRs) that cycle between the TGN and endosomes. Herein we report that maintenance of this cycling requires the function of the mammalian Golgi-associated retrograde protein (GARP) complex. Depletion of any of the three GARP subunits, Vps52, Vps53, or Vps54, by RNAi impairs sorting of the precursor of the acid hydrolase, cathepsin D, to lysosomes and leads to its secretion into the culture medium. As a consequence, lysosomes become swollen, likely due to a buildup of undegraded materials. Missorting of cathepsin D in GARP-depleted cells results from accumulation of recycling MPRs in a population of light, small vesicles downstream of endosomes. These vesicles might correspond to intermediates in retrograde transport from endosomes to the TGN. Depletion of GARP subunits also blocks the retrograde transport of the TGN protein, TGN46, and the B subunit of Shiga toxin. These observations indicate that the mammalian GARP complex plays a general role in the delivery of retrograde cargo into the TGN. We also report that a Vps54 mutant protein in the Wobbler mouse strain is active in retrograde transport, thus explaining the viability of these mutant mice.
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Affiliation(s)
- F Javier Pérez-Victoria
- Cell Biology and Metabolism Program, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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31
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Sahin A, Espiau B, Tetaud E, Cuvillier A, Lartigue L, Ambit A, Robinson DR, Merlin G. The leishmania ARL-1 and Golgi traffic. PLoS One 2008; 3:e1620. [PMID: 18286177 PMCID: PMC2237903 DOI: 10.1371/journal.pone.0001620] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Accepted: 01/19/2008] [Indexed: 12/20/2022] Open
Abstract
We present here the characterisation of the Leishmania small G protein ADP-Ribosylation Factor-Like protein 1 (ARL-1). The ARL-1 gene is present in one copy per haploid genome and conserved among trypanosomatids. It encodes a protein of 20 kDa, which is equally expressed in the insect promastigote and mammalian amastigote forms of the parasite. ARL-1 localises to the Trans-Golgi Network (TGN); N-terminal myristoylation is essential for TGN localisation. In vivo expression of the LdARL-1/Q74L and LdARL-1/T51N mutants (GTP- and GDP-bound blocked forms respectively) shows that GDP/GTP cycling occurs entirely within the TGN. This is contrary to previous reports in yeast and mammals, where the mutant empty form devoid of nucleotide has been considered as the GDP-blocked form. The dominant-negative empty form mutant LdARL-1/T34N inhibits endocytosis and intracellular trafficking from the TGN to the Lysosome/Multivesicular Tubule and to the acidocalcisomes; these defects are probably related to a mislocalisation of the GRIP domain-containing vesicle tethering factors which cannot be recruited to the TGN by the cytoplasmic LdARL-1/T34N. Thus, besides the functional characterization of a new mutant and a better understanding of ARL-1 GDP/GTP cycling, this work shows that Leishmania ARL-1 is a key component of an essential pathway worth future study.
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Affiliation(s)
- Annelise Sahin
- Laboratoire de Microbiologie Cellulaire et Moléculaire et Pathogénicité, UMR CNRS 5234, Université Bordeaux 2, Bordeaux, France
| | - Benoît Espiau
- Laboratoire de Microbiologie Cellulaire et Moléculaire et Pathogénicité, UMR CNRS 5234, Université Bordeaux 2, Bordeaux, France
| | - Emmanuel Tetaud
- Laboratoire de Microbiologie Cellulaire et Moléculaire et Pathogénicité, UMR CNRS 5234, Université Bordeaux 2, Bordeaux, France
| | - Armelle Cuvillier
- Laboratoire de Microbiologie Cellulaire et Moléculaire et Pathogénicité, UMR CNRS 5234, Université Bordeaux 2, Bordeaux, France
| | - Lydia Lartigue
- Laboratoire de Microbiologie Cellulaire et Moléculaire et Pathogénicité, UMR CNRS 5234, Université Bordeaux 2, Bordeaux, France
| | - Audrey Ambit
- Laboratoire de Microbiologie Cellulaire et Moléculaire et Pathogénicité, UMR CNRS 5234, Université Bordeaux 2, Bordeaux, France
| | - Derrick R. Robinson
- Laboratoire de Microbiologie Cellulaire et Moléculaire et Pathogénicité, UMR CNRS 5234, Université Bordeaux 2, Bordeaux, France
| | - Gilles Merlin
- Laboratoire de Microbiologie Cellulaire et Moléculaire et Pathogénicité, UMR CNRS 5234, Université Bordeaux 2, Bordeaux, France
- *E-mail:
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Matheson LA, Suri SS, Hanton SL, Chatre L, Brandizzi F. Correct targeting of plant ARF GTPases relies on distinct protein domains. Traffic 2008; 9:103-20. [PMID: 17988226 DOI: 10.1111/j.1600-0854.2007.00671.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Indispensable membrane trafficking events depend on the activity of conserved small guanosine triphosphatases (GTPases), anchored to individual organelle membranes. In plant cells, it is currently unknown how these proteins reach their correct target membranes and interact with their effectors. To address these important biological questions, we studied two members of the ADP ribosylation factor (ARF) GTPase family, ARF1 and ARFB, which are membrane anchored through the same N-terminal myristoyl group but to different target membranes. Specifically, we investigated how ARF1 is targeted to the Golgi and post-Golgi structures, whereas ARFB accumulates at the plasma membrane. While the subcellular localization of ARFB appears to depend on multiple domains including the C-terminal half of the GTPase, the correct targeting of ARF1 is dependent on two domains: an N-terminal ARF1 domain that is necessary for the targeting of the GTPase to membranes and a core domain carrying a conserved MxxE motif that influences the relative distribution of ARF1 between the Golgi and post-Golgi compartments. We also established that the N-terminal ARF1 domain alone was insufficient to maintain an interaction with membranes and that correct targeting is a protein-specific property that depends on the status of the GTP switch. Finally, an ARF1-ARFB chimera containing only the first 18 amino acids from ARF1 was shown to compete with ARF1 membrane binding loci. Although this chimera exhibited GTPase activity in vitro, it was unable to recruit coatomer, a known ARF1 effector, onto Golgi membranes. Our results suggest that the targeting of ARF GTPases to the correct membranes may not only depend on interactions with effectors but also relies on distinct protein domains and further binding partners on the Golgi surface.
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Affiliation(s)
- Loren A Matheson
- Department of Biology, 112 Science Place, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
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Abstract
Small G proteins play a central role in the organization of the secretory and endocytic pathways. The majority of such small G proteins are members of the Rab family, which are anchored to the bilayer by C-terminal prenyl groups. However, the recruitment of some effectors, including vesicle coat proteins, is mediated by a second class of small G proteins that is unique in having an N-terminal amphipathic helix that becomes available for membrane insertion upon GTP binding. Sar1, Arf1, and Arf6 are the best-characterized members of this ADP-ribosylation factor (Arf) family. In addition, all eukaryotes contain additional distantly related G proteins, often called Arf like, or Arls. The complete Arf family in humans has 29 members. The roles of these related G proteins are poorly understood, but recent work has shown that some are involved in membrane traffic or organizing the cytoskeleton. Here we review what is known about all the members of the Arf family, along with the known regulatory molecules that convert them between GDP- and GTP-bound states.
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Kolanus W. Guanine nucleotide exchange factors of the cytohesin family and their roles in signal transduction. Immunol Rev 2007; 218:102-13. [PMID: 17624947 DOI: 10.1111/j.1600-065x.2007.00542.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Members of the cytohesin protein family, a group of guanine nucleotide exchange factors for adenosine diphosphate ribosylation factor (ARF) guanosine triphosphatases, have recently emerged as important regulators of signal transduction in vertebrate and invertebrate biology. These proteins share a modular domain structure, comprising carboxy-terminal membrane recruitment elements, a Sec7 homology effector domain, and an amino-terminal coiled-coil domain that serve as a platform for their integration into larger signaling complexes. Although these proteins have a highly similar overall build, their individual biological functions appear to be at least partly specific. Cytohesin-1 had been identified as a regulator of beta2 integrin inside-out regulation in immune cells and was subsequently shown to be involved in mitogen-associated protein kinase signaling in tumor cell proliferation as well as in T-helper cell activation and differentiation. Cytohesin-3, which had been discovered to be strongly associated with T-cell anergy, was very recently described as an essential component of insulin signal transduction in Drosophila and in human and murine liver cells. Future work will aim to dissect the mechanistic details of the modes of action of the cytohesins as well as to define the precise roles of these versatile proteins in vertebrates at the genetic level.
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Affiliation(s)
- Waldemar Kolanus
- Laboratory of Molecular Immunology, Program Unit Molecular Immune and Cell Biology, LIMES (Life and Medical Sciences Bonn), University of Bonn, Bonn, Germany.
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Liu GY, Gao SZ, Ge CR, Zhang X. Isolation, sequence identification and tissue expression profile of three novel porcine genes – ARL1, ARL3and ARL4A. ACTA AGR SCAND A-AN 2007. [DOI: 10.1080/09064700701335936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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36
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Bonifacino JS, Rojas R. Retrograde transport from endosomes to the trans-Golgi network. Nat Rev Mol Cell Biol 2006; 7:568-79. [PMID: 16936697 DOI: 10.1038/nrm1985] [Citation(s) in RCA: 484] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A subset of intracellular transmembrane proteins such as acid-hydrolase receptors, processing peptidases and SNAREs, as well as extracellular protein toxins such as Shiga toxin and ricin, undergoes 'retrograde' transport from endosomes to the trans-Golgi network. Here, we discuss recent studies that have begun to unravel the molecular machinery that is involved in this process. We also propose a central role for a 'tubular endosomal network' in sorting to recycling pathways that lead not only to the trans-Golgi network but also to different plasma-membrane domains and to specialized storage vesicles.
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Affiliation(s)
- Juan S Bonifacino
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Stefano G, Renna L, Hanton SL, Chatre L, Haas TA, Brandizzi F. ARL1 plays a role in the binding of the GRIP domain of a peripheral matrix protein to the Golgi apparatus in plant cells. PLANT MOLECULAR BIOLOGY 2006; 61:431-49. [PMID: 16830178 DOI: 10.1007/s11103-006-0022-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Accepted: 02/02/2006] [Indexed: 05/10/2023]
Abstract
ARF GTPases play a central role in regulating membrane dynamics and protein transport in eukaryotic cells. ARF-like (ARL) proteins are close relatives of the ARF regulators of vesicular transport, but their function in plant cells is poorly characterized. Here, by means of live cell imaging and site-directed mutagenesis, we have investigated the cellular function of the plant GTPase ARL1. We provide direct evidence for a role of this ARL family member in the association of a plant golgin with the plant Golgi apparatus. Our data reveal the existence of key residues within the conserved GRIP-domain of the golgin and within the GTPase ARL1 that are central to ARL1-GRIP interaction. Mutations of these residues abolish the interaction of GRIP with the GTP-bound ARL1 and induce a redistribution of GRIP into the cytosol. This indicates that the localization of GRIP to the Golgi apparatus is strongly influenced by the interaction of GRIP with Golgi-localized ARL1. Our results assign a cellular role to a member of the Arabidopsis ARL family in the plant secretory pathway and propose mechanisms for localization of peripheral golgins to the plant Golgi apparatus.
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Affiliation(s)
- Giovanni Stefano
- Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, S7N 5E2, SK, Canada
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Su CW, Tharin S, Jin Y, Wightman B, Spector M, Meili D, Tsung N, Rhiner C, Bourikas D, Stoeckli E, Garriga G, Horvitz HR, Hengartner MO. The short coiled-coil domain-containing protein UNC-69 cooperates with UNC-76 to regulate axonal outgrowth and normal presynaptic organization in Caenorhabditis elegans. J Biol 2006; 5:9. [PMID: 16725058 PMCID: PMC1561584 DOI: 10.1186/jbiol39] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2005] [Revised: 12/23/2005] [Accepted: 04/05/2006] [Indexed: 01/18/2023] Open
Abstract
Background The nematode Caenorhabditis elegans has been used extensively to identify the genetic requirements for proper nervous system development and function. Key to this process is the direction of vesicles to the growing axons and dendrites, which is required for growth-cone extension and synapse formation in the developing neurons. The contribution and mechanism of membrane traffic in neuronal development are not fully understood, however. Results We show that the C. elegans gene unc-69 is required for axon outgrowth, guidance, fasciculation and normal presynaptic organization. We identify UNC-69 as an evolutionarily conserved 108-amino-acid protein with a short coiled-coil domain. UNC-69 interacts physically with UNC-76, mutations in which produce similar defects to loss of unc-69 function. In addition, a weak reduction-of-function allele, unc-69(ju69), preferentially causes mislocalization of the synaptic vesicle marker synaptobrevin. UNC-69 and UNC-76 colocalize as puncta in neuronal processes and cooperate to regulate axon extension and synapse formation. The chicken UNC-69 homolog is highly expressed in the developing central nervous system, and its inactivation by RNA interference leads to axon guidance defects. Conclusion We have identified a novel protein complex, composed of UNC-69 and UNC-76, which promotes axonal growth and normal presynaptic organization in C. elegans. As both proteins are conserved through evolution, we suggest that the mammalian homologs of UNC-69 and UNC-76 (SCOCO and FEZ, respectively) may function similarly.
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Affiliation(s)
- Cheng-Wen Su
- Institute for Molecular Biology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
- Neuroscience Center Zurich, ETH and University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Suzanne Tharin
- Program in Genetics, SUNY at Stony Brook, Stony Brook, NY 11794, USA
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
- Current address: Department of Neurosurgery, Brigham and Women's Hospital, Children's Hospital and Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Yishi Jin
- Howard Hughes Medical Institute, Department of Molecular, Cellular and Developmental Biology, Sinsheimer Laboratories, University of California, Santa Cruz, CA 95064, USA
| | - Bruce Wightman
- Biology Department, Muhlenberg College, Allentown, PA 18104, USA
| | - Mona Spector
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
| | - David Meili
- Institute for Molecular Biology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
- Zoological Institute, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
- Current address: Abteilung für Klinische Chemie und Biochemie, Universitäts-Kinderklinik, Steinwiesstrasse 75, CH-8032 Zürich, Switzerland
| | - Nancy Tsung
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Current address: Clinigen, Inc., 400 W. Cummings Park #5700, Woburn, MA 01801, USA
| | - Christa Rhiner
- Institute for Molecular Biology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
- Neuroscience Center Zurich, ETH and University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Dimitris Bourikas
- Neuroscience Center Zurich, ETH and University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
- Zoological Institute, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Esther Stoeckli
- Neuroscience Center Zurich, ETH and University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
- Zoological Institute, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Gian Garriga
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - H Robert Horvitz
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Michael O Hengartner
- Institute for Molecular Biology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
- Neuroscience Center Zurich, ETH and University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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Ho HH, He CY, de Graffenried CL, Murrells LJ, Warren G. Ordered assembly of the duplicating Golgi in Trypanosoma brucei. Proc Natl Acad Sci U S A 2006; 103:7676-81. [PMID: 16672362 PMCID: PMC1472504 DOI: 10.1073/pnas.0602595103] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The new Golgi in the protozoan parasite Trypanosoma brucei grows near to the old and adjacent to the growing new endoplasmic reticulum exit site. Growth is now shown to be at least a two-stage process, in which a representative matrix marker (GRASP) and enzyme (GntB) are delivered to the site of assembly, followed approximately 10 min later by a COPI component (epsilon-COP) and a trans-Golgi network (TGN) marker (GRIP70). A secretory cargo marker (signal sequence-YFP) appeared early near the new endoplasmic reticulum exit site but did not enter the Golgi until the second stage. Together these data suggest that structural and enzymatic components of the new Golgi stack are laid down first, followed by those needed to move and sort the cargo passing through it.
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Affiliation(s)
- Helen H. Ho
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520
| | - Cynthia Y. He
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520
| | | | - Lindsay J. Murrells
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520
| | - Graham Warren
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520
- *To whom correspondence should be addressed. E-mail:
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Hofmann I, Munro S. An N-terminally acetylated Arf-like GTPase is localised to lysosomes and affects their motility. J Cell Sci 2006; 119:1494-503. [PMID: 16537643 DOI: 10.1242/jcs.02958] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Small GTPases of the Arf and Rab families play key roles in the function of subcellular organelles. Each GTPase is usually found on only one compartment and, hence, they confer organelle specificity to many intracellular processes. However, there has so far been little evidence for specific GTPases present on lysosomes. Here, we report that two closely related human Arf-like GTPases, Arl8a and Arl8b (also known as Arl10b/c and Gie1/2), localise to lysosomes in mammalian cells, with the single homologue in Drosophila cells having a similar location. Conventionally, membrane binding of Arf and Arl proteins is mediated by both an N-terminal myristoyl group and an N-terminal amphipathic helix that is inserted into the lipid bilayer upon activation of the GTPase. Arl8a and Arl8b do not have N-terminal myristoylation sites, and we find that Arl8b is instead N-terminally acetylated, and an acetylated methionine is necessary for its lysosomal localization. Overexpression of Arl8a or Arl8b results in a microtubule-dependent redistribution of lysosomes towards the cell periphery. Live cell imaging shows that lysosomes move more frequently both toward and away from the cell periphery, suggesting a role for Arl8a and Arl8b as positive regulators of lysosomal transport.
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Affiliation(s)
- Irmgard Hofmann
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH, UK
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Wilson SJ, Smyth EM. Internalization and recycling of the human prostacyclin receptor is modulated through its isoprenylation-dependent interaction with the delta subunit of cGMP phosphodiesterase 6. J Biol Chem 2006; 281:11780-6. [PMID: 16527812 DOI: 10.1074/jbc.m513110200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Prostacyclin, the major cyclooxygenase-derived product of arachidonic acid formed in the vasculature, mediates its potent anti-thrombotic and anti-proliferative effects through its G protein-coupled receptor (GPCR) termed the IP. Unlike many GPCRs, agonist-induced internalization of the IP occurs in an arrestin/GPCR kinase-independent manner. However, deletion of the IP COOH-terminal region prevented internalization suggesting that protein interactions at this region are involved in IP regulation. Using the COOH-terminal region of IP as bait we identified the delta subunit of cGMP phosphodiesterase 6 (PDE6delta) as a novel hIP-interacting protein in two independent yeast two-hybrid screens. Interaction of IP and PDE6delta was confirmed by co-immunoprecipitation in HEK293 cells, and in HEPG2 cells, which endogenously express neither IP nor PDE6delta. IP isoprenylation was critical for this interaction, as PDE6delta was unable to associate with an isoprenylation-deficient mutant IP (IPSSLC). PDE6delta overexpression altered the temporal pattern of agonist-induced internalization of IP, but not IPSSLC, in HEPG2 cells, increasing initial internalization but facilitating the return of IP to the cell surface despite the continued presence of agonist. Depletion of PDE6delta using short interfering RNA abolished cicaprost-induced IP internalization in human aortic smooth muscle cells. Recycling of IP, but not IPSSLC, upon agonist removal was facilitated by overexpression of PDE6delta. Thus PDE6delta interacts specifically with IP to modulate receptor trafficking.
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Affiliation(s)
- Stephen J Wilson
- Institute of Translational Medicine and Therapeutics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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Latijnhouwers M, Hawes C, Carvalho C. Holding it all together? Candidate proteins for the plant Golgi matrix. CURRENT OPINION IN PLANT BIOLOGY 2005; 8:632-9. [PMID: 16194619 DOI: 10.1016/j.pbi.2005.09.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Accepted: 09/13/2005] [Indexed: 05/04/2023]
Abstract
A combination of electron microscopy and fluorescence microscopy has provided us with a global picture of the structure of the plant Golgi apparatus. However, the components that shape this structure remain elusive. In other organisms, members of the golgin family of coiled-coil proteins are essential for Golgi structure and organisation. Putative Arabidopsis and rice homologues of some golgin family members can be identified using database searches. Likewise, the heterogeneous group of multi-subunit-tethering complexes is responsible for crucial transport steps that affect Golgi structure and cisternal organisation in animals and yeasts. The Arabidopsis genome harbours possible homologues for the majority of the subunits of these complexes, suggesting that they also operate in the plant kingdom.
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Affiliation(s)
- Maita Latijnhouwers
- Cell-to-Cell Communication programme, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK.
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Gillingham AK, Whyte JRC, Panic B, Munro S. Mon2, a relative of large Arf exchange factors, recruits Dop1 to the Golgi apparatus. J Biol Chem 2005; 281:2273-80. [PMID: 16301316 DOI: 10.1074/jbc.m510176200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The protein Mon2 is distantly related to the guanine nucleotide exchange factors (GEFs) that activate Arf1 on Golgi membranes. However, unlike these "large" Arf GEFs, Mon2 lacks the Sec7 domain that catalyzes nucleotide exchange on Arf1. Here we report that yeast Mon2 shares extensive homology with the noncatalytic parts of both the BIG and Golgi brefeldin A resistance factor subfamilies of Arf GEFs and is located to the trans-Golgi. Moreover, we find that Mon2 forms a complex with Dop1, a large cytoplasmic protein conserved in evolution from humans to protozoa. Deletion of Mon2 results in mislocalization of Dop1 from the Golgi and defects in cycling between endosomes and the Golgi. However, unlike Mon2, Dop1 is essential for yeast viability. A conditional allele of Dop1 shows that loss of Dop1 activity not only affects endosome to Golgi transport but also causes a severe perturbation of the organization of the endoplasmic reticulum. Thus, it appears that Dop1 plays a widespread role in membrane organization, and Mon2 acts as a scaffold to recruit the Golgi-localized pool of Dop1.
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Affiliation(s)
- Alison K Gillingham
- Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom
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