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Sandhu A, Lyu X, Wan X, Meng X, Tang NH, Gonzalez G, Syed IN, Chen L, Jin Y, Chisholm AD. The microtubule regulator EFA-6 forms spatially restricted cortical foci dependent on its intrinsically disordered region and interactions with tubulins. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.14.588158. [PMID: 38645057 PMCID: PMC11030407 DOI: 10.1101/2024.04.14.588158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
Microtubules (MTs) are dynamic components of the cytoskeleton and play essential roles in morphogenesis and maintenance of tissue and cell integrity. Despite recent advances in understanding MT ultrastructure, organization, and growth control, how cells regulate MT organization at the cell cortex remains poorly understood. The EFA-6/EFA6 proteins are recently identified membrane-associated proteins that inhibit cortical MT dynamics. Here, combining visualization of endogenously tagged C. elegans EFA-6 with genetic screening, we uncovered tubulin-dependent regulation of EFA-6 patterning. In the mature epidermal epithelium, EFA-6 forms punctate foci in specific regions of the apical cortex, dependent on its intrinsically disordered region (IDR). We further show the EFA-6 IDR is sufficient to form biomolecular condensates in vitro. In screens for mutants with altered GFP::EFA-6 localization, we identified a novel gain-of-function (gf) mutation in an α-tubulin tba-1 that induces ectopic EFA-6 foci in multiple cell types. tba-1(gf) animals exhibit temperature-sensitive embryonic lethality, which is partially suppressed by efa-6(lf), indicating the interaction between tubulins and EFA-6 is important for normal development. TBA-1(gf) shows reduced incorporation into filamentous MTs but has otherwise mild effects on cellular MT organization. The ability of TBA-1(gf) to trigger ectopic EFA-6 foci formation requires β-tubulin TBB-2 and the chaperon EVL-20/Arl2. The tba-1(gf)-induced EFA-6 foci display slower turnover, contain the MT-associated protein TAC-1/TACC, and require the EFA-6 MTED. Our results reveal a novel crosstalk between cellular tubulins and cortical MT regulators in vivo.
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Affiliation(s)
- Anjali Sandhu
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, CA 92093 USA
| | - Xiaohui Lyu
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, CA 92093 USA
| | - Xinghaoyun Wan
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, CA 92093 USA
| | - Xuefeng Meng
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, CA 92093 USA
| | - Ngang Heok Tang
- Department of Cell and Developmental Biology, School of Biological Sciences, University of California San Diego, CA 92093 USA
| | - Gilberto Gonzalez
- Barshop Institute for Longevity and Aging Studies, Department of Cell Systems and Anatomy, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Ishana N. Syed
- Barshop Institute for Longevity and Aging Studies, Department of Cell Systems and Anatomy, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Lizhen Chen
- Barshop Institute for Longevity and Aging Studies, Department of Cell Systems and Anatomy, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Yishi Jin
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, CA 92093 USA
| | - Andrew D. Chisholm
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, CA 92093 USA
- Department of Cell and Developmental Biology, School of Biological Sciences, University of California San Diego, CA 92093 USA
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Riley AK, Grant M, Snell A, Vichas A, Moorthi S, Urisman A, Castel P, Wan L, Berger AH. The deubiquitinase USP9X regulates RIT1 protein abundance and oncogenic phenotypes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.30.569313. [PMID: 38077017 PMCID: PMC10705424 DOI: 10.1101/2023.11.30.569313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/24/2023]
Abstract
RIT1 is a rare and understudied oncogene in lung cancer. Despite structural similarity to other RAS GTPase proteins such as KRAS, oncogenic RIT1 activity does not appear to be tightly regulated by nucleotide exchange or hydrolysis. Instead, there is a growing understanding that the protein abundance of RIT1 is important for its regulation and function. We previously identified the deubiquitinase USP9X as a RIT1 dependency in RIT1-mutant cells. Here, we demonstrate that both wild-type and mutant forms of RIT1 are substrates of USP9X. Depletion of USP9X leads to decreased RIT1 protein stability and abundance and resensitizes cells to EGFR tyrosine kinase inhibitors. Our work expands upon the current understanding of RIT1 protein regulation and presents USP9X as a key regulator of RIT1-driven oncogenic phenotypes.
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Affiliation(s)
- Amanda K. Riley
- Human Biology Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
- Molecular and Cellular Biology Program, University of Washington, Seattle, WA, USA
| | - Michael Grant
- Department of Molecular Oncology, Molecular Medicine Program, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA
| | - Aidan Snell
- Department of Molecular Oncology, Molecular Medicine Program, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA
| | - Athea Vichas
- Human Biology Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
| | - Sitapriya Moorthi
- Human Biology Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
| | - Anatoly Urisman
- Department of Pathology, University of California San Francisco, CA, USA
| | - Pau Castel
- Department of Biochemistry and Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY, USA
| | - Lixin Wan
- Department of Molecular Oncology, Molecular Medicine Program, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA
| | - Alice H. Berger
- Human Biology Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
- Herbold Computational Biology Program, Public Health Science Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
- Lead contact:
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3
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EFA6B regulates a stop signal for collective invasion in breast cancer. Nat Commun 2021; 12:2198. [PMID: 33850160 PMCID: PMC8044243 DOI: 10.1038/s41467-021-22522-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Accepted: 03/18/2021] [Indexed: 02/07/2023] Open
Abstract
Cancer is initiated by somatic mutations in oncogenes or tumor suppressor genes. However, additional alterations provide selective advantages to the tumor cells to resist treatment and develop metastases. Their identification is of paramount importance. Reduced expression of EFA6B (Exchange Factor for ARF6, B) is associated with breast cancer of poor prognosis. Here, we report that loss of EFA6B triggers a transcriptional reprogramming of the cell-to-ECM interaction machinery and unleashes CDC42-dependent collective invasion in collagen. In xenograft experiments, MCF10 DCIS.com cells, a DCIS-to-IDC transition model, invades faster when knocked-out for EFA6B. In addition, invasive and metastatic tumors isolated from patients have lower expression of EFA6B and display gene ontology signatures identical to those of EFA6B knock-out cells. Thus, we reveal an EFA6B-regulated molecular mechanism that controls the invasive potential of mammary cells; this finding opens up avenues for the treatment of invasive breast cancer.
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Partisani M, Baron CL, Ghossoub R, Fayad R, Pagnotta S, Abélanet S, Macia E, Brau F, Lacas-Gervais S, Benmerah A, Luton F, Franco M. EFA6A, an exchange factor for Arf6, regulates early steps in ciliogenesis. J Cell Sci 2021; 134:237326. [PMID: 33483367 DOI: 10.1242/jcs.249565] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 11/20/2020] [Indexed: 12/13/2022] Open
Abstract
Ciliogenesis is a coordinated process initiated by the recruitment and fusion of pre-ciliary vesicles at the distal appendages of the mother centriole through mechanisms that remain unclear. Here, we report that EFA6A (also known as PSD), an exchange factor for the small G protein Arf6, is involved in early stage of ciliogenesis by promoting the fusion of distal appendage vesicles forming the ciliary vesicle. EFA6A is present in the vicinity of the mother centriole before primary cilium assembly and prior to the arrival of Arl13B-containing vesicles. During ciliogenesis, EFA6A initially accumulates at the mother centriole and later colocalizes with Arl13B along the ciliary membrane. EFA6A depletion leads to the inhibition of ciliogenesis, the absence of centrosomal Rab8-positive structures and the accumulation of Arl13B-positive vesicles around the distal appendages. Our results uncover a novel fusion machinery, comprising EFA6A, Arf6 and Arl13B, that controls the coordinated fusion of ciliary vesicles docked at the distal appendages of the mother centriole.
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Affiliation(s)
- Mariagrazia Partisani
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Carole L Baron
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Rania Ghossoub
- Centre de Recherche en Cancérologie de Marseille (CRCM), Inserm, U1068-CNRS UMR7258, Aix-Marseille Université, Institut Paoli-Calmettes, 13009 Marseille, France
| | - Racha Fayad
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Sophie Pagnotta
- Centre Commun de Microscopie Appliquée (CCMA), Université Côte d'Azur Parc Valrose, 06103 Nice cedex 2, France
| | - Sophie Abélanet
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Eric Macia
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Frédéric Brau
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Sandra Lacas-Gervais
- Centre Commun de Microscopie Appliquée (CCMA), Université Côte d'Azur Parc Valrose, 06103 Nice cedex 2, France
| | - Alexandre Benmerah
- Université de Paris, Imagine Institute, Laboratory of Inherited Kidney Diseases, INSERM UMR 1163, F-75015, Paris, France
| | - Frédéric Luton
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
| | - Michel Franco
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275 CNRS-Université Côte d'Azur, 660, route des lucioles, 06560 Valbonne, France
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5
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Li B, Wang R, Wang Y, Stief CG, Hennenberg M. Regulation of smooth muscle contraction by monomeric non-RhoA GTPases. Br J Pharmacol 2020; 177:3865-3877. [PMID: 32579705 PMCID: PMC7429483 DOI: 10.1111/bph.15172] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/05/2020] [Accepted: 06/09/2020] [Indexed: 12/13/2022] Open
Abstract
Smooth muscle contraction in the cardiovascular system, airways, prostate and lower urinary tract is involved in the pathophysiology of many diseases, including cardiovascular and obstructive lung disease plus lower urinary tract symptoms, which are associated with high prevalence of morbidity and mortality. This prominent clinical role of smooth muscle tone has led to the molecular mechanisms involved being subjected to extensive research. In general smooth muscle contraction is promoted by three major signalling pathways, including the monomeric GTPase RhoA pathway. However, emerging evidence suggests that monomeric GTPases other than RhoA may be involved in signal transduction in smooth muscle contraction, including Rac GTPases, cell division control protein 42 homologue, adenosine ribosylation factor 6, Ras, Rap1b and Rab GTPases. Here, we review these emerging functions of non-RhoA GTPases in smooth muscle contraction, which has now become increasingly more evident and constitutes an emerging and innovative research area of high clinical relevance.
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Affiliation(s)
- Bingsheng Li
- Department of Urology, University Hospital, LMU Munich, Munich, Germany
| | - Ruixiao Wang
- Department of Urology, University Hospital, LMU Munich, Munich, Germany
| | - Yiming Wang
- Department of Urology, University Hospital, LMU Munich, Munich, Germany
| | - Christian G Stief
- Department of Urology, University Hospital, LMU Munich, Munich, Germany
| | - Martin Hennenberg
- Department of Urology, University Hospital, LMU Munich, Munich, Germany
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The C-terminal domain of EFA6A interacts directly with F-actin and assembles F-actin bundles. Sci Rep 2019; 9:19209. [PMID: 31844082 PMCID: PMC6915736 DOI: 10.1038/s41598-019-55630-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 11/28/2019] [Indexed: 01/08/2023] Open
Abstract
The Arf6-specific exchange factor EFA6 is involved in the endocytic/recycling pathway for different cargos. In addition EFA6 acts as a powerful actin cytoskeleton organizer, a function required for its role in the establishment of the epithelial cell polarity and in neuronal morphogenesis. We previously showed that the C-terminus of EFA6 (EFA6-Ct) is the main domain which contributes to actin reorganization. Here, by in vitro and in vivo experiments, we sought to decipher, at the molecular level, how EFA6 controls the dynamic and structuring of actin filaments. We showed that EFA6-Ct interferes with actin polymerization by interacting with and capping actin filament barbed ends. Further, in the presence of actin mono-filaments, the addition of EFA6-Ct triggered the formation of actin bundles. In cells, when the EFA6-Ct was directed to the plasma membrane, as is the case for the full-length protein, its expression induced the formation of membrane protrusions enriched in actin cables. Collectively our data explain, at least in part, how EFA6 plays an essential role in actin organization by interacting with and bundling F-actin.
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7
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Chichger H, Rounds S, Harrington EO. Endosomes and Autophagy: Regulators of Pulmonary Endothelial Cell Homeostasis in Health and Disease. Antioxid Redox Signal 2019; 31:994-1008. [PMID: 31190562 PMCID: PMC6765061 DOI: 10.1089/ars.2019.7817] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 06/07/2019] [Indexed: 12/12/2022]
Abstract
Significance: Alterations in oxidant/antioxidant balance injure pulmonary endothelial cells and are important in the pathogenesis of lung diseases, such as Acute Respiratory Distress Syndrome (ARDS), ischemia/reperfusion injury, pulmonary arterial hypertension (PAH), and emphysema. Recent Advances: The endosomal and autophagic pathways regulate cell homeostasis. Both pathways support recycling or degradation of macromolecules or organelles, targeted to endosomes or lysosomes, respectively. Thus, both processes promote cell survival. However, with environmental stress or injury, imbalance in endosomal and autophagic pathways may enhance macromolecular or organelle degradation, diminish biosynthetic processes, and cause cell death. Critical Issues: While the role of autophagy in cellular homeostasis in pulmonary disease has been investigated, the role of the endosome in the lung vasculature is less known. Furthermore, autophagy can either decrease or exacerbate endothelial injury, depending upon inciting insult and disease process. Future Directions: Diseases affecting the pulmonary endothelium, such as emphysema, ARDS, and PAH, are linked to altered endosomal or autophagic processing, leading to enhanced degradation of macromolecules and potential cell death. Efforts to target this imbalance have yielded limited success as treatments for lung injuries, which may be due to the complexity of both processes. It is possible that endosomal trafficking proteins, such as Rab GTPases and late endosomal/lysosomal adaptor, MAPK and MTOR activator 1, may be novel therapeutic targets. While endocytosis or autophagy have been linked to improved function of the pulmonary endothelium in vitro and in vivo, further studies are needed to identify targets for modulating cellular homeostasis in the lung.
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Affiliation(s)
- Havovi Chichger
- Biomedical Research Group, Department of Biomedical and Forensic Sciences, Anglia Ruskin University, Cambridge, United Kingdom
| | - Sharon Rounds
- Vascular Research Laboratory, Providence Veterans Affairs Medical Center, Providence, Rhode Island
- Division of Pulmonary, Critical Care, and Sleep Medicine, 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
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island
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8
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Mazaki Y, Onodera Y, Higashi T, Horinouchi T, Oikawa T, Sabe H. ARF1 recruits RAC1 to leading edge in neutrophil chemotaxis. Cell Commun Signal 2017; 15:36. [PMID: 28969640 PMCID: PMC5625764 DOI: 10.1186/s12964-017-0193-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 09/22/2017] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND The small GTPase ARF1 mediates membrane trafficking mostly from the Golgi, and is essential for the G protein-coupled receptor (GPCR)-mediated chemotaxis of neutrophils. In this process, ARF1 is activated by the guanine nucleotide exchanger GBF1, and is inactivated by the GTPase-activating protein GIT2. Neutrophils generate the Gβγ-PAK1-αPIX-GIT2 linear complex during GPCR-induced chemotaxis, in which αPIX activates RAC1/CDC42, which then employs PAK1. However, it has remained unclear as to why GIT2 is included in this complex. RESULTS We investigated the association between ARF1 and RAC1/CDC42 during the fMLP-stimulated chemotaxis of HL60 cells. We found that the silencing of GBF1 significantly impaired the recruitment of RAC1 to the leading edges, but not PAK1, αPIX, RAC2, or CDC42. A significant population of RAC1 colocalized with ARF1 at the leading edges in stimulated cells, whereas fMLP activated both ARF1 and ARF5. Consistently, the silencing of ARF1, but not ARF5, impaired the recruitment of RAC1, whereas the silencing of RAC1 did not affect the recruitment of ARF1 to the leading edges. CONCLUSIONS Our results indicated that the activation of ARF1 triggers the plasma membrane recruitment of RAC1 in GPCR-mediated chemotaxis, which is essential for cortical actin remodeling. Thus, membrane remodeling at the leading edges appears to precede actin remodeling in chemotaxis. Together with the fact that GIT2, which inactivates ARF1, is an integral component of the machinery activating RAC1, we proposed a model in which the ARF1-RAC1 linkage enables the regulation of ARF1 by repetitive on/off cycles during GPCR-mediated neutrophil chemotaxis.
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Affiliation(s)
- Yuichi Mazaki
- Department of Cellular Pharmacology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Yasuhito Onodera
- Department of Molecular Biology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Tsunehito Higashi
- Department of Cellular Pharmacology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Takahiro Horinouchi
- Department of Cellular Pharmacology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Tsukasa Oikawa
- Department of Molecular Biology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Hisataka Sabe
- Department of Molecular Biology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan
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Eva R, Koseki H, Kanamarlapudi V, Fawcett JW. EFA6 regulates selective polarised transport and axon regeneration from the axon initial segment. J Cell Sci 2017; 130:3663-3675. [PMID: 28935671 PMCID: PMC5702059 DOI: 10.1242/jcs.207423] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 09/08/2017] [Indexed: 12/11/2022] Open
Abstract
Central nervous system (CNS) axons lose their intrinsic ability to regenerate upon maturity, whereas peripheral nervous system (PNS) axons do not. A key difference between these neuronal types is their ability to transport integrins into axons. Integrins can mediate PNS regeneration, but are excluded from adult CNS axons along with their Rab11 carriers. We reasoned that exclusion of the contents of Rab11 vesicles including integrins might contribute to the intrinsic inability of CNS neurons to regenerate, and investigated this by performing laser axotomy. We identify a novel regulator of selective axon transport and regeneration, the ARF6 guanine-nucleotide-exchange factor (GEF) EFA6 (also known as PSD). EFA6 exerts its effects from a location within the axon initial segment (AIS). EFA6 does not localise at the AIS in dorsal root ganglion (DRG) axons, and in these neurons, ARF6 activation is counteracted by an ARF GTPase-activating protein (GAP), which is absent from the CNS, ACAP1. Depleting EFA6 from cortical neurons permits endosomal integrin transport and enhances regeneration, whereas overexpressing EFA6 prevents DRG regeneration. Our results demonstrate that ARF6 is an intrinsic regulator of regenerative capacity, implicating EFA6 as a focal molecule linking the AIS, signalling and transport. This article has an associated First Person interview with the first author of the paper. Highlighted Article: EFA6 is shown to reside in the axon initial segment, where it functions to prevent growth-promoting molecules from entering mature CNS axons. Removing EFA6 elevates the regenerative potential of the axon.
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Affiliation(s)
- Richard Eva
- John Van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 OPY, U.K
| | - Hiroaki Koseki
- John Van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 OPY, U.K
| | | | - James W Fawcett
- John Van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 OPY, U.K .,Centre of Reconstructive Neuroscience, Institute of Experimental Medicine AVCR, Prague, Czech Republic
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10
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Herlemann A, Keller P, Schott M, Tamalunas A, Ciotkowska A, Rutz B, Wang Y, Yu Q, Waidelich R, Strittmatter F, Stief CG, Gratzke C, Hennenberg M. Inhibition of smooth muscle contraction and ARF6 activity by the inhibitor for cytohesin GEFs, secinH3, in the human prostate. Am J Physiol Renal Physiol 2017; 314:F47-F57. [PMID: 28855187 DOI: 10.1152/ajprenal.00125.2017] [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: 12/14/2022] Open
Abstract
Prostate smooth muscle contraction is critical for etiology and treatment of male lower urinary tract symptoms (LUTS) and is promoted by small monomeric GTPases (RhoA and Rac). GTPases may be activated by guanosine nucleotide exchange factors (GEFs). GEFs of the cytohesin family may indirectly activate Rac, or ADP ribosylation factor (ARF) GTPases directly. Here we investigated the expression of cytohesin family GEFs and effects of the cytohesin inhibitor Sec7 inhibitor H3 (secinH3) on smooth muscle contraction and GTPase activities in human prostate tissues. Of all four cytohesin isoforms, cytohesin-1 and -2 showed the highest expression in real-time PCR. Western blot and fluorescence staining suggested that cytohesin-2 may be the predominant isoform in prostate smooth muscle cells. Contractions induced by norepinephrine, the α1-adrenoceptor agonist phenylephrine, the thromboxane A2 analog U-46619 , and endothelin-1 and -3, as well as neurogenic contractions induced by electric field stimulation (EFS), were reduced by secinH3 (30 µM). Inhibition of EFS-induced contractions appeared to have efficacy similar to that of inhibition by the α1-adrenoceptor antagonist tamsulosin (300 nM). Combined application of secinH3 plus tamsulosin caused larger inhibition of EFS-induced contractions than tamsulosin alone. Pull-down assays demonstrated inhibition of the small monomeric GTPase ARF6 by secinH3, but no inhibition of RhoA or Rac1. In conclusion, we suggest that a cytohesin-ARF6 pathway takes part in smooth muscle contraction. This may open attractive new possibilities in medical treatment of male LUTS.
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Affiliation(s)
- Annika Herlemann
- Department of Urology, Ludwig-Maximilians-Universität München, Munich , Germany
| | - Patrick Keller
- Department of Urology, Ludwig-Maximilians-Universität München, Munich , Germany
| | - Melanie Schott
- Department of Urology, Ludwig-Maximilians-Universität München, Munich , Germany
| | - Alexander Tamalunas
- Department of Urology, Ludwig-Maximilians-Universität München, Munich , Germany
| | - Anna Ciotkowska
- Department of Urology, Ludwig-Maximilians-Universität München, Munich , Germany
| | - Beata Rutz
- Department of Urology, Ludwig-Maximilians-Universität München, Munich , Germany
| | - Yiming Wang
- Department of Urology, Ludwig-Maximilians-Universität München, Munich , Germany
| | - Qingfeng Yu
- Department of Urology, Ludwig-Maximilians-Universität München, Munich , Germany
| | - Raphaela Waidelich
- Department of Urology, Ludwig-Maximilians-Universität München, Munich , Germany
| | - Frank Strittmatter
- Department of Urology, Ludwig-Maximilians-Universität München, Munich , Germany
| | - Christian G Stief
- Department of Urology, Ludwig-Maximilians-Universität München, Munich , Germany
| | - Christian Gratzke
- Department of Urology, Ludwig-Maximilians-Universität München, Munich , Germany
| | - Martin Hennenberg
- Department of Urology, Ludwig-Maximilians-Universität München, Munich , Germany
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11
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Narayanan N, Wang Z, Li L, Yang Y. Arginine methylation of USP9X promotes its interaction with TDRD3 and its anti-apoptotic activities in breast cancer cells. Cell Discov 2017; 3:16048. [PMID: 28101374 PMCID: PMC5206711 DOI: 10.1038/celldisc.2016.48] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 11/20/2016] [Indexed: 12/23/2022] Open
Abstract
The Tudor domain-containing proteins are characterized by their specific interactions with methylated protein motifs, including methyl-arginines and methyl-lysines. The Tudor domain-containing protein 3 (TDRD3) is one of the major methyl-arginine effector molecules that recognizes methylated arginine residues on histones and the C-terminal domain of RNA polymerase II, and activates transcription. However, majority of the cellular TDRD3 localizes to the cytoplasm and its functions there are still elusive. Here, we have identified ubiquitin-specific protease 9 X-linked (USP9X) as a TDRD3-interacting protein by GST (glutathione S-transferase) pull-down and co-immunoprecipitation. Detailed characterization suggests that the interaction between TDRD3 and USP9X is mediated through the Tudor domain of TDRD3 and the arginine methylation of USP9X. This interaction plays a critical role in TDRD3 protein stability, as knockdown of USP9X expression leads to increased TDRD3 ubiquitination. We also found that USP9X co-localizes with TDRD3 in cytoplasmic stress granules and this localization is diminished in Tdrd3-null mouse embryonic fibroblast cells, suggesting that TDRD3 is essential for USP9X stress granule localization. Furthermore, we found that one of the USP9X de-ubiquitination targets, myeloid cell leukemia protein 1, is regulated by TDRD3, indicating that TDRD3 potentially regulates USP9X de-ubiquitinase activity. Finally, we show that knockdown of TDRD3 expression sensitizes breast cancer cells to chemotherapeutic drug-induced apoptosis, likely due to its regulation of USP9X. This study provides a novel candidate strategy for targeting apoptosis pathways in cancer therapy.
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Affiliation(s)
- Nithya Narayanan
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope Cancer Center , Duarte, CA, USA
| | - Zhihao Wang
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope Cancer Center , Duarte, CA, USA
| | - Ling Li
- Division of Hematopoietic Stem Cell and Leukemia Research, Department of Hematology and HCT, Beckman Research Institute, City of Hope Cancer Center , Duarte, CA, USA
| | - Yanzhong Yang
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope Cancer Center , Duarte, CA, USA
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12
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Milanini J, Fayad R, Partisani M, Lecine P, Borg JP, Franco M, Luton F. EFA6 regulates lumen formation through alpha-actinin 1. J Cell Sci 2017; 131:jcs.209361. [DOI: 10.1242/jcs.209361] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 12/11/2017] [Indexed: 01/07/2023] Open
Abstract
A key step of epithelial morphogenesis is the creation of the lumen. Luminogenesis by hollowing proceeds through the fusion of apical vesicles at cell-cell contact. The small nascent lumens grow through extension, coalescence and enlargement coordinated with cell division to give rise to a single central lumen. Here, using MDCK cells grown in 3D-culture, we show that EFA6A participates in luminogenesis. EFA6A recruits α-actinin 1 (ACTN1) through direct binding. In polarized cells, ACTN1 was found to be enriched at the tight junction where it acts as a primary effector of EFA6A for normal luminogenesis. Both proteins are essential for the lumen extension and enlargement, where they mediate their effect by regulating the cortical acto-myosin contractility. Finally, ACTN1 was also found to act as an effector for the isoform EFA6B in the human mammary tumoral MCF7 cell line. EFA6B restored the glandular morphology of this tumoral cell line in an ACTN1-dependent manner. Thus, we identified new regulators of cyst luminogenesis essential for the proper maturation of a newly-formed lumen into a single central lumen.
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Affiliation(s)
- Julie Milanini
- Université Côte d'Azur, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Valbonne, France
| | - Racha Fayad
- Université Côte d'Azur, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Valbonne, France
| | - Mariagrazia Partisani
- Université Côte d'Azur, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Valbonne, France
| | - Patrick Lecine
- Centre de Recherche en Cancérologie de Marseille (CRCM), "Cell Polarity, Cell Signalling and Cancer", Equipe Labellisée Ligue Contre le Cancer, Inserm U1068, Marseille, F-13009, France; CNRS, UMR7258, Marseille, F-13009, France; Institut Paoli-Calmettes, Marseille, F-13009, France; Aix-Marseille University, UM105, Marseille, F-13284, France
- present address: BIOASTER, Lyon, France
| | - Jean-Paul Borg
- Centre de Recherche en Cancérologie de Marseille (CRCM), "Cell Polarity, Cell Signalling and Cancer", Equipe Labellisée Ligue Contre le Cancer, Inserm U1068, Marseille, F-13009, France; CNRS, UMR7258, Marseille, F-13009, France; Institut Paoli-Calmettes, Marseille, F-13009, France; Aix-Marseille University, UM105, Marseille, F-13284, France
| | - Michel Franco
- Université Côte d'Azur, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Valbonne, France
| | - Frédéric Luton
- Université Côte d'Azur, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Valbonne, France
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13
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Abstract
Members of the ADP-ribosylation factor (Arf) family of small GTP-binding (G) proteins regulate several aspects of membrane trafficking, such as vesicle budding, tethering and cytoskeleton organization. Arf family members, including Arf-like (Arl) proteins have been implicated in several essential cellular functions, like cell spreading and migration. These functions are used by cancer cells to disseminate and invade the tissues surrounding the primary tumor, leading to the formation of metastases. Indeed, Arf and Arl proteins, as well as their guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) have been found to be abnormally expressed in different cancer cell types and human cancers. Here, we review the current evidence supporting the involvement of Arf family proteins and their GEFs and GAPs in cancer progression, focusing on 3 different mechanisms: cell-cell adhesion, integrin internalization and recycling, and actin cytoskeleton remodeling.
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Affiliation(s)
- Cristina Casalou
- a CEDOC, NOVA Medical School - Faculdade de Ciências Médicas, Universidade NOVA de Lisboa , Lisbon , Portugal
| | - Alexandra Faustino
- a CEDOC, NOVA Medical School - Faculdade de Ciências Médicas, Universidade NOVA de Lisboa , Lisbon , Portugal.,b ProRegeM PhD Program, NOVA Medical School - Faculdade de Ciências Médicas, Universidade NOVA de Lisboa , Lisbon , Portugal
| | - Duarte C Barral
- a CEDOC, NOVA Medical School - Faculdade de Ciências Médicas, Universidade NOVA de Lisboa , Lisbon , Portugal
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14
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ADP Ribosylation Factor 6 Regulates Neuronal Migration in the Developing Cerebral Cortex through FIP3/Arfophilin-1-dependent Endosomal Trafficking of N-cadherin. eNeuro 2016; 3:eN-NWR-0148-16. [PMID: 27622210 PMCID: PMC5002984 DOI: 10.1523/eneuro.0148-16.2016] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 07/29/2016] [Accepted: 08/02/2016] [Indexed: 12/15/2022] Open
Abstract
During neural development, endosomal trafficking controls cell shape and motility through the polarized transport of membrane proteins related to cell–cell and cell–extracellular matrix interactions. ADP ribosylation factor 6 (Arf6) is a critical small GTPase that regulates membrane trafficking between the plasma membrane and endosomes. We herein demonstrated that the knockdown of endogenous Arf6 in mouse cerebral cortices led to impaired neuronal migration in the intermediate zone and cytoplasmic retention of N-cadherin and syntaxin12 in migrating neurons. Rescue experiments with separation-of-function Arf6 mutants identified Rab11 family-interacting protein 3 (FIP3)/Arfophilin-1, a dual effector for Arf6 and Rab11, as a downstream effector of Arf6 in migrating neurons. The knockdown of FIP3 led to impaired neuronal migration in the intermediate zone and cytoplasmic retention of N-cadherin in migrating neurons, similar to that of Arf6, which could be rescued by the coexpression of wild-type FIP3 but not FIP3 mutants lacking the binding site for Arf6 or Rab11. These results suggest that Arf6 regulates cortical neuronal migration in the intermediate zone through the FIP3-dependent endosomal trafficking.
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15
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Abstract
The capacity of an axon to regenerate is regulated by its external environment and by cell-intrinsic factors. Studies in a variety of organisms suggest that alterations in axonal microtubule (MT) dynamics have potent effects on axon regeneration. We review recent findings on the regulation of MT dynamics during axon regeneration, focusing on the nematode Caenorhabditis elegans. In C. elegans the dual leucine zipper kinase (DLK) promotes axon regeneration, whereas the exchange factor for Arf6 (EFA-6) inhibits axon regeneration. Both DLK and EFA-6 respond to injury and control axon regeneration in part via MT dynamics. How the DLK and EFA-6 pathways are related is a topic of active investigation, as is the mechanism by which EFA-6 responds to axonal injury. We evaluate potential candidates, such as the MT affinity-regulating kinase PAR-1/MARK, in regulation of EFA-6 and axonal MT dynamics in regeneration.
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Affiliation(s)
- Ngang Heok Tang
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Andrew D Chisholm
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA, 92093, USA
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16
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Murtaza M, Jolly LA, Gecz J, Wood SA. La FAM fatale: USP9X in development and disease. Cell Mol Life Sci 2015; 72:2075-89. [PMID: 25672900 PMCID: PMC4427618 DOI: 10.1007/s00018-015-1851-0] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 02/02/2015] [Accepted: 02/04/2015] [Indexed: 11/12/2022]
Abstract
Deubiquitylating enzymes (DUBs), act downstream of ubiquitylation. As such, these post-post-translational modifiers function as the final arbitrators of a protein substrate’s ubiquitylation status, thus regulating its fate. In most instances, DUBs moderate the absolute level of a substrate, its locality or activity, rather than being an “all-or-none” phenomenon. Yet, disruption of this quantitative regulation can produce dramatic qualitative differences. The ubiquitin-specific protease 9X (USP9X/FAM) is a substrate-specific DUB, which displays an extraordinarily high level of sequence conservation from Drosophila to mammals. It is primarily the recent revelations of USP9X’s pivotal role in human cancers, both as oncogene or tumour suppressor, in developmental disorders including intellectual disability, epilepsy, autism and developmental delay that has led to a subsequent re-examination of its molecular and cellular functions. Results from experimental animal models have implicated USP9X in neurodegeneration, including Parkinson’s and Alzheimer’s disease, as well as autoimmune diseases. In this review, we describe the current and accumulated knowledge on the molecular, cellular and developmental aspects of USP9X function within the context of the biological consequences during normal development and disease.
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Affiliation(s)
- Mariyam Murtaza
- The Eskitis Institute for Drug Discovery, Griffith University, Brisbane, QLD, Australia
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17
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Barroso-González J, García-Expósito L, Puigdomènech I, de Armas-Rillo L, Machado JD, Blanco J, Valenzuela-Fernández A. Viral infection. Commun Integr Biol 2014. [DOI: 10.4161/cib.16716] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
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18
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Zangari J, Partisani M, Bertucci F, Milanini J, Bidaut G, Berruyer-Pouyet C, Finetti P, Long E, Brau F, Cabaud O, Chetaille B, Birnbaum D, Lopez M, Hofman P, Franco M, Luton F. EFA6B Antagonizes Breast Cancer. Cancer Res 2014; 74:5493-506. [DOI: 10.1158/0008-5472.can-14-0298] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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19
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Ngok SP, Lin WH, Anastasiadis PZ. Establishment of epithelial polarity--GEF who's minding the GAP? J Cell Sci 2014; 127:3205-15. [PMID: 24994932 DOI: 10.1242/jcs.153197] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cell polarization is a fundamental process that underlies epithelial morphogenesis, cell motility, cell division and organogenesis. Loss of polarity predisposes tissues to developmental disorders and contributes to cancer progression. The formation and establishment of epithelial cell polarity is mediated by the cooperation of polarity protein complexes, namely the Crumbs, partitioning defective (Par) and Scribble complexes, with Rho family GTPases, including RhoA, Rac1 and Cdc42. The activation of different GTPases triggers distinct downstream signaling pathways to modulate protein-protein interactions and cytoskeletal remodeling. The spatio-temporal activation and inactivation of these small GTPases is tightly controlled by a complex interconnected network of different regulatory proteins, including guanine-nucleotide-exchange factors (GEFs), GTPase-activating proteins (GAPs), and guanine-nucleotide-dissociation inhibitors (GDIs). In this Commentary, we focus on current understanding on how polarity complexes interact with GEFs and GAPs to control the precise location and activation of Rho GTPases (Crumbs for RhoA, Par for Rac1, and Scribble for Cdc42) to promote apical-basal polarization in mammalian epithelial cells. The mutual exclusion of GTPase activities, especially that of RhoA and Rac1, which is well established, provides a mechanism through which polarity complexes that act through distinct Rho GTPases function as cellular rheostats to fine-tune specific downstream pathways to differentiate and preserve the apical and basolateral domains. This article is part of a Minifocus on Establishing polarity.
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Affiliation(s)
- Siu P Ngok
- Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Griffin Cancer Research Building, Room 307, 4500 San Pablo Road, Jacksonville, FL 32224, USA
| | - Wan-Hsin Lin
- Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Griffin Cancer Research Building, Room 307, 4500 San Pablo Road, Jacksonville, FL 32224, USA
| | - Panos Z Anastasiadis
- Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Griffin Cancer Research Building, Room 307, 4500 San Pablo Road, Jacksonville, FL 32224, USA
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20
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Arf6 exchange factor EFA6 and endophilin directly interact at the plasma membrane to control clathrin-mediated endocytosis. Proc Natl Acad Sci U S A 2014; 111:9473-8. [PMID: 24979773 DOI: 10.1073/pnas.1401186111] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Members of the Arf family of small G proteins are involved in membrane traffic and organelle structure. They control the recruitment of coat proteins, and modulate the structure of actin filaments and the lipid composition of membranes. The ADP-ribosylation factor 6 (Arf6) isoform and the exchange factor for Arf6 (EFA6) are known to regulate the endocytic pathway of many different receptors. To determine the molecular mechanism of the EFA6/Arf6 function in vesicular transport, we searched for new EFA6 partners. In a two-hybrid screening using the catalytic Sec7 domain as a bait, we identified endophilin as a new partner of EFA6. Endophilin contains a Bin/Amphiphysin/Rvs (BAR) domain responsible for membrane bending, and an SH3 domain responsible for the recruitment of dynamin and synaptojanin, two proteins involved, respectively, in the fission and uncoating of clathrin-coated vesicles. By using purified proteins, we confirmed the direct interaction, and identified the N-BAR domain as the binding motif to EFA6A. We showed that endophilin stimulates the catalytic activity of EFA6A on Arf6. In addition, we observed that the Sec7 domain competes with flat but not with highly curved lipid membranes to bind the N-BAR. In cells, expression of EFA6A recruits endophilin to EFA6A-positive plasma membrane ruffles, whereas expression of endophilin rescues the EFA6A-mediated inhibition of transferrin internalization. Overall, our results support a model whereby EFA6 recruits endophilin on flat areas of the plasma membrane to control Arf6 activation and clathrin-mediated endocytosis.
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21
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Van Itallie CM, Aponte A, Tietgens AJ, Gucek M, Fredriksson K, Anderson JM. The N and C termini of ZO-1 are surrounded by distinct proteins and functional protein networks. J Biol Chem 2013; 288:13775-88. [PMID: 23553632 DOI: 10.1074/jbc.m113.466193] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Biotin ligase tagging with ZO-1 was applied to identify a more complete tight junction proteome. RESULTS Identical but also different proteins and functional networks were identified near the N and C ends of ZO-1. CONCLUSION The ends of ZO-1 are embedded in different functional subcompartments of the tight junction. SIGNIFICANCE Biotin tagging with ZO-1 expands the tight junction proteome and defines subcompartments of the junction. The proteins and functional protein networks of the tight junction remain incompletely defined. Among the currently known proteins are barrier-forming proteins like occludin and the claudin family; scaffolding proteins like ZO-1; and some cytoskeletal, signaling, and cell polarity proteins. To define a more complete list of proteins and infer their functional implications, we identified the proteins that are within molecular dimensions of ZO-1 by fusing biotin ligase to either its N or C terminus, expressing these fusion proteins in Madin-Darby canine kidney epithelial cells, and purifying and identifying the resulting biotinylated proteins by mass spectrometry. Of a predicted proteome of ∼9000, we identified more than 400 proteins tagged by biotin ligase fused to ZO-1, with both identical and distinct proteins near the N- and C-terminal ends. Those proximal to the N terminus were enriched in transmembrane tight junction proteins, and those proximal to the C terminus were enriched in cytoskeletal proteins. We also identified many unexpected but easily rationalized proteins and verified partial colocalization of three of these proteins with ZO-1 as examples. In addition, functional networks of interacting proteins were tagged, such as the basolateral but not apical polarity network. These results provide a rich inventory of proteins and potential novel insights into functions and protein networks that should catalyze further understanding of tight junction biology. Unexpectedly, the technique demonstrates high spatial resolution, which could be generally applied to defining other subcellular protein compartmentalization.
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Affiliation(s)
- Christina M Van Itallie
- Laboratory of Tight Junction Structure and Function, NHLBI, National Institutes of Health, Bethesda, MD 20892, USA.
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22
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Abstract
Small GTP-binding proteins of the ADP-ribosylation factor (Arf) family control various cell functional responses including protein transport and recycling between different cellular compartments, phagocytosis, proliferation, cytoskeletal remodelling, and migration. The activity of Arfs is tightly regulated. GTPase-activating proteins (GAPs) inactivate Arfs by stimulating GTP hydrolysis, and guanine nucleotide exchange factors (GEFs) stimulate the conversion of inactive GDP-bound Arf to the active GTP-bound conformation. There is increasing evidence that Arf small GTPases contribute to cancer growth and invasion. Increased expression of Arf6 and of Arf-GEPs, or deregulation Arf-GAP functions have been correlated with enhanced invasive capacity of tumor cells and metastasis. The spatiotemporal specificity of Arf activation is dictated by their GEFs that integrate various signals in stimulated cells. Brefeldin A (BFA), which inactivates a subset of Arf-GEFs, has been very useful for assessing the function of Golgi-localized Arfs. However, specific inhibitors to investigate the individual function of BFA-sensitive and insensitive Arf-GEFs are lacking. In recent years, specific screens have been developed, and new inhibitors with improved selectivity and potency to study cell functional responses regulated by BFA-sensitive and BFA-insensitive Arf pathways have been identified. These inhibitors have been instrumental for our understanding of the spatiotemporal activation of Arf proteins in cells and demonstrate the feasibility of developing small molecules interfering with Arf activation to prevent tumor invasion and metastasis.
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23
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Macia E, Partisani M, Paleotti O, Luton F, Franco M. Arf6 negatively controls the rapid recycling of the β2 adrenergic receptor. J Cell Sci 2012; 125:4026-35. [PMID: 22611259 DOI: 10.1242/jcs.102343] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
β2-adrenergic receptor (β2AR), a member of the GPCR (G-protein coupled receptor) family, is internalized in a ligand- and β-arrestin-dependent manner into early endosomes, and subsequently recycled back to the plasma membrane. Here, we report that β-arrestin promotes the activation of the small G protein Arf6, which regulates the recycling and degradation of β2AR. We demonstrate in vitro that the C-terminal region of β-arrestin1 interacts directly and simultaneously with Arf6GDP and its specific exchange factor EFA6, to promote Arf6 activation. Similarly, the ligand-mediated activation of β2AR leads to the formation of Arf6GTP in vivo in a β-arrestin-dependent manner. Expression of either EFA6 or an activated Arf6 mutant caused accumulation of β2AR in the degradation pathway. This phenotype could be rescued by the expression of an activated mutant of Rab4, suggesting that Arf6 acts upstream of Rab4. We propose a model in which Arf6 plays an essential role in β2AR desensitization. The ligand-mediated stimulation of β2AR relocates β-arrestin to the plasma membrane, and triggers the activation of Arf6 by EFA6. The activation of Arf6 leads to accumulation of β2AR in the degradation pathway, and negatively controls Rab4-dependent fast recycling to prevent the re-sensitization of β2AR.
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Affiliation(s)
- Eric Macia
- Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275 CNRS-Université de Nice-Sophia Antipolis, 660 route des Lucioles, 06560 Valbonne, France
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24
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Mazaki Y, Nishimura Y, Sabe H. GBF1 bears a novel phosphatidylinositol-phosphate binding module, BP3K, to link PI3Kγ activity with Arf1 activation involved in GPCR-mediated neutrophil chemotaxis and superoxide production. Mol Biol Cell 2012; 23:2457-67. [PMID: 22573891 PMCID: PMC3386210 DOI: 10.1091/mbc.e12-01-0062] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
In neutrophils, Arf1 is activated upon GPCR stimulation. GBF1, a GEF for Arf, is primarily responsible for Arf1 activation upon GPCR stimulation and is important for chemotaxis and superoxide production. GBF1 also binds to products of PI3Kγ . The results indicate a novel mechanism that links PI3Kγ with chemotaxis and superoxide production. Most chemoattractants for neutrophils bind to the Gαi family of heterotrimeric G protein–coupled receptors (GPCRs) and release Gβγ subunits to activate chemotaxis and superoxide production. GIT2, a GTPase-activating protein for Arf1, forms a complex with Gβγ and is integral for directional sensing and suppression of superoxide production. Here we show that GBF1, a guanine nucleotide exchanging factor for Arf-GTPases, is primarily responsible for Arf1 activation upon GPCR stimulation and is important for neutrophil chemotaxis and superoxide production. We find that GBF1 bears a novel module, namely binding to products of phosphatidyl inositol 3-kinase (PI3K), which binds to products of PI3Kγ. Through this binding, GBF1 is translocated from the Golgi to the leading edge upon GPCR stimulation to activate Arf1 and recruit p22phox and GIT2 to the leading edge. Moreover, GBF1-mediated Arf1 activation is necessary to unify cell polarity during chemotaxis. Our results identify a novel mechanism that links PI3Kγ activity with chemotaxis and superoxide production in GPCR signaling.
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Affiliation(s)
- Yuichi Mazaki
- Priority Organization for Innovation and Excellence, Kumamoto University, Kumamoto, Japan.
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25
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Gopalakrishnan S, Tripathi A, Tamiz AP, Alkan SS, Pandey NB. Larazotide acetate promotes tight junction assembly in epithelial cells. Peptides 2012; 35:95-101. [PMID: 22401910 DOI: 10.1016/j.peptides.2012.02.016] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 02/20/2012] [Accepted: 02/20/2012] [Indexed: 12/13/2022]
Abstract
Tight junctions (TJ) control paracellular permeability and apical-basolateral polarity of epithelial cells. Dysregulated permeability is associated with pathological conditions, such as celiac disease and inflammatory bowel disease. TJ formation is dependent on E-cadherin-mediated cell-cell adhesion and actin rearrangement, and is regulated by the Rho family GTPase and aPKC signaling pathways. Larazotide acetate, an 8-mer peptide and TJ modulator, inhibits TJ disassembly and dysfunction caused by endogenous and exogenous stimuli in intestinal epithelial cells. Here, we examined the effect of larazotide acetate on de novo TJ assembly using 2 different model systems. In MDCK cells, larazotide acetate promoted TJ assembly in a calcium switch assay. Larazotide acetate also promoted actin rearrangement, and junctional distribution of zonula occludens-1 (ZO-1), occludin, claudins, and E-cadherin. Larazotide acetate promoted TJ maturation and decreased paracellular permeability in "leaky" Caco-2 cells. Taken together, our data indicate that larazotide acetate enhances TJ assembly and barrier function by promoting actin rearrangement and redistribution of TJ and AJ proteins.
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Affiliation(s)
- Shobha Gopalakrishnan
- Alba Therapeutics, 650 S. Exeter, Suite 1040, 10th floor, Baltimore, MD 21202, United States
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26
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Shteyn E, Pigati L, Fölsch H. Arf6 regulates AP-1B-dependent sorting in polarized epithelial cells. J Cell Biol 2011; 194:873-87. [PMID: 21911479 PMCID: PMC3207291 DOI: 10.1083/jcb.201106010] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Accepted: 08/12/2011] [Indexed: 11/22/2022] Open
Abstract
The epithelial cell-specific clathrin adaptor complex AP-1B facilitates the sorting of various transmembrane proteins from recycling endosomes (REs) to the basolateral plasma membrane. Despite AP-1B's clear importance in polarized epithelial cells, we still do not fully understand how AP-1B orchestrates basolateral targeting. Here we identify the ADP-ribosylation factor 6 (Arf6) as an important regulator of AP-1B. We show that activated Arf6 pulled down AP-1B in vitro. Furthermore, interfering with Arf6 function through overexpression of dominant-active Arf6Q67L or dominant-negative Arf6D125N, as well as depletion of Arf6 with short hairpin RNA (shRNA), led to apical missorting of AP-1B-dependent cargos. In agreement with these data, we found that Arf6 colocalized with AP-1B and transferrin receptor (TfnR) in REs. In addition, we observed specific recruitment of AP-1B into Arf6-induced membrane ruffles in nonpolarized cells. We conclude that activated Arf6 directs membrane recruitment of AP-1B, thus regulating AP-1B's functions in polarized epithelial cells.
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Affiliation(s)
- Elina Shteyn
- Department of Cell and Molecular Biology, Northwestern University, Chicago, IL 60611, USA
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27
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Barroso-González J, García-Expósito L, Puigdomènech I, de Armas-Rillo L, Machado JD, Blanco J, Valenzuela-Fernández A. Viral infection: Moving through complex and dynamic cell-membrane structures. Commun Integr Biol 2011; 4:398-408. [PMID: 21966556 DOI: 10.4161/cib.4.4.16716] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Accepted: 05/31/2011] [Indexed: 01/19/2023] Open
Abstract
Viruses have developed different survival strategies in host cells by crossing cell-membrane compartments, during different steps of their viral life cycle. In fact, the non-regenerative viral membrane of enveloped viruses needs to encounter the dynamic cell-host membrane, during early steps of the infection process, in which both membranes fuse, either at cell-surface or in an endocytic compartment, to promote viral entry and infection. Once inside the cell, many viruses accomplish their replication process through exploiting or modulating membrane traffic, and generating specialized compartments to assure viral replication, viral budding and spreading, which also serve to evade the immune responses against the pathogen. In this review, we have attempted to present some data that highlight the importance of membrane dynamics during viral entry and replicative processes, in order to understand how viruses use and move through different complex and dynamic cell-membrane structures and how they use them to persist.
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Affiliation(s)
- Jonathan Barroso-González
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
| | - Laura García-Expósito
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
| | - Isabel Puigdomènech
- Fundació irsiCaixa-HIVACAT; Institut de Recerca en Ciències de la Salut Germans Trias i Pujol (IGTP); Hospital Germans Trias i Pujol; Universitat Autònoma de Barcelona; Barcelona, Catalonia Spain
| | - Laura de Armas-Rillo
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
| | - José-David Machado
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
| | - Julià Blanco
- Fundació irsiCaixa-HIVACAT; Institut de Recerca en Ciències de la Salut Germans Trias i Pujol (IGTP); Hospital Germans Trias i Pujol; Universitat Autònoma de Barcelona; Barcelona, Catalonia Spain
| | - Agustín Valenzuela-Fernández
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
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ARF family G proteins and their regulators: roles in membrane transport, development and disease. Nat Rev Mol Cell Biol 2011; 12:362-75. [PMID: 21587297 PMCID: PMC3245550 DOI: 10.1038/nrm3117] [Citation(s) in RCA: 669] [Impact Index Per Article: 51.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The ADP-ribosylation factor (ARF) family of guanine-nucleotide-binding (G) proteins, including the ARF proteins, ARF-like (ARL) proteins and SAR1, regulates membrane traffic and organelle structure, and each family member is regulated through a cycle of GTP binding and GTP hydrolysis, which activate and inactivate, respectively, the G protein. Traditionally, ARFs have been characterized for their immediate effects in the recruitment of coat proteins to drive cargo sorting, the recruitment of enzymes that can alter membrane lipid composition and the regulation of cytoskeletal factors. Now, new roles for ARFs have been discovered at the Golgi complex, for example in driving lipid transport. ARL proteins are also being increasingly linked to coordination of trafficking with cytoskeletal processes, for example during ciliogenesis. There is particular interest in the mechanisms that control recruitment of the ARF guanine nucleotide exchange factors (GEFs) that mediate GTP binding to ARFs and, in the case of the cytohesin (also known as ARNO) GEF, membrane recruitment is coupled to relief of autoinhibition. GEFs such as cytohesin may also participate in a cascade of activation between particular pairs of ARFs. Traditionally, G protein signalling has been viewed as a linear pathway, with the GDP-bound form of an ARF protein being inactive; however, more recent studies have highlighted novel roles for these GDP-bound forms and have also shown that GEFs and GTPase-activating proteins (GAPs) themselves can engage in distinct signalling responses through scaffolding functions.
The ADP-ribosylation factor (ARF) and ARF-like (ARL) family of G proteins, which are known to regulate membrane traffic and organelle structure, are emerging as regulators of diverse processes, including lipid and cytoskeletal transport. Although traditionally viewed as part of a linear signalling pathway, ARFs and their regulators must now be considered to exist within functional networks, in which both the 'inactive' ARF and the regulators themselves can mediate distinct effects. Members of the ADP-ribosylation factor (ARF) family of guanine-nucleotide-binding (G) proteins, including the ARF-like (ARL) proteins and SAR1, regulate membrane traffic and organelle structure by recruiting cargo-sorting coat proteins, modulating membrane lipid composition, and interacting with regulators of other G proteins. New roles of ARF and ARL proteins are emerging, including novel functions at the Golgi complex and in cilia formation. Their function is under tight spatial control, which is mediated by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) that catalyse GTP exchange and hydrolysis, respectively. Important advances are being gained in our understanding of the functional networks that are formed not only by the GEFs and GAPs themselves but also by the inactive forms of the ARF proteins.
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Akiyama M, Zhou M, Sugimoto R, Hongu T, Furuya M, Funakoshi Y, Kato M, Hasegawa H, Kanaho Y. Tissue- and development-dependent expression of the small GTPase Arf6 in mice. Dev Dyn 2010; 239:3416-35. [DOI: 10.1002/dvdy.22481] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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30
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Torii T, Miyamoto Y, Sanbe A, Nishimura K, Yamauchi J, Tanoue A. Cytohesin-2/ARNO, through its interaction with focal adhesion adaptor protein paxillin, regulates preadipocyte migration via the downstream activation of Arf6. J Biol Chem 2010; 285:24270-81. [PMID: 20525696 DOI: 10.1074/jbc.m110.125658] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The formation of primitive adipose tissue is the initial process in adipose tissue development followed by the migration of preadipocytes into adipocyte clusters. Comparatively little is known about the molecular mechanism controlling preadipocyte migration. Here, we show that cytohesin-2, the guanine-nucleotide exchange factor for the Arf family GTP-binding proteins, regulates migration of mouse preadipocyte 3T3-L1 cells through Arf6. SecinH3, a specific inhibitor of the cytohesin family, markedly inhibits migration of 3T3-L1 cells. 3T3-L1 cells express cytohesin-2 and cytohesin-3, and knockdown of cytohesin-2 with its small interfering RNA effectively decreases cell migration. Cytohesin-2 preferentially acts upstream of Arf6 in this signaling pathway. Furthermore, we find that the focal adhesion protein paxillin forms a complex with cytohesin-2. Paxillin colocalizes with cytohesin-2 at the leading edges of migrating cells. This interaction is mediated by the LIM2 domain of paxillin and the isolated polybasic region of cytohesin-2. Importantly, migration is inhibited by expression of the constructs containing these regions. These results suggest that cytohesin-2, through a previously unexplored complex formation with paxillin, regulates preadipocyte migration and that paxillin plays a previously unknown role as a scaffold protein of Arf guanine-nucleotide exchange factor.
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Affiliation(s)
- Tomohiro Torii
- Department of Pharmacology, National Research Institute for Child Health and Development, Setagaya, Okura, Tokyo 157-8535, Japan
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31
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Théard D, Labarrade F, Partisani M, Milanini J, Sakagami H, Fon EA, Wood SA, Franco M, Luton F. USP9x-mediated deubiquitination of EFA6 regulates de novo tight junction assembly. EMBO J 2010; 29:1499-509. [PMID: 20339350 DOI: 10.1038/emboj.2010.46] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2010] [Accepted: 03/03/2010] [Indexed: 11/09/2022] Open
Abstract
In epithelial cells, the tight junction (TJ) functions as a permeability barrier and is involved in cellular differentiation and proliferation. Although many TJ proteins have been characterized, little is known about the sequence of events and temporal regulation of TJ assembly in response to adhesion cues. We report here that the deubiquitinating enzyme USP9x has a critical function in TJ biogenesis by controlling the levels of the exchange factor for Arf6 (EFA6), a protein shown to facilitate TJ formation, during a narrow temporal window preceding the establishment of cell polarity. At steady state, EFA6 is constitutively ubiquitinated and turned over by the proteasome. However, at newly forming contacts, USP9x-mediated deubiquitination protects EFA6 from proteasomal degradation, leading to a transient increase in EFA6 levels. Consistent with this model, USP9x and EFA6 transiently co-localize at primordial epithelial junctions. Furthermore, knockdown of either EFA6 or USP9x impairs TJ biogenesis and EFA6 overexpression rescues TJ biogenesis in USP9x-knockdown cells. As the loss of cell polarity is a critical event in the metastatic spread of cancer, these findings may help to understand the pathology of human carcinomas.
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Affiliation(s)
- Delphine Théard
- Institut de Pharmacologie Moléculaire et Cellulaire, Université de Nice Sophia-Antipolis, Valbonne, France
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FRMD4A regulates epithelial polarity by connecting Arf6 activation with the PAR complex. Proc Natl Acad Sci U S A 2009; 107:748-53. [PMID: 20080746 DOI: 10.1073/pnas.0908423107] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Par-3/Par-6/aPKC/Cdc42 complex regulates the conversion of primordial adherens junctions (AJs) into belt-like AJs and the formation of linear actin cables during epithelial polarization. However, the mechanisms by which this complex functions are not well elucidated. In the present study, we found that activation of Arf6 is spatiotemporally regulated as a downstream signaling pathway of the Par protein complex. When primordial AJs are formed, Par-3 recruits a scaffolding protein, termed the FERM domain containing 4A (FRMD4A). FRMD4A connects Par-3 and the Arf6 guanine-nucleotide exchange factor (GEF), cytohesin-1. We propose that the Par-3/FRMD4A/cytohesin-1 complex ensures accurate activation of Arf6, a central player in actin cytoskeleton dynamics and membrane trafficking, during junctional remodeling and epithelial polarization.
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Klein S, Partisani M, Franco M, Luton F. EFA6 facilitates the assembly of the tight junction by coordinating an Arf6-dependent and -independent pathway. J Biol Chem 2008; 283:30129-38. [PMID: 18779331 DOI: 10.1074/jbc.m803375200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
We have previously reported that EFA6, exchange factor for Arf6, is implicated upon E-cadherin engagement in the process of epithelial cell polarization. We had found that EFA6 acts through stabilization of the apical actin ring onto which the tight junction is anchored. Mutagenesis experiments showed that both the catalytic domain of EFA6 and its C-terminal domain were required for full EFA6 function. Here we address the contribution of the specific substrate of EFA6, the small G protein Arf6. Unexpectedly, depletion of Arf6 by RNA interference or expression of the constitutively active fast-cycling mutant (Arf6T157N) revealed that Arf6 plays an opposing role to EFA6 by destabilizing the apical actin cytoskeleton and the associated tight junction. However, in complementation experiments, when the C-terminal domain of EFA6 is co-expressed with Arf6T157N, it reverts the effects of Arf6T157N expressed alone to faithfully mimic the phenotypes induced by EFA6. In addition, we find that the two signaling pathways downstream of EFA6, i.e. the one originating from the activated Arf6GTP and the other one from the EFA6 C-terminal domain, need to be tightly balanced to promote the proper reorganization of the actin cytoskeleton. Altogether, our results indicate that to regulate the tight junction, EFA6 activates Arf6 through its Sec7 catalytic domain as it modulates this activity through its C-terminal domain.
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Affiliation(s)
- Stéphanie Klein
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-UMR 6097, Université de Nice Sophia-Antipolis, 660 route des Lucioles, 06560 Valbonne, France
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Macia E, Partisani M, Favard C, Mortier E, Zimmermann P, Carlier MF, Gounon P, Luton F, Franco M. The pleckstrin homology domain of the Arf6-specific exchange factor EFA6 localizes to the plasma membrane by interacting with phosphatidylinositol 4,5-bisphosphate and F-actin. J Biol Chem 2008; 283:19836-44. [PMID: 18490450 DOI: 10.1074/jbc.m800781200] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The Arf6-specific exchange factor EFA6 coordinates membrane trafficking with actin cytoskeleton remodeling. It localizes to the plasma membrane where it catalyzes Arf6 activation and induces the formation of actin-based membrane ruffles. We have shown previously that the pleckstrin homology (PH) domain of EFA6 was responsible for its membrane localization. In this study we looked for the partners of the PH domain at the plasma membrane. Mutations of the conserved basic residues suspected to be involved in the binding to phosphoinositides redistribute EFA6-PH to the cytosol. In addition, phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) breakdown also leads to the solubilization of EFA6-PH. Direct binding measured by surface plasmon resonance gives an apparent affinity of approximately 0.5 microm EFA6-PH for PI(4,5)P2. Moreover, we observed in vitro that the catalytic activity of EFA6 is strongly increased by PI(4,5)P2. These results indicate that the plasma membrane localization of EFA6-PH is based on its interaction with PI(4,5)P2, and this interaction is necessary for an optimal catalytic activity of EFA6. Furthermore, we demonstrated by fluorescence recovery after photobleaching and Triton X-100 detergent solubility experiments that in addition to the phophoinositides, EFA6-PH is linked to the actin cytoskeleton. We observed both in vivo and in vitro that EFA6-PH interacts directly with F-actin. Finally, we demonstrated that EFA6 could bind simultaneously filamentous actin and phospholipids vesicles. Our results explain how the exchange factor EFA6 via its PH domain could coordinate at the plasma membrane actin cytoskeleton organization with membrane trafficking.
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Affiliation(s)
- Eric Macia
- Institut de Pharmacologie Moléculaire et Cellulaire, UMR 6097 CNRS-Université de Nice-Sophia Antipolis, 660, route des lucioles, 06560 Valbonne, France
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Yano H, Kobayashi I, Onodera Y, Luton F, Franco M, Mazaki Y, Hashimoto S, Iwai K, Ronai Z, Sabe H. Fbx8 makes Arf6 refractory to function via ubiquitination. Mol Biol Cell 2007; 19:822-32. [PMID: 18094045 DOI: 10.1091/mbc.e07-08-0763] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The small GTP-binding protein Arf6 regulates membrane remodeling at cell peripheries and plays crucial roles in higher orders of cellular functions including tumor invasion. Here we show that Fbx8, an F-box protein bearing the Sec7 domain, mediates ubiquitination of Arf6. This ubiquitination did not appear to be linked to immediate proteasomal degradation of Arf6, whereas Fbx8 knockdown caused hyperactivation of Arf6. Expression of Fbx8 protein was substantially lost in several breast tumor cell lines, in which Arf6 activity is pivotal for their invasion. Forced expression of Fbx8 in these cells suppressed their Arf6 activities and invasive activities, in which the F-box and Sec7 domains of Fbx8 are required. Together with the possible mechanism as to how Fbx8-mediated ubiquitination interferes with the functions of Arf6, we propose that Fbx8 provides a novel suppressive control of Arf6 activity through noncanonical ubiquitination. Our results indicate that dysfunction of Fbx8 expression may contribute to the invasiveness of some breast cancer cells.
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Affiliation(s)
- Hajime Yano
- Department of Molecular Biology, Osaka Bioscience Institute, Osaka 565-0874, Japan
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Abstract
The ADP ribosylation factors (Arfs) are a family of small, ubiquitously expressed and evolutionarily conserved guanosine triphosphatases that are key regulators of vesicular transport in eukaryotic cells (D'Souza-Schorey C, Chavrier P. ARF proteins: roles in membrane traffic and beyond. Nat Rev Mol Cell Biol 2006;7:347-358). Although Arfs are best known for their role in the nucleation of coat protein assembly at a variety of intracellular locations, it is increasingly apparent that they are also integral components in a number of important signaling pathways that are regulated by extracellular cues. The activation of Arfs is catalyzed by a family of guanine nucleotide exchange factors (GEFs), referred to as the Sec7 family, based on homology of their catalytic domains to the yeast Arf GEF, sec7p. While there are only six mammalian Arfs, the human genome encodes 15 Sec7 family members, which can be divided into five classes based on related domain organization. Some of this diversity arises from the tissue-specific expression of certain isoforms, but all mammalian cells appear to express at least six Arf GEFs, suggesting that Arf activation is under extensive regulatory control. Here we review recent progress in our understanding of the structure, localization and biology of the different classes of Arf GEFs.
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Affiliation(s)
- James E Casanova
- Department of Cell Biology, University of Virginia Health System, Charlottesville, VA 22908-0732, USA.
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Shultz T, Shmuel M, Hyman T, Altschuler Y. Beta-tubulin cofactor D and ARL2 take part in apical junctional complex disassembly and abrogate epithelial structure. FASEB J 2007; 22:168-82. [PMID: 17704193 DOI: 10.1096/fj.06-7786com] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
In epithelial cells, the apical junctional complex (AJC), composed of tight junctions (TJs) and adherens junctions (AJs), maintains cell-surface polarity by forming a fence that prevents lateral movement and diffusion of proteins and lipids between the apical and basolateral PM and holds the epithelial monolayer intact through cell-cell contacts. Disassembly of this complex is a prime event in development and cell transformation. Maintenance of the AJC has been shown to involve mainly the actin cytoskeleton. Recent findings also point to the involvement of the microtubule (MT) system. Here we show the first evidence that in polarized epithelial MDCK cells, ARF-like protein 2 (ARL2) and beta-tubulin cofactor D, known to be involved in MT dynamics, have a role in disassembly of the AJC followed by cell dissociation from the epithelial monolayer, which is not dependent on MT depolymerization. In addition, we show that beta-tubulin cofactor D is partially localized to the lateral PM through its 15 C-terminal amino acids and intact MTs. ARL2 inhibited beta-tubulin cofactor D-dependent cell dissociation from the monolayer and AJC disassembly. To our knowledge, this is the first evidence that beta-tubulin cofactor D plays a role in cells independent of its presumed role in folding tubulin heterodimers. We conclude that ARL2 and beta-tubulin cofactor D participate in AJC disassembly and epithelial depolarization.
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Affiliation(s)
- Tamar Shultz
- Department of Pharmacology, School of Pharmacy, Faculty of Medicine, Hebrew University of Jerusalem, Israel
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Tang VW. Proteomic and bioinformatic analysis of epithelial tight junction reveals an unexpected cluster of synaptic molecules. Biol Direct 2006; 1:37. [PMID: 17156438 PMCID: PMC1712231 DOI: 10.1186/1745-6150-1-37] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Accepted: 12/08/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Zonula occludens, also known as the tight junction, is a specialized cell-cell interaction characterized by membrane "kisses" between epithelial cells. A cytoplasmic plaque of approximately 100 nm corresponding to a meshwork of densely packed proteins underlies the tight junction membrane domain. Due to its enormous size and difficulties in obtaining a biochemically pure fraction, the molecular composition of the tight junction remains largely unknown. RESULTS A novel biochemical purification protocol has been developed to isolate tight junction protein complexes from cultured human epithelial cells. After identification of proteins by mass spectroscopy and fingerprint analysis, candidate proteins are scored and assessed individually. A simple algorithm has been devised to incorporate transmembrane domains and protein modification sites for scoring membrane proteins. Using this new scoring system, a total of 912 proteins have been identified. These 912 hits are analyzed using a bioinformatics approach to bin the hits in 4 categories: configuration, molecular function, cellular function, and specialized process. Prominent clusters of proteins related to the cytoskeleton, cell adhesion, and vesicular traffic have been identified. Weaker clusters of proteins associated with cell growth, cell migration, translation, and transcription are also found. However, the strongest clusters belong to synaptic proteins and signaling molecules. Localization studies of key components of synaptic transmission have confirmed the presence of both presynaptic and postsynaptic proteins at the tight junction domain. To correlate proteomics data with structure, the tight junction has been examined using electron microscopy. This has revealed many novel structures including end-on cytoskeletal attachments, vesicles fusing/budding at the tight junction membrane domain, secreted substances encased between the tight junction kisses, endocytosis of tight junction double membranes, satellite Golgi apparatus and associated vesicular structures. A working model of the tight junction consisting of multiple functions and sub-domains has been generated using the proteomics and structural data. CONCLUSION This study provides an unbiased proteomics and bioinformatics approach to elucidate novel functions of the tight junction. The approach has revealed an unexpected cluster associating with synaptic function. This surprising finding suggests that the tight junction may be a novel epithelial synapse for cell-cell communication. REVIEWERS This article was reviewed by Gáspár Jékely, Etienne Joly and Neil Smalheiser.
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Affiliation(s)
- Vivian W Tang
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
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Shultz T, Nash-Livni N, Shmuel M, Altschuler Y. EFA6 regulates endosomal trafficking and affects early endosomes in polarized MDCK cells. Biochem Biophys Res Commun 2006; 351:106-12. [PMID: 17054918 DOI: 10.1016/j.bbrc.2006.10.024] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2006] [Accepted: 10/03/2006] [Indexed: 12/21/2022]
Abstract
The small-GTPase family of ADP ribosylation factors (ARFs) recruit coat proteins to promote vesicle budding. ARFs are activated by an association with sec7-containing exchange factors which load them with GTP. In epithelial cells, the small GTPase ARF6 operates within the endocytic system and has been shown to associate with ARNO to promote apical endocytosis and early to late endosomal trafficking. EFA6 has been shown to stimulate tight-junction formation and maintenance. Here, we show that in polarized epithelial MDCK cells, EFA6 is localized to early endosomes, causes their dramatic enlargement, and promotes basolateral targeting of IgA, which is normally targeted to the apical PM. These results suggest that the physiological function of ARF6 within the endocytic system is regulated by the exchange factor it associates with.
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Affiliation(s)
- Tamar Shultz
- Department of Pharmacology, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
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Hiroi T, Someya A, Thompson W, Moss J, Vaughan M. GEP100/BRAG2: activator of ADP-ribosylation factor 6 for regulation of cell adhesion and actin cytoskeleton via E-cadherin and alpha-catenin. Proc Natl Acad Sci U S A 2006; 103:10672-7. [PMID: 16807291 PMCID: PMC1502290 DOI: 10.1073/pnas.0604091103] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
GEP(100) (p100) was identified as an ADP-ribosylation factor (ARF) guanine nucleotide-exchange protein (GEP) that partially colocalized with ARF6 in the cell periphery. p100 preferentially accelerated guanosine 5[gamma-thio]triphosphate (GTPgammaS) binding by ARF6, which participates in protein trafficking near the plasma membrane, including receptor recycling, cell adhesion, and cell migration. Here we report that yeast two-hybrid screening of a human fetal brain cDNA library using p100 as bait revealed specific interaction with alpha-catenin, which is known as a regulator of adherens junctions and actin cytoskeleton remodeling. Interaction of p100 with alpha-catenin was confirmed by coimmunoprecipitation of the endogenous proteins from human HepG2 or CaSki cells, although colocalization was difficult to demonstrate microscopically. alpha-Catenin enhanced GTPgammaS binding by ARF6 in vitro in the presence of p100. Depletion of p100 by small interfering RNA (siRNA) treatment in HepG2 cells resulted in E-cadherin content 3-fold that in control cells and blocked hepatocyte growth factor-induced redistribution of E-cadherin, consistent with a known role of ARF6 in this process. F-actin was markedly decreased in normal rat kidney (NRK) cells overexpressing wild-type p100, but not its GEP-inactive mutants, also consistent with the conclusion that p100 has an important role in the activation of ARF6 for its functions in both E-cadherin recycling and actin remodeling.
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Affiliation(s)
- Toyoko Hiroi
- Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
- *To whom correspondence may be addressed at:
Building 10, Room 5N307, MSC 1434, National Institutes of Health, Bethesda, MD 20892. E-mail:
or
| | - Akimasa Someya
- Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Walter Thompson
- Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Joel Moss
- Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Martha Vaughan
- Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
- *To whom correspondence may be addressed at:
Building 10, Room 5N307, MSC 1434, National Institutes of Health, Bethesda, MD 20892. E-mail:
or
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Mazaki Y, Hashimoto S, Tsujimura T, Morishige M, Hashimoto A, Aritake K, Yamada A, Nam JM, Kiyonari H, Nakao K, Sabe H. Neutrophil direction sensing and superoxide production linked by the GTPase-activating protein GIT2. Nat Immunol 2006; 7:724-31. [PMID: 16715100 DOI: 10.1038/ni1349] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2005] [Accepted: 04/24/2006] [Indexed: 11/09/2022]
Abstract
In neutrophils, superoxide anion production generally accompanies chemotaxis and functions in killing invading pathogens. The GIT2 GTPase-activating protein binds to the guanine nucleotide-exchange factor alphaPIX. Here we show that GIT2 was necessary for directional chemotaxis and for the suppression of superoxide production in G protein-coupled receptor-stimulated neutrophils. GIT2 was also necessary for the orientation of superoxide production toward chemoattractant sources. GIT2 suppressed the activity of ADP ribosylation factor 1 and was a component of the Gbetagamma subunit-mediated direction-sensing machinery 'downstream' of G protein-coupled receptor signaling. This study establishes a function for GIT2 in linking chemotaxis and superoxide production in neutrophils and shows that loss of GIT2 in vivo leads to an immunodeficient state.
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Affiliation(s)
- Yuichi Mazaki
- Department of Molecular Biology, Osaka Bioscience Institute, Suita 565-0874, Japan
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Li M, Ng SSM, Wang J, Lai L, Leung SY, Franco M, Peng Y, He ML, Kung HF, Lin MCM. EFA6A enhances glioma cell invasion through ADP ribosylation factor 6/extracellular signal-regulated kinase signaling. Cancer Res 2006; 66:1583-90. [PMID: 16452216 DOI: 10.1158/0008-5472.can-05-2424] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
EFA6A, or Pleckstrin and Sec7 domain protein, is a member of guanine nucleotide exchange factors for ADP ribosylation factor 6 (ARF6). Whereas EFA6A is specifically expressed in the brain, little is known about its function in glial cells or glioma. Here we show that elevated EFA6A expression is detectable in both low-grade and high-grade human glioma tissues samples. To investigate the role of EFA6A in glioma carcinogenesis, we generated a human glioblastoma cell line which conditionally overexpresses EFA6A (U373-EFA6A). We showed that overexpression of EFA6A had no effect on cell proliferation, apoptosis, or cell cycle control. However, as shown by wound healing and in vitro cell invasion assays, it significantly enhanced the cell motility and invasiveness whereas silencing EFA6A by its dominant negative mutant EFA6A(E242K) produced opposite effects. We further showed that ARF6/extracellular signal-regulated kinase (ERK) signaling is required for the EFA6A-mediated cell invasion because both EFA6A(E242K) and ARF6 dominant negative mutant ARF6(T27N) markedly reduced the phosphorylated ERK level and EFA6A-mediated invasive capacity. Consistently, mitogen-activated protein kinase/ERK kinase inhibitor U0126 could abolish the EFA6A-induced cell invasion. These results suggest for the first time a potential role of EFA6A/ARF6/ERK signal cascade in glioma cell migration and invasion.
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Affiliation(s)
- Ming Li
- Department of Chemistry, Open Laboratory of Chemical Biology, Institute of Molecular Technology for Drug Discovery and Synthesis, University of Hong Kong, Pokfulam Road, Hong Kong, China
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Shmuel M, Santy LC, Frank S, Avrahami D, Casanova JE, Altschuler Y. ARNO through its coiled-coil domain regulates endocytosis at the apical surface of polarized epithelial cells. J Biol Chem 2006; 281:13300-13308. [PMID: 16484220 DOI: 10.1074/jbc.m513723200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
ARNO is a guanine-nucleotide exchange protein for the ARF family of GTPases. Here we show that in polarized epithelial cells, ARNO is localized exclusively to the apical plasma membrane, where it regulates endocytosis. Expression of ARNO stimulates apical endocytosis of the polymeric immunoglobulin receptor, and coexpression of ARF6 with ARNO leads to a synergistic stimulation of apical endocytosis. Expression of a dominant negative ARF6 mutant, ARF6-T27N, antagonizes this stimulatory effect. Deletion of the N-terminal coiled-coil (CC) domain of ARNO causes the mutant ARNO to localize to both the apical and basolateral plasma membranes. Expression of the CC domain alone abolishes ARNO-induced apical endocytosis as well as co-localization of IgA-receptor complexes with ARNO and clathrin. These results suggest that the CC domain contributes to the specificity of apical localization of ARNO through association with components of the apical plasma membrane. We conclude that ARNO acts together with ARF6 to regulate apical endocytosis.
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Affiliation(s)
- Miriam Shmuel
- Department of Pharmacology, School of Pharmacy, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Lorraine C Santy
- Department of Pharmacology, School of Pharmacy, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Scott Frank
- Department of Pharmacology, School of Pharmacy, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Dana Avrahami
- Department of Pharmacology, School of Pharmacy, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - James E Casanova
- Department of Cell Biology, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908
| | - Yoram Altschuler
- Department of Pharmacology, School of Pharmacy, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem 91120, Israel.
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Tong Q, Vassilieva EV, Ivanov AI, Wang Z, Brown GT, Parkos CA, Nusrat A. Interferon-gamma inhibits T84 epithelial cell migration by redirecting transcytosis of beta1 integrin from the migrating leading edge. THE JOURNAL OF IMMUNOLOGY 2005; 175:4030-8. [PMID: 16148152 DOI: 10.4049/jimmunol.175.6.4030] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Intestinal inflammation is associated with epithelial damage and formation of mucosal wounds. Epithelial cells migration is required for wound closure. In inflammatory status, migrating epithelial cells are exposed to proinflammatory cytokines such as IFN-gamma. However, influence of such cytokines on intestinal epithelial wound closure remains unknown. The present study was designed to investigate the effect of IFN-gamma on migration of model T84 intestinal epithelial cells and recovery of epithelial wounds. IFN-gamma significantly inhibited rate of T84 cell migration and closure of epithelial wounds. This effect was accompanied by the formation of large aberrant lamellipodia at the leading edge as well as significant decrease in the number of beta(1) integrin containing focal adhesions. IFN-gamma exposure increased endocytosis of beta(1) integrin and shifted its accumulation from early/recycling endosomes at the leading edge to a yet unidentified compartment at the cell base. This redirection in beta(1) integrin transcytosis was inhibited by depolymerization of microtubules with nocodazole and was unaffected by stabilization of microtubules with docetaxel. These results suggest that IFN-gamma attenuates epithelial wound closure by microtubule-dependent redirection of beta(1) integrin transcytosis from the leading edge of migrating cells thereby inhibiting adequate turnover of focal adhesion complexes and cell migration.
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Affiliation(s)
- Qiao Tong
- Epithelial Pathology Research Unit, Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA 30322, USA
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Matsuya S, Sakagami H, Tohgo A, Owada Y, Shin HW, Takeshima H, Nakayama K, Kokubun S, Kondo H. Cellular and subcellular localization of EFA6C, a third member of the EFA6 family, in adult mouse Purkinje cells. J Neurochem 2005; 93:674-85. [PMID: 15836626 DOI: 10.1111/j.1471-4159.2005.03072.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
EFA6C is a third member of the EFA6 family of guanine nucleotide exchange factors (GEFs) for ADP-ribosylation factor 6 (ARF6). In this study, we first demonstrated that EFA6C indeed activated ARF6 more selectively than ARF1 by ARF pull-down assay. In situ hybridization histochemistry revealed that EFA6C mRNA was expressed predominantly in mature Purkinje cells and the epithelial cells of the choroid plexus in contrast to the ubiquitous expression of ARF6 mRNA throughout the brain. EFA6C mRNA was already detectable in the Purkinje cells at embryonic day 13, increased progressively during post-natal development and peaked during post-natal second week. In Purkinje cells, the immunoreactivity for EFA6C was localized particularly in the post-synaptic density as well as the plasma membranes of the cell somata, dendritic shafts and spines, while the immunoreactivity in their axon terminals in the deep cerebellar nuclei was very faint. These findings suggest that EFA6C may be involved in the regulation of the membrane dynamics of the somatodendritic compartments of Purkinje cells through the activation of ARF6.
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Affiliation(s)
- Shigetsune Matsuya
- Division of Histology, Department of Cell Biology, Tohoku University Graduate School of Medicine, Sendai, Japan
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Decressac S, Franco M, Bendahhou S, Warth R, Knauer S, Barhanin J, Lazdunski M, Lesage F. ARF6-dependent interaction of the TWIK1 K+ channel with EFA6, a GDP/GTP exchange factor for ARF6. EMBO Rep 2005; 5:1171-5. [PMID: 15540117 PMCID: PMC1299187 DOI: 10.1038/sj.embor.7400292] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2004] [Revised: 09/17/2004] [Accepted: 10/13/2004] [Indexed: 11/09/2022] Open
Abstract
TWIK1 belongs to a family of K(+) channels involved in neuronal excitability and cell volume regulation. Its tissue distribution suggests a role in epithelial potassium transport. Here we show that TWIK1 is expressed in a subapical compartment in renal proximal tubules and in polarized MDCK cells. In nonpolarized cells, this compartment corresponds to pericentriolar recycling endosomes. We identified EFA6, an exchange factor for the small G protein ADP-ribosylation factor 6 (ARF6), as a protein binding to TWIK1. EFA6 interacts with TWIK1 only when it is bound to ARF6. Because ARF6 modulates endocytosis at the apical surface of epithelial cells, the ARF6/EFA6/TWIK1 association is probably important for channel internalization and recycling.
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Affiliation(s)
- Sonia Decressac
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097/UNSA, Institut Paul Hamel, 660, route des lucioles, 06560 Valbonne, France
| | - Michel Franco
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097/UNSA, Institut Paul Hamel, 660, route des lucioles, 06560 Valbonne, France
| | - Said Bendahhou
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097/UNSA, Institut Paul Hamel, 660, route des lucioles, 06560 Valbonne, France
| | - Richard Warth
- Institute of Physiology, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Sebastian Knauer
- Institute of Physiology, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Jacques Barhanin
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097/UNSA, Institut Paul Hamel, 660, route des lucioles, 06560 Valbonne, France
| | - Michel Lazdunski
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097/UNSA, Institut Paul Hamel, 660, route des lucioles, 06560 Valbonne, France
- Tel: +33 4 93 95 77 01; Fax: 33 4 93 95 77 04; E-mail:
| | - Florian Lesage
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097/UNSA, Institut Paul Hamel, 660, route des lucioles, 06560 Valbonne, France
- Service de Neurologie, Hôpital Pasteur, Centre Hospitalo-Universitaire de Nice, 30, avenue de la voie romaine, BP 69, 06002 Nice cedex 01, France
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Luton F. The role of EFA6, exchange factor for Arf6, for tight junction assembly, functions, and interaction with the actin cytoskeleton. Methods Enzymol 2005; 404:332-45. [PMID: 16413280 DOI: 10.1016/s0076-6879(05)04029-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In polarized epithelial cells, the tight junction has been ascribed several functions including the regulation of the paracellular permeability, an impediment to the diffusion of molecules between the apical and basolateral domains, a site of delivery of transport vesicles for basolateral proteins, and a scaffold for structural and signaling molecules. The tight junction is anchored physically into the apical actin cytoskeleton circumscribing the cell, which is known as the perijunctional actomyosin ring. This connection was first suggested by experiments using the actin depolymerizing drug cytochalasin, which was also found to disrupt the transepithelial permeability. Since then a large number of studies have reported the effects of drugs, molecular tools, or physiological and pathological conditions that alter coordinately actin organization and the tight junction. In support of this model, proteins of the tight junction, such as the members of the ZO family and occludin, have been shown to bind to actin. However, very little is known regarding the molecular mechanisms by which the actin cytoskeleton modulates tight junction functions. We have studied the role of the Exchange Factor for Arf6, EFA6, in tight junction assembly. By combining a large panel of methods, including morphological, physiological, and biochemical, described in detail hereafter we demonstrated that EFA6 plays a role in the physical association of the tight junction to the perijunctional actomyosin ring.
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Affiliation(s)
- Frédéric Luton
- Institut de Pharmacologie, Moléculaire et Cellulaire, CNRS, Valbonne Sophia-Antipolis, France
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