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Gasilina A, Yoon HY, Jian X, Luo R, Randazzo PA. A lysine-rich cluster in the N-BAR domain of ARF GTPase-activating protein ASAP1 is necessary for binding and bundling actin filaments. J Biol Chem 2022; 298:101700. [PMID: 35143843 PMCID: PMC8902617 DOI: 10.1016/j.jbc.2022.101700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 01/25/2022] [Accepted: 01/28/2022] [Indexed: 12/05/2022] Open
Abstract
Actin filament maintenance is critical for both normal cell homeostasis and events associated with malignant transformation. The ADP-ribosylation factor GTPase-activating protein ASAP1 regulates the dynamics of filamentous actin-based structures, including stress fibers, focal adhesions, and circular dorsal ruffles. Here, we have examined the molecular basis for ASAP1 association with actin. Using a combination of structural modeling, mutagenesis, and in vitro and cell-based assays, we identify a putative-binding interface between the N-Bin-Amphiphysin-Rvs (BAR) domain of ASAP1 and actin filaments. We found that neutralization of charges and charge reversal at positions 75, 76, and 79 of ASAP1 reduced the binding of ASAP1 BAR-pleckstrin homology tandem to actin filaments and abrogated actin bundle formation in vitro. In addition, overexpression of actin-binding defective ASAP1 BAR-pleckstrin homology [K75, K76, K79] mutants prevented cellular actin remodeling in U2OS cells. Exogenous expression of [K75E, K76E, K79E] mutant of full-length ASAP1 did not rescue the reduction of cellular actin fibers consequent to knockdown of endogenous ASAP1. Taken together, our results support the hypothesis that the lysine-rich cluster in the N-BAR domain of ASAP1 is important for regulating actin filament organization.
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Affiliation(s)
- Anjelika Gasilina
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA; Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, District of Columbia, USA
| | - Hye-Young Yoon
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Ruibai Luo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.
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2
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Cross-Kingdom Activation of Vibrio Toxins by ADP-Ribosylation Factor Family GTPases. J Bacteriol 2020; 202:JB.00278-20. [PMID: 32900828 DOI: 10.1128/jb.00278-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pathogenic Vibrio species use many different approaches to subvert, attack, and undermine the host response. The toxins they produce are often responsible for the devastating effects associated with their diseases. These toxins target a variety of host proteins, which leads to deleterious effects, including dissolution of cell organelle integrity and inhibition of protein secretion. Becoming increasingly prevalent as cofactors for Vibrio toxins are proteins of the small GTPase families. ADP-ribosylation factor small GTPases (ARFs) in particular are emerging as a common host cofactor necessary for full activation of Vibrio toxins. While ARFs are not the direct target of Vibrio cholerae cholera toxin (CT), ARF binding is required for its optimal activity as an ADP-ribosyltransferase. The makes caterpillars floppy (MCF)-like and the domain X (DmX) effectors of the Vibrio vulnificus multifunctional autoprocessing repeats-in-toxin (MARTX) toxin also both require ARFs to initiate autoprocessing and activation as independent effectors. ARFs are ubiquitously expressed in eukaryotes and are key regulators of many cellular processes, and as such they are ideal cofactors for Vibrio pathogens that infect many host species. In this review, we cover in detail the known Vibrio toxins that use ARFs as cross-kingdom activators to both stimulate and optimize their activity. We further discuss how these contrast to toxins and effectors from other bacterial species that coactivate, stimulate, or directly modify host ARFs as their mechanisms of action.
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Kotelevets L, Chastre E. Rac1 Signaling: From Intestinal Homeostasis to Colorectal Cancer Metastasis. Cancers (Basel) 2020; 12:cancers12030665. [PMID: 32178475 PMCID: PMC7140047 DOI: 10.3390/cancers12030665] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 03/06/2020] [Accepted: 03/08/2020] [Indexed: 12/14/2022] Open
Abstract
The small GTPase Rac1 has been implicated in a variety of dynamic cell biological processes, including cell proliferation, cell survival, cell-cell contacts, epithelial mesenchymal transition (EMT), cell motility, and invasiveness. These processes are orchestrated through the fine tuning of Rac1 activity by upstream cell surface receptors and effectors that regulate the cycling Rac1-GDP (off state)/Rac1-GTP (on state), but also through the tuning of Rac1 accumulation, activity, and subcellular localization by post translational modifications or recruitment into molecular scaffolds. Another level of regulation involves Rac1 transcripts stability and splicing. Downstream, Rac1 initiates a series of signaling networks, including regulatory complex of actin cytoskeleton remodeling, activation of protein kinases (PAKs, MAPKs) and transcription factors (NFkB, Wnt/β-catenin/TCF, STAT3, Snail), production of reactive oxygen species (NADPH oxidase holoenzymes, mitochondrial ROS). Thus, this GTPase, its regulators, and effector systems might be involved at different steps of the neoplastic progression from dysplasia to the metastatic cascade. After briefly placing Rac1 and its effector systems in the more general context of intestinal homeostasis and in wound healing after intestinal injury, the present review mainly focuses on the several levels of Rac1 signaling pathway dysregulation in colorectal carcinogenesis, their biological significance, and their clinical impact.
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Affiliation(s)
- Larissa Kotelevets
- Institut National de la Santé et de la Recherche Médicale, UMR S 938, Centre de Recherche Saint-Antoine, 75012 Paris, France
- Sorbonne Université, Hôpital Saint-Antoine, Site Bâtiment Kourilsky, 75012 Paris, France
- Correspondence: (L.K.); (E.C.)
| | - Eric Chastre
- Institut National de la Santé et de la Recherche Médicale, UMR S 938, Centre de Recherche Saint-Antoine, 75012 Paris, France
- Sorbonne Université, Hôpital Saint-Antoine, Site Bâtiment Kourilsky, 75012 Paris, France
- Correspondence: (L.K.); (E.C.)
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4
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Li B, Li Y, Wang Q, Li F, Li F. Corosolic acid impairs human lung adenocarcinoma A549 cells proliferation by inhibiting cell migration. Oncol Lett 2019; 17:5747-5753. [PMID: 31186800 DOI: 10.3892/ol.2019.10262] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 01/15/2019] [Indexed: 12/11/2022] Open
Abstract
The present study aimed to investigate the anticancer effects of corosolic acid (CA) in the human lung adenocarcinoma A549 cell line. A549 cells were treated with increasing concentrations of CA, prior to assessing cell viability, migration rate, vascular endothelial growth factor receptor 2 (VEGFR2) kinase activity and cytoskeleton structure. In addition, in vivo imaging system was used to analyze the anticancer effects of CA in vivo. Results demonstrated that CA exhibited a low cytotoxicity with a half maximal inhibitory concentration of 65 µM. In addition, 4 µM CA efficiently inhibited A549 cell migration. Furthermore, CA inhibited VEGFR2 kinase activity and disrupted tubulin structure. Data also revealed that CA inhibited A549 cell proliferation in a xenograft mouse model. In conclusion, results from the present study suggested that CA may be used as a novel potential therapy for lung cancer.
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Affiliation(s)
- Biao Li
- Department of Thoracic Surgery, The Second Affiliated Hospital of Hainan Medical University, Haikou, Hainan 570311, P.R. China
| | - Yongjie Li
- Department of Thoracic Surgery, The Second Affiliated Hospital of Hainan Medical University, Haikou, Hainan 570311, P.R. China
| | - Qiongyu Wang
- Department of Thoracic Surgery, The Second Affiliated Hospital of Hainan Medical University, Haikou, Hainan 570311, P.R. China
| | - Fan Li
- Department of Thoracic Surgery, The Second Affiliated Hospital of Hainan Medical University, Haikou, Hainan 570311, P.R. China
| | - Fu Li
- Department of Thoracic Surgery, The Second Affiliated Hospital of Hainan Medical University, Haikou, Hainan 570311, P.R. China
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Judith D, Jefferies HBJ, Boeing S, Frith D, Snijders AP, Tooze SA. ATG9A shapes the forming autophagosome through Arfaptin 2 and phosphatidylinositol 4-kinase IIIβ. J Cell Biol 2019; 218:1634-1652. [PMID: 30917996 PMCID: PMC6504893 DOI: 10.1083/jcb.201901115] [Citation(s) in RCA: 118] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 02/28/2019] [Accepted: 03/14/2019] [Indexed: 12/24/2022] Open
Abstract
ATG9A is a multispanning membrane protein essential for autophagy. Normally resident in Golgi membranes and endosomes, during amino acid starvation, ATG9A traffics to sites of autophagosome formation. ATG9A is not incorporated into autophagosomes but is proposed to supply so-far-unidentified proteins and lipids to the autophagosome. To address this function of ATG9A, a quantitative analysis of ATG9A-positive compartments immunoisolated from amino acid-starved cells was performed. These ATG9A vesicles are depleted of Golgi proteins and enriched in BAR-domain containing proteins, Arfaptins, and phosphoinositide-metabolizing enzymes. Arfaptin2 regulates the starvation-dependent distribution of ATG9A vesicles, and these ATG9A vesicles deliver the PI4-kinase, PI4KIIIβ, to the autophagosome initiation site. PI4KIIIβ interacts with ATG9A and ATG13 to control PI4P production at the initiation membrane site and the autophagic response. PI4KIIIβ and PI4P likely function by recruiting the ULK1/2 initiation kinase complex subunit ATG13 to nascent autophagosomes.
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Affiliation(s)
- Delphine Judith
- Molecular Cell Biology of Autophagy, The Francis Crick Institute, London, UK
| | | | - Stefan Boeing
- Bioinformatics and Biostatistics, The Francis Crick Institute, London, UK
| | - David Frith
- Proteomics, The Francis Crick Institute, London, UK
| | | | - Sharon A Tooze
- Molecular Cell Biology of Autophagy, The Francis Crick Institute, London, UK
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Spatiotemporal Control of Lipid Conversion, Actin-Based Mechanical Forces, and Curvature Sensors during Clathrin/AP-1-Coated Vesicle Biogenesis. Cell Rep 2018; 20:2087-2099. [PMID: 28854360 DOI: 10.1016/j.celrep.2017.08.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 06/29/2017] [Accepted: 07/31/2017] [Indexed: 01/03/2023] Open
Abstract
Clathrin/adaptor protein-1-coated carriers connect the secretory and the endocytic pathways. Carrier biogenesis relies on distinct protein networks changing membrane shape at the trans-Golgi network, each regulating coat assembly, F-actin-based mechanical forces, or the biophysical properties of lipid bilayers. How these different hubs are spatiotemporally coordinated remains largely unknown. Using in vitro reconstitution systems, quantitative proteomics, and lipidomics, as well as in vivo cell-based assays, we characterize the protein networks controlling membrane lipid composition, membrane shape, and carrier scission. These include PIP5K1A and phospholipase C-beta 3 controlling the conversion of PI[4]P into diacylglycerol. PIP5K1A binding to RAC1 provides a link to F-actin-based mechanical forces needed to tubulate membranes. Tubular membranes then recruit the BAR-domain-containing arfaptin-1/2 guiding carrier scission. These findings provide a framework for synchronizing the chemical/biophysical properties of lipid bilayers, F-actin-based mechanical forces, and the activity of proteins sensing membrane shape during clathrin/adaptor protein-1-coated carrier biogenesis.
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7
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Salzer U, Kostan J, Djinović-Carugo K. Deciphering the BAR code of membrane modulators. Cell Mol Life Sci 2017; 74:2413-2438. [PMID: 28243699 PMCID: PMC5487894 DOI: 10.1007/s00018-017-2478-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 01/25/2017] [Accepted: 01/27/2017] [Indexed: 01/06/2023]
Abstract
The BAR domain is the eponymous domain of the “BAR-domain protein superfamily”, a large and diverse set of mostly multi-domain proteins that play eminent roles at the membrane cytoskeleton interface. BAR domain homodimers are the functional units that peripherally associate with lipid membranes and are involved in membrane sculpting activities. Differences in their intrinsic curvatures and lipid-binding properties account for a large variety in membrane modulating properties. Membrane activities of BAR domains are further modified and regulated by intramolecular or inter-subunit domains, by intermolecular protein interactions, and by posttranslational modifications. Rather than providing detailed cell biological information on single members of this superfamily, this review focuses on biochemical, biophysical, and structural aspects and on recent findings that paradigmatically promote our understanding of processes driven and modulated by BAR domains.
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Affiliation(s)
- Ulrich Salzer
- Max F. Perutz Laboratories, Department of Medical Biochemistry, Medical University of Vienna, Dr. Bohr-Gasse 9, 1030, Vienna, Austria
| | - Julius Kostan
- Max F. Perutz Laboratories, Department of Structural and Computational Biology, University of Vienna, Campus Vienna Biocenter 5, 1030, Vienna, Austria
| | - Kristina Djinović-Carugo
- Max F. Perutz Laboratories, Department of Structural and Computational Biology, University of Vienna, Campus Vienna Biocenter 5, 1030, Vienna, Austria.
- Department of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 119, 1000, Ljubljana, Slovenia.
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Higgins AM, Banik BL, Brown JL. Geometry sensing through POR1 regulates Rac1 activity controlling early osteoblast differentiation in response to nanofiber diameter. Integr Biol (Camb) 2015; 7:229-36. [PMID: 25539497 DOI: 10.1039/c4ib00225c] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Bone grafting procedures in the United States rely heavily upon autografts and allografts, which are donor-dependent, cause donor site pain, and can transmit disease. Synthetic bone grafts can reduce these risks; however, synthetics lack the bone differentiating (osteoinductive) abilities of auto- and allografts. Achieving innate osteoinductive properties of synthetics through surface modifications is currently under investigation. This study focuses on nanofibers, with emphasis on how fiber diameter and the potential curvature sensor POR1 affect the activation of the signaling molecules Rac1 and Arf1, and leading to expression of alkaline phosphatase (ALP), an osteoinductive marker. Diameters of 0.1, 0.3, and 1.0 μm were compared against a flat control. The highest level of Rac1 activation was achieved on the smallest fibers (0.1 μm), a trend that was lost in POR1 knockdowns. This supports the hypothesis that on small nanofibers, POR1 favorably binds to highly curved cell membranes, which allows Rac1 to subsequently dissociate and activate. When the curvature is insufficient to bind POR1, POR1 binds to inactive Rac1 and competitively inhibits its activation. Arf1 activation followed an opposite trend, with the largest nanofibers exhibiting the highest activity. This trend reinforces the known interaction between Rac1 and Arf1 through the GIT-PIX complex, an Arf1 GAP and Rac1 GEF, respectively. Large, (1.0 μm), nanofibers demonstrated the highest ALP activity, indicating that ALP expression is inversely dependent on Rac1 activation. Knockdown of POR1 resulted in increased ALP activity across the substrates but without regard to the curvature sensing trend seen previously. Thus, POR1 senses curvature and increases Rac1 activity, which negatively regulates bone differentiation.
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Affiliation(s)
- A M Higgins
- Department of Biomedical Engineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, USA.
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9
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Eiseler T, Wille C, Koehler C, Illing A, Seufferlein T. Protein Kinase D2 Assembles a Multiprotein Complex at the Trans-Golgi Network to Regulate Matrix Metalloproteinase Secretion. J Biol Chem 2015; 291:462-77. [PMID: 26507660 DOI: 10.1074/jbc.m115.673582] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Indexed: 11/06/2022] Open
Abstract
Vesicle formation and fission are tightly regulated at the trans-Golgi network (TGN) during constitutive secretion. Two major protein families regulate these processes: members of the adenosyl-ribosylation factor family of small G-proteins (ARFs) and the protein kinase D (PKD) family of serine/threonine kinases. The functional relationship between these two key regulators of protein transport from the TGN so far is elusive. We here demonstrate the assembly of a novel functional protein complex at the TGN and its key members: cytosolic PKD2 binds ARF-like GTPase (ARL1) and shuttles ARL1 to the TGN. ARL1, in turn, localizes Arfaptin2 to the TGN. At the TGN, where PKD2 interacts with active ARF1, PKD2, and ARL1 are required for the assembly of a complex comprising of ARF1 and Arfaptin2 leading to secretion of matrix metalloproteinase-2 and -7. In conclusion, our data indicate that PKD2 is a core factor in the formation of this multiprotein complex at the TGN that controls constitutive secretion of matrix metalloproteinase cargo.
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Affiliation(s)
- Tim Eiseler
- From the Department of Internal Medicine I, Ulm University, Albert Einstein Allee 23, D-89081 Ulm, Germany and
| | - Christoph Wille
- From the Department of Internal Medicine I, Ulm University, Albert Einstein Allee 23, D-89081 Ulm, Germany and
| | - Conny Koehler
- the Department of Internal Medicine I, Martin-Luther University Halle-Wittenberg, Ernst-Grube, Strasse 40, D-06120 Halle (Saale), Germany
| | - Anett Illing
- From the Department of Internal Medicine I, Ulm University, Albert Einstein Allee 23, D-89081 Ulm, Germany and
| | - Thomas Seufferlein
- From the Department of Internal Medicine I, Ulm University, Albert Einstein Allee 23, D-89081 Ulm, Germany and
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10
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Abstract
Protein Interacting with C Kinase 1 (PICK1) is a Bin/Amphiphysin/Rvs (BAR) domain protein involved in AMPA receptor trafficking. Here, we identify a selective role for PICK1 in the biogenesis of large, dense core vesicles (LDCVs) in mouse chromaffin cells. PICK1 colocalized with syntaxin-6, a marker for immature granules. In chromaffin cells isolated from a PICK1 knockout (KO) mouse the amount of exocytosis was reduced, while release kinetics and Ca(2+) sensitivity were unaffected. Vesicle-fusion events had a reduced frequency and released lower amounts of transmitter per vesicle (i.e., reduced quantal size). This was paralleled by a reduction in the mean single-vesicle capacitance, estimated by averaging time-locked capacitance traces. EM confirmed that LDCVs were fewer and of markedly reduced size in the PICK1 KO, demonstrating that all phenotypes can be explained by reductions in vesicle number and size, whereas the fusion competence of generated vesicles was unaffected by the absence of PICK1. Viral rescue experiments demonstrated that long-term re-expression of PICK1 is necessary to restore normal vesicular content and secretion, while short-term overexpression is ineffective, consistent with an upstream role for PICK1. Disrupting lipid binding of the BAR domain (2K-E mutation) or of the PDZ domain (CC-GG mutation) was sufficient to reproduce the secretion phenotype of the null mutant. The same mutations are known to eliminate PICK1 function in receptor trafficking, indicating that the multiple functions of PICK1 involve a conserved mechanism. Summarized, our findings demonstrate that PICK1 functions in vesicle biogenesis and is necessary to maintain normal vesicle numbers and size.
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Abstract
Secretory granule biogenesis is a pivotal process for regulated release of hormones and neurotransmitters. A prominent example is the pancreatic β cell that secretes insulin, a major anabolic hormone controlling cellular metabolism upon nutrient availability. We recently described a checkpoint mechanism that halts scission of nascent secretory granules at the trans-Golgi network (TGN) until complete loading of insulin is achieved. We demonstrated that the Bin/Amphiphysin/Rvs (BAR) domain-containing protein Arfaptin-1 prevents granule scission until it is phosphorylated by Protein Kinase D (PKD). Arfaptin-1 phosphorylation releases its binding to ADP-rybosylation factor (ARF) allowing scission to occur. Lack of this control mechanism in β cells resulted in premature scission, generation of dysfunctional insulin granules and impaired regulated insulin secretion without affecting constitutive release of other transport carriers. Here we discuss two important questions related to this work: How might completion of granule loading be sensed by PKD, and how does Arfaptin-1 specifically regulate insulin granule formation in beta cells?
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Affiliation(s)
- Helmuth Gehart
- IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire); INSERM; CNRS; Université de Strasbourg; Illkirch, France ; Institute of Cell Biology; ETH Zurich; Zurich, Switzerland
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12
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Chang L, Kreko T, Davison H, Cusmano T, Wu Y, Rothenfluh A, Eaton BA. Normal dynactin complex function during synapse growth in Drosophila requires membrane binding by Arfaptin. Mol Biol Cell 2013; 24:1749-64, S1-5. [PMID: 23596322 PMCID: PMC3667727 DOI: 10.1091/mbc.e12-09-0697] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 04/04/2013] [Accepted: 04/08/2013] [Indexed: 01/11/2023] Open
Abstract
Mutations in DCTN1, a component of the dynactin complex, are linked to neurodegenerative diseases characterized by a broad collection of neuropathologies. Because of the pleiotropic nature of dynactin complex function within the neuron, defining the causes of neuropathology in DCTN1 mutants has been difficult. We combined a genetic screen with cellular assays of dynactin complex function to identify genes that are critical for dynactin complex function in the nervous system. This approach identified the Drosophila homologue of Arfaptin, a multifunctional protein that has been implicated in membrane trafficking. We find that Arfaptin and the Drosophila DCTN1 homologue, Glued, function in the same pathway during synapse growth but not during axonal transport or synapse stabilization. Arfaptin physically associates with Glued and other dynactin complex components in the nervous system of both flies and mice and colocalizes with Glued at the Golgi in motor neurons. Mechanistically, membrane binding by Arfaptin mediates membrane association of the dynactin complex in motor neurons and is required for normal synapse growth. Arfaptin represents a novel dynactin complex-binding protein that specifies dynactin complex function during synapse growth.
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Affiliation(s)
- Leo Chang
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Tabita Kreko
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Holly Davison
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Tim Cusmano
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Yimin Wu
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Adrian Rothenfluh
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Benjamin A. Eaton
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
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Cruz-Garcia D, Ortega-Bellido M, Scarpa M, Villeneuve J, Jovic M, Porzner M, Balla T, Seufferlein T, Malhotra V. Recruitment of arfaptins to the trans-Golgi network by PI(4)P and their involvement in cargo export. EMBO J 2013; 32:1717-29. [PMID: 23695357 DOI: 10.1038/emboj.2013.116] [Citation(s) in RCA: 214] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Accepted: 04/25/2013] [Indexed: 11/09/2022] Open
Abstract
The BAR (Bin/Amphiphysin/Rvs) domain proteins arfaptin1 and arfaptin2 are localized to the trans-Golgi network (TGN) and, by virtue of their ability to sense and/or generate membrane curvature, could play an important role in the biogenesis of transport carriers. We report that arfaptins contain an amphipathic helix (AH) preceding the BAR domain, which is essential for their binding to phosphatidylinositol 4-phosphate (PI(4)P)-containing liposomes and the TGN of mammalian cells. The binding of arfaptin1, but not arfaptin2, to PI(4)P is regulated by protein kinase D (PKD) mediated phosphorylation at Ser100 within the AH. We also found that only arfaptin1 is required for the PKD-dependent trafficking of chromogranin A by the regulated secretory pathway. Altogether, these findings reveal the importance of PI(4)P and PKD in the recruitment of arfaptins at the TGN and their requirement in the events leading to the biogenesis of secretory storage granules.
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Arf1 and membrane curvature cooperate to recruit Arfaptin2 to liposomes. PLoS One 2013; 8:e62963. [PMID: 23638170 PMCID: PMC3639266 DOI: 10.1371/journal.pone.0062963] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 03/27/2013] [Indexed: 11/19/2022] Open
Abstract
Arfaptin2 contains a Bin/Amphiphysin/Rvs (BAR) domain and directly interacts with proteins of the Arf/Arl family in their active GTP-bound state. It has been proposed that BAR domains are able to sense membrane curvature and to induce membrane tubulation. We report here that active Arf1 is required for the recruitment of Arfaptin2 to artificial liposomes mimicking the Golgi apparatus lipid composition. The Arf1-dependent recruitment of Arfaptin2 increases with membrane curvature, while the recruitment of Arf1 itself is not sensitive to curvature. At high protein concentrations, the binding of Arfaptin2 induces membrane tubulation. Finally, membrane-bound Arfaptin2 is released from the liposome when ArfGAP1 catalyzes the hydrolysis of GTP to GDP in Arf1. These results show that both Arf1 activation and high membrane curvature are required for efficient recruitment of Arfaptin2 to membranes.
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Adult neuronal Arf6 controls ethanol-induced behavior with Arfaptin downstream of Rac1 and RhoGAP18B. J Neurosci 2013; 32:17706-13. [PMID: 23223291 DOI: 10.1523/jneurosci.1944-12.2012] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Alcohol use disorders affect millions of individuals. However, the genes and signaling pathways involved in behavioral ethanol responses and addiction are poorly understood. Here we identify a conserved biochemical pathway that underlies the sedating effects of ethanol in Drosophila. Mutations in the Arf6 small GTPase signaling pathway cause hypersensitivity to ethanol-induced sedation. We show that Arf6 functions in the adult nervous system to control ethanol-induced behavior. We also find that the Drosophila Arfaptin protein directly binds to the activated forms of Arf6 and Rac1 GTPases, and mutants in Arfaptin also display ethanol sensitivity. Arf6 acts downstream of Rac1 and Arfaptin to regulate ethanol-induced behaviors, and we thus demonstrate that this conserved Rac1/Arfaptin/Arf6 pathway is a major mediator of ethanol-induced behavioral responses.
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16
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Gehart H, Goginashvili A, Beck R, Morvan J, Erbs E, Formentini I, De Matteis M, Schwab Y, Wieland F, Ricci R. The BAR Domain Protein Arfaptin-1 Controls Secretory Granule Biogenesis at the trans-Golgi Network. Dev Cell 2012; 23:756-68. [DOI: 10.1016/j.devcel.2012.07.019] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 07/02/2012] [Accepted: 07/24/2012] [Indexed: 12/29/2022]
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17
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Wong KA, Wilson J, Russo A, Wang L, Okur MN, Wang X, Martin NP, Scappini E, Carnegie GK, O'Bryan JP. Intersectin (ITSN) family of scaffolds function as molecular hubs in protein interaction networks. PLoS One 2012; 7:e36023. [PMID: 22558309 PMCID: PMC3338775 DOI: 10.1371/journal.pone.0036023] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 03/28/2012] [Indexed: 11/29/2022] Open
Abstract
Members of the intersectin (ITSN) family of scaffold proteins consist of multiple modular domains, each with distinct ligand preferences. Although ITSNs were initially implicated in the regulation of endocytosis, subsequent studies have revealed a more complex role for these scaffold proteins in regulation of additional biochemical pathways. In this study, we performed a high throughput yeast two-hybrid screen to identify additional pathways regulated by these scaffolds. Although several known ITSN binding partners were identified, we isolated more than 100 new targets for the two mammalian ITSN proteins, ITSN1 and ITSN2. We present the characterization of several of these new targets which implicate ITSNs in the regulation of the Rab and Arf GTPase pathways as well as regulation of the disrupted in schizophrenia 1 (DISC1) interactome. In addition, we demonstrate that ITSN proteins form homomeric and heteromeric complexes with each other revealing an added level of complexity in the function of these evolutionarily conserved scaffolds.
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Affiliation(s)
- Katy A. Wong
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- Center for Cardiovascular Research, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- UIC Cancer Center, University of Illinois College of Medicine, Chicago, Illinois, United States of America
| | - Jessica Wilson
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- Center for Cardiovascular Research, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- UIC Cancer Center, University of Illinois College of Medicine, Chicago, Illinois, United States of America
| | - Angela Russo
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- Center for Cardiovascular Research, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- UIC Cancer Center, University of Illinois College of Medicine, Chicago, Illinois, United States of America
| | - Li Wang
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois, United States of America
| | - Mustafa Nazir Okur
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- Center for Cardiovascular Research, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- UIC Cancer Center, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- Department of Biochemistry and Molecular Genetics, University of Illinois College of Medicine, Chicago, Illinois, United States of America
| | - Xuerong Wang
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- Center for Cardiovascular Research, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- UIC Cancer Center, University of Illinois College of Medicine, Chicago, Illinois, United States of America
| | - Negin P. Martin
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, United States of America
| | - Erica Scappini
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, United States of America
| | - Graeme K. Carnegie
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois, United States of America
| | - John P. O'Bryan
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- Center for Cardiovascular Research, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- UIC Cancer Center, University of Illinois College of Medicine, Chicago, Illinois, United States of America
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18
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Figueiredo J, Simões-Correia J, Söderberg O, Suriano G, Seruca R. ADP-ribosylation factor 6 mediates E-cadherin recovery by chemical chaperones. PLoS One 2011; 6:e23188. [PMID: 21853084 PMCID: PMC3154279 DOI: 10.1371/journal.pone.0023188] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Accepted: 07/11/2011] [Indexed: 12/16/2022] Open
Abstract
E-cadherin plays a powerful tumor suppressor role. Germline E-cadherin mutations justify 30% of Hereditary Diffuse Gastric Cancer (HDGC) and missense mutations are found in 30% of these families. We found possible to restore in vitro mutant E-cadherin associated to HDGC syndrome by using Chemical Chaperones (CCs). Herein, our aim was to disclose the molecular mechanisms underlying the CCs effects in E-cadherin regulation. Using cells stably expressing WT E-cadherin or two HDGC-associated missense mutations, we show that upon DMSO treatment, not only mutant E-cadherin is restored and stabilized at the plasma membrane (PM), but also Arf6 and PIPKIγ expressions are altered. We show that modulation of Arf6 expression partially mimics the effect of CCs, suggesting that the cellular effects observed upon CCs treatment are mediated by Arf6. Further, we show that E-cadherin expression recovery is specifically linked to Arf6 due to its role on endocytosis and recycling pathways. Finally, we demonstrated that, as DMSO, several others CCs are able to modulate the trafficking machinery through an Arf6 dependent mechanism. Interestingly, the more effective compounds in E-cadherin recovery to PM are those that simultaneously inhibit Arf6 and stimulate PIPKIγ expression and binding to E-cadherin. Here, we present the first evidence of a direct influence of CCs in cellular trafficking machinery and we show that this effect is of crucial importance in the context of juxtamembrane E-cadherin missense mutations associated to HDGC. We propose that this influence should be taken into account when exploring the therapeutic potential of this type of chemicals in genetic diseases associated to protein-misfolding.
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Affiliation(s)
- Joana Figueiredo
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
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19
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Prosser DC, Tran D, Schooley A, Wendland B, Ngsee JK. A novel, retromer-independent role for sorting nexins 1 and 2 in RhoG-dependent membrane remodeling. Traffic 2011; 11:1347-62. [PMID: 20604901 DOI: 10.1111/j.1600-0854.2010.01100.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The sorting nexins SNX1 and SNX2 are members of the retromer complex involved in protein sorting within the endocytic pathway. While retromer-dependent functions of SNX1 and SNX2 have been well documented, potential retromer-independent roles remain unclear. Here, we show that SNX1 and SNX2 interact with the Rac1 and RhoG guanine nucleotide exchange factor Kalirin-7. Simultaneous overexpression of SNX1 or SNX2 and Kalirin-7 in epithelial cells causes partial redistribution of both SNX isoforms to the plasma membrane, and results in RhoG-dependent lamellipodia formation that requires functional Phox homology (PX) and Bin/Amphiphysin/Rvs (BAR) domains of SNX, but is Rac1- and retromer-independent. Conversely, depletion of endogenous SNX1 or SNX2 inhibits Kalirin-7-mediated lamellipodia formation. Finally, we demonstrate that SNX1 and SNX2 interact directly with inactive RhoG, suggesting a novel role for these SNX proteins in recruiting an inactive Rho GTPase to its exchange factor.
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Affiliation(s)
- Derek C Prosser
- Department of Cellular and Molecular Medicine, Ottawa Hospital Research Institute, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, K1H 8M5, Canada
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20
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Man Z, Kondo Y, Koga H, Umino H, Nakayama K, Shin HW. Arfaptins are localized to the trans-Golgi by interaction with Arl1, but not Arfs. J Biol Chem 2011; 286:11569-78. [PMID: 21239483 DOI: 10.1074/jbc.m110.201442] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Arfaptins (arfaptin-1 and arfaptin-2/POR1) were originally identified as binding partners of the Arf small GTPases. Both proteins contain a BAR (Bin/Amphiphysin/Rvs) domain, which participates in membrane deformation. Here we show that arfaptins associate with trans-Golgi membranes. Unexpectedly, Arl1 (Arf-like 1), but not Arfs, determines the trans-Golgi association of arfaptins. We also demonstrate that arfaptins interact with Arl1 through their BAR domain-containing region and compete for Arl1 binding with golgin-97 and golgin-245/p230, both of which also bind to Arl1 through their GRIP (golgin-97/RanBP2/Imh1p/p230) domains. However, arfaptins and these golgins show only limited colocalization at the trans-Golgi. Time-lapse imaging of cells overexpressing fluorescent protein-tagged arfaptins and golgin-97 reveals that arfaptins, but not golgin-97, are included in vesicular and tubular structures emanating from the Golgi region. These observations indicate that arfaptins are recruited onto trans-Golgi membranes by interacting with Arl1, and capable of inducing membrane deformation via their BAR domains.
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Affiliation(s)
- Zhiqiu Man
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, Japan
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21
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Bhanot H, Young AM, Overmeyer JH, Maltese WA. Induction of nonapoptotic cell death by activated Ras requires inverse regulation of Rac1 and Arf6. Mol Cancer Res 2010; 8:1358-74. [PMID: 20713492 DOI: 10.1158/1541-7786.mcr-10-0090] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Methuosis is a unique form of nonapoptotic cell death triggered by alterations in the trafficking of clathrin-independent endosomes, ultimately leading to extreme vacuolization and rupture of the cell. Methuosis can be induced in glioblastoma cells by expression of constitutively active Ras. This study identifies the small GTPases, Rac1 and Arf6, and the Arf6 GTPase-activating protein, GIT1, as key downstream components of the signaling pathway underlying Ras-induced methuosis. The extent to which graded expression of active H-Ras(G12V) triggers cytoplasmic vacuolization correlates with the amount of endogenous Rac1 in the active GTP state. Blocking Rac1 activation with the specific Rac inhibitor, EHT 1864, or coexpression of dominant-negative Rac1(T17N), prevents the accumulation of vacuoles induced by H-Ras(G12V). Coincident with Rac1 activation, H-Ras(G12V) causes a decrease in the amount of active Arf6, a GTPase that functions in the recycling of clathrin-independent endosomes. The effect of H-Ras(G12V) on Arf6 is blocked by EHT 1864, indicating that the decrease in Arf6-GTP is directly linked to the activation of Rac1. Constitutively active Rac1(G12V) interacts with GIT1 in immunoprecipitation assays. Ablation of GIT1 by short hairpin RNA prevents the decrease in active Arf6, inhibits vacuolization, and prevents loss of cell viability in cells expressing Rac1(G12V). Together, the results suggest that perturbations of endosome morphology associated with Ras-induced methuosis are due to downstream activation of Rac1 combined with reciprocal inactivation of Arf6. The latter seems to be mediated through Rac1 stimulation of GIT1. Further insights into this pathway could suggest opportunities for the induction of methuosis in cancers that are resistant to apoptotic cell death.
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Affiliation(s)
- Haymanti Bhanot
- Department of Biochemistry and Cancer Biology, University of Toledo College of Medicine, Toledo, Ohio 43614, USA
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22
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Campos-Parra A, Hernández-Cuevas N, Hernandez-Rivas R, Vargas M. EhNCABP166: A nucleocytoplasmic actin-binding protein from Entamoeba histolytica. Mol Biochem Parasitol 2010; 172:19-30. [DOI: 10.1016/j.molbiopara.2010.03.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 03/09/2010] [Accepted: 03/15/2010] [Indexed: 01/06/2023]
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23
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Sanda M, Ohara N, Kamata A, Hara Y, Tamaki H, Sukegawa J, Yanagisawa T, Fukunaga K, Kondo H, Sakagami H. Vezatin, a potential target for ADP-ribosylation factor 6, regulates the dendritic formation of hippocampal neurons. Neurosci Res 2010; 67:126-36. [PMID: 20188128 DOI: 10.1016/j.neures.2010.02.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Revised: 02/12/2010] [Accepted: 02/18/2010] [Indexed: 12/16/2022]
Abstract
ADP-ribosylation factor 6 (ARF6) is a small GTPase that regulates neuronal morphogenesis processes such as axonal, dendritic, and spine formation possibly through the actin cytoskeleton and membrane trafficking. In an attempt to define the molecular mechanisms that regulate neuronal morphogenesis by ARF6, we identified vezatin as a novel binding partner of active GTP-bound ARF6 using yeast two-hybrid screening. Vezatin was able to bind specifically to GTP-ARF6 among the ARF family. In the adult mouse brain, vezatin exhibited widespread gene expression with high levels in the hippocampus and medial habenular nucleus. In hippocampal neurons, vezatin was localized at dendrites as well as cell bodies. Knockdown of endogenous vezatin significantly reduced total dendritic length and arborization of cultured hippocampal neurons, while overexpression of vezatin increased dendritic length. Our present study suggests that vezatin may regulate dendritic formation as a downstream effector of ARF6.
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Affiliation(s)
- Masashi Sanda
- Department of Anatomy, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara 228-8555, Kanagawa, Japan
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24
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Felkl M, Leube RE. Interaction assays in yeast and cultured cells confirm known and identify novel partners of the synaptic vesicle protein synaptophysin. Neuroscience 2008; 156:344-52. [PMID: 18706977 DOI: 10.1016/j.neuroscience.2008.07.033] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 07/16/2008] [Accepted: 07/16/2008] [Indexed: 01/15/2023]
Abstract
Synaptophysin (SYP) is a major protein of neurotransmitter-containing vesicles spanning the membrane four times and contributing to various aspects of the synaptic vesicle cycle. The split-ubiquitin yeast two-hybrid system was used to characterize molecular interactions of membrane-bound, full-length murine SYP. In this way, the known homophilic SYP-SYP association could be confirmed and heterophilic binding of SYP to other tetraspan vesicle membrane proteins of the secretory carrier-associated membrane- and synaptogyrin-type could be detected for the first time. SYP-binding was also observed for the vSNARE synaptobrevin2 and various membrane and membrane-associated proteins. Double labeling immunofluorescence microscopy of murine retina, co-immunoprecipitation experiments and fluorescence energy resonance transfer (FRET) analyses between fluorescent protein-tagged polypeptides were carried out to validate and further characterize the association of SYP with the tetraspan vesicle membrane proteins secretory carrier-associated membrane protein 1 and synaptogyrin3, with synaptobrevin2, and the newly identified binding partners phospholipase D4, stathmin-like3, Rho family GTPase2 and ADP-ribosylation factor interacting protein2. It was observed that the carboxyterminus of SYP is dispensable for association with integral membrane proteins while it is needed for binding to membrane-associated polypeptides. The latter appears to be regulated by phosphorylation, since src homology 2-domains were shown to attach to the multiple carboxyterminal phosphotyrosine residues of SYP. In conclusion, the association of SYP with different tetraspan vesicle membrane proteins suggests shared functions and the multiple other interactions identify SYP as part of a membrane platform acting as a facilitator of various steps of the synaptic vesicle cycle.
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Affiliation(s)
- M Felkl
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Wendlingweg 2, 52074 Aachen, Germany
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25
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Karim ZA, Choi W, Whiteheart SW. Primary platelet signaling cascades and integrin-mediated signaling control ADP-ribosylation factor (Arf) 6-GTP levels during platelet activation and aggregation. J Biol Chem 2008; 283:11995-2003. [PMID: 18326492 DOI: 10.1074/jbc.m800146200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Previous studies showed that ADP-ribosylation factor 6 (Arf6) is important for platelet function; however, little is known about which signaling events regulate this small GTP-binding protein. Arf6-GTP was monitored in platelets stimulated with a number of agonists (TRAP, thrombin, convulxin, collagen, PMA, thapsigargin, or A23187) and all led to a time-dependent decrease in Arf6-GTP. ADP and U46619 were without effect. Using inhibitors, it was shown that the decrease of Arf6-GTP is a direct consequence of known signaling cascades. Upon stimulation via PAR receptors, Arf6-GTP loss could be blocked by treatment with U-73122, BAPTA/AM, Ro-31-8220, or Gö6976, indicating requirements for phospholipase C, calcium, and protein kinase C (PKC) alpha/beta, respectively. The Arf6-GTP decrease in convulxin-stimulated platelets showed similar requirements and was also sensitive to piceatannol, wortmannin, and LY294002, indicating additional requirements for Syk and phosphatidylinositol 3-kinase. The convulxin-induced decrease was sensitive to both PKCalpha/beta and delta inhibitors. Outside-in signaling, potentially via integrin engagement, caused a second wave of signaling that affected Arf6. Inclusion of RGDS peptides or EGTA, during activation, led to a biphasic response; Arf6-GTP levels partially recovered upon continued incubation. A similar response was seen in beta3 integrin-null platelets. These data show that Arf6-GTP decreases in response to known signaling pathways associated with PAR and GPVI. They further reveal a second, aggregation-dependent, process that dampens Arf6-GTP recovery. This study demonstrates that the nucleotide state of Arf6 in platelets is regulated during the initial phases of activation and during the later stages of aggregation.
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Affiliation(s)
- Zubair A Karim
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, Kentucky 40536-0509, USA
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26
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Coemans B, Takahashi Y, Berberich T, Ito A, Kanzaki H, Matsumura H, Saitoh H, Tsuda S, Kamoun S, Sági L, Swennen R, Terauchi R. High-throughput in planta expression screening identifies an ADP-ribosylation factor (ARF1) involved in non-host resistance and R gene-mediated resistance. MOLECULAR PLANT PATHOLOGY 2008; 9:25-36. [PMID: 18705881 PMCID: PMC6640410 DOI: 10.1111/j.1364-3703.2007.00440.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
To identify positive regulators of cell death in plants, we performed a high-throughput screening, employing potato virus X-based overexpression in planta of a cDNA library derived from paraquat-treated Nicotiana benthamiana leaves. The screening of 30,000 cDNA clones enabled the identification of an ADP-ribosylation factor 1 (ARF1) that induces cell death when overexpressed in N. benthamiana. Overexpression of the guanosine diphosphate (GDP)-locked mutant of ARF1 did not trigger cell death, suggesting that ARF1 guanosine triphosphatase (GTPase) activity is necessary for the observed cell death-inducing activity. The ARF1 transcript level increased strongly following treatment with Phytophthora infestans elicitor INF1, as well as inoculation with a non-host pathogen Pseudomonas cichorii in N. benthamiana. In addition, ARF1 was induced in the interaction between the N gene and tobacco mosaic virus (TMV) in Nicotiana tabacum. By contrast, inoculation with the virulent pathogen Pseudomonas syringae pv. tabaci did not affect ARF1 expression in N. benthamiana. Virus-induced gene silencing of ARF1 in N. benthamiana resulted in a stunted phenotype, and severely hampered non-host resistance towards P. cichorii. In addition, ARF1 silencing partially compromised resistance towards TMV in N. benthamiana containing the N resistance gene. By contrast, and in accordance with the ARF1 gene expression profile, silencing of ARF1 transcription did not alter the susceptibility of N. benthamiana towards the pathogen P. syringae pv. tabaci. These results strongly implicate ARF1 in the non-host resistance to bacteria and N gene-mediated resistance in N. benthamiana.
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Affiliation(s)
- Bert Coemans
- Laboratory of Tropical Crop Improvement, Division of Crop Biotechnics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 13, 3001 Leuven, Belgium
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27
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Saito K, Williams S, Bulankina A, Höning S, Mustelin T. Association of Protein-tyrosine Phosphatase MEG2 via Its Sec14p Homology Domain with Vesicle-trafficking Proteins. J Biol Chem 2007; 282:15170-8. [PMID: 17387180 DOI: 10.1074/jbc.m608682200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The protein-tyrosine phosphatase PTPMEG2 is located on the cytoplasmic face of the enclosing membrane of secretory vesicles, where it regulates vesicle size by promoting homotypic vesicle fusion by dephosphorylating N-ethylmaleimide-sensitive factor, a key regulator of vesicle fusion. Here we address the question of how PTPMEG2 is targeted to this subcellular location. Using a series of deletion mutants, we pinpointed the N-terminal Sec14p homology (SEC14) domain of PTPMEG2, residues 1-261, as the region containing the secretory vesicle targeting signal. This domain, alone or appended to a heterologous protein, was localized to intracellular vesicle membranes. Yeast two-hybrid screening identified a number of secretory vesicle proteins that interacted directly with the SEC14 domain of PTPMEG2, providing a mechanism for PTPMEG2 targeting to secretory vesicles. Two such proteins, mannose 6-phosphate receptor-interacting protein TIP47 and Arfaptin2, were found to alter PTPMEG2 localization when overexpressed, and elimination of TIP47 resulted in loss of PTPMEG2 function. We conclude that the N terminus of PTPMEG2 is necessary for the targeting of this phosphatase to the secretory vesicle compartment by association with other proteins involved in intracellular transport.
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Affiliation(s)
- Kan Saito
- Program on Inflammatory Disease Research, Infectious and Inflammatory Disease Center, and Program of Signal Transduction, Cancer Center, The Burnham Institute for Medical Research, La Jolla, California 92037, USA
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28
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Abstract
The ADP-ribosylation factor (ARF) small GTPases regulate vesicular traffic and organelle structure by recruiting coat proteins, regulating phospholipid metabolism and modulating the structure of actin at membrane surfaces. Recent advances in our understanding of the signalling pathways that are regulated by ARF1 and ARF6, two of the best characterized ARF proteins, provide a molecular context for ARF protein function in fundamental biological processes, such as secretion, endocytosis, phagocytosis, cytokinesis, cell adhesion and tumour-cell invasion.
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Affiliation(s)
- Crislyn D'Souza-Schorey
- Department of Biological Sciences and the Walther Cancer Institute, University of Notre Dame, Notre Dame, Indiana, USA.
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29
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Shin OH, Exton JH. Assays and properties of arfaptin 2 binding to Rac1 and ADP-ribosylation factors (Arfs). Methods Enzymol 2006; 404:359-67. [PMID: 16413282 DOI: 10.1016/s0076-6879(05)04031-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Arfaptin 1 and 2 were identified as targets for GTP bound ADP-ribosylation factors (Arfs). Arfaptin 1 had no significant effects on guanine nucleotide binding to Arfs, nor enzymatic activities of guanine nucleotide exchange factor (GEF) and GTPase activating protein (GAP) acting on Arfs. However, arfaptin 1 inhibited Arf activation of cholera toxin and phospholipase D (PLD) in a dose-dependent manner. Only GTP-bound forms of Arf1, 5, and 6 interacted with arfaptin 1 and 2, but GTP-Arf1 showed the strongest binding to the arfaptins. In contrast to the binding of Arfs to arfaptins, GDP-Rac1 or dominant negative Rac1-N17N bound to arfaptin 2, whereas GTP-Rac1 or dominant active Rac1-Q61L did not bind to arfaptin 2. Neither GTP-Rac1 nor GDP-Rac1 bound to arfaptin 1. Based on our observation, we propose that arfaptin 2 is a target for GDP-Rac1 and for GTP-Arf1, and is involved in interactions between the Rac1 and Arfs signaling pathways. This chapter describes methods for investigating the interactions of arfaptins 1 and 2 with GTP- or GDP-liganded Arfs and Rac1.
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Affiliation(s)
- Ok-Ho Shin
- Center for Basic Neuroscience, University of Texas Southwestern Medical Center, Dallas, USA
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30
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Choi W, Karim ZA, Whiteheart SW. Arf6 plays an early role in platelet activation by collagen and convulxin. Blood 2005; 107:3145-52. [PMID: 16352809 PMCID: PMC1895749 DOI: 10.1182/blood-2005-09-3563] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Small GTPases play critical roles in hemostasis, though the roster of such molecules in platelets is not complete. In this study, we report the presence of Ras-related GTPases of the ADP-ribosylation factor (Arf) family. Platelets contain Arf1 or 3 and Arf6, with the latter being predominantly membrane associated. Using effector domain pull-down assays, we show, counter to other GTPases, that Arf6-GTP is present in resting platelets and decreases rapidly upon activation with collagen or convulxin. This decrease does not completely rely on secondary agonists (ADP and thromboxane A2) or require integrin signaling. The decrease in free Arf6-GTP temporally precedes activation of Rho family GTPases (RhoA, Cdc42, and Rac1). Using a membrane-permeant, myristoylated peptide, which mimics the N-terminus of Arf6, we show that the Arf6-GTP decrease is essential for collagen- and convulxin-induced aggregation, platelet adherence, and spreading on collagen-coated glass. Treatment with this peptide also affects the activation of Rho family GTPases, but has little effect on RalA and Rap1 or on agonist-induced calcium mobilization. These data show that Arf6 is a key element in activation through GPVI, and is required for activation of the Rho family GTPases and the subsequent cytoskeletal rearrangements needed for full platelet function.
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Affiliation(s)
- Wangsun Choi
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY 40536-0509, USA
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31
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Gombart AF, Krug U, O'Kelly J, An E, Vegesna V, Koeffler HP. Aberrant expression of neutrophil and macrophage-related genes in a murine model for human neutrophil-specific granule deficiency. J Leukoc Biol 2005; 78:1153-65. [PMID: 16204633 DOI: 10.1189/jlb.0504286] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Neutrophil-specific granule deficiency involves inheritance of germline mutations in the CCAAT/enhancer-binding protein epsilon (C/EBPE) gene. Humans and mice lacking active C/EBPepsilon suffer frequent bacterial infections as a result of functionally defective neutrophils and macrophages. We hypothesized that these defects reflected dysregulation of important immune response genes. To test this, gene expression differences of peritoneally derived neutrophils and macrophages from C/EBPepsilon-/- and wild-type mice were determined with DNA microarrays. Of 283 genes, 146 known genes and 21 expressed sequence tags (ESTs) were down-regulated, and 85 known genes and 31 ESTs were up-regulated in the C/EBP-/- mice. These included genes involved in cell adhesion/chemotaxis, cytoskeletal organization, signal transduction, and immune/inflammatory responses. The cytokines CC chemokine ligand 4, CXC chemokine ligand 2, and interleukin (IL)-6, as well as cytokine receptors IL-8RB and granulocyte-colony stimulating factor, were down-regulated. Chromatin immunoprecipitation analysis identified binding of C/EBPepsilon to their promoter regions. Increased expression for lipid metabolism genes apolipoprotein E (APOE), scavenger receptor class B-1, sorting protein-related receptor containing low-density lipoprotein receptor class A repeat 1, and APOC2 in the C/EBPepsilon-/- mice correlated with reduced total cholesterol levels in these mice before and after maintenance on a high-fat diet. Also, C/EBPepsilon-deficient macrophages showed a reduced capacity to accumulate lipids. In summary, dysregulation of numerous, novel C/EBPepsilon target genes impairs innate immune response and possibly other important biological processes mediated by neutrophils and macrophages.
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Affiliation(s)
- Adrian F Gombart
- Cedars-Sinai Medical Center, Division of Hematology/Oncology, Burns & Allen Research Institute and David Geffen School of Medicine at University of California Los Angeles, USA.
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32
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Rangone H, Pardo R, Colin E, Girault JA, Saudou F, Humbert S. Phosphorylation of Arfaptin 2 at Ser260 by Akt Inhibits PolyQ-huntingtin-induced Toxicity by Rescuing Proteasome Impairment. J Biol Chem 2005; 280:22021-8. [PMID: 15809304 DOI: 10.1074/jbc.m407528200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Huntington disease (HD) is caused by an abnormal expanded polyglutamine repeat in the huntingtin protein. Insulin-like growth factor-1 is of particular interest in HD because it strongly inhibits polyQ-huntingtin-induced neurotoxicity. This neuroprotective effect involves the phosphorylation of huntingtin at Ser(421) by the prosurvival kinase Akt (Humbert, S., Bryson, E. A., Cordelieres, F. P., Connors, N. C., Datta, S. R., Finkbeiner, S., Greenberg, M. E., and Saudou, F. (2002) Dev. Cell 2, 831-837). Here, we report that Akt inhibits polyQ-huntingtin-induced toxicity in the absence of phosphorylation of huntingtin at Ser(421), suggesting that Akt also acts on other downstream effector(s) to prevent neuronal death in HD. We show that this survival effect involves the ADP-ribosylation factor-interacting protein arfaptin 2, the levels of which are increased in HD patients. Akt phosphorylated arfaptin 2 at Ser(260). Lack of phosphorylation of arfaptin 2 at this site substantially modified its subcellular distribution and increased neuronal death and intranuclear inclusions caused by polyQ-huntingtin. In contrast, arfaptin 2 had a neuroprotective effect on striatal neurons when phosphorylated by Akt. This effect is mediated through the proteasome, as phosphorylated arfaptin 2 inhibited the blockade of the proteasome induced by polyQ-huntingtin. This study points out a new mechanism by which Akt promotes neuroprotection in HD, emphasizing the potential therapeutic interest of this pathway in the disease.
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Affiliation(s)
- Hélène Rangone
- UMR 146 CNRS/Institut Curie, Centre Universitaire, 91405 Orsay Cedex, France
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33
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Hiroyama M, Exton JH. Studies of the roles of ADP-ribosylation factors and phospholipase D in phorbol ester-induced membrane ruffling. J Cell Physiol 2005; 202:608-22. [PMID: 15389577 DOI: 10.1002/jcp.20156] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In this study, we have explored the roles of ADP-ribosylation factors (ARFs), phospholipase D (PLD) isozymes, and arfaptins in phorbol ester (PMA)-induced membrane ruffling in HeLa cells. PMA stimulation induced ruffling and translocated cortactin to the plasma membrane. The cortactin translocation was inhibited by dominant negative (DN)-ARF6, DN-ARF1, and DN-Rac1, but not by DN-RhoA and DN-Cdc42. The inability of DN-forms of ARF6, ARF1, and Rac1 to affect PLD activity in response to PMA indicated that this enzyme was not activated via these small G proteins and that its activation was not essential for the induction of ruffling. Endogenous-ARF1, -ARF6, and -Rac1 existed in the ruffling region along with cortactin after PMA stimulation. DN-ARF1 had no effect on the ruffling induced by DA-ARF6 or DA-Rac1, and DN-ARF6 had no effect on that induced by DA-ARF1 or DA-Rac1. On the other hand DN-Rac1 suppressed the effect of DA-ARF6 but not that of DA-ARF1. These results suggest that PMA causes membrane ruffling via an ARF6-Rac1 pathway and also an ARF1 pathway operating in parallel. Overexpression of PLD1 and PLD2 inhibited PMA-induced cortactin translocation and actin-cortactin complex formation, supporting the view that these enzymes are not required for ruffling, but actually suppress it. We conclude that PMA-induced membrane ruffling is caused via ARF6-Rac1 and ARF1 pathways operating in parallel and that PLD may be inhibitory.
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Affiliation(s)
- Masami Hiroyama
- Howard Hughes Medical Institute and Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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34
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Abstract
Many features of cell behavior are regulated by Rho family GTPases, but the most profound effects of these proteins are on the actin cytoskeleton and it was these that first drew attention to this family of signaling proteins. Focusing on Rho and Rac, we will discuss how their effectors regulate the actin cytoskeleton. We will describe how the activity of Rho proteins is regulated downstream from growth factor receptors and cell adhesion molecules by guanine nucleotide exchange factors and GTPase activating proteins. Additionally, we will discuss how there is signaling crosstalk between family members and how various bacterial pathogens have developed strategies to manipulate Rho protein activity so as to enhance their own survival.
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Affiliation(s)
- Keith Burridge
- Department of Cell and Developmental Biology and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA.
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35
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Peter BJ, Kent HM, Mills IG, Vallis Y, Butler PJG, Evans PR, McMahon HT. BAR domains as sensors of membrane curvature: the amphiphysin BAR structure. Science 2003; 303:495-9. [PMID: 14645856 DOI: 10.1126/science.1092586] [Citation(s) in RCA: 1303] [Impact Index Per Article: 62.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The BAR (Bin/amphiphysin/Rvs) domain is the most conserved feature in amphiphysins from yeast to human and is also found in endophilins and nadrins. We solved the structure of the Drosophila amphiphysin BAR domain. It is a crescent-shaped dimer that binds preferentially to highly curved negatively charged membranes. With its N-terminal amphipathic helix and BAR domain (N-BAR), amphiphysin can drive membrane curvature in vitro and in vivo. The structure is similar to that of arfaptin2, which we find also binds and tubulates membranes. From this, we predict that BAR domains are in many protein families, including sorting nexins, centaurins, and oligophrenins. The universal and minimal BAR domain is a dimerization, membrane-binding, and curvature-sensing module.
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Affiliation(s)
- Brian J Peter
- Medical Research Council (MRC) Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
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36
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Abstract
Arf GTP-binding proteins regulate membrane traffic and actin remodeling. Similar to other GTP-binding proteins, a complex of Arf-GTP with an effector protein mediates Arf function. Arf interacts with at least three qualitatively different types of effectors. First, it interacts with structural proteins, the vesicle coat proteins. The second type of effector is lipid-metabolizing enzymes, and the third comprises those proteins that bind to Arf-GTP but whose biochemical or biological functions are not yet clearly defined. Arf interacts with two other families of proteins, the exchange factors and the GTPase-activating proteins. Recent work examining the functional relationships among the diverse Arf interactors has led to reconsideration of the prevailing paradigms for Arf action.
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Affiliation(s)
- Zhongzhen Nie
- Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, Building 37, Room 4118, Bethesda, MD 20892, USA
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37
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Krauss M, Kinuta M, Wenk MR, De Camilli P, Takei K, Haucke V. ARF6 stimulates clathrin/AP-2 recruitment to synaptic membranes by activating phosphatidylinositol phosphate kinase type Igamma. J Cell Biol 2003; 162:113-24. [PMID: 12847086 PMCID: PMC2172713 DOI: 10.1083/jcb.200301006] [Citation(s) in RCA: 227] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Clathrin-mediated endocytosis of synaptic vesicle membranes involves the recruitment of clathrin and AP-2 adaptor complexes to the presynaptic plasma membrane. Phosphoinositides have been implicated in nucleating coat assembly by directly binding to several endocytotic proteins including AP-2 and AP180. Here, we show that the stimulatory effect of ATP and GTPgammaS on clathrin coat recruitment is mediated at least in part by increased levels of PIP2. We also provide evidence for a role of ADP-ribosylation factor 6 (ARF6) via direct stimulation of a synaptically enriched phosphatidylinositol 4-phosphate 5-kinase type Igamma (PIPKIgamma), in this effect. These data suggest a model according to which activation of PIPKIgamma by ARF6-GTP facilitates clathrin-coated pit assembly at the synapse.
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Affiliation(s)
- Michael Krauss
- Department of Biochemistry II, Zentrum für Biochemie und Molekulare Zellbiologie, University of Göttingen, D-37073 Göttingen, Germany
| | - Masahiro Kinuta
- Department of Neuroscience, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan
| | - Markus R. Wenk
- Department of Cell Biology and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510
| | - Pietro De Camilli
- Department of Cell Biology and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510
| | - Kohji Takei
- Department of Neuroscience, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan
| | - Volker Haucke
- Department of Biochemistry II, Zentrum für Biochemie und Molekulare Zellbiologie, University of Göttingen, D-37073 Göttingen, Germany
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38
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Hickson GRX, Matheson J, Riggs B, Maier VH, Fielding AB, Prekeris R, Sullivan W, Barr FA, Gould GW. Arfophilins are dual Arf/Rab 11 binding proteins that regulate recycling endosome distribution and are related to Drosophila nuclear fallout. Mol Biol Cell 2003; 14:2908-20. [PMID: 12857874 PMCID: PMC165686 DOI: 10.1091/mbc.e03-03-0160] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Arfophilin is an ADP ribosylation factor (Arf) binding protein of unknown function. It is identical to the Rab11 binding protein eferin/Rab11-FIP3, and we show it binds both Arf5 and Rab11. We describe a related protein, arfophilin-2, that interacts with Arf5 in a nucleotide-dependent manner, but not Arf1, 4, or 6 and also binds Rab11. Arfophilin-2 localized to a perinuclear compartment, the centrosomal area, and focal adhesions. The localization of arfophilin-2 to the perinuclear compartment was selectively blocked by overexpression of Arf5-T31N. In contrast, a green fluorescent protein-arfophilin-2 chimera or arfophilin-2 deletions were localized around the centrosome in a region that was also enriched for transferrin receptors and Rab11 but not early endosome markers, suggesting that the distribution of the endosomal recycling compartment was altered. The arfophilins belong to a conserved family that includes Drosophila melanogaster nuclear fallout, a centrosomal protein required for cellularization. Expression of green fluorescent protein-nuclear fallout in HeLa cells resulted in a similar phenotype, indicative of functional homology and thus implicating the arfophilins in mitosis/cytokinesis. We suggest that the novel dual GTPase-binding capacity of the arfophilins could serve as an interface of signals from Rab and Arf GTPases to regulate membrane traffic and integrate distinct signals in the late endosomal recycling compartment.
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Affiliation(s)
- Gilles R X Hickson
- The Henry Wellcome Laboratory of Cell Biology, Division of Biochemistry and Molecular Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland
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39
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Wehrle-Haller B, Imhof BA. Actin, microtubules and focal adhesion dynamics during cell migration. Int J Biochem Cell Biol 2003; 35:39-50. [PMID: 12467646 DOI: 10.1016/s1357-2725(02)00071-7] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Cell migration is a complex cellular behavior that results from the coordinated changes in the actin cytoskeleton and the controlled formation and dispersal of cell-substrate adhesion sites. While the actin cytoskeleton provides the driving force at the cell front, the microtubule network assumes a regulatory function in coordinating rear retraction. The polarity within migrating cells is further highlighted by the stationary behavior of focal adhesions in the front and their sliding in trailing ends. We discuss here the cross-talk of the actin cytoskeleton with the microtubule network and the potential mechanisms that control the differential behavior of focal adhesions sites during cell migration.
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Affiliation(s)
- Bernhard Wehrle-Haller
- Department of Pathology, Centre Médical Universitaire, 1 Rue Michel-Servet, 1211 4, Geneva, Switzerland.
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40
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Peters PJ, Ning K, Palacios F, Boshans RL, Kazantsev A, Thompson LM, Woodman B, Bates GP, D'Souza-Schorey C. Arfaptin 2 regulates the aggregation of mutant huntingtin protein. Nat Cell Biol 2002; 4:240-5. [PMID: 11854752 DOI: 10.1038/ncb761] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Huntington's disease (HD) is an inherited neurodegenerative disorder. Here we demonstrate that expression of arfaptin 2/POR1 (partner of Rac1) in cultured cells induces the formation of pericentriolar and nuclear aggregates, which morphologically resemble mutant huntingtin aggregates characteristic of HD. Endogenous arfaptin 2 localizes to aggregates induced by expression of an abnormal amino-terminal fragment of huntingtin that contains polyglutamine (polyQ) expansions. A dominant inhibitory mutant of arfaptin 2 inhibits aggregation of mutant huntingtin, but not in the presence of proteasome inhibitors. Using cell-free biochemical assays, we show that arfaptin 2 inhibits proteasome activity. Finally, we show that expression of arfaptin 2 is increased at sites of neurodegeneration and the protein localizes to huntingtin aggregates in HD transgenic mouse brains. Our data suggest that arfaptin 2 is involved in regulating huntingtin protein aggregation, possibly by impairing proteasome function.
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Affiliation(s)
- Peter J Peters
- Division of Tumor Biology, Netherlands Cancer Institute, Amsterdam, The Netherlands
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41
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Cherfils J. Structural mimicry of DH domains by Arfaptin suggests a model for the recognition of Rac-GDP by its guanine nucleotide exchange factors. FEBS Lett 2001; 507:280-4. [PMID: 11696355 DOI: 10.1016/s0014-5793(01)02970-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Small G proteins cycle between an inactive form bound to GDP, and an active form bound to GTP. The two forms have different conformations and interact specifically with different partners, hence, the ability of G proteins to function as molecular switches. This view has been challenged by recent structural and biochemical studies of the Arfaptin/Por protein, which interacts equally well with the GDP- and GTP-bound forms of the G protein Rac. Here it is shown that the dimeric helical domain of Arfaptin superimposes with a monomeric helical domain from the Dbl homology domain of Tiam, a guanine nucleotide exchange factor (GEF) for Rac, in their respective complexes with Rac. This unexpected structural mimicry suggests that the Rac-GDP-Arfaptin complex resembles the low-affinity Rac-GDP-GEF complex that initiates the exchange reaction. This provides a model for the exchange mechanism where DH domains first dock onto Rac-GDP at the switch 2 before they undergo domain closure to catalyze GDP dissociation.
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Affiliation(s)
- J Cherfils
- Laboratoire d'Enzymologie et Biochimie Structurales, UPR 9063 CNRS, 1 avenue de la Terrasse, 91198 Cedex, Gif sur Yvette, France.
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