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Stefanini L, Bergmeier W. RAP GTPases and platelet integrin signaling. Platelets 2018; 30:41-47. [PMID: 29863951 PMCID: PMC6312509 DOI: 10.1080/09537104.2018.1476681] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 04/26/2018] [Accepted: 04/27/2018] [Indexed: 12/31/2022]
Abstract
Platelets are highly specialized cells that continuously patrol the vasculature to ensure its integrity (hemostasis). At sites of vascular injury, they are able to respond to trace amounts of agonists and to rapidly transition from an anti-adhesive/patrolling to an adhesive state (integrin inside-out activation) required for hemostatic plug formation. Pathological conditions that disturb the balance in the underlying signaling processes can lead to unwanted platelet activation (thrombosis) or to an increased bleeding risk. The small GTPases of the RAP subfamily, highly expressed in platelets, are critical regulators of cell adhesion, cytoskeleton remodeling, and MAP kinase signaling. Studies by our group and others demonstrate that RAP GTPases, in particular RAP1A and RAP1B, are the key molecular switches that turn on platelet activation/adhesiveness at sites of injury. In this review, we will summarize major findings on the role of RAP GTPases in platelet biology with a focus on the signaling pathways leading to the conversion of integrins to a high-affinity state.
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Affiliation(s)
- Lucia Stefanini
- Department of Internal Medicine and Medical Specialties, Sapienza University of Rome, Rome, Italy
| | - Wolfgang Bergmeier
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill (NC), USA
- McAllister Heart Institute, University of North Carolina at Chapel Hill (NC), USA
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2
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In-depth PtdIns(3,4,5)P 3 signalosome analysis identifies DAPP1 as a negative regulator of GPVI-driven platelet function. Blood Adv 2017; 1:918-932. [PMID: 29242851 DOI: 10.1182/bloodadvances.2017005173] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The class I phosphoinositide 3-kinase (PI3K) isoforms play important roles in platelet priming, activation, and stable thrombus formation. Class I PI3Ks predominantly regulate cell function through their catalytic product, the signaling phospholipid phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P3], which coordinates the localization and/or activity of a diverse range of binding proteins. Notably, the complete repertoire of these class I PI3K effectors in platelets remains unknown, limiting mechanistic understanding of class I PI3K-mediated control of platelet function. We measured robust agonist-driven PtdIns (3,4,5)P3 generation in human platelets by lipidomic mass spectrometry (MS), and then used affinity-capture coupled to high-resolution proteomic MS to identify the targets of PtdIns (3,4,5)P3 in these cells. We reveal for the first time a diverse platelet PtdIns(3,4,5)P3 interactome, including kinases, signaling adaptors, and regulators of small GTPases, many of which are previously uncharacterized in this cell type. Of these, we show dual adaptor for phosphotyrosine and 3-phosphoinositides (DAPP1) to be regulated by Src-family kinases and PI3K, while platelets from DAPP1-deficient mice display enhanced thrombus formation on collagen in vitro. This was associated with enhanced platelet α/δ granule secretion and αIIbβ3 integrin activation downstream of the collagen receptor glycoprotein VI. Thus, we present the first comprehensive analysis of the PtdIns(3,4,5)P3 signalosome of human platelets and identify DAPP1 as a novel negative regulator of platelet function. This work provides important new insights into how class I PI3Ks shape platelet function.
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3
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Stefanini L, Bergmeier W. RAP1-GTPase signaling and platelet function. J Mol Med (Berl) 2015; 94:13-9. [PMID: 26423530 DOI: 10.1007/s00109-015-1346-3] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 09/10/2015] [Accepted: 09/17/2015] [Indexed: 10/23/2022]
Abstract
Platelets are critical for hemostasis, i.e., the body's ability to prevent blood loss at sites of vascular injury. They patrol the vasculature in a quiescent, non-adhesive state for approximately 10 days, after which they are removed from circulation by phagocytic cells of the reticulo-endothelial system. At sites of vascular injury, they promptly shift to an activated, adhesive state required for the formation of a hemostatic plug. The small GTPase RAP1 is a critical regulator of platelet adhesiveness. Our recent studies demonstrate that the antagonistic balance between the RAP1 regulators, CalDAG-GEFI and RASA3, is critical for the modulation of platelet adhesiveness, both in circulation and at sites of vascular injury. The RAP1 activator CalDAG-GEFI responds to small changes in the cytoplasmic calcium concentration and thus provides sensitivity and speed to the activation response, essential for efficient platelet adhesion under conditions of hemodynamic shear stress. The RAP1 inhibitor RASA3 ensures that circulating platelets remain quiescent by restraining CalDAG-GEFI-dependent RAP1 activation. Upon cellular stimulation, it is turned off by P2Y12 signaling to enable sustained RAP1 activation, required for the formation of a stable hemostatic plug. This review will summarize important studies that elucidated the signaling pathways that control RAP1 activation in platelets.
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Affiliation(s)
- Lucia Stefanini
- Institute for Cardiovascular and Metabolic Research, University of Reading, Reading, UK
| | - Wolfgang Bergmeier
- Department of Biochemistry and Biophysics, McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
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4
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Specificity and Commonality of the Phosphoinositide-Binding Proteome Analyzed by Quantitative Mass Spectrometry. Cell Rep 2014; 6:578-91. [DOI: 10.1016/j.celrep.2013.12.038] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Revised: 12/03/2013] [Accepted: 12/26/2013] [Indexed: 01/03/2023] Open
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5
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King PD, Lubeck BA, Lapinski PE. Nonredundant functions for Ras GTPase-activating proteins in tissue homeostasis. Sci Signal 2013; 6:re1. [PMID: 23443682 DOI: 10.1126/scisignal.2003669] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Inactivation of the small guanosine triphosphate-binding protein Ras during receptor signal transduction is mediated by Ras guanosine triphosphatase (GTPase)-activating proteins (RasGAPs). Ten different RasGAPs have been identified and have overlapping patterns of tissue distribution. However, genetic analyses are revealing critical nonredundant functions for each RasGAP in tissue homeostasis and as regulators of disease processes in mouse and man. Here, we discuss advances in understanding the role of RasGAPs in the maintenance of tissue integrity.
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Affiliation(s)
- Philip D King
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
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6
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Leander R, Dai S, Schlesinger LS, Friedman A. A mathematical model of CR3/TLR2 crosstalk in the context of Francisella tularensis infection. PLoS Comput Biol 2012; 8:e1002757. [PMID: 23133361 PMCID: PMC3486853 DOI: 10.1371/journal.pcbi.1002757] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 09/05/2012] [Indexed: 02/04/2023] Open
Abstract
Complement Receptor 3 (CR3) and Toll-like Receptor 2 (TLR2) are pattern recognition receptors expressed on the surface of human macrophages. Although these receptors are essential components for recognition by the innate immune system, pathogen coordinated crosstalk between them can suppress the production of protective cytokines and promote infection. Recognition of the virulent Schu S4 strain of the intracellular pathogen Francisella tularensis by host macrophages involves CR3/TLR2 crosstalk. Although experimental data provide evidence that Lyn kinase and PI3K are essential components of the CR3 pathway that influences TLR2 activity, additional responsible upstream signaling components remain unknown. In this paper we construct a mathematical model of CR3 and TLR2 signaling in response to F. tularensis. After demonstrating that the model is consistent with experimental results we perform numerical simulations to evaluate the contributions that Akt and Ras-GAP make to ERK inhibition. The model confirms that phagocytosis-associated changes in the composition of the cell membrane can inhibit ERK activity and predicts that Akt and Ras-GAP synergize to inhibit ERK.
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Affiliation(s)
- Rachel Leander
- Mathematical Biosciences Institute, The Ohio State University, Columbus, Ohio, United States of America
| | - Shipan Dai
- Center for Microbial Interface Biology, Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, United States of America
| | - Larry S. Schlesinger
- Center for Microbial Interface Biology, Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, United States of America
| | - Avner Friedman
- Mathematical Biosciences Institute, The Ohio State University, Columbus, Ohio, United States of America
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7
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Abstract
Ever since their discovery as cellular counterparts of viral oncogenes more than 25 years ago, much progress has been made in understanding the complex networks of signal transduction pathways activated by oncogenic Ras mutations in human cancers. The activity of Ras is regulated by nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs), and much emphasis has been put into the biochemical and structural analysis of the Ras/GAP complex. The mechanisms by which GAPs catalyze Ras-GTP hydrolysis have been clarified and revealed that oncogenic Ras mutations confer resistance to GAPs and remain constitutively active. However, it is yet unclear how cells coordinate the large and divergent GAP protein family to promote Ras inactivation and ensure a certain biological response. Different domain arrangements in GAPs to create differential protein-protein and protein-lipid interactions are probably key factors determining the inactivation of the 3 Ras isoforms H-, K-, and N-Ras and their effector pathways. In recent years, in vitro as well as cell- and animal-based studies examining GAP activity, localization, interaction partners, and expression profiles have provided further insights into Ras inactivation and revealed characteristics of several GAPs to exert specific and distinct functions. This review aims to summarize knowledge on the cell biology of RasGAP proteins that potentially contributes to differential regulation of spatiotemporal Ras signaling.
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Affiliation(s)
- Thomas Grewal
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
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8
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Nafisi H, Banihashemi B, Daigle M, Albert PR. GAP1(IP4BP)/RASA3 mediates Galphai-induced inhibition of mitogen-activated protein kinase. J Biol Chem 2008; 283:35908-17. [PMID: 18952607 DOI: 10.1074/jbc.m803622200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The dopamine D2S receptor (short isoform) couples to inhibitory Galphai/o proteins to inhibit thyrotropin-releasing hormone (TRH)-stimulated p42/p44 mitogen-activated protein kinase (ERK1/2) phosphorylation in GH4ZR7 rat pituitary cells, consistent with its actions to inhibit prolactin gene transcription and cell proliferation. However, the underlying mechanism is unclear. To identify novel Galphai effectors, yeast two-hybrid screening of a GH4ZR7 cDNA library was done using constitutively active Galphai3-Q204L, and multiple clones of the RasGAP cDNA GAP1(IP4BP)/RASA3 were identified. In yeast mating assay, RASA3 preferentially interacted with activated forms of Galphai/o/z proteins, but not with Galphas. A direct interaction was indicated by in vitro pull-down assay, in which S-His-RASA3 preferentially bound guanosine 5'-O-(gamma-thio)triphosphate-activated Galphai3 and Galphai2 compared with guanosine 5'-O-(beta-thio)diphosphate-inactivated proteins. Similarly, in co-immunoprecipitation studies in HEK-293 cells, FLAG-tagged RASA3 preferentially interacted with activated mutants of Galphai3 and Galphai2 compared with wild type proteins. In GH4ZR7 cells, co-immunoprecipitation studies of endogenous proteins demonstrated a Galphai3-RASA3 complex that was induced upon TRH/D2S receptor co-activation. To address RASA3 function in dopamine D2S receptor-induced inhibition of ERK1/2 activity, endogenous RASA3 protein expression was suppressed (70% knockdown) in GH4ZR7 cells stably transfected with full-length antisense cDNA of RASA3. The selected antisense clones had similar levels of dopamine D2S receptor binding and D2S-induced inhibition of cAMP formation compared with parental GH4ZR7 cells. In these clones, D2S-mediated inhibition of TRH-induced phospho-ERK1/2 was reversed by 70-80% compared with parental GH4ZR7 cells. Our results provide a novel mechanism for dopamine D2S-induced inhibition of ERK1/2 and indicate that RASA3 links Galphai proteins to inhibit Gq-induced Ras/ERK1/2 activation.
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Affiliation(s)
- Houman Nafisi
- Ottawa Health Research Institute (Neuroscience), Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa K1H 8M5, Canada
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9
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Haubert D, Gharib N, Rivero F, Wiegmann K, Hösel M, Krönke M, Kashkar H. PtdIns(4,5)P-restricted plasma membrane localization of FAN is involved in TNF-induced actin reorganization. EMBO J 2007; 26:3308-21. [PMID: 17599063 PMCID: PMC1933409 DOI: 10.1038/sj.emboj.7601778] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Accepted: 06/06/2007] [Indexed: 11/08/2022] Open
Abstract
The WD-repeat protein factor associated with nSMase activity (FAN) is a member of the family of TNF receptor adaptor proteins that are coupled to specific signaling cascades. However, the precise functional involvement of FAN in specific cellular TNF responses remain unclear. Here, we report the involvement of FAN in TNF-induced actin reorganization and filopodia formation mediated by activation of Cdc42. The pleckstrin-homology (PH) domain of FAN specifically binds to phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P), which targets FAN to the plasma membrane. Site-specific mutagenesis revealed that the ability of FAN to mediate filopodia formation was blunted either by the destruction of the PtdIns(4,5)P binding motif, or by the disruption of intramolecular interactions between the PH domain and the adjacent beige and Chediak-Higashi (BEACH) domain. Furthermore, FAN was shown to interact with the actin cytoskeleton in TNF-stimulated cells via direct filamentous actin (F-actin) binding. The results of this study suggest that PH-mediated plasma membrane targeting of FAN is critically involved in TNF-induced Cdc42 activation and cytoskeleton reorganization.
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Affiliation(s)
- Dirk Haubert
- Institute for Medical Microbiology, Immunology and Hygiene, Medical Faculty, University of Cologne, Cologne, Germany
| | - Nina Gharib
- Institute for Medical Microbiology, Immunology and Hygiene, Medical Faculty, University of Cologne, Cologne, Germany
| | - Francisco Rivero
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
- Institute for Biochemistry I, Medical Faculty, University of Cologne, Cologne, Germany
| | - Katja Wiegmann
- Institute for Medical Microbiology, Immunology and Hygiene, Medical Faculty, University of Cologne, Cologne, Germany
| | - Marianna Hösel
- Institute for Medical Microbiology, Immunology and Hygiene, Medical Faculty, University of Cologne, Cologne, Germany
| | - Martin Krönke
- Institute for Medical Microbiology, Immunology and Hygiene, Medical Faculty, University of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
| | - Hamid Kashkar
- Institute for Medical Microbiology, Immunology and Hygiene, Medical Faculty, University of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstrasse 19-21, 50935 Köln, Germany. Tel.: +49 221 478 7286; Fax: +49 221 478 7288; E-mail:
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10
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Takaya A, Kamio T, Masuda M, Mochizuki N, Sawa H, Sato M, Nagashima K, Mizutani A, Matsuno A, Kiyokawa E, Matsuda M. R-Ras regulates exocytosis by Rgl2/Rlf-mediated activation of RalA on endosomes. Mol Biol Cell 2007; 18:1850-60. [PMID: 17344481 PMCID: PMC1855010 DOI: 10.1091/mbc.e06-08-0765] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
R-Ras is a Ras-family small GTPase that regulates various cellular functions such as apoptosis and cell adhesion. Here, we demonstrate a role of R-Ras in exocytosis. By the use of specific anti-R-Ras antibody, we found that R-Ras was enriched on both early and recycling endosomes in a wide range of cell lines. Using a fluorescence resonance energy transfer-based probe for R-Ras activity, R-Ras activity was found to be higher on endosomes than on the plasma membrane. This high R-Ras activity on the endosomes correlated with the accumulation of an R-Ras effector, the Rgl2/Rlf guanine nucleotide exchange factor for RalA, and also with high RalA activity. The essential role played by R-Ras in inducing high levels of RalA activity on the endosomes was evidenced by the short hairpin RNA (shRNA)-mediated suppression of R-Ras and by the expression of R-Ras GAP. In agreement with the reported role of RalA in exocytosis, the shRNA of either R-Ras or RalA was found to suppress calcium-triggered exocytosis in PC12 pheochromocytoma cells. These data revealed that R-Ras activates RalA on endosomes and that it thereby positively regulates exocytosis.
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Affiliation(s)
- Akiyuki Takaya
- *Department of Signal Transduction, Research Institute for Microbial Diseases, Osaka University, Yamadaoka, Osaka 565-0871, Japan
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
| | - Takahiro Kamio
- *Department of Signal Transduction, Research Institute for Microbial Diseases, Osaka University, Yamadaoka, Osaka 565-0871, Japan
| | - Michitaka Masuda
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
| | - Naoki Mochizuki
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
| | - Hirofumi Sawa
- Laboratory of Molecular and Cellular Pathology, Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Japan
| | - Mami Sato
- Laboratory of Molecular and Cellular Pathology, Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Japan
| | - Kazuo Nagashima
- Laboratory of Molecular and Cellular Pathology, Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Japan
| | - Akiko Mizutani
- Basic Medical Science and Molecular Medicine, Tokai University School of Medicine, Kanagawa 259-1193, Japan; and
| | - Akira Matsuno
- Department of Neurosurgery, Teikyo University Ichihara Hospital, Chiba 299-0111, Japan
| | - Etsuko Kiyokawa
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
| | - Michiyuki Matsuda
- *Department of Signal Transduction, Research Institute for Microbial Diseases, Osaka University, Yamadaoka, Osaka 565-0871, Japan
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
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11
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Yarwood S, Bouyoucef-Cherchalli D, Cullen PJ, Kupzig S. The GAP1 family of GTPase-activating proteins: spatial and temporal regulators of small GTPase signalling. Biochem Soc Trans 2007; 34:846-50. [PMID: 17052212 DOI: 10.1042/bst0340846] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Ras proteins are binary switches that, by cycling between inactive GDP-bound and active GTP-bound conformations, regulate multiple cellular signalling pathways including those that control cell growth, differentiation and survival. Approximately 30% of all human tumours express Ras-containing oncogenic mutations that lock the protein into a constitutively active conformation. The activation status of Ras is regulated by two groups of proteins: GEFs (guanine nucleotide-exchange factors) bind to Ras and enhance the exchange of GDP for GTP, thereby activating it, whereas GAPs (GTPase-activating proteins) inactivate Ras by binding to the GTP-bound form and enhancing the hydrolysis of the bound nucleotide back to GDP. In this review, we focus on a group of key regulators of Ras inactivation, the GAP1 family of Ras-GAPs. The members of this family are GAP1m, GAP1IP4BP, CAPRI (Ca2+-promoted Ras inactivator) and RASAL (Ras-GTPase-activating-like protein) and, as we will discuss, they are emerging as important modulators of Ras and small GTPase signalling that are subject to regulation by a diverse array of events and second messenger signals.
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Affiliation(s)
- S Yarwood
- The Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
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12
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Carlton JG, Bujny MV, Peter BJ, Oorschot VMJ, Rutherford A, Arkell RS, Klumperman J, McMahon HT, Cullen PJ. Sorting nexin-2 is associated with tubular elements of the early endosome, but is not essential for retromer-mediated endosome-to-TGN transport. J Cell Sci 2006; 118:4527-39. [PMID: 16179610 PMCID: PMC1904489 DOI: 10.1242/jcs.02568] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sorting nexins are a large family of phox-homology-domain-containing proteins that have been implicated in the control of endosomal sorting. Sorting nexin-1 is a component of the mammalian retromer complex that regulates retrieval of the cation-independent mannose 6-phosphate receptor from endosomes to the trans-Golgi network. In yeast, retromer is composed of Vps5p (the orthologue of sorting nexin-1), Vps17p (a related sorting nexin) and a cargo selective subcomplex composed of Vps26p, Vps29p and Vps35p. With the exception of Vps17p, mammalian orthologues of all yeast retromer components have been identified. For Vps17p, one potential mammalian orthologue is sorting nexin-2. Here we show that, like sorting nexin-1, sorting nexin-2 binds phosphatidylinositol 3-monophosphate and phosphatidylinositol 3,5-bisphosphate, and possesses a Bin/Amphiphysin/Rvs domain that can sense membrane curvature. However, in contrast to sorting nexin-1, sorting nexin-2 could not induce membrane tubulation in vitro or in vivo. Functionally, we show that endogenous sorting nexin-1 and sorting nexin-2 co-localise on high curvature tubular elements of the 3-phosphoinositide-enriched early endosome, and that suppression of sorting nexin-2 does not perturb the degradative sorting of receptors for epidermal growth factor or transferrin, nor the steady-state distribution of the cation-independent mannose 6-phosphate receptor. However, suppression of sorting nexin-2 results in a subtle alteration in the kinetics of cation-independent mannose 6-phosphate receptor retrieval. These data suggest that although sorting nexin-2 may be a component of the retromer complex, its presence is not essential for the regulation of endosome-to-trans Golgi network retrieval of the cation-independent mannose 6-phosphate receptor.
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Affiliation(s)
- Jez G. Carlton
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Miriam V. Bujny
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Brian J. Peter
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
| | - Viola M. J. Oorschot
- Cell Microscopy Center, Department of Cell Biology and Institute for Biomembranes, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Anna Rutherford
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Rebecca S. Arkell
- Signalling Programme, The Babraham Institute, Babraham Hall, Cambridge CB2 4AT, UK
| | - Judith Klumperman
- Cell Microscopy Center, Department of Cell Biology and Institute for Biomembranes, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Harvey T. McMahon
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
| | - Peter J. Cullen
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
- Author for correspondence (e-mail: )
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13
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Abstract
Phosphoinositide phosphates (PIPs) correspond to phosphorylated derivatives of phosphatidylinositol (PI). Despite their relatively low abundance in the plasma membrane, PIPs play a crucial role as precursors of second messengers and are themselves important signaling and targeting molecules. Indeed, modulation of levels of PIPs affects, for example, cortical actin organization, membrane dynamics, and cell migration. The focus of this review is on selected interesting targets of PIPs. Those proteins that bind PIPs and are involved in regulation of actin assembly, actin membrane linkage, and actin contractility are discussed, as well as those that are involved in signaling, such as small GTPases, protein kinases, and phosphatases, or in regulation of membrane dynamics.
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Affiliation(s)
- Verena Niggli
- Department of Pathology, University of Bern, CH-3010 Bern, Switzerland.
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14
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Kupzig S, Walker SA, Cullen PJ. The frequencies of calcium oscillations are optimized for efficient calcium-mediated activation of Ras and the ERK/MAPK cascade. Proc Natl Acad Sci U S A 2005; 102:7577-82. [PMID: 15890781 PMCID: PMC1103707 DOI: 10.1073/pnas.0409611102] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2004] [Indexed: 01/10/2023] Open
Abstract
Ras proteins are binary switches that, by cycling through inactive GDP- and active GTP-bound conformations, regulate multiple cellular signaling pathways, including those that control growth and differentiation. For some time, it has been known that receptor-mediated increases in the concentration of intracellular free calcium ([Ca(2+)](i)) can modulate Ras activation. Increases in [Ca(2+)](i) often occur as repetitive Ca(2+) spikes or oscillations. Induced by electrical or receptor stimuli, these repetitive Ca(2+) oscillations increase in frequency with the amplitude of receptor stimuli, a phenomenon critical for the induction of selective cellular functions. Here, we show that Ca(2+) oscillations are optimized for Ca(2+)-mediated activation of Ras and signaling through the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) cascade. We present additional evidence that Ca(2+) oscillations reduce the effective Ca(2+) threshold for the activation of Ras and that the oscillatory frequency is optimized for activation of Ras and the ERK/MAPK pathway. Our results describe a hitherto unrecognized link between complex Ca(2+) signals and the modulation of the Ras/ERK/MAPK signaling cascade.
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Affiliation(s)
- Sabine Kupzig
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
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15
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Kim JA, Yeh DC, Ver M, Li Y, Carranza A, Conrads TP, Veenstra TD, Harrington MA, Quon MJ. Phosphorylation of Ser24 in the pleckstrin homology domain of insulin receptor substrate-1 by Mouse Pelle-like kinase/interleukin-1 receptor-associated kinase: cross-talk between inflammatory signaling and insulin signaling that may contribute to insulin resistance. J Biol Chem 2005; 280:23173-83. [PMID: 15849359 DOI: 10.1074/jbc.m501439200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Inflammation contributes to insulin resistance in diabetes and obesity. Mouse Pelle-like kinase (mPLK, homolog of human IL-1 receptor-associated kinase (IRAK)) participates in inflammatory signaling. We evaluated IRS-1 as a novel substrate for mPLK that may contribute to linking inflammation with insulin resistance. Wild-type mPLK, but not a kinase-inactive mutant (mPLK-KD), directly phosphorylated full-length IRS-1 in vitro. This in vitro phosphorylation was increased when mPLK was immunoprecipitated from tumor necrosis factor (TNF)-alpha-treated cells. In NIH-3T3(IR) cells, wild-type mPLK (but not mPLK-KD) co-immunoprecipitated with IRS-1. This association was increased by treatment of cells with TNF-alpha. Using mass spectrometry, we identified Ser(24) in the pleckstrin homology (PH) domain of IRS-1 as a specific phosphorylation site for mPLK. IRS-1 mutants S24D or S24E (mimicking phosphorylation at Ser(24)) had impaired ability to associate with insulin receptors resulting in diminished tyrosine phosphorylation of IRS-1 and impaired ability of IRS-1 to bind and activate PI-3 kinase in response to insulin. IRS-1-S24D also had an impaired ability to mediate insulin-stimulated translocation of GLUT4 in rat adipose cells. Importantly, endogenous mPLK/IRAK was activated in response to TNF-alpha or interleukin 1 treatment of primary adipose cells. In addition, using a phospho-specific antibody against IRS-1 phosphorylated at Ser(24), we found that interleukin-1 or TNF-alpha treatment of Fao cells stimulated increased phosphorylation of endogenous IRS-1 at Ser(24). We conclude that IRS-1 is a novel physiological substrate for mPLK. TNF-alpha-regulated phosphorylation at Ser(24) in the pleckstrin homology domain of IRS-1 by mPLK/IRAK represents an additional mechanism for cross-talk between inflammatory signaling and insulin signaling that may contribute to metabolic insulin resistance.
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Affiliation(s)
- Jeong-a Kim
- Diabetes Unit, National Center for Complementary and Alternative Medicine, National Institutes of Health, Bethesda, Maryland 20892, USA
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16
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Abstract
The small GTPases of the Ras superfamily mediate numerous biological processes through their ability to cycle between an inactive GDP-bound and an active GTP-bound form. Among the key regulators of GTPase cycling are the GTPase-activating proteins (GAPs), which stimulate the weak intrinsic GTP-hydrolysis activity of the GTPases, thereby inactivating them. Despite the abundance of GAPs and the fact that mutations in GAP-encoding genes underlie several human diseases, these proteins have received relatively little attention. Recent studies have addressed the regulatory mechanisms that influence GAP activity. So far, findings suggest that GAP activity is regulated by several mechanisms, including protein-protein interactions, phospholipid interactions, phosphorylation, subcellular translocation and proteolytic degradation.
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Affiliation(s)
- Andre Bernards
- MGH Cancer Center and Harvard Medical School, 149 13th Street, Charlestown, MA 02129, USA
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Walker SA, Kupzig S, Bouyoucef D, Davies LC, Tsuboi T, Bivona TG, Cozier GE, Lockyer PJ, Buckler A, Rutter GA, Allen MJ, Philips MR, Cullen PJ. Identification of a Ras GTPase-activating protein regulated by receptor-mediated Ca2+ oscillations. EMBO J 2004; 23:1749-60. [PMID: 15057271 PMCID: PMC394250 DOI: 10.1038/sj.emboj.7600197] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2004] [Accepted: 03/05/2004] [Indexed: 02/02/2023] Open
Abstract
Receptor-mediated increases in the concentration of intracellular free calcium ([Ca2+]i) are responsible for controlling a plethora of physiological processes including gene expression, secretion, contraction, proliferation, neural signalling, and learning. Increases in [Ca2+]i often occur as repetitive Ca2+ spikes or oscillations. Induced by electrical or receptor stimuli, these repetitive Ca2+ spikes increase their frequency with the amplitude of the receptor stimuli, a phenomenon that appears critical for the induction of selective cellular functions. Here we report the characterisation of RASAL, a Ras GTPase-activating protein that senses the frequency of repetitive Ca2+ spikes by undergoing synchronous oscillatory associations with the plasma membrane. Importantly, we show that only during periods of plasma membrane association does RASAL inactivate Ras signalling. Thus, RASAL senses the frequency of complex Ca2+ signals, decoding them through a regulation of the activation state of Ras. Our data provide a hitherto unrecognised link between complex Ca2+ signals and the regulation of Ras.
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Affiliation(s)
- Simon A Walker
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | - Sabine Kupzig
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | - Dalila Bouyoucef
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | - Louise C Davies
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | - Takashi Tsuboi
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | - Trever G Bivona
- Department of Medicine, Cell Biology and Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Gyles E Cozier
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | - Peter J Lockyer
- Signalling Programme, The Babraham Institute, Babraham, Cambridge, UK
| | - Alan Buckler
- Ardais Corporation, One Ledgemont Center, Lexington, MA, USA
| | - Guy A Rutter
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | | | - Mark R Philips
- Department of Medicine, Cell Biology and Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Peter J Cullen
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK. Tel.: +44 117 954 6426; Fax: +44 117 928 8274; E-mail:
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