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Igolkina AA, Armoskus C, Newman JRB, Evgrafov OV, McIntyre LM, Nuzhdin SV, Samsonova MG. Analysis of Gene Expression Variance in Schizophrenia Using Structural Equation Modeling. Front Mol Neurosci 2018; 11:192. [PMID: 29942251 PMCID: PMC6004421 DOI: 10.3389/fnmol.2018.00192] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 05/15/2018] [Indexed: 01/02/2023] Open
Abstract
Schizophrenia (SCZ) is a psychiatric disorder of unknown etiology. There is evidence suggesting that aberrations in neurodevelopment are a significant attribute of schizophrenia pathogenesis and progression. To identify biologically relevant molecular abnormalities affecting neurodevelopment in SCZ we used cultured neural progenitor cells derived from olfactory neuroepithelium (CNON cells). Here, we tested the hypothesis that variance in gene expression differs between individuals from SCZ and control groups. In CNON cells, variance in gene expression was significantly higher in SCZ samples in comparison with control samples. Variance in gene expression was enriched in five molecular pathways: serine biosynthesis, PI3K-Akt, MAPK, neurotrophin and focal adhesion. More than 14% of variance in disease status was explained within the logistic regression model (C-value = 0.70) by predictors accounting for gene expression in 69 genes from these five pathways. Structural equation modeling (SEM) was applied to explore how the structure of these five pathways was altered between SCZ patients and controls. Four out of five pathways showed differences in the estimated relationships among genes: between KRAS and NF1, and KRAS and SOS1 in the MAPK pathway; between PSPH and SHMT2 in serine biosynthesis; between AKT3 and TSC2 in the PI3K-Akt signaling pathway; and between CRK and RAPGEF1 in the focal adhesion pathway. Our analysis provides evidence that variance in gene expression is an important characteristic of SCZ, and SEM is a promising method for uncovering altered relationships between specific genes thus suggesting affected gene regulation associated with the disease. We identified altered gene-gene interactions in pathways enriched for genes with increased variance in expression in SCZ. These pathways and loci were previously implicated in SCZ, providing further support for the hypothesis that gene expression variance plays important role in the etiology of SCZ.
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Affiliation(s)
- Anna A Igolkina
- Institute of Applied Mathematics and Mechanics, Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia
| | - Chris Armoskus
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States
| | - Jeremy R B Newman
- Department of Molecular Genetics & Microbiology, Genetics Institute, University of Florida, Gainesville, FL, United States
| | - Oleg V Evgrafov
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, NY, United States
| | - Lauren M McIntyre
- Department of Molecular Genetics & Microbiology, Genetics Institute, University of Florida, Gainesville, FL, United States
| | - Sergey V Nuzhdin
- Institute of Applied Mathematics and Mechanics, Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia.,Molecular and Computation Biology, University of Southern California, Los Angeles, CA, United States
| | - Maria G Samsonova
- Institute of Applied Mathematics and Mechanics, Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia
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Next-generation sequencing identifies rare variants associated with Noonan syndrome. Proc Natl Acad Sci U S A 2014; 111:11473-8. [PMID: 25049390 DOI: 10.1073/pnas.1324128111] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Noonan syndrome (NS) is a relatively common genetic disorder, characterized by typical facies, short stature, developmental delay, and cardiac abnormalities. Known causative genes account for 70-80% of clinically diagnosed NS patients, but the genetic basis for the remaining 20-30% of cases is unknown. We performed next-generation sequencing on germ-line DNA from 27 NS patients lacking a mutation in the known NS genes. We identified gain-of-function alleles in Ras-like without CAAX 1 (RIT1) and mitogen-activated protein kinase kinase 1 (MAP2K1) and previously unseen loss-of-function variants in RAS p21 protein activator 2 (RASA2) that are likely to cause NS in these patients. Expression of the mutant RASA2, MAP2K1, or RIT1 alleles in heterologous cells increased RAS-ERK pathway activation, supporting a causative role in NS pathogenesis. Two patients had more than one disease-associated variant. Moreover, the diagnosis of an individual initially thought to have NS was revised to neurofibromatosis type 1 based on an NF1 nonsense mutation detected in this patient. Another patient harbored a missense mutation in NF1 that resulted in decreased protein stability and impaired ability to suppress RAS-ERK activation; however, this patient continues to exhibit a NS-like phenotype. In addition, a nonsense mutation in RPS6KA3 was found in one patient initially diagnosed with NS whose diagnosis was later revised to Coffin-Lowry syndrome. Finally, we identified other potential candidates for new NS genes, as well as potential carrier alleles for unrelated syndromes. Taken together, our data suggest that next-generation sequencing can provide a useful adjunct to RASopathy diagnosis and emphasize that the standard clinical categories for RASopathies might not be adequate to describe all patients.
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Molina-Ortiz P, Polizzi S, Ramery E, Gayral S, Delierneux C, Oury C, Iwashita S, Schurmans S. Rasa3 controls megakaryocyte Rap1 activation, integrin signaling and differentiation into proplatelet. PLoS Genet 2014; 10:e1004420. [PMID: 24967784 PMCID: PMC4072513 DOI: 10.1371/journal.pgen.1004420] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 04/20/2014] [Indexed: 01/17/2023] Open
Abstract
Rasa3 is a GTPase activating protein of the GAP1 family which targets Ras and Rap1. Ubiquitous Rasa3 catalytic inactivation in mouse results in early embryonic lethality. Here, we show that Rasa3 catalytic inactivation in mouse hematopoietic cells results in a lethal syndrome characterized by severe defects during megakaryopoiesis, thrombocytopenia and a predisposition to develop preleukemia. The main objective of this study was to define the cellular and the molecular mechanisms of terminal megakaryopoiesis alterations. We found that Rasa3 catalytic inactivation altered megakaryocyte development, adherence, migration, actin cytoskeleton organization and differentiation into proplatelet forming megakaryocytes. These megakaryocyte alterations were associated with an increased active Rap1 level and a constitutive integrin activation. Thus, these mice presented a severe thrombocytopenia, bleeding and anemia associated with an increased percentage of megakaryocytes in the bone marrow, bone marrow fibrosis, extramedular hematopoiesis, splenomegaly and premature death. Altogether, our results indicate that Rasa3 catalytic activity controls Rap1 activation and integrin signaling during megakaryocyte differentiation in mouse. Megakaryocytes are the bone marrow cellular precursors of circulating blood platelets and give rise to nascent platelets by forming branching filaments called proplatelets. Terminal differentiation of round megakaryocytes into branched proplatelet forming megakaryocytes is a complex cytoskeletal-driven process which is affected in rare human familial thrombocytopenias. Interactions of megakaryocytes with extracellular matrix proteins are essential in this process since constitutive megakaryocyte integrin activity caused by specific mutations in ITGA2B or ITGB3 genes encoding for extracellular matrix protein receptors may result in abnormal adherent megakaryocytes, defect in proplatelet formation and thrombocytopenia. Here, we show that Rasa3, a GTPase activating protein of the GAP1 family, controls Rap1 activation and integrin signaling during megakaryocyte differentiation. We found that Rasa3 catalytic inactivation in mice altered megakaryocyte development, adherence, migration, actin cytoskeleton organization and differentiation into proplatelet. Thus, these mice presented a severe thrombocytopenia, bleeding and anemia.
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Affiliation(s)
- Patricia Molina-Ortiz
- Laboratory of Functional Genetics, GIGA-Research Centre, Université de Liège, Liège, and Welbio, Belgium
| | - Séléna Polizzi
- Institut de Recherches Interdisciplinaires en Biologie Humaine et Moléculaire (IRIBHM), Institut de Biologie et de Médecine Moléculaires (IBMM), Faculté de Médecine, Université Libre de Bruxelles, Gosselies, Belgium
| | - Eve Ramery
- Laboratoire de Biologie Clinique, Faculté de Médecine-vétérinaire, Université de Liège, Liège, Belgium
| | - Stéphanie Gayral
- Institut de Recherches Interdisciplinaires en Biologie Humaine et Moléculaire (IRIBHM), Institut de Biologie et de Médecine Moléculaires (IBMM), Faculté de Médecine, Université Libre de Bruxelles, Gosselies, Belgium
| | - Céline Delierneux
- Laboratory of Thrombosis and Hemostasis, GIGA-Research Centre, Université de Liège, Liège, Belgium
| | - Cécile Oury
- Laboratory of Thrombosis and Hemostasis, GIGA-Research Centre, Université de Liège, Liège, Belgium
| | - Shintaro Iwashita
- Mitsubishi Kagaku Institute of Life Sciences and Faculty of Pharmacy, Iwaki Meisei University, Iwaki, Japan
| | - Stéphane Schurmans
- Laboratory of Functional Genetics, GIGA-Research Centre, Université de Liège, Liège, and Welbio, Belgium
- Institut de Recherches Interdisciplinaires en Biologie Humaine et Moléculaire (IRIBHM), Institut de Biologie et de Médecine Moléculaires (IBMM), Faculté de Médecine, Université Libre de Bruxelles, Gosselies, Belgium
- * E-mail:
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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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A two-dimensional ERK-AKT signaling code for an NGF-triggered cell-fate decision. Mol Cell 2011; 45:196-209. [PMID: 22206868 DOI: 10.1016/j.molcel.2011.11.023] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Revised: 08/23/2011] [Accepted: 11/04/2011] [Indexed: 11/22/2022]
Abstract
Growth factors activate Ras, PI3K, and other signaling pathways. It is not well understood how these signals are translated by individual cells into a decision to proliferate or differentiate. Here, using single-cell image analysis of nerve growth factor (NGF)-stimulated PC12 cells, we identified a two-dimensional phospho-ERK (pERK)-phospho-AKT (pAKT) response map with a curved boundary that separates differentiating from proliferating cells. The boundary position remained invariant when different stimuli were used or upstream signaling components perturbed. We further identified Rasa2 as a negative feedback regulator that links PI3K to Ras, placing the stochastically distributed pERK-pAKT signals close to the decision boundary. This allows for uniform NGF stimuli to create a subpopulation of cells that differentiates with each cycle of proliferation. Thus, by linking a complex signaling system to a simpler intermediate response map, cells gain unique integration and control capabilities to balance cell number expansion with differentiation.
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The ability of GAP1IP4BP to function as a Rap1 GTPase-activating protein (GAP) requires its Ras GAP-related domain and an arginine finger rather than an asparagine thumb. Mol Cell Biol 2009; 29:3929-40. [PMID: 19433443 DOI: 10.1128/mcb.00427-09] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
GAP1(IP4BP) is a member of the GAP1 family of Ras GTPase-activating proteins (GAPs) that includes GAP1(m), CAPRI, and RASAL. Composed of a central Ras GAP-related domain (RasGRD), surrounded by amino-terminal C2 domains and a carboxy-terminal PH/Btk domain, these proteins, with the notable exception of GAP1(m), possess an unexpected arginine finger-dependent GAP activity on the Ras-related protein Rap1 (S. Kupzig, D. Deaconescu, D. Bouyoucef, S. A. Walker, Q. Liu, C. L. Polte, O. Daumke, T. Ishizaki, P. J. Lockyer, A. Wittinghofer, and P. J. Cullen, J. Biol. Chem. 281:9891-9900, 2006). Here, we have examined the mechanism through which GAP1(IP4BP) can function as a Rap1 GAP. We show that deletion of domains on either side of the RasGRD, while not affecting Ras GAP activity, do dramatically perturb Rap1 GAP activity. By utilizing GAP1(IP4BP)/GAP1(m) chimeras, we establish that although the C2 and PH/Btk domains are required to stabilize the RasGRD, it is this domain which contains the catalytic machinery required for Rap1 GAP activity. Finally, a key residue in Rap1-specific GAPs is a catalytic asparagine, the so-called asparagine thumb. By generating a molecular model describing the predicted Rap1-binding site in the RasGRD of GAP1(IP4BP), we show that mutagenesis of individual asparagine or glutamine residues that lie in close proximity to the predicted binding site has no detectable effect on the in vivo Rap1 GAP activity of GAP1(IP4BP). In contrast, we present evidence consistent with a model in which the RasGRD of GAP1(IP4BP) functions to stabilize the switch II region of Rap1, allowing stabilization of the transition state during GTP hydrolysis initiated by the arginine finger.
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7
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Jin H, Wang X, Ying J, Wong AHY, Cui Y, Srivastava G, Shen ZY, Li EM, Zhang Q, Jin J, Kupzig S, Chan ATC, Cullen PJ, Tao Q. Epigenetic silencing of a Ca(2+)-regulated Ras GTPase-activating protein RASAL defines a new mechanism of Ras activation in human cancers. Proc Natl Acad Sci U S A 2007; 104:12353-8. [PMID: 17640920 PMCID: PMC1941473 DOI: 10.1073/pnas.0700153104] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Ras has achieved notoriety as an oncogene aberrantly activated in multiple human tumors. Approximately 30% of all human tumors express an oncogenic form of this GTPase that is locked in an active conformation as a result of being insensitive to Ras GTPase-activating proteins (GAPs), proteins that normally regulate the inactivation of Ras by enhancing its intrinsic GTPase activity. Besides oncogenic mutations in Ras, signaling by wild-type Ras is also frequently deregulated in tumors through aberrant coupling to activated cell surface receptors. This indicates that alternative mechanisms of aberrant wild-type Ras activation may be involved in tumorigenesis. Here, we describe another mechanism through which aberrant Ras activation is achieved in human cancers. We have established that Ras GTPase-activating-like protein (RASAL), a Ca(2+)-regulated Ras GAP that decodes the frequency of Ca(2+) oscillations, is silenced through CpG methylation in multiple tumors. With the finding that ectopic expression of catalytically active RASAL leads to growth inhibition of these tumor cells by Ras inactivation, we have provided evidence that epigenetically silencing of this Ras GAP represents a mechanism of aberrant Ras activation in certain cancers. Our demonstration that RASAL constitutes a tumor suppressor gene has therefore further emphasized the importance of Ca(2+) in the regulation of Ras signaling and has established that deregulation of this pathway is an important step in Ras-mediated tumorigenesis.
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Affiliation(s)
- Hongchuan Jin
- *Cancer Epigenetics Laboratory, State Key Laboratory in Oncology in South China, Sir Y. K. Pao Center for Cancer, Department of Clinical Oncology, Hong Kong Cancer Institute and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
| | - Xian Wang
- *Cancer Epigenetics Laboratory, State Key Laboratory in Oncology in South China, Sir Y. K. Pao Center for Cancer, Department of Clinical Oncology, Hong Kong Cancer Institute and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
| | - Jianming Ying
- *Cancer Epigenetics Laboratory, State Key Laboratory in Oncology in South China, Sir Y. K. Pao Center for Cancer, Department of Clinical Oncology, Hong Kong Cancer Institute and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
| | - Ada H. Y. Wong
- *Cancer Epigenetics Laboratory, State Key Laboratory in Oncology in South China, Sir Y. K. Pao Center for Cancer, Department of Clinical Oncology, Hong Kong Cancer Institute and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
| | - Yan Cui
- *Cancer Epigenetics Laboratory, State Key Laboratory in Oncology in South China, Sir Y. K. Pao Center for Cancer, Department of Clinical Oncology, Hong Kong Cancer Institute and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
| | | | - Zhong-Ying Shen
- Shantou University Medical College/Chinese University of Hong Kong Joint Epigenetics Group, Shantou University Medical College, Shantou 515041, China
| | - En-Min Li
- Shantou University Medical College/Chinese University of Hong Kong Joint Epigenetics Group, Shantou University Medical College, Shantou 515041, China
| | - Qian Zhang
- Department of Urology, Peking University First Hospital and Institute of Urology, Beijing 100034, China; and
| | - Jie Jin
- Department of Urology, Peking University First Hospital and Institute of Urology, Beijing 100034, China; and
| | - Sabine Kupzig
- The Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Anthony T. C. Chan
- *Cancer Epigenetics Laboratory, State Key Laboratory in Oncology in South China, Sir Y. K. Pao Center for Cancer, Department of Clinical Oncology, Hong Kong Cancer Institute and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
| | - Peter J. Cullen
- The Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
- To whom correspondence may be addressed. E-mail: or
| | - Qian Tao
- *Cancer Epigenetics Laboratory, State Key Laboratory in Oncology in South China, Sir Y. K. Pao Center for Cancer, Department of Clinical Oncology, Hong Kong Cancer Institute and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
- Shantou University Medical College/Chinese University of Hong Kong Joint Epigenetics Group, Shantou University Medical College, Shantou 515041, China
- To whom correspondence may be addressed. E-mail: or
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Kupzig S, Deaconescu D, Bouyoucef D, Walker SA, Liu Q, Polte CL, Daumke O, Ishizaki T, Lockyer PJ, Wittinghofer A, Cullen PJ. GAP1 family members constitute bifunctional Ras and Rap GTPase-activating proteins. J Biol Chem 2006; 281:9891-900. [PMID: 16431904 PMCID: PMC1904491 DOI: 10.1074/jbc.m512802200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
GAP1(IP4BP) is a member of the GAP1 family of Ras GTPase-activating proteins (Ras GAPs) that includes GAP1(m), CAPRI, and RASAL. Composed of a central Ras GAP domain, surrounded by amino-terminal C(2) domains and a carboxyl-terminal pleckstrin homology/Bruton's tyrosine kinase domain, GAP1(IP4BP) has previously been shown to possess an unexpected GAP activity on the Ras-related protein Rap, besides the predicted Ras GAP activity (Cullen, P. J., Hsuan, J. J., Truong, O., Letcher, A. J., Jackson, T. R., Dawson, A. P., and Irvine, R. F. (1995) Nature 376, 527-530). Here we have shown that GAP1(IP4BP) is indeed an efficient Ras/Rap GAP, having K(m)s of 213 and 42 microm and estimated k(cat)s of 48 and 16 s(-1) for Ras and Rap, respectively. For this dual activity, regions outside the Ras GAP domain are required, as the isolated domain (residues 291-569) retains a pronounced Ras GAP activity yet has very low activity toward Rap. Interestingly, mutagenesis of the Ras GAP arginine finger, and surrounding residues important in Ras binding, inhibit both Ras and Rap GAP activity of GAP1(IP4BP). Although the precise details by which GAP1(IP4BP) can function as a Rap GAP remain to be determined, these data are consistent with Rap associating with GAP1(IP4BP) through the Ras-binding site within the Ras GAP domain. Finally, we have established that such dual Ras/Rap GAP activity is not restricted to GAP1(IP4BP). Although GAP1(m) appears to constitute a specific Ras GAP, CAPRI and RASAL display dual activity. For CAPRI, its Rap GAP activity is modulated upon its Ca(2+)-induced association with the plasma membrane.
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Affiliation(s)
- Sabine Kupzig
- From the Henry Wellcome Integrated Signaling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Delia Deaconescu
- Max-Planck-Institut für Molekulare Physiologie, Postfach 50 02 47, 44202 Dortmund, Germany, and
| | - Dalila Bouyoucef
- From the Henry Wellcome Integrated Signaling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Simon A. Walker
- Signaling Programme, The Babraham Institute, Cambridge CB2 4AT, United Kingdom
| | - Qing Liu
- Signaling Programme, The Babraham Institute, Cambridge CB2 4AT, United Kingdom
| | - Christian L. Polte
- Max-Planck-Institut für Molekulare Physiologie, Postfach 50 02 47, 44202 Dortmund, Germany, and
| | - Oliver Daumke
- Max-Planck-Institut für Molekulare Physiologie, Postfach 50 02 47, 44202 Dortmund, Germany, and
| | - Toshimasa Ishizaki
- Max-Planck-Institut für Molekulare Physiologie, Postfach 50 02 47, 44202 Dortmund, Germany, and
| | - Peter J. Lockyer
- Signaling Programme, The Babraham Institute, Cambridge CB2 4AT, United Kingdom
| | - Alfred Wittinghofer
- Max-Planck-Institut für Molekulare Physiologie, Postfach 50 02 47, 44202 Dortmund, Germany, and
| | - Peter J. Cullen
- From the Henry Wellcome Integrated Signaling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
- To whom correspondence should be addressed. Tel.: 44-117-954-6426; Fax: 44-117-928-8274; E-mail:
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Ito S, Ito Y, Senga T, Hattori S, Matsuo S, Hamaguchi M. v-Src requires Ras signaling for the suppression of gap junctional intercellular communication. Oncogene 2005; 25:2420-4. [PMID: 16301992 DOI: 10.1038/sj.onc.1209263] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Cell transformation by v-Src causes suppression of gap junctional intercellular communication (GJIC). Although tyrosine phosphorylation of connexin43 (Cx43), a gap junctional component, appears to be necessary for the suppression, involvement of other signaling remains unclear. We investigated the role of Ras signaling in the suppression of GJIC by v-Src. Conditional expression of either S17N Ras or mtGap1m dramatically recovered GJIC in v-Src-transformed cells. Although expression of S17N Ras or mtGap1m substantially decreased the levels of active Ras, tyrosine phosphorylation of cellular proteins including Cx43 remained unchanged. Similarly, treatment of v-Src-transfomed cells with a Ras farnesyltransferase inhibitor, manumycin A, restored GJIC, whereas tyrosine phosphorylation of Cx43 remained unchanged. Thus, these results strongly suggest that, in addition to Cx43 phosphorylation, constitutive activation of Ras signaling is required for the suppression of GJIC by v-Src.
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Affiliation(s)
- S Ito
- Division of Cancer Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
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10
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Zhang J, Guo J, Dzhagalov I, He YW. An essential function for the calcium-promoted Ras inactivator in Fcgamma receptor-mediated phagocytosis. Nat Immunol 2005; 6:911-9. [PMID: 16041389 PMCID: PMC1464573 DOI: 10.1038/ni1232] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2004] [Accepted: 06/01/2005] [Indexed: 01/05/2023]
Abstract
Fc receptor (FcR)-mediated phagocytosis requires activation of the Rho GTPases Cdc42 and Rac1, but how they are recruited to the FcR is unknown. Here we show that the calcium-promoted Ras inactivator (CAPRI), a Ras GTPase-activating protein, functions as an adaptor for Cdc42 and Rac1 during FcR-mediated phagocytosis. CAPRI-deficient macrophages had impaired FcgammaR-mediated phagocytosis and oxidative burst, as well as defective activation of Cdc42 and Rac1. CAPRI interacted constitutively with both Cdc42 and Rac1 and translocated to phagocytic cups during FcgammaR-mediated phagocytosis. CAPRI-deficient mice had an impaired innate immune response to bacterial infection. These results suggest that CAPRI provides a link between FcgammaR and Cdc42 and Rac1 and is essential for innate immune responses.
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Affiliation(s)
- Jun Zhang
- Department of Immunology, Duke University Medical Center, Durham, North Carolina 27710, USA
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Chautard H, Jacquet M, Schoentgen F, Bureaud N, Bénédetti H. Tfs1p, a member of the PEBP family, inhibits the Ira2p but not the Ira1p Ras GTPase-activating protein in Saccharomyces cerevisiae. EUKARYOTIC CELL 2004; 3:459-70. [PMID: 15075275 PMCID: PMC387632 DOI: 10.1128/ec.3.2.459-470.2004] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Ras proteins are guanine nucleotide-binding proteins that are highly conserved among eukaryotes. They are involved in signal transduction pathways and are tightly regulated by two sets of antagonistic proteins: GTPase-activating proteins (GAPs) inhibit Ras proteins, whereas guanine exchange factors activate them. In this work, we describe Tfs1p, the first physiological inhibitor of a Ras GAP, Ira2p, in Saccharomyces cerevisiae. TFS1 is a multicopy suppressor of the cdc25-1 mutation in yeast and corresponds to the so-called Ic CPY cytoplasmic inhibitor. Moreover, Tfs1p belongs to the phosphatidylethanolamine-binding protein (PEBP) family, one member of which is RKIP, a kinase and serine protease inhibitor and a metastasis inhibitor in prostate cancer. In this work, the results of (i) a two-hybrid screen of a yeast genomic library, (ii) glutathione S-transferase pulldown experiments, (iii) multicopy suppressor tests of cdc25-1 mutants, and (iv) stress resistance tests to evaluate the activation level of Ras demonstrate that Tfs1p interacts with and inhibits Ira2p. We further show that the conserved ligand-binding pocket of Tfs1-the hallmark of the PEBP family-is important for its inhibitory activity.
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Affiliation(s)
- Hélène Chautard
- Centre de Biophysique Moléculaire, Centre National de la Recherche Scientifique, UPR 4301, University of Orléans and INSERM, 45071 Orléans Cedex 2, France
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12
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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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13
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Eerola I, Boon LM, Mulliken JB, Burrows PE, Dompmartin A, Watanabe S, Vanwijck R, Vikkula M. Capillary malformation-arteriovenous malformation, a new clinical and genetic disorder caused by RASA1 mutations. Am J Hum Genet 2003; 73:1240-9. [PMID: 14639529 PMCID: PMC1180390 DOI: 10.1086/379793] [Citation(s) in RCA: 444] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2003] [Accepted: 09/09/2003] [Indexed: 11/04/2022] Open
Abstract
Capillary malformation (CM), or "port-wine stain," is a common cutaneous vascular anomaly that initially appears as a red macular stain that darkens over years. CM also occurs in several combined vascular anomalies that exhibit hypertrophy, such as Sturge-Weber syndrome, Klippel-Trenaunay syndrome, and Parkes Weber syndrome. Occasional familial segregation of CM suggests that there is genetic susceptibility, underscored by the identification of a large locus, CMC1, on chromosome 5q. We used genetic fine mapping with polymorphic markers to reduce the size of the CMC1 locus. A positional candidate gene, RASA1, encoding p120-RasGAP, was screened for mutations in 17 families. Heterozygous inactivating RASA1 mutations were detected in six families manifesting atypical CMs that were multiple, small, round to oval in shape, and pinkish red in color. In addition to CM, either arteriovenous malformation, arteriovenous fistula, or Parkes Weber syndrome was documented in all the families with a mutation. We named this newly identified association caused by RASA1 mutations "CM-AVM," for capillary malformation-arteriovenous malformation. The phenotypic variability can be explained by the involvement of p120-RasGAP in signaling for various growth factor receptors that control proliferation, migration, and survival of several cell types, including vascular endothelial cells.
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Affiliation(s)
- Iiro Eerola
- Laboratory of Human Molecular Genetics, Christian de Duve Institute of Cellular Pathology, and Centre for Vascular Anomalies, Division of Plastic Surgery, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels; Vascular Anomalies Center, Division of Plastic Surgery, and Division of Interventional Radiology, Children’s Hospital, Harvard Medical School, Boston; Division of Dermatology, CHU Caen, France; and Department of Plastic and Reconstructive Surgery, Showa University School of Medicine, Tokyo
| | - Laurence M. Boon
- Laboratory of Human Molecular Genetics, Christian de Duve Institute of Cellular Pathology, and Centre for Vascular Anomalies, Division of Plastic Surgery, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels; Vascular Anomalies Center, Division of Plastic Surgery, and Division of Interventional Radiology, Children’s Hospital, Harvard Medical School, Boston; Division of Dermatology, CHU Caen, France; and Department of Plastic and Reconstructive Surgery, Showa University School of Medicine, Tokyo
| | - John B. Mulliken
- Laboratory of Human Molecular Genetics, Christian de Duve Institute of Cellular Pathology, and Centre for Vascular Anomalies, Division of Plastic Surgery, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels; Vascular Anomalies Center, Division of Plastic Surgery, and Division of Interventional Radiology, Children’s Hospital, Harvard Medical School, Boston; Division of Dermatology, CHU Caen, France; and Department of Plastic and Reconstructive Surgery, Showa University School of Medicine, Tokyo
| | - Patricia E. Burrows
- Laboratory of Human Molecular Genetics, Christian de Duve Institute of Cellular Pathology, and Centre for Vascular Anomalies, Division of Plastic Surgery, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels; Vascular Anomalies Center, Division of Plastic Surgery, and Division of Interventional Radiology, Children’s Hospital, Harvard Medical School, Boston; Division of Dermatology, CHU Caen, France; and Department of Plastic and Reconstructive Surgery, Showa University School of Medicine, Tokyo
| | - Anne Dompmartin
- Laboratory of Human Molecular Genetics, Christian de Duve Institute of Cellular Pathology, and Centre for Vascular Anomalies, Division of Plastic Surgery, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels; Vascular Anomalies Center, Division of Plastic Surgery, and Division of Interventional Radiology, Children’s Hospital, Harvard Medical School, Boston; Division of Dermatology, CHU Caen, France; and Department of Plastic and Reconstructive Surgery, Showa University School of Medicine, Tokyo
| | - Shoji Watanabe
- Laboratory of Human Molecular Genetics, Christian de Duve Institute of Cellular Pathology, and Centre for Vascular Anomalies, Division of Plastic Surgery, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels; Vascular Anomalies Center, Division of Plastic Surgery, and Division of Interventional Radiology, Children’s Hospital, Harvard Medical School, Boston; Division of Dermatology, CHU Caen, France; and Department of Plastic and Reconstructive Surgery, Showa University School of Medicine, Tokyo
| | - Romain Vanwijck
- Laboratory of Human Molecular Genetics, Christian de Duve Institute of Cellular Pathology, and Centre for Vascular Anomalies, Division of Plastic Surgery, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels; Vascular Anomalies Center, Division of Plastic Surgery, and Division of Interventional Radiology, Children’s Hospital, Harvard Medical School, Boston; Division of Dermatology, CHU Caen, France; and Department of Plastic and Reconstructive Surgery, Showa University School of Medicine, Tokyo
| | - Miikka Vikkula
- Laboratory of Human Molecular Genetics, Christian de Duve Institute of Cellular Pathology, and Centre for Vascular Anomalies, Division of Plastic Surgery, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels; Vascular Anomalies Center, Division of Plastic Surgery, and Division of Interventional Radiology, Children’s Hospital, Harvard Medical School, Boston; Division of Dermatology, CHU Caen, France; and Department of Plastic and Reconstructive Surgery, Showa University School of Medicine, Tokyo
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14
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Requirement of Ras for the activation of mitogen-activated protein kinase by calcium influx, cAMP, and neurotrophin in hippocampal neurons. J Neurosci 2001. [PMID: 11517234 DOI: 10.1523/jneurosci.21-17-06459.2001] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Mitogen-activated protein (MAP) kinase plays important roles in the establishment of long-term potentiation both in vitro and in living animals. MAP kinase is activated in response to a broad range of stimuli, including calcium influx through NMDA receptor and L-type calcium channel, cAMP, and neurotrophins. To investigate the role of Ras in the activation of MAP kinase and cAMP response element-binding protein (CREB) in hippocampal neurons, we inhibited Ras function by overexpressing a Ras GTPase-activating protein, Gap1(m), or dominant negative Ras by means of adenovirus vectors. Gap1(m) expression almost completely suppressed MAP kinase activation in response to NMDA, calcium ionophore, membrane depolarization, forskolin, and brain-derived neurotrophic factor (BDNF). Dominant negative Ras also showed similar effects. On the other hand, Rap1GAP did not significantly inhibit the forskolin-induced activation of MAP kinase. In contrast to MAP kinase activation, the inactivation of Ras activity did not inhibit significantly NMDA-induced CREB phosphorylation, whereas BDNF-induced CREB phosphorylation was inhibited almost completely. These results demonstrate that Ras transduces signals elicited by a broad range of stimuli to MAP kinase in hippocampal neurons and further suggest that CREB phosphorylation depends on multiple pathways.
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15
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Baba K, Takeshita A, Majima K, Ueda R, Kondo S, Juni N, Yamamoto D. The Drosophila Bruton's tyrosine kinase (Btk) homolog is required for adult survival and male genital formation. Mol Cell Biol 1999; 19:4405-13. [PMID: 10330180 PMCID: PMC104399 DOI: 10.1128/mcb.19.6.4405] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/1998] [Accepted: 02/23/1999] [Indexed: 11/20/2022] Open
Abstract
We isolated a Drosophila fickleP (ficP) mutant with a shortened copulatory duration and reduced adult-stage life span. The reduced copulatory duration is ascribable to incomplete fusion of the left and right halves of the apodeme that holds the penis during copulation. ficP is an intronic mutation occurring in the Btk gene, a gene which encodes two forms (type 1 and type 2) of a Bruton's tyrosine kinase (Btk) family cytoplasmic tyrosine kinase as a result of alternative exon usage. The ficP mutation prevents the formation of the type 2 isoform but leaves expression of the type 1 transcript intact. Ubiquitous overexpression of the wild-type cDNA by using a heat shock 70 promoter during the late larval or pupal stages rescued the life span and genital defects in the mutant, respectively, establishing the causal relationship between the ficP phenotypes and the Btk gene mutation. The stage specificity of the rescuing ability suggests that the Btk gene is required for the development of male genitalia and substrates required for adult survival.
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Affiliation(s)
- K Baba
- Developmental Genetics Group, Mitsubishi Kasei Institute of Life Sciences, Machida, Tokyo 194-8511, Japan
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16
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Feldmann P, Eicher EN, Leevers SJ, Hafen E, Hughes DA. Control of growth and differentiation by Drosophila RasGAP, a homolog of p120 Ras-GTPase-activating protein. Mol Cell Biol 1999; 19:1928-37. [PMID: 10022880 PMCID: PMC83986 DOI: 10.1128/mcb.19.3.1928] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mammalian Ras GTPase-activating protein (GAP), p120 Ras-GAP, has been implicated as both a downregulator and effector of Ras proteins, but its precise role in Ras-mediated signal transduction pathways is unclear. To begin a genetic analysis of the role of p120 Ras-GAP we identified a homolog from the fruit fly Drosophila melanogaster through its ability to complement the sterility of a Schizosaccharomyces pombe (fission yeast) gap1 mutant strain. Like its mammalian homolog, Drosophila RasGAP stimulated the intrinsic GTPase activity of normal mammalian H-Ras but not that of the oncogenic Val12 mutant. RasGAP was tyrosine phosphorylated in embryos and its Src homology 2 (SH2) domains could bind in vitro to a small number of tyrosine-phosphorylated proteins expressed at various developmental stages. Ectopic expression of RasGAP in the wing imaginal disc reduced the size of the adult wing by up to 45% and suppressed ectopic wing vein formation caused by expression of activated forms of Breathless and Heartless, two Drosophila receptor tyrosine kinases of the fibroblast growth factor receptor family. The in vivo effects of RasGAP overexpression required intact SH2 domains, indicating that intracellular localization of RasGAP through SH2-phosphotyrosine interactions is important for its activity. These results show that RasGAP can function as an inhibitor of signaling pathways mediated by Ras and receptor tyrosine kinases in vivo. Genetic interactions, however, suggested a Ras-independent role for RasGAP in the regulation of growth. The system described here should enable genetic screens to be performed to identify regulators and effectors of p120 Ras-GAP.
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Affiliation(s)
- P Feldmann
- Cancer Research Campaign Center for Cell and Molecular Biology, The Institute of Cancer Research, Chester Beatty Laboratories, London SW3 6JB, United Kingdom
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17
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Loomis-Husselbee JW, Walker CD, Bottomley JR, Cullen PJ, Irvine RF, Dawson AP. Modulation of Ins(2,4,5)P3-stimulated Ca2+ mobilization by ins(1,3,4, 5)P4: enhancement by activated G-proteins, and evidence for the involvement of a GAP1 protein, a putative Ins(1,3,4,5)P4 receptor. Biochem J 1998; 331 ( Pt 3):947-52. [PMID: 9560326 PMCID: PMC1219439 DOI: 10.1042/bj3310947] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We have previously shown that addition of Ins(1,3,4,5)P4 to permeabilized L1210 cells increases the amount of Ca2+ mobilized by a submaximal concentration of Ins(2,4,5)P3, and we suggested that, in doing this, Ins(1,3,4,5)P4 is not working via an InsP3 receptor but indirectly via an InsP4 receptor [Loomis-Husselbee, Cullen, Dreikhausen, Irvine and Dawson (1996) Biochem. J. 314, 811-816]. Here we have investigated whether this effect might be mediated by GAP1(IP4BP), recently identified as a putative receptor for Ins(1,3, 4,5)P4. GAP1(IP4BP) is a protein that interacts with one or more monomeric G-proteins, so we sought evidence for involvement of monomeric G-proteins in the effects of Ins(1,3,4,5)P4 in permeabilized L1210 cells. Guanosine 5'-[gamma-thio]triphosphate (GTP[S]) enhanced the effect of Ins(1,3,4,5)P4 on Ins(2,4, 5)P3-stimulated Ca2+ mobilization, but had no effect on the action of Ins(2,4,5)P3 alone. A specific enhancement of only the action of Ins(1,3,4,5)P4 was also seen with GTP[S]-loaded R-Ras or Rap1a (two G-proteins known to interact with GAP1(IP4BP)), whereas H-Ras was inactive at similar concentrations. Guanosine 5'-[beta-thio]diphosphate (GDP[S]) did not alter the action of either Ins(2,4,5)P3 or Ins(1,3,4,5)P4. Finally, the addition of exogenous GAP1(IP4BP), purified from platelets, markedly enhanced the effect of Ins(1,3,4,5)P4, and again, the amount of Ca2+ mobilized by Ins(2,4,5)P3 alone was unaltered. We conclude that the increase in Ins(2,4,5)P3-stimulated Ca2+ mobilization by Ins(1,3,4, 5)P4 may be mediated by GAP1(IP4BP) or a closely related protein (such as GAP1(m)), and if so, the action of the GAP1 is not solely to regulate GTP loading of a G-protein, but rather it acts with a G-protein to cause its effect.
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Affiliation(s)
- J W Loomis-Husselbee
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QJ, UK.
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18
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Feldkamp MM, Lau N, Guha A. Signal transduction pathways and their relevance in human astrocytomas. J Neurooncol 1997; 35:223-48. [PMID: 9440022 DOI: 10.1023/a:1005800114912] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Aberrations in a number of signal transduction pathways have been identified as playing a key role in the molecular pathogenesis of astrocytomas and their progression to high grade glioblastoma multiforme (GBM). GBMs are characterized by overexpression of the Platelet Derived Growth Factor Receptors (PDGFR) and their ligands (PDGF), as well as the Epidermal Growth Factor Receptor (EGF-R). These receptors activate the Ras pathway, a key cellular signal transduction pathway, culminating in the activation of a wide range of Ras-dependent cellular events. GBMs have also been found to either overexpression or lose expression of various Protein Kinase C (PKC) isoforms. Major strides are being made in developing pharmacological agents which specifically inhibit these growth factor receptors and intracellular signal transduction pathways. Elucidating the role of these pathways in GBMs is thus of major clinical importance, as these novel molecularly-targeted agents may prove of use in the clinical management of GBMs in the future.
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Affiliation(s)
- M M Feldkamp
- Division of Neurosurgery, Toronto Hospital, Ontario, Canada
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19
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Hajnal A, Whitfield CW, Kim SK. Inhibition of Caenorhabditis elegans vulval induction by gap-1 and by let-23 receptor tyrosine kinase. Genes Dev 1997; 11:2715-28. [PMID: 9334333 PMCID: PMC316612 DOI: 10.1101/gad.11.20.2715] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
During induction of the Caenorhabditis elegans hermaphrodite vulva, a signal from the anchor cell activates the LET-23 epidermal growth factor receptor (EGFR)/LET-60 Ras/MPK-1 MAP kinase signaling pathway in the vulval precursor cells. We have characterized two mechanisms that limit the extent of vulval induction. First, we found that gap-1 may directly inhibit the LET-60 Ras signaling pathway. We identified the gap-1 gene in a genetic screen for inhibitors of vulval induction. gap-1 is predicted to encode a protein similar to GTPase-activating proteins that likely functions to inhibit the signaling activity of LET-60 Ras. A loss-of-function mutation in gap-1 suppresses the vulvaless phenotype of mutations in the let-60 ras signaling pathway, but a gap-1 single mutant does not exhibit excess vulval induction. Second, we found that let-23 EGFR prevents vulval induction in a cell-nonautonomous manner, in addition to its cell-autonomous role in activating the let-60 ras/mpk-1 signaling pathway. Using genetic mosaic analysis, we show that let-23 activity in the vulval precursor cell closest to the anchor cell (P6.p) prevents induction of vulval precursor cells further away from the anchor cell (P3.p, P4.p, and P8.p). This result suggests that LET-23 in proximal vulval precursor cells might bind and sequester the inductive signal LIN-3 EGF, thereby preventing diffusion of the inductive signal to distal vulval precursor cells.
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Affiliation(s)
- A Hajnal
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, California 94305 USA
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20
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Fukuda M, Kojima T, Mikoshiba K. Regulation by bivalent cations of phospholipid binding to the C2A domain of synaptotagmin III. Biochem J 1997; 323 ( Pt 2):421-5. [PMID: 9163333 PMCID: PMC1218336 DOI: 10.1042/bj3230421] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Synaptotagmins are Ca2+-and phospholipid-binding proteins of synaptic vesicles that might function as Ca2+ receptors for neurotransmitter release via their first C2 (C2A) domain. Here we describe the effect of Mg2+ on phospholipid binding to the C2A domains of multiple synaptotagmins (II-VI), and demonstrate that only synaptotagmin III can bind negatively charged phospholipids [phosphatidylserine (PS) and phosphatidylinositol] in a Mg2+-dependent manner. The Mg2+-dependent interaction with PS was found to have an EC50 of approx. 30 microM Mg2+, which is comparable to that of Sr2+ and Ba2+ (EC50 values of approx. 10 microM). This binding property of the C2A domain is specific to synaptotagmin III, because none of the C2A domains of other proteins, such as rabphilin 3A, Doc2alpha, Doc2beta or Gap1(m), showed phospholipid binding activity in the presence of 1 mM Mg2+. Our results suggest that synaptotagmin III is involved in presynaptic functions different from those of synaptotagmins I and II.
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Affiliation(s)
- M Fukuda
- Molecular Neurobiology Laboratory, Tsukuba Life Science Center, The Institute of Physical and Chemical Research (RIKEN), 3-1-1 Koyadai, Tsukuba, Ibaraki 305, Japan
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21
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van der Geer P, Henkemeyer M, Jacks T, Pawson T. Aberrant Ras regulation and reduced p190 tyrosine phosphorylation in cells lacking p120-Gap. Mol Cell Biol 1997; 17:1840-7. [PMID: 9121432 PMCID: PMC232031 DOI: 10.1128/mcb.17.4.1840] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The Ras guanine nucleotide-binding protein functions as a molecular switch in signalling downstream of protein-tyrosine kinases. Ras is activated by exchange of GDP for GTP and is turned off by hydrolysis of bound GTP to GDP. Ras itself has a low intrinsic GTPase activity that can be stimulated by GTPase-activating proteins (GAPs), including p120-Gap and neurofibromin. These GAPs possess a common catalytic domain but contain distinct regulatory elements that may couple different external signals to control of the Ras pathway. p120-Gap, for example, has two N-terminal SH2 domains that directly recognize phosphotyrosine motifs on activated growth factor receptors and cytoplasmic phosphoproteins. To analyze the role of p120-Gap in Ras regulation in vivo, we have used fibroblasts derived from mouse embryos with a null mutation in the gene for p120-Gap (Gap). Platelet-derived growth factor stimulation of Gap-/- cells led to an abnormally large increase in the level of Ras-GTP and in the duration of mitogen-activated protein (MAP) kinase activation compared with wild-type cells, suggesting that p120-Gap is specifically activated following growth factor stimulation. Induction of DNA synthesis in response to platelet-derived growth factor and morphological transformation by the v-src and EJ-ras oncogenes were not significantly affected by the absence of p120-Gap. However, we found that normal tyrosine phosphorylation of p190-rhoGap, a cytoplasmic protein that associates with the p120-Gap SH2 domains, was dependent on the presence of p120-Gap. Our results suggest that p120-Gap has specific functions in downregulating the Ras/MAP kinase pathway following growth factor stimulation, and in modulating the phosphorylation of p190-rhoGap, but is not required for mitogenic signalling.
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Affiliation(s)
- P van der Geer
- Programme in Molecular Biology and Cancer, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
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22
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Sundaram V, Lee JH, Harwalkar JA, Stein DJ, Roudebush M, Stacey DW, Golubic M. Reduced expression of neurofibromin in human meningiomas. Br J Cancer 1997; 76:747-56. [PMID: 9310240 PMCID: PMC2228040 DOI: 10.1038/bjc.1997.456] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Meningiomas are common, mostly benign, tumours arising from leptomeningeal cells of the meninges, which frequently contain mutations in the neurofibromatosis type 2 (NF2) gene. In this study, we analysed a protein product of the neurofibromatosis type 1 (NF1) gene, neurofibromin, in human established leptomeningeal cells LTAg2B, in 17 sporadic meningiomas and in a meningioma from a patient affected by NF2. The expression level of neurofibromin was determined by immunoblotting and immunoprecipitation with anti-neurofibromin antibodies. The functional status of neurofibromin was analysed through its ability to stimulate the intrinsic GTPase activity of p21 ras. In the cytosolic extracts of four sporadic meningiomas and in the NF2-related meningioma, the expression level and the GTPase stimulatory activity of neurofibromin were drastically reduced compared with the level present in the human brain, human established leptomeningeal cells LTAg2B and the remaining 13 meningiomas. Our results suggest that neurofibromin is expressed in leptomeningeal cells LTAg2B and in most meningiomas, i.e. tumours derived from these cells. The reduced expression and GTPase stimulatory activity of neurofibromin was found in about 23% of meningiomas and in the single NF2-related meningioma analysed. These results suggest that decreased levels of neurofibromin in these tumours may contribute to their tumorigenesis.
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Affiliation(s)
- V Sundaram
- Department of Molecular Biology, Cleveland Clinic Foundation, OH 44195, USA
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23
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Abstract
The C2 domain is a Ca(2+)-binding motif of approximately 130 residues in length originally identified in the Ca(2+)-dependent isoforms of protein kinase C. Single and multiple copies of C2 domains have been identified in a growing number of eukaryotic signalling proteins that interact with cellular membranes and mediate a broad array of critical intracellular processes, including membrane trafficking, the generation of lipid-second messengers, activation of GTPases, and the control of protein phosphorylation. As a group, C2 domains display the remarkable property of binding a variety of different ligands and substrates, including Ca2+, phospholipids, inositol polyphosphates, and intracellular proteins. Expanding this functional diversity is the fact that not all proteins containing C2 domains are regulated by Ca2+, suggesting that some C2 domains may play a purely structural role or may have lost the ability to bind Ca2+. The present review summarizes the information currently available regarding the structure and function of the C2 domain and provides a novel sequence alignment of 65 C2 domain primary structures. This alignment predicts that C2 domains form two distinct topological folds, illustrated by the recent crystal structures of C2 domains from synaptotagmin 1 and phosphoinositide-specific phospholipase C-delta 1, respectively. The alignment highlights residues that may be critical to the C2 domain fold or required for Ca2+ binding and regulation.
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Affiliation(s)
- E A Nalefski
- Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309-0215, USA
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24
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Hashii M, Nakashima S, Yokoyama S, Enomoto K, Minabe Y, Nozawa Y, Higashida H. Bradykinin B2 receptor-induced and inositol tetrakisphosphate-evoked Ca2+ entry is sensitive to a protein tyrosine phosphorylation inhibitor in ras-transformed NIH/3T3 fibroblasts. Biochem J 1996; 319 ( Pt 2):649-56. [PMID: 8912707 PMCID: PMC1217816 DOI: 10.1042/bj3190649] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Signal transduction from mouse bradykinin B2 receptors to calcium influx was studied in ras-transformed NIH/3T3 (DT) fibroblasts. DT cells were preloaded with fura-2 and whole-cell voltage-clamped. Activation of B2 receptors resulted in a decrease of cellular fluorescence at the excitation wavelength of 340, or 360 nm after MnCl2 application, in both the presence and absence of external Ca2+ in DT cells, at a holding potential of -40 mV. This Mn2+ entry through the Ca2+ influx pathway increased with membrane hyperpolarization. Internal application of inositol 1,3,4,5-tetrakisphosphate (InsP4), but not of inositol 1,4,5-trisphosphate, mimicked membrane potential-dependent Mn2+ entry. Bradykinin- and InsP4-induced Ca2+ influx was blocked by 10-100 microM genistein, a tyrosine kinase inhibitor. B2 receptor activation induced time-dependent tyrosine phosphorylation of mitogen-activated protein kinase and 120 kDa protein, which was dose-dependently inhibited by genistein. Bradykinin was unable to induce Ca2+ oscillations in genistein-treated DT cells. Our results show that bradykinin-induced Ca2+ influx and oscillations depend upon protein tyrosine phosphorylation. The results suggest that two bradykinin B2 receptor-activated signal pathways, protein tyrosine phosphorylation and formation of InsP4, merge at the Ca2+ influx process in ras-transformed NIH/3T3 fibroblasts.
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Affiliation(s)
- M Hashii
- Department of Cortical Function Disorder, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
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25
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Denhardt DT. Signal-transducing protein phosphorylation cascades mediated by Ras/Rho proteins in the mammalian cell: the potential for multiplex signalling. Biochem J 1996; 318 ( Pt 3):729-47. [PMID: 8836113 PMCID: PMC1217680 DOI: 10.1042/bj3180729] [Citation(s) in RCA: 366] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The features of three distinct protein phosphorylation cascades in mammalian cells are becoming clear. These signalling pathways link receptor-mediated events at the cell surface or intracellular perturbations such as DNA damage to changes in cytoskeletal structure, vesicle transport and altered transcription factor activity. The best known pathway, the Ras-->Raf-->MEK-->ERK cascade [where ERK is extracellular-signal-regulated kinase and MEK is mitogen-activated protein (MAP) kinase/ERK kinase], is typically stimulated strongly by mitogens and growth factors. The other two pathways, stimulated primarily by assorted cytokines, hormones and various forms of stress, predominantly utilize p21 proteins of the Rho family (Rho, Rac and CDC42), although Ras can also participate. Diagnostic of each pathway is the MAP kinase component, which is phosphorylated by a unique dual-specificity kinase on both tyrosine and threonine in one of three motifs (Thr-Glu-Tyr, Thr-Phe-Tyr or Thr-Gly-Tyr), depending upon the pathway. In addition to activating one or more protein phosphorylation cascades, the initiating stimulus may also mobilize a variety of other signalling molecules (e.g. protein kinase C isoforms, phospholipid kinases, G-protein alpha and beta gamma subunits, phospholipases, intracellular Ca2+). These various signals impact to a greater or lesser extent on multiple downstream effectors. Important concepts are that signal transmission often entails the targeted relocation of specific proteins in the cell, and the reversible formation of protein complexes by means of regulated protein phosphorylation. The signalling circuits may be completed by the phosphorylation of upstream effectors by downstream kinases, resulting in a modulation of the signal. Signalling is terminated and the components returned to the ground state largely by dephosphorylation. There is an indeterminant amount of cross-talk among the pathways, and many of the proteins in the pathways belong to families of closely related proteins. The potential for more than one signal to be conveyed down a pathway simultaneously (multiplex signalling) is discussed. The net effect of a given stimulus on the cell is the result of a complex intracellular integration of the intensity and duration of activation of the individual pathways. The specific outcome depends on the particular signalling molecules expressed by the target cells and on the dynamic balance among the pathways.
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Affiliation(s)
- D T Denhardt
- Department of Biological Sciences, Rutgers University, Piscataway, NJ 08855, USA
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Ponting CP, Parker PJ. Extending the C2 domain family: C2s in PKCs delta, epsilon, eta, theta, phospholipases, GAPs, and perforin. Protein Sci 1996; 5:162-6. [PMID: 8771209 PMCID: PMC2143250 DOI: 10.1002/pro.5560050120] [Citation(s) in RCA: 142] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Various membrane lipid metabolites, generated by phospholipases C and D (PLCs, PLDs), are known to regulate the activities of protein kinases C (PKCs) and GTP-ase activating proteins (GAPs) in a range of cellular processes. Conventional Ca(2+)-dependent PKCs (alpha, beta I, beta II, and gamma), PLCs and various GAPs are all known to contain copies of a phospholipid-binding domain, termed C2 or CalB. Here we recognize that C2 domains are also present in "new" Ca(2+)-independent PKCs (delta, epsilon, eta, and theta), other kinases, a eukaryotic PLD, the breakpoint cluster region (BCR) gene product, and two further GAPS. Twenty-two previously unrecognized C2 domain sequences are presented, which include a single copy in the mammalian poreforming proteins, perforin.
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Affiliation(s)
- C P Ponting
- University of Oxford, Fibrinolysis Research Unit, United Kingdom.
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Haire RN, Litman GW. The murine form of TXK, a novel TEC kinase expressed in thymus maps to chromosome 5. Mamm Genome 1995; 6:476-80. [PMID: 7579892 DOI: 10.1007/bf00360659] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- R N Haire
- Department of Pediatrics, University of South Florida, All Children's Hospital, St. Petersburg 33701, USA
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