1
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RUNX1 positively regulates the ErbB2/HER2 signaling pathway through modulating SOS1 expression in gastric cancer cells. Sci Rep 2018; 8:6423. [PMID: 29686309 PMCID: PMC5913281 DOI: 10.1038/s41598-018-24969-w] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 04/11/2018] [Indexed: 12/29/2022] Open
Abstract
The dual function of runt-related transcriptional factor 1 (RUNX1) as an oncogene or oncosuppressor has been extensively studied in various malignancies, yet its role in gastric cancer remains elusive. Up-regulation of the ErbB2/HER2 signaling pathway is frequently-encountered in gastric cancer and contributes to the maintenance of these cancer cells. This signaling cascade is partly mediated by son of sevenless homolog (SOS) family, which function as adaptor proteins in the RTK cascades. Herein we report that RUNX1 regulates the ErbB2/HER2 signaling pathway in gastric cancer cells through transactivating SOS1 expression, rendering itself an ideal target in anti-tumor strategy toward this cancer. Mechanistically, RUNX1 interacts with the RUNX1 binding DNA sequence located in SOS1 promoter and positively regulates it. Knockdown of RUNX1 led to the decreased expression of SOS1 as well as dephosphorylation of ErbB2/HER2, subsequently suppressed the proliferation of gastric cancer cells. We also found that our novel RUNX inhibitor (Chb-M’) consistently led to the deactivation of the ErbB2/HER2 signaling pathway and was effective against several gastric cancer cell lines. Taken together, our work identified a novel interaction of RUNX1 and the ErbB2/HER2 signaling pathway in gastric cancer, which can potentially be exploited in the management of this malignancy.
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2
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Imai-Sumida M, Chiyomaru T, Majid S, Saini S, Nip H, Dahiya R, Tanaka Y, Yamamura S. Silibinin suppresses bladder cancer through down-regulation of actin cytoskeleton and PI3K/Akt signaling pathways. Oncotarget 2017; 8:92032-92042. [PMID: 29190895 PMCID: PMC5696161 DOI: 10.18632/oncotarget.20734] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 08/07/2017] [Indexed: 01/17/2023] Open
Abstract
Silibinin is the major active constituent of silymarin, an extract of milk thistle seeds. Silibinin has been shown to have significant anti-cancer effects in a variety of malignancies. However, the molecular mechanisms of silibinin action in bladder cancer have not been studied extensively. In the present study, we found that silibinin (10 μM) significantly suppressed proliferation, migration, invasion and induced apoptosis of T24 and UM-UC-3 human bladder cancer cells. Silibinin down-regulated the actin cytoskeleton and phosphatidylinositide 3-kinase (PI3K)/Akt signaling pathways in these cancer cell lines. These pathways were found to crosstalk through RAS cascades. We found that silibinin suppressed levels of trimethylated histone H3 lysine 4 and acetylated H3 at the KRAS promoter. Furthermore, silibinin targets long non-coding RNA: HOTAIR and ZFAS1, which are known to play roles as oncogenic factors in various cancers. This study shows that silibinin exerts anti-cancer effects through down-regulation of actin cytoskeleton and PI3K/Akt pathways and thus suppresses bladder cancer growth and progression.
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Affiliation(s)
- Mitsuho Imai-Sumida
- Department of Urology, San Francisco Veterans Affairs Medical Center and University of California, San Francisco, CA, USA
| | - Takeshi Chiyomaru
- Department of Urology, San Francisco Veterans Affairs Medical Center and University of California, San Francisco, CA, USA.,Current address: Department of Urology, National Hospital Organization Kagoshima Medical Center, Kagoshima, Japan
| | - Shahana Majid
- Department of Urology, San Francisco Veterans Affairs Medical Center and University of California, San Francisco, CA, USA
| | - Sharanjot Saini
- Department of Urology, San Francisco Veterans Affairs Medical Center and University of California, San Francisco, CA, USA
| | - Hannah Nip
- Department of Urology, San Francisco Veterans Affairs Medical Center and University of California, San Francisco, CA, USA
| | - Rajvir Dahiya
- Department of Urology, San Francisco Veterans Affairs Medical Center and University of California, San Francisco, CA, USA
| | - Yuichiro Tanaka
- Department of Urology, San Francisco Veterans Affairs Medical Center and University of California, San Francisco, CA, USA
| | - Soichiro Yamamura
- Department of Urology, San Francisco Veterans Affairs Medical Center and University of California, San Francisco, CA, USA
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3
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Anta B, Pérez-Rodríguez A, Castro J, García-Domínguez CA, Ibiza S, Martínez N, Durá LM, Hernández S, Gragera T, Peña-Jiménez D, Yunta M, Zarich N, Crespo P, Serrador JM, Santos E, Muñoz A, Oliva JL, Rojas-Cabañeros JM. PGA1-induced apoptosis involves specific activation of H-Ras and N-Ras in cellular endomembranes. Cell Death Dis 2016; 7:e2311. [PMID: 27468687 PMCID: PMC4973357 DOI: 10.1038/cddis.2016.219] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Revised: 06/20/2016] [Accepted: 06/21/2016] [Indexed: 12/14/2022]
Abstract
The cyclopentenone prostaglandin A1 (PGA1) is an inducer of cell death in cancer cells. However, the mechanism that initiates this cytotoxic response remains elusive. Here we report that PGA1 triggers apoptosis by a process that entails the specific activation of H- and N-Ras isoforms, leading to caspase activation. Cells without H- and N-Ras did not undergo apoptosis upon PGA1 treatment; in these cells, the cellular demise was rescued by overexpression of either H-Ras or N-Ras. Consistently, the mutant H-Ras-C118S, defective for binding PGA1, did not produce cell death. Molecular analysis revealed a key role for the RAF-MEK-ERK signaling pathway in the apoptotic process through the induction of calpain activity and caspase-12 cleavage. We propose that PGA1 evokes a specific physiological cell death program, through H- and N-Ras, but not K-Ras, activation at endomembranes. Our results highlight a novel mechanism that may be of potential interest for tumor treatment.
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Affiliation(s)
- B Anta
- Unidad de Biología Celular, Unidad Funcional de Investigación de Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III, Madrid 28220, Spain
| | - A Pérez-Rodríguez
- Unidad de Biología Celular, Unidad Funcional de Investigación de Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III, Madrid 28220, Spain
| | - J Castro
- Unidad de Biología Celular, Unidad Funcional de Investigación de Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III, Madrid 28220, Spain
| | - C A García-Domínguez
- Unidad de Biología Celular, Unidad Funcional de Investigación de Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III, Madrid 28220, Spain
| | - S Ibiza
- Fundación Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid 28029, Spain
| | - N Martínez
- Unidad de Biología Celular, Unidad Funcional de Investigación de Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III, Madrid 28220, Spain
| | - L M Durá
- Unidad de Biología Celular, Unidad Funcional de Investigación de Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III, Madrid 28220, Spain
| | - S Hernández
- Unidad de Biología Celular, Unidad Funcional de Investigación de Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III, Madrid 28220, Spain
| | - T Gragera
- Unidad de Biología Celular, Unidad Funcional de Investigación de Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III, Madrid 28220, Spain
| | - D Peña-Jiménez
- Unidad de Biología Celular, Unidad Funcional de Investigación de Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III, Madrid 28220, Spain
| | - M Yunta
- Unidad de Biología Celular, Unidad Funcional de Investigación de Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III, Madrid 28220, Spain
| | - N Zarich
- Unidad de Biología Celular, Unidad Funcional de Investigación de Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III, Madrid 28220, Spain
| | - P Crespo
- Departamento de Biologia Molecular, Facultad de Medicina, Instituto de Biomedicina y Biotecnología de Cantabria, Consejo Superior de Investigaciones Cientificas (CSIC)-IDICAN, Universidad de Cantabria, Santander 39011, Spain
| | - J M Serrador
- Departamento de Biología Celular e Inmunología, Centro de Biología Molecular Severo Ochoa (CBMSO), CSIC-UAM, Madrid 28049, Spain
| | - E Santos
- Centro de Investigación del Cancer, IBMCC (CSIC-USAL), Universidad de Salamanca, Salamanca 37007, Spain
| | - A Muñoz
- Instituto de Investigaciones Biomédicas 'Alberto Sols', Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Arturo Duperier 4, Madrid 28029, Spain
| | - J L Oliva
- Unidad de Biología Celular, Unidad Funcional de Investigación de Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III, Madrid 28220, Spain
| | - J M Rojas-Cabañeros
- Unidad de Biología Celular, Unidad Funcional de Investigación de Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III, Madrid 28220, Spain
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4
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EGF receptor uses SOS1 to drive constitutive activation of NFκB in cancer cells. Proc Natl Acad Sci U S A 2014; 111:11721-6. [PMID: 25071181 DOI: 10.1073/pnas.1412390111] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Activation of nuclear factor κB (NFκB) is a central event in the responses of normal cells to inflammatory signals, and the abnormal constitutive activation of NFκB is important for the survival of most cancer cells. In nonmalignant human cells, EGF stimulates robust activation of NFκB. The kinase activity of the EGF receptor (EGFR) is required, because the potent and specific inhibitor erlotinib blocks the response. Down-regulating EGFR expression or inhibiting EGFR with erlotinib impairs constitutive NFκB activation in several different types of cancer cells and, conversely, increased activation of NFκB leads to erlotinib resistance in these cells. We conclude that EGF is an important mediator of NFκB activation in cancer cells. To explore the mechanism, we selected an erlotinib-resistant cell line in which the guanine nucleotide exchange factor Son of Sevenless 1 (SOS1), well known to be important for EGF-dependent signaling to MAP kinases, is overexpressed. Increased expression of SOS1 increases NFκB activation in several different types of cancer cells, and ablation of SOS1 inhibits EGF-induced NFκB activation in these cells, indicating that SOS1 is a functional component of the pathway connecting EGFR to NFκB activation. Importantly, the guanine nucleotide exchange activity of SOS1 is not required for NFκB activation.
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5
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Sánchez-Molina S, Estarás C, Oliva JL, Akizu N, Asensio-Juan E, Rojas JM, Martínez-Balbás MA. Regulation of CBP and Tip60 coordinates histone acetylation at local and global levels during Ras-induced transformation. Carcinogenesis 2014; 35:2194-202. [DOI: 10.1093/carcin/bgu111] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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McDonald CB, Bhat V, Kurouski D, Mikles DC, Deegan BJ, Seldeen KL, Lednev IK, Farooq A. Structural landscape of the proline-rich domain of Sos1 nucleotide exchange factor. Biophys Chem 2013; 175-176:54-62. [PMID: 23528987 DOI: 10.1016/j.bpc.2013.02.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 02/08/2013] [Accepted: 02/25/2013] [Indexed: 10/27/2022]
Abstract
Despite its key role in mediating a plethora of cellular signaling cascades pertinent to health and disease, little is known about the structural landscape of the proline-rich (PR) domain of Sos1 guanine nucleotide exchange factor. Herein, using a battery of biophysical tools, we provide evidence that the PR domain of Sos1 is structurally disordered and adopts an extended random coil-like conformation in solution. Of particular interest is the observation that while chemical denaturation of PR domain results in the formation of a significant amount of polyproline II (PPII) helices, it has little or negligible effect on its overall size as measured by its hydrodynamic radius. Our data also show that the PR domain displays a highly dynamic conformational basin in agreement with the knowledge that the intrinsically unstructured proteins rapidly interconvert between an ensemble of conformations. Collectively, our study provides new insights into the conformational equilibrium of a key signaling molecule with important consequences on its physiological function.
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Affiliation(s)
- Caleb B McDonald
- Department of Biochemistry & Molecular Biology, Leonard Miller School of Medicine, University of Miami, Miami, FL 33136, USA
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7
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Rojas JM, Oliva JL, Santos E. Mammalian son of sevenless Guanine nucleotide exchange factors: old concepts and new perspectives. Genes Cancer 2011; 2:298-305. [PMID: 21779500 DOI: 10.1177/1947601911408078] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The Son of Sevenless (Sos) factors were originally discovered 2 decades ago as specialized Ras activators in signaling pathways controlling the process of R7 cell development in the eye of Drosophila melanogaster. The 2 known members of the mammalian Sos family (Sos1 and Sos2) code for ubiquitously expressed, highly homologous (69% overall) proteins involved in coupling signals originated by cell surface receptor tyrosine kinases (RTKs) to downstream, Ras-dependent mitogenic signaling pathways. Mechanistically, the Sos proteins function as enzymatic factors interacting with Ras proteins in response to upstream stimuli to promote guanine nucleotide exchange (GDP/GTP) and subsequent formation of the active Ras-GTP complex. In this review, we summarize current knowledge on structural, regulatory, and functional aspects of the Sos family, focusing on specific aspects of Sos biology such as structure-function relationship, crosstalk with different signaling pathways, and in vivo functional significance as deduced from phenotypic characterization of Sos knockout mice and human genetic syndromes caused by germline hSos1 mutations.
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Affiliation(s)
- José M Rojas
- Unidad de Biología Celular, Área de Biología Celular y del Desarrollo, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain
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8
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Sacco E, Farina M, Greco C, Lamperti S, Busti S, Degioia L, Alberghina L, Liberati D, Vanoni M. Regulation of hSos1 activity is a system-level property generated by its multi-domain structure. Biotechnol Adv 2011; 30:154-68. [PMID: 21851854 DOI: 10.1016/j.biotechadv.2011.07.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Revised: 07/22/2011] [Accepted: 07/25/2011] [Indexed: 12/22/2022]
Abstract
The multi-domain protein hSos1 plays a major role in cell growth and differentiation through its Ras-specific guanine nucleotide exchange domain whose complex regulation involves intra-molecular, inter-domain rearrangements. We present a stochastic mathematical model describing intra-molecular regulation of hSos1 activity. The population macroscopic effect is reproduced through a Monte-Carlo approach. Key model parameters have been experimentally determined by BIAcore analysis. Complementation experiments of a Saccharomyces cerevisiae cdc25(ts) strain with Sos deletion mutants provided a comprehensive data set for estimation of unknown parameters and model validation. The model is robust against parameter alteration and describes both the behavior of Sos deletion mutants and modulation of activity of the full length molecule under physiological conditions. By incorporating the calculated effect of amino acid changes at an inter-domain interface, the behavior of a mutant correlating with a developmental syndrome could be simulated, further validating the model. The activation state of Ras-specific guanine nucleotide exchange domain of hSos1 arises as an "emergent property" of its multi-domain structure that allows multi-level integration of a complex network of intra- and inter-molecular signals.
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Affiliation(s)
- Elena Sacco
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano, Italy
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9
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Pierre S, Bats AS, Coumoul X. Understanding SOS (Son of Sevenless). Biochem Pharmacol 2011; 82:1049-56. [PMID: 21787760 DOI: 10.1016/j.bcp.2011.07.072] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2011] [Revised: 07/02/2011] [Accepted: 07/05/2011] [Indexed: 10/17/2022]
Abstract
Son of Sevenless (SOS) was discovered in Drosophila melanogaster. Essential for normal eye development in Drosophila, SOS has two human homologues, SOS1 and SOS2. The SOS1 gene encodes the Son of Sevenless 1 protein, a Ras and Rac guanine nucleotide exchange factor. This protein is composed of several important domains. The CDC25 and REM domains provide the catalytic activity of SOS1 towards Ras and the histone fold DH/PH (Dbl homology and Pleckstrin homology) domains function, in tandem, to stimulate GTP/GDP exchange for Rac. In contrast to Ras, there have been few studies that implicate SOS1 in human disease and, initially, less attention was given to this gene. However, mutations in SOS1 have been reported recently in Noonan syndrome and in type 1 hereditary gingival fibromatosis. Although, there have been very few studies that focus on the regulation of this important gene by physiological or exogenous factors, we recently found that the SOS1 gene was induced by the environmental toxin, dioxin, and that this effect was mediated by the aryl hydrocarbon receptor (AhR). These recent observations raise the possibility that alterations in the expression of the SOS1 gene and, consequently, in the activity of the SOS1 protein may affect toxicological endpoints and lead to clinical disease. These possibilities, thus, have stimulated much interest in SOS1 recently. In this article, we review the functions of SOS1 and the evidence for its roles in physiology and pathology across species.
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Affiliation(s)
- Stéphane Pierre
- INSERM UMR-S 747, Toxicologie Pharmacologie et Signalisation Cellulaire, 45 rue des Saints Pères, 75006 Paris, France
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10
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Allosteric gating of Son of sevenless activity by the histone domain. Proc Natl Acad Sci U S A 2010; 107:3436-40. [PMID: 20133694 DOI: 10.1073/pnas.0914315107] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Regulated activation of Ras by receptor tyrosine kinases (RTK) constitutes a key transduction step in signaling processes that control an array of fundamental cellular functions including proliferation, differentiation, and survival. The principle mechanism by which Ras is activated down stream of RTKs involves the stimulation of guanine nucleotide exchange by the ubiquitous guanine nucleotide exchange factor Son of sevenless (Sos). In resting conditions, Sos activity is constrained by intramolecular interactions that maintain the protein in an autoinhibited conformation. Structural, biochemical, and genetic studies have implicated the histone domain (Sos-H), which comprises the most N-terminal region of Sos, in the regulation of Sos autoinhibition. However, the molecular underpinnings of this regulatory function are not well understood. In the present study we demonstrate that Sos-H possesses in vitro and in vivo membrane binding activity that is mediated, in part, by the interactions between a cluster of basic residues and phosphatidic acid. This interaction is required for Sos-dependent activation of Ras following EGF stimulation. The inducible association of Sos-H with membranes contributes to the catalytic activity of Sos by forcing the domain to adopt a conformation that destabilizes the autoinhibitory state. Thus, Sos-H plays a critical role in governing the catalytic output of Sos through the coupling of membrane recruitment to the release of autoinhibition.
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11
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Bedoya LM, Márquez N, Martínez N, Gutiérrez-Eisman S, Álvarez A, Calzado MA, Rojas JM, Appendino G, Muñoz E, Alcamí J. SJ23B, a jatrophane diterpene activates classical PKCs and displays strong activity against HIV in vitro. Biochem Pharmacol 2009; 77:965-78. [DOI: 10.1016/j.bcp.2008.11.025] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Revised: 11/24/2008] [Accepted: 11/25/2008] [Indexed: 10/21/2022]
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12
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Boykevisch S, Zhao C, Sondermann H, Philippidou P, Halegoua S, Kuriyan J, Bar-Sagi D. Regulation of ras signaling dynamics by Sos-mediated positive feedback. Curr Biol 2007; 16:2173-9. [PMID: 17084704 DOI: 10.1016/j.cub.2006.09.033] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2006] [Revised: 09/05/2006] [Accepted: 09/11/2006] [Indexed: 12/20/2022]
Abstract
The RTK-Ras-ERK cascade is a central signaling module implicated in the control of diverse biological processes including cell proliferation, differentiation, and survival. The coupling of RTK to Ras is mediated by the Ras-specific nucleotide-exchange factor Son of Sevenless (Sos), which activates Ras by inducing the exchange of GDP for GTP . Considerable evidence indicates that the duration and amplitude of Ras signals are important determinants in controlling the biological outcome . However, the mechanisms that regulate the quantitative output of Ras signaling remain poorly understood. We define a previously unrecognized regulatory component of the machinery that specifies the kinetic properties of signals propagated through the RTK-Ras-ERK cascade. We demonstrate that the establishment of a positive feedback loop involving Ras.GTP and Sos leads to an increase in the amplitude and duration of Ras activation in response to EGF stimulation. This effect is propagated to downstream elements of the pathway as reflected by sustained EGF-induced ERK phosphorylation and enhanced SRE-dependent transcription. As a consequence, the physiological endpoint of EGF action is switched from proliferation to differentiation. We propose that the engagement of Ras/Sos positive feedback loop may contribute to the mechanism by which ligand stimulation is coupled to discrete biological responses.
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Affiliation(s)
- Sean Boykevisch
- Department of Molecular Genetics and Microbiology, State University of New York, at Stony Brook, Stony Brook, New York 11794, USA
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Sánchez-Molina S, Oliva J, García-Vargas S, Valls E, Rojas J, Martínez-Balbás M. The histone acetyltransferases CBP/p300 are degraded in NIH 3T3 cells by activation of Ras signalling pathway. Biochem J 2006; 398:215-24. [PMID: 16704373 PMCID: PMC1550303 DOI: 10.1042/bj20060052] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Revised: 04/07/2006] [Accepted: 05/17/2006] [Indexed: 11/17/2022]
Abstract
The CBP [CREB (cAMP-response-element-binding protein)-binding protein]/p300 acetyltransferases function as transcriptional co-activators and play critical roles in cell differentiation and proliferation. Accumulating evidence shows that alterations of the CBP/p300 protein levels are linked to human tumours. In the present study, we show that the levels of the CBP/p300 co-activators are decreased dramatically by continuous PDGF (platelet-derived growth factor) and Ras signalling pathway activation in NIH 3T3 fibroblasts. This effect occurs by reducing the expression levels of the CBP/p300 genes. In addition, CBP and p300 are degraded by the 26 S proteasome pathway leading to an overall decrease in the levels of the CBP/p300 proteins. Furthermore, we provide evidence that Mdm2 (murine double minute 2), in the presence of active H-Ras or N-Ras, induces CBP/p300 degradation in NIH 3T3 cells. These findings support a novel mechanism for modulating other signalling transduction pathways that require these common co-activators.
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Key Words
- acetylation
- camp-response-element-binding-protein-binding protein/p300 (cbp/p300)
- histone acetyltransferase activity (hat activity)
- murine double minute 2 (mdm2)
- nih 3t3 cell
- ras pathway
- alln, n-acetyl-l-leucyl-l-leucylnorleucinal
- creb, camp-response-element-binding protein
- cbp, creb-binding protein
- cs, calf serum
- dapi, 4′,6-diamidino-2-phenylindole
- erk, extracellular-signal-regulated kinase
- gds, guanine nucleotide dissociation stimulator
- gst, glutathione s-transferase
- ha, haemagglutinin
- hat, histone acetyltransferase
- hdac, histone deacetylase
- mapk, mitogen-activated protein kinase
- mdm2, murine double minute 2
- mek, mapk/erk kinase
- p/caf, p300/cbp-associated factor
- pdgf, platelet-derived growth factor
- pi3k, phosphoinositide 3-kinase
- ra, retinoic acid
- ral-bd, ral-binding domain
- rts, rubinstein–taybi syndrome
- sirna, small interfering rna
- tafii, tata-box-binding-protein-associated factor
- tgase, transglutaminase
- tk, thymidine kinase
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Affiliation(s)
- Sara Sánchez-Molina
- *Instituto de Biología Molecular de Barcelona, CID, Consejo Superior de Investigaciones Científicas (CSIC), Parc Cientific de Barcelona (PCB), Josep Samitier 1–5, 08028 Barcelona, Spain
| | - José Luis Oliva
- †Unidad de Biología Celular, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain
| | - Susana García-Vargas
- †Unidad de Biología Celular, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain
| | - Ester Valls
- *Instituto de Biología Molecular de Barcelona, CID, Consejo Superior de Investigaciones Científicas (CSIC), Parc Cientific de Barcelona (PCB), Josep Samitier 1–5, 08028 Barcelona, Spain
| | - José M. Rojas
- †Unidad de Biología Celular, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain
| | - Marian A. Martínez-Balbás
- *Instituto de Biología Molecular de Barcelona, CID, Consejo Superior de Investigaciones Científicas (CSIC), Parc Cientific de Barcelona (PCB), Josep Samitier 1–5, 08028 Barcelona, Spain
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14
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Suárez Y, González-Santiago L, Zarich N, Dávalos A, Aranda JF, Alonso MA, Lasunción MA, Rojas JM, Muñoz A. Plitidepsin Cellular Binding and Rac1/JNK Pathway Activation Depend on Membrane Cholesterol Content. Mol Pharmacol 2006; 70:1654-63. [PMID: 16928956 DOI: 10.1124/mol.106.025569] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Plitidepsin (aplidin) is a marine cyclic depsipeptide in phase II clinical development against several neoplasias. Plitidepsin is a potent inducer of apoptosis through the sustained activation of Jun N-terminal kinase (JNK). We have reported that this activation depends on the early induction of oxidative stress, activation of Rac1 small GTPase, and the later down-regulation of MKP-1 phosphatase. Using Scatchard and saturation binding analyses, we have found that (14)C-labeled plitidepsin binds to a moderately high-affinity receptor (K(d) of 44.8 +/- 3.1 and 35.5 +/- 4.8 nM, respectively) in MDA-MB-231 breast cancer cells. Two minutes after addition to cells, half of the drug was membrane-bound and was subsequently found in the cytosolic fraction. At 4 degrees C, plitidepsin cellular binding was around 10-fold lower than at 37 degrees C but sufficed to induce cell death, suggesting that this process is triggered from the membrane. Depletion of plasma membrane cholesterol by short treatment with methyl-beta-cyclodextrin diminished plitidepsin binding and Rac1 and JNK activation. Rac1 is targeted to the plasma membrane by plitidepsin as shown by subcellular fractioning and immunofluorescence analysis followed by confocal microscopy. Methyl-beta-cyclodextrin blocked this effect. A subline of HeLa cells (HeLa-R), partially resistant to plitidepsin, showed similar affinity (K(d) of 79.5 +/- 2.5 versus 37.7 +/- 8.2 nM) but 7.5-fold lower binding capacity than wild-type HeLa cells. Moreover, HeLa-R cells had lower total (71%) and membrane (67%) cholesterol content and membrane-bound Rac1, and showed no Rac1 activation upon plitidepsin treatment. In conclusion, cellular plitidepsin uptake and induction of apoptosis via activation of the Rac1-JNK pathway is membrane-cholesterol dependent.
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Affiliation(s)
- Yajaira Suárez
- Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Cientificas, Universidad Autónoma de Madrid, Arturo Duperier, 4, E-28029 Madrid, Spain
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15
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Zarich N, Oliva JL, Martínez N, Jorge R, Ballester A, Gutiérrez-Eisman S, García-Vargas S, Rojas JM. Grb2 is a negative modulator of the intrinsic Ras-GEF activity of hSos1. Mol Biol Cell 2006; 17:3591-7. [PMID: 16760435 PMCID: PMC1525251 DOI: 10.1091/mbc.e05-12-1104] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
hSos1 is a Ras guanine-nucleotide exchange factor. It was suggested that the carboxyl-terminal region of hSos1 down-regulates hSos1 functionality and that the intrinsic guanine-nucleotide exchange activity of this protein may be different before and after stimulation of tyrosine kinase receptors. Using different myristoylated hSos1 full-length and carboxyl-terminal truncated mutants, we show that Grb2 function accounts not only for recruitment of hSos1 to the plasma membrane but also for modulation of hSos1 activity. Our results demonstrate that the first two canonical Grb2 binding sites, inside the carboxyl-terminal region of hSos1, are responsible for this regulation. Following different approaches, such as displacement of Grb2 from the hSos1-Grb2 complex or depletion of Grb2 levels by small interfering RNA, we found that the full-length Grb2 proteins mediate negative regulation of the intrinsic Ras guanine-nucleotide exchange activity of hSos1.
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Affiliation(s)
- Natasha Zarich
- Unidad de Biología Celular, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain
| | - José Luis Oliva
- Unidad de Biología Celular, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain
| | - Natalia Martínez
- Unidad de Biología Celular, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain
| | - Rocío Jorge
- Unidad de Biología Celular, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain
| | - Alicia Ballester
- Unidad de Biología Celular, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain
| | - Silvia Gutiérrez-Eisman
- Unidad de Biología Celular, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain
| | - Susana García-Vargas
- Unidad de Biología Celular, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain
| | - José M. Rojas
- Unidad de Biología Celular, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain
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16
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González-Santiago L, Suárez Y, Zarich N, Muñoz-Alonso MJ, Cuadrado A, Martínez T, Goya L, Iradi A, Sáez-Tormo G, Maier JV, Moorthy A, Cato ACB, Rojas JM, Muñoz A. Aplidin® induces JNK-dependent apoptosis in human breast cancer cells via alteration of glutathione homeostasis, Rac1 GTPase activation, and MKP-1 phosphatase downregulation. Cell Death Differ 2006; 13:1968-81. [PMID: 16543941 DOI: 10.1038/sj.cdd.4401898] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Aplidin is an antitumor agent in phase II clinical trials that induces apoptosis through the sustained activation of Jun N-terminal kinase (JNK). We report that Aplidin alters glutathione homeostasis increasing the ratio of oxidized to reduced forms (GSSG/GSH). Aplidin generates reactive oxygen species and disrupts the mitochondrial membrane potential. Exogenous GSH inhibits these effects and also JNK activation and cell death. We found two mechanisms by which Aplidin activates JNK: rapid activation of Rac1 small GTPase and downregulation of MKP-1 phosphatase. Rac1 activation was diminished by GSH and enhanced by L-buthionine (SR)-sulfoximine, which inhibits GSH synthesis. Downregulation of Rac1 by transfection of small interfering RNA (siRNA) duplexes or the use of a specific Rac1 inhibitor decreased Aplidin-induced JNK activation and cytotoxicity. Our results show that Aplidin induces apoptosis by increasing the GSSG/GSH ratio, a necessary step for induction of oxidative stress and sustained JNK activation through Rac1 activation and MKP-1 downregulation.
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Affiliation(s)
- L González-Santiago
- Instituto de Investigaciones Biomédicas 'Alberto Sols', Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Arturo Duperier, 4, Madrid E-28029, Spain
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17
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Millán O, Rico D, Peinado H, Zarich N, Stamatakis K, Pérez-Sala D, Rojas JM, Cano A, Boscá L. Potentiation of tumor formation by topical administration of 15-deoxy-delta12,14-prostaglandin J2 in a model of skin carcinogenesis. Carcinogenesis 2006; 27:328-36. [PMID: 16113051 DOI: 10.1093/carcin/bgi213] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The effect of prostaglandins on the development of papillomas has been investigated in mice receiving prostaglandins E2 (PGE2) or the cyclopentenone 15-deoxy-delta(12,14)-PGJ2 (15dPGJ2) topically, using the 7,12-dimethylbenz[a]anthracene (DMBA)-induced tetradecanoylphorbol acetate (TPA)-promoted model of skin carcinogenesis. The presence of 15dPGJ2 during DMBA and TPA treatment inhibited apoptosis and increased the rate, number, size and vascularization of the papillomas, some of them progressing into carcinomas. Moreover, skin sections from mice treated for one week with DMBA and 15dPGJ2 showed a much reduced rate of apoptotic cells, and an enhanced expression of vascular epithelial growth factor when compared with animals receiving DMBA, with or without PGE2. The analysis of molecular events in the MCA3D keratinocyte cell line showed that 15dPGJ2 activated Ras and improved cell viability by inhibiting DMBA-dependent apoptosis. In addition to this, cell adhesion was impaired in MCA3D keratinocytes co-treated with 15dPGJ2 and DMBA, at the same time when the expression of cyclooxygenase-2 (COX-2) was observed under these conditions. These effects mediated by 15dPGJ2 might contribute to understand the role of COX-2 metabolites in carcinogenesis, leading to an increase of cell viability after mutagenic injury and therefore in the progression of tumors.
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Affiliation(s)
- Olga Millán
- Instituto de Bioquímica, CSIC-UCM, 28040 Madrid, Spain
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18
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Greco C, Fantucci P, De Gioia L. In silico functional characterization of a double histone fold domain from the Heliothis zea virus 1. BMC Bioinformatics 2005; 6 Suppl 4:S15. [PMID: 16351741 PMCID: PMC1866393 DOI: 10.1186/1471-2105-6-s4-s15] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Background Histones are short proteins involved in chromatin packaging; in eukaryotes, two H2a-H2b and H3-H4 histone dimers form the nucleosomal core, which acts as the fundamental DNA-packaging element. The double histone fold is a rare globular protein fold in which two consecutive regions characterized by the typical structure of histones assemble together, thus originating a histone pseudodimer. This fold is included in a few prokaryotic histones and in the regulatory region of guanine nucleotide exchange factors of the Sos family. For the prokaryotic histones, there is no direct structural counterpart in the nucleosomal core particle, while the pseudodimer from Sos proteins is very similar to the dimer formed by histones H2a and H2b Results The absence of a H3-H4-like histone pseudodimer in the available structural databases prompted us to search for proteins that could assume such fold. The application of several secondary structure prediction and fold recognition methods allowed to show that the viral protein gi|22788712 is compatible with the structure of a H3-H4-like histone pseudodimer. Further in silico analyses revealed that this protein module could retain the ability of mediating protein-DNA interactions, and could consequently act as a DNA-binding domain. Conclusion Our results suggest a possible functional role in viral pathogenicity for this novel double histone fold domain; thus, the computational analyses here reported will be helpful in directing future biochemical studies on gi|22788712 protein.
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Affiliation(s)
- Claudio Greco
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi Milano-Bicocca, P.zza della Scienza 2, 20126 Milano, Italy
| | - Piercarlo Fantucci
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi Milano-Bicocca, P.zza della Scienza 2, 20126 Milano, Italy
| | - Luca De Gioia
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi Milano-Bicocca, P.zza della Scienza 2, 20126 Milano, Italy
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19
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Sondermann H, Nagar B, Bar-Sagi D, Kuriyan J. Computational docking and solution x-ray scattering predict a membrane-interacting role for the histone domain of the Ras activator son of sevenless. Proc Natl Acad Sci U S A 2005; 102:16632-7. [PMID: 16267129 PMCID: PMC1276615 DOI: 10.1073/pnas.0508315102] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Ras-specific nucleotide exchange factor son of sevenless (SOS) is a large, multidomain protein with complex regulation, including a Ras-dependent allosteric mechanism. The N-terminal segment of SOS, the histone domain, contains two histone folds, which is highly unusual for a cytoplasmic protein. Using a combination of computational docking, small-angle x-ray scattering, mutagenesis, and calorimetry, we show that the histone domain folds into the rest of SOS and docks onto a helical linker that connects the pleckstrin-homology (PH) and Dbl-homology (DH) domains of SOS to the catalytic domain. In this model, a positively charged surface region on the histone domain is positioned so as to provide a fourth potential anchorage site on the membrane for SOS in addition to the PH domain, the allosteric Ras molecule, and the C-terminal adapter-binding site. The histone domain in SOS interacts with the helical linker, using a region of the surface that in nucleosomes is involved in histone tetramerization. Adjacent surface elements on the histone domain that correspond to the DNA-binding surface of nucleosomes form the predicted interaction site with the membrane. The orientation and position of the histone domain in the SOS model implicates it as a potential mediator of membrane-dependent activation signals.
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Affiliation(s)
- Holger Sondermann
- Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
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20
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Greco C, Sacco E, Vanoni M, De Gioia L. Identification and in silico analysis of a new group of double-histone fold-containing proteins. J Mol Model 2005; 12:76-84. [PMID: 16247600 DOI: 10.1007/s00894-005-0008-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2005] [Accepted: 06/27/2005] [Indexed: 11/30/2022]
Abstract
The double-histone fold is a rare protein fold in which two consecutive regions characterized by the typical structure of histones assemble together, thus giving a histone pseudodimer. Previously, this fold was found in a few prokaryotic histones and in the regulatory region of guanine-nucleotide exchange factors of the Sos family. Standard methods of sequence comparison did not allow us to find new proteins containing a histone pseudodimer, as previously reported (Sondermann et al. 2003). However, a deeper investigation of protein sequences showed that the two histone folds included in Sos proteins share significant sequence similarity with nucleosomal histones. On the basis of this observation, we applied a specific strategy of sequence-homology search, which led to the identification of a new group of histone pseudodimers in Cca3 and proteins similar to Cca3 (Cca3S). A homology model of the histone pseudodimer included in rat Cca3 was constructed. A subsequent structure-function relationship study revealed that the histone pseudodimers included in Cca3 and Cca3S proteins, but not those present in Sos proteins, could retain the ability of mediating protein-DNA interactions, and could consequently act as DNA-binding modules.
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Affiliation(s)
- Claudio Greco
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi Milano-Bicocca, P.zza della Scienza 2, 20126 Milano, Italy
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21
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Sondermann H, Soisson SM, Bar-Sagi D, Kuriyan J. Tandem histone folds in the structure of the N-terminal segment of the ras activator Son of Sevenless. Structure 2004; 11:1583-93. [PMID: 14656442 DOI: 10.1016/j.str.2003.10.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The Ras activator Son of Sevenless (Sos) contains a Cdc25 homology domain, responsible for nucleotide exchange, as well as Dbl/Pleckstrin homology (DH/PH) domains. We have determined the crystal structure of the N-terminal segment of human Sos1 (residues 1-191) and show that it contains two tandem histone folds. While the N-terminal domain is monomeric in solution, its structure is surprisingly similar to that of histone dimers, with both subunits of the histone "dimer" being part of the same peptide chain. One histone fold corresponds to the region of Sos that is clearly similar in sequence to histones (residues 91-191), whereas the other is formed by residues in Sos (1-90) that are unrelated in sequence to histones. Residues that form a contiguous patch on the surface of the histone domain of Sos are conserved from C. elegans to humans, suggesting a potential role for this domain in protein-protein interactions.
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Affiliation(s)
- Holger Sondermann
- Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley, CA 94720, USA
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22
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Oliva JL, Zarich N, Martínez N, Jorge R, Castrillo A, Azañedo M, García-Vargas S, Gutiérrez-Eisman S, Juarranz A, Boscá L, Gutkind JS, Rojas JM. The P34G mutation reduces the transforming activity of K-Ras and N-Ras in NIH 3T3 cells but not of H-Ras. J Biol Chem 2004; 279:33480-91. [PMID: 15181015 DOI: 10.1074/jbc.m404058200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Ras proteins (H-, N-, and K-Ras) operate as molecular switches in signal transduction cascades controlling cell proliferation, differentiation, or apoptosis. The interaction of Ras with its effectors is mediated by the effector-binding loop, but different data about Ras location to plasma membrane subdomains and new roles for some docking/scaffold proteins point to signaling specificities of the different Ras proteins. To investigate the molecular mechanisms for these specificities, we compared an effector loop mutation (P34G) of three Ras isoforms (H-, N-, and K-Ras4B) for their biological and biochemical properties. Although this mutation diminished the capacity of Ras proteins to activate the Raf/ERK and the phosphatidylinositol 3-kinase/AKT pathways, the H-Ras V12G34 mutant retained the ability to cause morphological transformation of NIH 3T3 fibroblasts, whereas both the N-Ras V12G34 and the K-Ras4B V12G34 mutants were defective in this biological activity. On the other hand, although both the N-Ras V12G34 and the K-Ras4B V12G34 mutants failed to promote activation of the Ral-GDS/Ral A/PLD and the Ras/Rac pathways, the H-Ras V12G34 mutant retained the ability to activate these signaling pathways. Interestingly, the P34G mutation reduced specifically the N-Ras and K-Ras4B in vitro binding affinity to Ral-GDS, but not in the case of H-Ras. Thus, independently of Ras location to membrane subdomains, there are marked differences among Ras proteins in the sensitivity to an identical mutation (P34G) affecting the highly conserved effector-binding loop.
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Affiliation(s)
- José Luis Oliva
- Unidad de Biología Celular, Centro Nacional de Microbiología, Instituto de Salud Carlos III (ISCIII), 28220 Majadahonda, Madrid, Spain
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23
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Caloca MJ, Zugaza JL, Vicente-Manzanares M, Sánchez-Madrid F, Bustelo XR. F-actin-dependent Translocation of the Rap1 GDP/GTP Exchange Factor RasGRP2. J Biol Chem 2004; 279:20435-46. [PMID: 14988412 DOI: 10.1074/jbc.m313013200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
RasGRPs constitute a new group of diacylglycerol-dependent GDP/GTP exchange factors that activate Ras subfamily GTPases. Despite a common structure, Ras-GRPs diverge in their GTPase specificity, subcellular distribution, and downstream biological effects. The more divergent family member is RasGRP2, a Rap1-specific exchange factor with low affinity toward diacylglycerol. The regulation of RasGRP2 during signal transduction has remained elusive up to now. In this report, we show that the subcellular localization of Ras-GRP2 is highly dependent on actin dynamics. Thus, the induction of F-actin by cytoskeletal regulators such as Vav, Vav2, Dbl, and Rac1 leads to the shift of RasGRP2 from the cytosol to membrane ruffles and its co-localization with F-actin. Treatment of cells with cytoskeletal disrupting drugs abolishes this effect, leading to an abnormal localization of RasGRP2 in cytoplasmic clusters of actin. The use of Rac1 effector mutants indicates that the RasGRP2 translocation is linked exclusively to actin polymerization and is independent of other pathways such as p21-activated kinase JNK, or superoxide production. Biochemical experiments demonstrate that the translocation of RasGRP2 to membrane ruffles is mediated by the direct association of this protein with F-actin, a property contained within its 150 first amino acids. Finally, we show that the RasGRP2/F-actin interaction promotes the regionalized activation of Rap1 in juxtamembrane areas of the cell. These results reveal a novel function of the actin cytoskeleton in mediating the spatial activation of Ras subfamily GTPases through the selective recruitment of GDP/GTP exchange factors.
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Affiliation(s)
- Mariía J Caloca
- Centro de Investigación del Cáncer, University of Salamanca-Consejo Superior de Investigaciones Cientiíficas, Campus Unamuno, E-37007 Salamanca, Spain
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