101
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Holen HL, Nustad K, Aasheim HC. Activation of EphA receptors on CD4+CD45RO+ memory cells stimulates migration. J Leukoc Biol 2010; 87:1059-68. [PMID: 20160140 DOI: 10.1189/jlb.0709497] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
We have demonstrated previously that binding of ephrin-A1 to EphA receptors on human CD4(+) and CD8(+) T cells stimulates migration. Two EphA receptors have been reported in T cells: EphA1 at the protein level and EphA4 at the mRNA level. In this study, we wanted to investigate the expression profile of these receptors in T cell subpopulations and to test if expression differences would affect the potential of cells to migrate upon ephrin-A1 binding. We have generated an anti-EphA4 mAb for expression analysis. Our data show that functional EphA4 is expressed on the cell surface of CD4(+) and CD8(+) T cells. In addition, EphA4 receptor expression is induced after overnight incubation in serum-free medium, in particular, on CD4(+)CD45RO(+) T cells. Migration of CD4(+) T cells in response to ephrin-A1 is observed for memory cells (CD45RO(+)) and much weaker for naïve cells (CD45RA(+)). A signaling complex associated with the EphA4 receptor has also been isolated and includes EphA1, the Src family kinases Fyn and Lck, Slp76, and Vav1. To conclude, T cells express EphA1 and EphA4 receptors. Expression differences of EphA4 are observed in subpopulations of CD4(+) T cells. This is related to the cell migration potential after ephrin-A1 binding.
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Affiliation(s)
- H L Holen
- Department of Medical Genetics, Ullevaal University Hospital, Kirkeveien 166, 0407 Oslo, Norway
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102
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Thalappilly S, Soubeyran P, Iovanna JL, Dusetti NJ. VAV2 regulates epidermal growth factor receptor endocytosis and degradation. Oncogene 2010; 29:2528-39. [PMID: 20140013 DOI: 10.1038/onc.2010.1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Vav proteins are guanine nucleotide exchange factors for Rho GTPases that regulate cell adhesion, motility, spreading and proliferation in response to growth factor signalling. In this work, we show that Vav2 expression delayed epidermal growth factor receptor (EGFR) internalization and degradation, and enhanced EGFR, ERK and Akt phosphorylations. This effect of Vav2 on EGFR degradation is dependent on its guanine nucleotide exchange function. Knockdown of Vav2 in HeLa cells enhanced EGFR degradation and reduced cell proliferation. epidermal growth factor stimulation led to co-localization of Vav2 with EGFR and Rab5 in endosomes. We further show that the effect of Vav2 on EGFR stability is modulated by its interaction with two endosome-associated proteins and require RhoA function. Thus, in this work, we report for the first time that Vav2 can regulate growth factors receptor signalling by slowing receptor internalization and degradation through its interaction with endosome-associated proteins.
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Affiliation(s)
- S Thalappilly
- INSERM U624, Stress Cellulaire, Marseille F-13288, France
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103
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Li L, Fridley BL, Kalari K, Jenkins G, Batzler A, Weinshilboum RM, Wang L. Gemcitabine and arabinosylcytosin pharmacogenomics: genome-wide association and drug response biomarkers. PLoS One 2009; 4:e7765. [PMID: 19898621 PMCID: PMC2770319 DOI: 10.1371/journal.pone.0007765] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2009] [Accepted: 10/02/2009] [Indexed: 11/18/2022] Open
Abstract
Cancer patients show large individual variation in their response to chemotherapeutic agents. Gemcitabine (dFdC) and AraC, two cytidine analogues, have shown significant activity against a variety of tumors. We previously used expression data from a lymphoblastoid cell line-based model system to identify genes that might be important for the two drug cytotoxicity. In the present study, we used that same model system to perform a genome-wide association (GWA) study to test the hypothesis that common genetic variation might influence both gene expression and response to the two drugs. Specifically, genome-wide single nucleotide polymorphisms (SNPs) and mRNA expression data were obtained using the Illumina 550K(R) HumanHap550 SNP Chip and Affymetrix U133 Plus 2.0 GeneChip, respectively, for 174 ethnically-defined "Human Variation Panel" lymphoblastoid cell lines. Gemcitabine and AraC cytotoxicity assays were performed to obtain IC(50) values for the cell lines. We then performed GWA studies with SNPs, gene expression and IC(50) of these two drugs. This approach identified SNPs that were associated with gemcitabine or AraC IC(50) values and with the expression regulation for 29 genes or 30 genes, respectively. One SNP in IQGAP2 (rs3797418) was significantly associated with variation in both the expression of multiple genes and gemcitabine and AraC IC(50). A second SNP in TGM3 (rs6082527) was also significantly associated with multiple gene expression and gemcitabine IC50. To confirm the association results, we performed siRNA knock down of selected genes with expression that was associated with rs3797418 and rs6082527 in tumor cell and the knock down altered gemcitabine or AraC sensitivity, confirming our association study results. These results suggest that the application of GWA approaches using cell-based model systems, when combined with complementary functional validation, can provide insights into mechanisms responsible for variation in cytidine analogue response.
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Affiliation(s)
- Liang Li
- Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Brooke L. Fridley
- Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Krishna Kalari
- Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Gregory Jenkins
- Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Anthony Batzler
- Health Sciences Research, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Richard M. Weinshilboum
- Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Liewei Wang
- Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota, United States of America
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104
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Duan L, Chen G, Virmani S, Ying G, Raja SM, Chung BM, Rainey MA, Dimri M, Ortega-Cava CF, Zhao X, Clubb RJ, Tu C, Reddi AL, Naramura M, Band V, Band H. Distinct roles for Rho versus Rac/Cdc42 GTPases downstream of Vav2 in regulating mammary epithelial acinar architecture. J Biol Chem 2009; 285:1555-68. [PMID: 19826000 DOI: 10.1074/jbc.m109.057976] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Non-malignant mammary epithelial cells (MECs) undergo acinar morphogenesis in three-dimensional Matrigel culture, a trait that is lost upon oncogenic transformation. Rho GTPases are thought to play important roles in regulating epithelial cell-cell junctions, but their contributions to acinar morphogenesis remain unclear. Here we report that the activity of Rho GTPases is down-regulated in non-malignant MECs in three-dimensional culture with particular suppression of Rac1 and Cdc42. Inducible expression of a constitutively active form of Vav2, a Rho GTPase guanine nucleotide exchange factor activated by receptor tyrosine kinases, in three-dimensional MEC culture activated Rac1 and Cdc42; Vav2 induction from early stages of culture impaired acinar morphogenesis, and induction in preformed acini disrupted the pre-established acinar architecture and led to cellular outgrowths. Knockdown studies demonstrated that Rac1 and Cdc42 mediate the constitutively active Vav2 phenotype, whereas in contrast, RhoA knockdown intensified the Vav2-induced disruption of acini, leading to more aggressive cell outgrowth and branching morphogenesis. These results indicate that RhoA plays an antagonistic role to Rac1/Cdc42 in the control of mammary epithelial acinar morphogenesis.
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Affiliation(s)
- Lei Duan
- Eppley Institute for Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA.
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105
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Mechanical stretch-induced RhoA activation is mediated by the RhoGEF Vav2 in mesangial cells. Cell Signal 2009; 22:34-40. [PMID: 19755152 DOI: 10.1016/j.cellsig.2009.09.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Revised: 09/03/2009] [Accepted: 09/04/2009] [Indexed: 11/20/2022]
Abstract
Increased intraglomerular pressure is an important hemodynamic determinant of glomerulosclerosis, and can be modelled in vitro by exposing mesangial cells (MC) to cyclic mechanical stretch. We have previously shown that the GTPase RhoA mediates stretch-induced fibronectin production. Here we investigate the role of the RhoGEF Vav2 in the activation of RhoA by stretch. Primary rat MC were exposed to 1 Hz cyclic stretch, previously shown to induce maximal RhoA activation at 1 min. Total Vav2 tyrosine phosphorylation and specific phosphorylation on Y172, required for activation, were increased by 1 min of stretch. Overexpression of dominant-negative Vav2 Y172/159F in COS-1 cells or downregulation of Vav2 by siRNA in MC prevented stretch-induced RhoA activation. Vav2 is known to be activated in response to growth factors, and we have previously shown the epidermal growth factor receptor (EGFR) to be transactivated by stretch in MC. Both Vav2 Y172 phosphorylation and RhoA activation were blocked by the EGFR inhibitor AG1478 and prevented in MC overexpressing kinase inactive EGFR. Stretch led to physical association between the EGFR and Vav2, and this was dependent on EGFR activation. EGFR Y992 phosphorylation, required for growth factor-induced Vav2 phosphorylation, was also induced by stretch. Activation of both Src and PI3K were necessary upstream mediators of stretch-induced Vav2 Y172 phosphorylation and RhoA activation. In summary, stretch-induced RhoA activation is dependent on transactivation of the EGFR and activation of the RhoGEF Vav2. Src and PI3K are both required upstream of Vav2 and RhoA activation.
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106
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p210(Bcr-Abl) desensitizes Cdc42 GTPase signaling for SDF-1alpha-directed migration in chronic myeloid leukemia cells. Oncogene 2009; 28:4105-15. [PMID: 19718053 DOI: 10.1038/onc.2009.260] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Chronic myeloid leukemia (CML) is a lethal hematological disorder caused by the p210(Bcr-Abl) oncogene. Previous studies have suggested that p210(Bcr-Abl) transformation contributes to homing and retention defects, typical of immature myeloid cells in CML, by attenuating chemotactic response to stromal-derived factor-1alpha (SDF-1alpha). As Rho family GTPases are key regulators of the cytoskeleton and have been previously found to interact with p210(Bcr-Abl), this study aimed to determine whether p210(Bcr-Abl) signaling affects SDF-1alpha chemotaxis through Rho GTPase signaling. We found that SDF-1alpha stimulated Cdc42 GTPase activation in myeloid progenitor 32D, but not in p210(Bcr-Abl)-transformed (32Dp210) cells. In fact, the basal level of active Cdc42 was elevated in 32Dp210 cells and mononuclear cells isolated from bone marrow of CML patients. Inhibition of p210(Bcr-Abl) kinase activity decreased basal Cdc42 activity and restored SDF-1alpha-induced Cdc42 and migration responses. Transduction of active Tat-Cdc42V12 abolished this reconstituted chemotactic response. As Cdc42 is particularly important in cytoskeletal remodeling and directional sensing, these results suggest that sustained activation of Cdc42 GTPase through p210(Bcr-Abl) tyrosine kinase signaling in CML cells contributes to defects in SDF-1alpha-chemotactic response due to desensitization of the actin polarization signal required for directional migration.
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107
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Spurrell DR, Luckashenak NA, Minney DC, Chaplin A, Penninger JM, Liwski RS, Clements JL, West KA. Vav1 regulates the migration and adhesion of dendritic cells. THE JOURNAL OF IMMUNOLOGY 2009; 183:310-8. [PMID: 19542442 DOI: 10.4049/jimmunol.0802096] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Dendritic cells (DCs) are the most potent APCs for activating naive T cells, a process facilitated by the ability of immature DCs to mature and home to lymph nodes after encountering an inflammatory stimulus. Proteins involved in cytoskeletal rearrangement play an important role in regulating the adherence and motility of DCs. Vav1, a guanine nucleotide exchange factor for Rho family GTPases, mediates cytoskeletal rearrangement in hematopoietic cells following integrin ligation. We show that Vav1 is not required for the normal maturation of DCs in vitro; however, it is critical for DC binding to fibronectin and regulates the distribution but not the formation of podosomes. We also found that DC Vav1 was an important component of a signaling pathway involving focal adhesion kinase, phospholipase C-gamma2, and ERK1/2 following integrin ligation. Surprisingly, Vav1(-/-) DCs had increased rates of migration in vivo compared with wild-type control DCs. In vitro findings show that the presence of adhesive substrates such as fibronectin resulted in inhibition of migration. However, there was less inhibition in the absence of Vav1. These findings suggest that DC migration is negatively regulated by adhesion and integrin-mediated signaling and that Vav1 has a central role in this process.
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Affiliation(s)
- David R Spurrell
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, Canada
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108
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Age-related changes in lck-Vav signaling pathways in mouse CD4 T cells. Cell Immunol 2009; 259:100-4. [PMID: 19577230 DOI: 10.1016/j.cellimm.2009.06.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2009] [Revised: 05/28/2009] [Accepted: 06/01/2009] [Indexed: 11/24/2022]
Abstract
Activation of lck-fyn kinases during T cell receptor signaling leads to Vav phosphorylation, activation of downstream targets including Rac1, and a transient decline in ezrin and moesin phosphorylation. We have shown that age increases Rac1 activity and lowers ezrin and moesin phosphorylation in resting mouse CD4 cells, changes that could be the results of alterations in lck-Vav signaling. Analysis of Vav in CD4 cells from old mice shows increases in the phosphorylation of two key regulatory residues, Tyr160 and Tyr174, suggesting enhancement of Vav GTPase activity. In addition, analysis of lck status also shows age-related increases in phosphorylation of two key residues, Tyr394 and Tyr505, which have opposite effects on lck function. These changes in lck-Vav signals in resting CD4 cells may contribute in turn to age-related increases in Rac1 activity and declines in phosphorylation of cytoskeletal proteins including Ezrin and Moesin.
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109
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Katzav S. Vav1: A hematopoietic signal transduction molecule involved in human malignancies. Int J Biochem Cell Biol 2009; 41:1245-8. [DOI: 10.1016/j.biocel.2008.11.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2008] [Revised: 11/23/2008] [Accepted: 11/24/2008] [Indexed: 11/29/2022]
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110
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Lazer G, Idelchuk Y, Schapira V, Pikarsky E, Katzav S. The haematopoietic specific signal transducer Vav1 is aberrantly expressed in lung cancer and plays a role in tumourigenesis. J Pathol 2009; 219:25-34. [DOI: 10.1002/path.2579] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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111
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A functional genomics approach reveals novel quantitative trait loci associated with platelet signaling pathways. Blood 2009; 114:1405-16. [PMID: 19429868 DOI: 10.1182/blood-2009-02-202614] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Platelet response to activation varies widely between individuals but shows interindividual consistency and strong heritability. The genetic basis of this variation has not been properly explored. We therefore systematically measured the effect on function of sequence variation in 97 candidate genes in the collagen and adenosine-diphosphate (ADP) signaling pathways. Resequencing of the genes in 48 European DNA samples nearly doubled the number of known single nucleotide polymorphisms (SNPs) and informed the selection of 1327 SNPs for genotyping in 500 healthy Northern European subjects with known platelet responses to collagen-related peptide (CRP-XL) and ADP. This identified 17 novel associations with platelet function (P < .005) accounting for approximately 46% of the variation in response. Further investigations with platelets of known genotype explored the mechanisms behind some of the associations. SNPs in PEAR1 associated with increased platelet response to CRP-XL and increased PEAR1 protein expression after platelet degranulation. The minor allele of a 3' untranslated region (UTR) SNP (rs2769668) in VAV3 was associated with higher protein expression (P = .03) and increased P-selectin exposure after ADP activation (P = .004). Furthermore the minor allele of the intronic SNP rs17786144 in ITPR1 modified Ca(2+) levels after activation with ADP (P < .004). These data provide novel insights into key hubs within platelet signaling networks.
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112
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Shah VB, Ozment-Skelton TR, Williams DL, Keshvara L. Vav1 and PI3K are required for phagocytosis of β-glucan and subsequent superoxide generation by microglia. Mol Immunol 2009; 46:1845-53. [DOI: 10.1016/j.molimm.2009.01.014] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2008] [Accepted: 01/07/2009] [Indexed: 12/28/2022]
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113
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Pendyala S, Usatyuk PV, Gorshkova IA, Garcia JG, Natarajan V. Regulation of NADPH oxidase in vascular endothelium: the role of phospholipases, protein kinases, and cytoskeletal proteins. Antioxid Redox Signal 2009; 11:841-60. [PMID: 18828698 PMCID: PMC2850292 DOI: 10.1089/ars.2008.2231] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The generation of reactive oxygen species (ROS) in the vasculature plays a major role in the genesis of endothelial cell (EC) activation and barrier function. Of the several potential sources of ROS in the vasculature, the endothelial NADPH oxidase family of proteins is a major contributor of ROS associated with lung inflammation, ischemia/reperfusion injury, sepsis, hyperoxia, and ventilator-associated lung injury. The NADPH oxidase in lung ECs has most of the components found in phagocytic oxidase, and recent studies show the expression of several homologues of Nox proteins in vascular cells. Activation of NADPH oxidase of nonphagocytic vascular cells is complex and involves assembly of the cytosolic (p47(phox), p67(phox), and Rac1) and membrane-associated components (Noxes and p22(phox)). Signaling pathways leading to NADPH oxidase activation are not completely defined; however, they do appear to involve the cytoskeleton and posttranslation modification of the components regulated by protein kinases, protein phosphatases, and phospholipases. Furthermore, several key components regulating NADPH oxidase recruitment, assembly, and activation are enriched in lipid microdomains to form a functional signaling platform. Future studies on temporal and spatial localization of Nox isoforms will provide new insights into the role of NADPH oxidase-derived ROS in the pathobiology of lung diseases.
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114
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de la Puerta ML, Trinidad AG, Rodríguez MDC, Bogetz J, Sánchez Crespo M, Mustelin T, Alonso A, Bayón Y. Characterization of new substrates targeted by Yersinia tyrosine phosphatase YopH. PLoS One 2009; 4:e4431. [PMID: 19221593 PMCID: PMC2637541 DOI: 10.1371/journal.pone.0004431] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Accepted: 12/17/2008] [Indexed: 12/24/2022] Open
Abstract
YopH is an exceptionally active tyrosine phosphatase that is essential for virulence of Yersinia pestis, the bacterium causing plague. YopH breaks down signal transduction mechanisms in immune cells and inhibits the immune response. Only a few substrates for YopH have been characterized so far, for instance p130Cas and Fyb, but in view of YopH potency and the great number of proteins involved in signalling pathways it is quite likely that more proteins are substrates of this phosphatase. In this respect, we show here YopH interaction with several proteins not shown before, such as Gab1, Gab2, p85, and Vav and analyse the domains of YopH involved in these interactions. Furthermore, we show that Gab1, Gab2 and Vav are not dephosphorylated by YopH, in contrast to Fyb, Lck, or p85, which are readily dephosphorylated by the phosphatase. These data suggests that YopH might exert its actions by interacting with adaptors involved in signal transduction pathways, what allows the phosphatase to reach and dephosphorylate its susbstrates.
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Affiliation(s)
| | - Antonio G. Trinidad
- Instituto de Biología y Genética Molecular, CSIC-Universidad de Valladolid, Valladolid, Spain
| | | | - Jori Bogetz
- Program of Inflammation, Inflammatory and Infectious Disease Center, and Program of Signal Transduction, Burnham Institute for Medical Research, La Jolla, California, United States of America
| | - Mariano Sánchez Crespo
- Instituto de Biología y Genética Molecular, CSIC-Universidad de Valladolid, Valladolid, Spain
| | - Tomas Mustelin
- Program of Inflammation, Inflammatory and Infectious Disease Center, and Program of Signal Transduction, Burnham Institute for Medical Research, La Jolla, California, United States of America
| | - Andrés Alonso
- Instituto de Biología y Genética Molecular, CSIC-Universidad de Valladolid, Valladolid, Spain
| | - Yolanda Bayón
- Instituto de Biología y Genética Molecular, CSIC-Universidad de Valladolid, Valladolid, Spain
- * E-mail:
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115
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Carvajal-Gonzalez JM, Mulero-Navarro S, Roman AC, Sauzeau V, Merino JM, Bustelo XR, Fernandez-Salguero PM. The dioxin receptor regulates the constitutive expression of the vav3 proto-oncogene and modulates cell shape and adhesion. Mol Biol Cell 2009; 20:1715-27. [PMID: 19158396 DOI: 10.1091/mbc.e08-05-0451] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The dioxin receptor (AhR) modulates cell plasticity and migration, although the signaling involved remains unknown. Here, we report a mechanism that integrates AhR into these cytoskeleton-related functions. Immortalized and mouse embryonic fibroblasts lacking AhR (AhR-/-) had increased cell area due to spread cytoplasms that reverted to wild-type morphology upon AhR re-expression. The AhR-null phenotype included increased F-actin stress fibers, depolarized focal adhesions, and enhanced spreading and adhesion. The cytoskeleton alterations of AhR-/- cells were due to down-regulation of constitutive Vav3 expression, a guanosine diphosphate/guanosine triphosphate exchange factor for Rho/Rac GTPases and a novel transcriptional target of AhR. AhR was recruited to the vav3 promoter and maintained constitutive mRNA expression in a ligand-independent manner. Consistently, AhR-/- fibroblasts had reduced Rac1 activity and increased activation of the RhoA/Rho kinase (Rock) pathway. Pharmacological inhibition of Rac1 shifted AhR+/+ fibroblasts to the null phenotype, whereas Rock inhibition changed AhR-null cells to the AhR+/+ morphology. Knockdown of vav3 transcripts by small interfering RNA induced cytoskeleton defects and changes in adhesion and spreading mimicking those of AhR-null cells. Moreover, vav3-/- MEFs, as AhR-/- mouse embryonic fibroblasts, had increased cell area and enhanced stress fibers. By modulating Vav3-dependent signaling, AhR could regulate cell shape, adhesion, and migration under physiological conditions and, perhaps, in certain pathological states.
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Affiliation(s)
- Jose M Carvajal-Gonzalez
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain
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116
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Molli PR, Adam L, Kumar R. Therapeutic IMC-C225 antibody inhibits breast cancer cell invasiveness via Vav2-dependent activation of RhoA GTPase. Clin Cancer Res 2008; 14:6161-70. [PMID: 18829495 DOI: 10.1158/1078-0432.ccr-07-5288] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Abnormalities in the expression and signaling pathways downstream of epidermal growth factor receptor (EGFR) contribute to progression, invasion, and maintenance of the malignant phenotype in human cancers. Accordingly, biological agents, such as the EGFR-blocking antibody IMC-C225 have promising anticancer potential and are currently in various stages of clinical development. Because use of IMC-C225 is limited, at present, only for treatment of cancer with high EGFR expression, the goal of the present study was to determine the effect of IMC-C225 on the invasiveness of breast cancer cells with high and low levels of EGFR expression. EXPERIMENTAL DESIGN The effect of IMC-C225 on invasion was studied using breast cancer cell lines with high and low levels of EGFR expression. RESULTS The addition of EGF led to progressive stress fiber dissolution. In contrast, cells treated with IMC-C225 showed reduced invasiveness and increased stress-fiber formation. Interestingly, IMC-C225 pretreatment was accompanied by EGFR phosphorylation, as detected using an anti-phosphorylated tyrosine antibody (PY99), which correlated with phosphorylation of Vav2 guanine nucleotide exchange factor and activation of RhoA GTPase irrespective of EGFR level, and Vav2 interacted with EGFR only in IMC-C225-treated cells. The underlying mechanism involved an enhanced interaction between beta1 integrins and EGFR upon IMC-C225 treatment. CONCLUSION Here, we defined a new mechanism for IMC-C225 that cross-links integrins with EGFR, leading to activation of RhoA and inhibition of breast cancer cell invasion irrespective of the level of EGFR in the cells, thus providing a rationale for using IMC-C225 in the metastatic setting independent of the levels of EGFR.
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Affiliation(s)
- Poonam R Molli
- Department of Molecular and Cellular Oncology, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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117
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Yi F, Xia M, Li N, Zhang C, Tang L, Li PL. Contribution of guanine nucleotide exchange factor Vav2 to hyperhomocysteinemic glomerulosclerosis in rats. Hypertension 2008; 53:90-6. [PMID: 19029489 DOI: 10.1161/hypertensionaha.108.115675] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We currently reported that Vav2, a member of the guanine nucleotide exchange factor-Vav subfamily, participates in homocysteine-induced increases in Rac1 activity and consequent activation of NADPH oxidase in rat mesangial cells. However, the physiological relevance of this cellular action of Vav2 remains unknown. The present study tested a hypothesis that Vav2 importantly mediates the injurious action of homocysteine on glomeruli and thereby contributes to the development of glomerulosclerosis during hyperhomocysteinemia. We found that, among Vav members, Vav2 was abundantly expressed in glomeruli. When Vav2 short hairpin RNA was transfected into the kidneys of Sprague-Dawley rats, hyperhomocysteinemia induced by folate-free diet failed to significantly enhance Rac1 activity and increase NADPH-dependent superoxide production. In these rats with silenced renal Vav2 gene, glomerular injury during hyperhomocysteinemia was markedly attenuated compared with those rats only receiving mock vector transfection, as shown by ameliorated albuminuria and extracellular matrix metabolism. In the rat kidneys with transfection of a dominant-active Vav2 variant (onco-Vav2), we found that overexpression of Vav2 led to significant increases in Rac1 activity, superoxide production, and glomerular injury, which was similar to that induced by hyperhomocysteinemia. However, this Vav2 overexpression was unable to further enhance homocysteine-induced glomerular injury. We concluded that Vav2-mediated activation of NADPH oxidase is an important initiating mechanism resulting in hyperhomocysteinemic glomerular injury through enhanced local oxidative stress.
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Affiliation(s)
- Fan Yi
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, 410 N 12th St, Richmond, VA 23298, USA
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118
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Contributions of F-BAR and SH2 domains of Fes protein tyrosine kinase for coupling to the FcepsilonRI pathway in mast cells. Mol Cell Biol 2008; 29:389-401. [PMID: 19001085 DOI: 10.1128/mcb.00904-08] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
This study investigates the roles of Fer-CIP4 homology (FCH)-Bin/amphiphysin/Rvs (F-BAR) and SH2 domains of Fes protein tyrosine kinase in regulating its activation and signaling downstream of the high-affinity immunoglobulin G (IgE) receptor (FcepsilonRI) in mast cells. Homology modeling of the Fes F-BAR domain revealed conservation of some basic residues implicated in phosphoinositide binding (R113/K114). The Fes F-BAR can bind phosphoinositides and induce tubulation of liposomes in vitro. Mutation of R113/K114 to uncharged residues (RK/QQ) caused a significant reduction in phosphoinositide binding in vitro and a more diffuse cytoplasmic localization in transfected COS-7 cells. RBL-2H3 mast cells expressing full-length Fes carrying the RK/QQ mutation show defects in FcepsilonRI-induced Fes tyrosine phosphorylation and degranulation compared to cells expressing wild-type Fes. This correlated with reduced localization to Lyn kinase-containing membrane fractions for the RK/QQ mutant compared to wild-type Fes in mast cells. The Fes SH2 domain also contributes to Fes signaling in mast cells, via interactions with the phosphorylated FcepsilonRI beta chain and the actin regulatory protein HS1. We show that Fes phosphorylates C-terminal tyrosine residues in HS1 implicated in actin stabilization. Thus, coordinated actions of the F-BAR and SH2 domains of Fes allow for coupling to FcepsilonRI signaling and potential regulation the actin reorganization in mast cells.
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119
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Mamchak AA, Sullivan BM, Hou B, Lee LM, Gilden JK, Krummel MF, Locksley RM, DeFranco AL. Normal development and activation but altered cytokine production of Fyn-deficient CD4+ T cells. THE JOURNAL OF IMMUNOLOGY 2008; 181:5374-85. [PMID: 18832694 DOI: 10.4049/jimmunol.181.8.5374] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The Src family kinase Fyn is expressed in T cells and has been shown to phosphorylate proteins involved in TCR signaling, cytoskeletal reorganization, and IL-4 production. Fyn-deficient mice have greatly decreased numbers of NKT cells and have thymocytes and T cells with compromised responses following Ab crosslinking of their TCRs. Herein we have addressed the role of Fyn in peptide/MHC class II-induced CD4(+) T cell responses. In Fyn-deficient mice, CD4(+) T cells expressing the DO11.10 TCR transgene developed normally, and the number and phenotype of naive and regulatory DO11.10(+)CD4(+) T cells in the periphery were comparable with their wild-type counterparts. Conjugation with chicken OVA peptide 323-339-loaded APCs, and the subsequent proliferation in vitro or in vivo of DO11.10(+) Fyn-deficient CD4(+) T cells, was virtually indistinguishable from the response of DO11.10(+) wild-type CD4(+) T cells. Proliferation of Fyn-deficient T cells was not more dependent on costimulation through CD28. Additionally, we have found that differentiation, in vitro or in vivo, of transgenic CD4(+) Fyn-deficient T cells into IL-4-secreting effector cells was unimpaired, and under certain conditions DO11.10(+) Fyn-deficient CD4(+) T cells were more potent cytokine-producing cells than DO11.10(+) wild-type CD4(+) T cells. These data demonstrate that ablation of Fyn expression does not alter most Ag-driven CD4(+) T cell responses, with the exception of cytokine production, which under some circumstances is enhanced in Fyn-deficient CD4(+) T cells.
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Affiliation(s)
- Alusha A Mamchak
- Department of Microbiology and Immunology, University of California, San Francisco, CA 94143, USA
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Lane J, Martin TA, Mansel RE, Jiang WG. The expression and prognostic value of the guanine nucleotide exchange factors (GEFs) Trio, Vav1 and TIAM-1 in human breast cancer. INTERNATIONAL SEMINARS IN SURGICAL ONCOLOGY : ISSO 2008; 5:23. [PMID: 18925966 PMCID: PMC2576462 DOI: 10.1186/1477-7800-5-23] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Accepted: 10/16/2008] [Indexed: 11/10/2022]
Abstract
BACKGROUND Development of metastasis in breast cancer is a multi-step process comprising changes in cytoskeletal structure and gene expression of tumour cells leading to changes in cell adhesion and motility. The Rho GTPase proteins, which function as guanine nucleotide regulated binary switches, govern a variety of cellular processes including cell motility and migration, changes in cell adhesion as well as actin cytoskeletal reorganisation and gene expression/transcription. One group of activators which regulate the Rho-GTPases is the guanine nucleotide exchange factors (GEFs), and this study looked at three such GEFs, Trio, Vav1 and TIAM-1. The purpose of this study was to investigate the expression of these GEFs, in human breast cancer and assess the affect on clinical outcome. METHODS Specimens of fresh, frozen breast tumour tissue (n = 113) and normal background tissue (n = 30) were processed for quantitative PCR analysis. The expression and levels of expression of Trio, Vav1 and TIAM-1 were analysed using RT-PCR and real-time Q-PCR respectively. Sections were also immunostained with Trio and Tiam-1 antibodies. RESULTS Tumour tissue exhibited high levels of all three Rho activators Trio, Vav1 and TIAM-1 compared with normal background breast tissue, reaching a level of significance for the GEF Trio (p = 0.013). Trio levels also increased significantly in patients with a poor prognostic index (p = 0.04).Levels of TIAM-1 were significantly higher in tumour tissue from patients who died from breast cancer compared with those who survived (p = 0.04). No significant correlation was found between tumour grade and histology types. CONCLUSION High expression levels of Trio, Vav1 and TIAM-1 were seen in breast tumours, especially in those with poor prognosis. This suggests that aberrant regulation of Rho family activities by GEFs may have an important prognostic value in breast cancer.
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Affiliation(s)
- Jane Lane
- Metastasis research Group, University Department of Surgery, Cardiff University School of Medicine, Heath Park, Cardiff, CF4 4XN, UK
| | - Tracey A Martin
- Metastasis research Group, University Department of Surgery, Cardiff University School of Medicine, Heath Park, Cardiff, CF4 4XN, UK
| | - Robert E Mansel
- Metastasis research Group, University Department of Surgery, Cardiff University School of Medicine, Heath Park, Cardiff, CF4 4XN, UK
| | - Wen G Jiang
- Metastasis research Group, University Department of Surgery, Cardiff University School of Medicine, Heath Park, Cardiff, CF4 4XN, UK
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Acquaviva J, Wong R, Charest A. The multifaceted roles of the receptor tyrosine kinase ROS in development and cancer. Biochim Biophys Acta Rev Cancer 2008; 1795:37-52. [PMID: 18778756 DOI: 10.1016/j.bbcan.2008.07.006] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Accepted: 07/21/2008] [Indexed: 12/26/2022]
Abstract
The proto-oncogene receptor tyrosine kinase ROS was originally discovered through the identification of oncogenic variants isolated from tumors. These discoveries spearheaded a body of work aimed at elucidating the function of this evolutionarily conserved receptor in development and cancer. Through genetic and biochemical approaches, progress in the characterization of ROS points to distinctive roles in the program of epithelial cell differentiation during the development of a variety of organs. Although substantial, these advances remain hampered by the absence of an identified ligand, making ROS one of the last two remaining orphan receptor tyrosine kinases. Recent studies on the oncogenic activation of ROS as a result of different chromosomal rearrangements found in brain and lung cancers have shed light on the molecular mechanisms underlying ROS transforming activities. ROS and its oncogenic variants therefore constitute clinically relevant targets for cancer therapeutic intervention. This review highlights the various roles that this receptor plays in multiple system networks in normalcy and disease and points to future directions towards the elucidation of ROS function in the context of ligand identification, signaling pathways and clinical applications.
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Affiliation(s)
- Jaime Acquaviva
- Molecular Oncology Research Institute, Tufts University School of Medicine, Tufts Medical Center, Boston, MA 02111, USA
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122
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Weber M, Treanor B, Depoil D, Shinohara H, Harwood NE, Hikida M, Kurosaki T, Batista FD. Phospholipase C-gamma2 and Vav cooperate within signaling microclusters to propagate B cell spreading in response to membrane-bound antigen. ACTA ACUST UNITED AC 2008; 205:853-68. [PMID: 18362175 PMCID: PMC2292224 DOI: 10.1084/jem.20072619] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
B cell receptor (BCR) recognition of membrane-bound antigen initiates a spreading and contraction response, the extent of which is controlled through the formation of signaling-active BCR-antigen microclusters and ultimately affects the outcome of B cell activation. We followed a genetic approach to define the molecular requirements of BCR-induced spreading and microcluster formation. We identify a key role for phospholipase C-γ2 (PLCγ2), Vav, B cell linker, and Bruton's tyrosine kinase in the formation of highly coordinated “microsignalosomes,” the efficient assembly of which is absolutely dependent on Lyn and Syk. Using total internal reflection fluorescence microscopy, we examine at high resolution the recruitment of PLCγ2 and Vav to microsignalosomes, establishing a novel synergistic relationship between the two. Thus, we demonstrate the importance of cooperation between components of the microsignalosome in the amplification of signaling and propagation of B cell spreading, which is critical for appropriate B cell activation.
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Affiliation(s)
- Michele Weber
- Lymphocyte Interaction Laboratory, London Research Institute, Cancer Research UK, London WC2A 3PX, England, UK
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123
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Elwell CA, Ceesay A, Kim JH, Kalman D, Engel JN. RNA interference screen identifies Abl kinase and PDGFR signaling in Chlamydia trachomatis entry. PLoS Pathog 2008; 4:e1000021. [PMID: 18369471 PMCID: PMC2267011 DOI: 10.1371/journal.ppat.1000021] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Accepted: 02/01/2008] [Indexed: 11/19/2022] Open
Abstract
To elucidate the mechanisms involved in early events in Chlamydia trachomatis infection, we conducted a large scale unbiased RNA interference screen in Drosophila melanogaster S2 cells. This allowed identification of candidate host factors in a simple non-redundant, genetically tractable system. From a library of 7,216 double stranded RNAs (dsRNA), we identified ∼226 host genes, including two tyrosine kinases, Abelson (Abl) kinase and PDGF- and VEGF-receptor related (Pvr), a homolog of the Platelet-derived growth factor receptor (PDGFR). We further examined the role of these two kinases in C. trachomatis binding and internalization into mammalian cells. Both kinases are phosphorylated upon infection and recruited to the site of bacterial attachment, but their roles in the infectious process are distinct. We provide evidence that PDGFRβ may function as a receptor, as inhibition of PDGFRβ by RNA interference or by PDGFRβ neutralizing antibodies significantly reduces bacterial binding, whereas depletion of Abl kinase has no effect on binding. Bacterial internalization can occur through activation of PDGFRβ or through independent activation of Abl kinase, culminating in phosphorylation of the Rac guanine nucleotide exchange factor (GEF), Vav2, and two actin nucleators, WAVE2 and Cortactin. Finally, we show that TARP, a bacterial type III secreted actin nucleator implicated in entry, is a target of Abl kinase. Together, our results demonstrate that PDGFRβ and Abl kinases function redundantly to promote efficient uptake of this obligate intracellular parasite. Chlamydia trachomatis infections are a worldwide problem; they are the leading cause of preventable blindness in developing nations and the most common cause of sexually transmitted disease in the Western world. Binding and entry into host cells are critical steps to the pathogenesis of this obligate intracellular parasite; however little is known regarding the mechanism of these processes. In this work, we describe a large scale RNA interference screen to identify host factors essential for early steps in C. trachomatis infection. We discover that the Platelet Derived Growth Factor Receptor β (PDGFRβ) can function as a receptor for C. trachomatis, and that activation of both PDGFRβ and Abl kinase signaling pathways by C. trachomatis leads to phosphorylation of a Rac guanine nucleotide exchange factor, Vav2, and several actin nucleators, including WAVE2, Cortactin, and TARP, a Chlamydia type III secreted effector. Our work suggests a model of redundant activation of PDGFRβ and Abl kinase upon C. trachomatis binding that culminates in cytoskeletal rearrangements that modulate efficient uptake of this obligate intracellular parasite.
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Affiliation(s)
- Cherilyn A. Elwell
- Department of Medicine, University of California San Francisco, San Francisco, California, United States of America
| | - Alhaji Ceesay
- Department of Medicine, University of California San Francisco, San Francisco, California, United States of America
| | - Jung Hwa Kim
- Department of Medicine, University of California San Francisco, San Francisco, California, United States of America
| | - Daniel Kalman
- Department of Pathology and Laboratory of Medicine, Emory University, Atlanta, Georgia, United States of America
| | - Joanne N. Engel
- Department of Medicine, University of California San Francisco, San Francisco, California, United States of America
- Department of Microbiology and Immunology, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
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Mazzeu JF, Krepischi-Santos AC, Rosenberg C, Szuhai K, Knijnenburg J, Weiss JMM, Kerkis I, Mustacchi Z, Colin G, Mombach R, Pavanello RDCM, Otto PA, Vianna-Morgante AM. Chromosome abnormalities in two patients with features of autosomal dominant Robinow syndrome. Am J Med Genet A 2008; 143A:1790-5. [PMID: 17603805 DOI: 10.1002/ajmg.a.31661] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Juliana F Mazzeu
- Centro de Estudos do Genoma Humano, Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
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125
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Yu Y, Wang Y, Feng M. Human leukocyte antigen–G1 inhibits natural killer cytotoxicity through blocking the activating signal transduction pathway and formation of activating immunologic synapse. Hum Immunol 2008; 69:16-23. [DOI: 10.1016/j.humimm.2007.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Revised: 11/05/2007] [Accepted: 11/13/2007] [Indexed: 11/16/2022]
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126
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Yi F, Chen QZ, Jin S, Li PL. Mechanism of homocysteine-induced Rac1/NADPH oxidase activation in mesangial cells: role of guanine nucleotide exchange factor Vav2. Cell Physiol Biochem 2007; 20:909-18. [PMID: 17982273 DOI: 10.1159/000110451] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/16/2007] [Indexed: 01/19/2023] Open
Abstract
We have demonstrated that homocysteine (Hcys) stimulates de novo ceramide synthesis and thereby induces NADPH oxidase activation by increase of Rac GTPase activity in rat mesangial cells (RMCs). However, which isofrom of Rac GTPases is involved in Hcys-induced NADPH oxidase activity and what mechanism mediates Hcys-induced Rac GTPase activation remain unknown. The present study first addressed the role of Rac1 and then determined the contribution of a subfamily of Guanine Nucleotide Exchange Factors (GEFs), Vav, to the action of Hcys on Rac and NADPH oxidase activities in RMCs. By small interfering RNA (siRNA), it was found that Rac1-siRNA attenuated Hcys-induced superoxide (O(2)(-)) production. To explore the mechanism activating Rac by Hcys, GEF-Vav was examined. Vav2 was found to be a predominant isoform among Vav family in RMCs. In Vav2-siRNA transfected RMCs, Hcys-induced Rac activity was blocked, which was accompanied by significant reduction of Hcys-induced O(2)(-). production. This Vav2-siRNA also blocked Rac activation induced by C16-Ceramide (C16-Cer), an intermediate lipid product stimulated by Hcys. Furthermore, we found that Hcys induced Vav2 phosphorylation in a time-dependent manner, which could be induced by C16-Cer and blocked by inhibition of de novo ceramide synthesis. These results suggest that Vav2 importantly contributes to Hcys-induced increase in Rac1 activity and consequent activation of NADPH oxidase in RMCs via ceramide-associated tyrosine phosphorylation.
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Affiliation(s)
- Fan Yi
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298, USA
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127
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Koncz G, Kerekes K, Chakrabandhu K, Hueber AO. Regulating Vav1 phosphorylation by the SHP-1 tyrosine phosphatase is a fine-tuning mechanism for the negative regulation of DISC formation and Fas-mediated cell death signaling. Cell Death Differ 2007; 15:494-503. [DOI: 10.1038/sj.cdd.4402282] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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128
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Lazer G, Pe'er L, Schapira V, Richard S, Katzav S. The association of Sam68 with Vav1 contributes to tumorigenesis. Cell Signal 2007; 19:2479-86. [PMID: 17855053 DOI: 10.1016/j.cellsig.2007.07.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2007] [Accepted: 07/26/2007] [Indexed: 10/23/2022]
Abstract
Vav1 functions in the hematopoietic system as a specific GDP/GTP nucleotide exchange factor regulated by tyrosine phosphorylation. An intact C-terminal SH3 domain of Vav1 (Vav1SH3C) was shown to be necessary for Vav1-induced transformation, yet the associating protein(s) necessary for this activity have not yet been identified. Using a proteomics approach, we identified Sam68 as a Vav1SH3C-associating protein. Sam68 (Src-associated in mitosis of 68 kD) belongs to the heteronuclear ribonucleoprotein particle K (hnRNP-K) homology (KH) domain family of RNA-binding proteins. The Vav1/Sam68 interaction was observed in vitro and in vivo. Mutants of Vav1SH3C previously shown to lose their transforming potential did not associate with Sam68. Co-expression of Vav1 and Sam68 in Jurkat T cells led to increased localization of Vav1 in the nucleus and changes in cell morphology. We then tested the contribution of Sam68 to known functions of Vav1, such as focus-forming in NIH3T3 fibroblasts and NFAT stimulation in T cells. Co-expression of oncogenic Vav1 with Sam68 in NIH3T3 fibroblasts resulted in a dose-dependent increase in foci, yet no further enhancement of NFAT activity was observed in Jurkat T cells, as compared to cells overexpressing only Vav1 or Sam68. Our results strongly suggest that Sam68 contributes to transformation by oncogenic Vav1.
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Affiliation(s)
- Galit Lazer
- The Hubert H. Humphrey Center for Experimental Medicine and Cancer Research, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
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129
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Dubash AD, Wennerberg K, García-Mata R, Menold MM, Arthur WT, Burridge K. A novel role for Lsc/p115 RhoGEF and LARG in regulating RhoA activity downstream of adhesion to fibronectin. J Cell Sci 2007; 120:3989-98. [DOI: 10.1242/jcs.003806] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Adhesion of cells to extracellular matrix proteins such as fibronectin initiates signaling cascades that affect cell morphology, migration and survival. Some of these signaling pathways involve the Rho family of GTPases, such as Cdc42, Rac1 and RhoA, which play a key role in regulating the organization of the cytoskeleton. Although significant advances have been made in understanding how Rho proteins control cytoskeletal architecture, less is known about the signals controlling activation of the GTPases themselves. The focus of this study was to determine which guanine nucleotide exchange factor(s) are responsible for activation of RhoA downstream of adhesion to fibronectin. Using an affinity pulldown assay for activated exchange factors, we show that the RhoA-specific exchange factors Lsc/p115 RhoGEF and LARG are activated when cells are plated onto fibronectin, but not other exchange factors such as Ect2 or Dbl. Knockdown of Lsc and LARG together significantly decreases RhoA activation and formation of stress fibers and focal adhesions downstream of fibronectin adhesion. Similarly, overexpression of a catalytically inactive mutant of Lsc/p115 RhoGEF inhibits RhoA activity and formation of stress fibers and focal adhesions on fibronectin. These data establish a previously uncharacterized role for the exchange factors Lsc/p115 RhoGEF and LARG in linking fibronectin signals to downstream RhoA activation.
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Affiliation(s)
- Adi D. Dubash
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill NC 27599, USA
| | - Krister Wennerberg
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill NC 27599, USA
| | - Rafael García-Mata
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill NC 27599, USA
| | - Marisa M. Menold
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill NC 27599, USA
| | - William T. Arthur
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill NC 27599, USA
| | - Keith Burridge
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill NC 27599, USA
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Colomba A, Courilleau D, Ramel D, Billadeau DD, Espinos E, Delsol G, Payrastre B, Gaits-Iacovoni F. Activation of Rac1 and the exchange factor Vav3 are involved in NPM-ALK signaling in anaplastic large cell lymphomas. Oncogene 2007; 27:2728-36. [PMID: 17998938 DOI: 10.1038/sj.onc.1210921] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The majority of anaplastic large cell lymphomas (ALCLs) express the nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) fusion protein, which is oncogenic due to its constitutive tyrosine kinase activity. Transformation by NPM-ALK not only increases proliferation, but also modifies cell shape and motility in both lymphoid and fibroblastic cells. We report that the Rac1 GTPase, a known cytoskeletal regulator, is activated by NPM-ALK in ALCL cell lines (Karpas 299 and Cost) and transfected cells (lymphoid Ba/F3 cells, NIH-3T3 fibroblasts). We have identified Vav3 as one of the exchange factors involved in Rac1 activation. Stimulation of Vav3 and Rac1 by NPM-ALK is under the control of Src kinases. It involves formation of a signaling complex between NPM-ALK, pp60(c-src), Lyn and Vav3, in which Vav3 associates with tyrosine 343 of NPM-ALK via its SH2 domain. Moreover, Vav3 is phosphorylated in NPM-ALK positive biopsies from patients suffering from ALCL, demonstrating the pathological relevance of this observation. The use of Vav3-specific shRNA and a dominant negative Rac1 mutant demonstrates the central role of GTPases in NPM-ALK elicited motility and invasion.
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Affiliation(s)
- A Colomba
- INSERM, U563, Centre de Physiopathologie de Toulouse Purpan, Toulouse, France
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131
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Brezski RJ, Monroe JG. B cell antigen receptor-induced Rac1 activation and Rac1-dependent spreading are impaired in transitional immature B cells due to levels of membrane cholesterol. THE JOURNAL OF IMMUNOLOGY 2007; 179:4464-72. [PMID: 17878342 DOI: 10.4049/jimmunol.179.7.4464] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The BCR-triggered responses of mature and transitional immature B cells differ at both the biochemical and functional level. In this study, we show that in mature B cells, BCR signaling triggers Vav phosphorylation and Rac1 activation. Furthermore, we demonstrate that although downstream actin-dependent BCR capping is independent of Rac1 activation, actin-dependent membrane ruffling and cell spreading are Rac1-dependent processes. In contrast, BCR-induced Vav phosphorylation and Rac1 activation is impaired in transitional immature B cells, resulting in defects in actin polymerization-dependent spreading and membrane ruffling while Rac1-independent BCR capping remains intact. Because transitional immature murine B cells maintain lower steady-state levels of plasma membrane cholesterol, we augmented their levels to that of mature B cells and found that BCR-induced Rac1 activation and Rac1-dependent membrane ruffling and cell spreading were restored. These studies provide a direct link between B cell cholesterol levels and downstream cellular signaling processes.
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Affiliation(s)
- Randall J Brezski
- Department of Pathology and Laboratory Medicine, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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132
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Huang H, Li L, Wu C, Schibli D, Colwill K, Ma S, Li C, Roy P, Ho K, Songyang Z, Pawson T, Gao Y, Li SSC. Defining the specificity space of the human SRC homology 2 domain. Mol Cell Proteomics 2007; 7:768-84. [PMID: 17956856 DOI: 10.1074/mcp.m700312-mcp200] [Citation(s) in RCA: 171] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Src homology 2 (SH2) domains are the largest family of interaction modules encoded by the human genome to recognize tyrosine-phosphorylated sequences and thereby play pivotal roles in transducing and controlling cellular signals emanating from protein-tyrosine kinases. Different SH2 domains select for distinct phosphopeptides, and the function of a given SH2 domain is often dictated by the specific motifs that it recognizes. Therefore, deciphering the phosphotyrosyl peptide motif recognized by an SH2 domain is the key to understanding its cellular function. Here we cloned all 120 SH2 domains identified in the human genome and determined the phosphotyrosyl peptide binding properties of 76 SH2 domains by screening an oriented peptide array library. Of these 76, we defined the selectivity for 43 SH2 domains and refined the binding motifs for another 33 SH2 domains. We identified a number of novel binding motifs, which are exemplified by the BRDG1 SH2 domain that selects specifically for a bulky, hydrophobic residue at P + 4 relative to the Tyr(P) residue. Based on the oriented peptide array library data, we developed scoring matrix-assisted ligand identification (or SMALI), a Web-based program for predicting binding partners for SH2-containing proteins. When applied to SH2D1A/SAP (SLAM-associated protein), a protein whose mutation or deletion underlies the X-linked lymphoproliferative syndrome, SMALI not only recapitulated known interactions but also identified a number of novel interacting proteins for this disease-associated protein. SMALI also identified a number of potential interactors for BRDG1, a protein whose function is largely unknown. Peptide in-solution binding analysis demonstrated that a SMALI score correlates well with the binding energy of a peptide to a given SH2 domain. The definition of the specificity space of the human SH2 domain provides both the necessary molecular basis and a platform for future exploration of the functions for SH2-containing proteins in cells.
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Affiliation(s)
- Haiming Huang
- Department of Biochemistry, Siebens-Drake Medical Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario N6A 5C1, Canada
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133
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Katzav S. Flesh and blood: The story of Vav1, a gene that signals in hematopoietic cells but can be transforming in human malignancies. Cancer Lett 2007; 255:241-54. [PMID: 17590270 DOI: 10.1016/j.canlet.2007.04.015] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Revised: 04/30/2007] [Accepted: 04/30/2007] [Indexed: 01/08/2023]
Abstract
Cancer results from the interaction of multiple aberrations including activation of dominant oncogenes and upregulation of signal transduction pathways. Identification of the genes involved in malignant transformation is a pre-requisite for understanding cancer and improving its diagnosis and treatment. Quite a few of the genes that have been implicated in cancer are mutant or aberrantly expressed versions of genes that are important mediators of the normal growth that occurs during development. An important example of this is Vav1, a cytoplasmic signal transducer protein initially identified as an oncogene. Physiological expression of Vav1 is restricted to the hematopoietic system, where its best-known function is as a GDP/GTP nucleotide exchange factor for Rho/Rac GTPases, an activity strictly controlled by tyrosine phosphorylation. Vav1 was shown to regulate cytoskeletal rearrangement during activation of hematopoietic cells. Vav1 can also mediate other cellular functions including activation of the JNK, ERK, Ras, NF-kB, and NFAT pathways, in addition to association with numerous adapter proteins such as Shc, NCK, SLP-76, GRB2, and Crk. Although the oncogenic form of Vav1 has not been detected in clinical human tumors, its wild-type form has recently been implicated in mammalian malignancies such as neuroblastoma, melanoma, pancreatic tumors and B-cell chronic lymphocytic leukemia. This review addresses the physiological function of wild-type Vav1, its mode of activation as an oncogene, and its emerging role as a transforming protein in human cancer.
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Affiliation(s)
- Shulamit Katzav
- The Hubert H. Humphrey center for Experimental Medicine & Cancer Research, The Hebrew University-Hadassah Medical School, P.O. Box 12272, Jerusalem 91120, Israel.
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Garrett TA, Van Buul JD, Burridge K. VEGF-induced Rac1 activation in endothelial cells is regulated by the guanine nucleotide exchange factor Vav2. Exp Cell Res 2007; 313:3285-97. [PMID: 17686471 PMCID: PMC2034315 DOI: 10.1016/j.yexcr.2007.05.027] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2007] [Revised: 05/11/2007] [Accepted: 05/29/2007] [Indexed: 01/13/2023]
Abstract
Vascular endothelial growth factor (VEGF) signaling is critical for both normal and disease-associated vascular development. Dysregulated VEGF signaling has been implicated in ischemic stroke, tumor angiogenesis, and many other vascular diseases. VEGF signals through several effectors, including the Rho family of small GTPases. As a member of this family, Rac1 promotes VEGF-induced endothelial cell migration by stimulating the formation of lamellipodia and membrane ruffles. To form these membrane protrusions, Rac1 is activated by guanine nucleotide exchange factors (GEFs) that catalyze the exchange of GDP for GTP. The goal of this study was to identify the GEF responsible for activating Rac1 in response to VEGF stimulation. We have found that VEGF stimulates biphasic activation of Rac1 and for these studies we focused on the peak of activation that occurs at 30 min. Inhibition of VEGFR-2 signaling blocks VEGF-induced Rac1 activation. Using a Rac1 nucleotide-free mutant (G15ARac1), which has a high affinity for binding activated GEFs, we show that the Rac GEF Vav2 associates with G15ARac1 after VEGF stimulation. Additionally, we show that depleting endothelial cells of endogenous Vav2 with siRNA prevents VEGF-induced Rac1 activation. Moreover, Vav2 is tyrosine phosphorylated upon VEGF treatment, which temporally correlates with Rac1 activation and requires VEGFR-2 signaling and Src kinase activity. Finally, we show that depressing Vav2 expression by siRNA impairs VEGF-induced endothelial cell migration. Taken together, our results provide evidence that Vav2 acts downstream of VEGF to activate Rac1.
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Affiliation(s)
- Tiana A. Garrett
- Department of Cell and Developmental Biology and Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, North Carolina 27599
- *Address correspondence to: Tiana Garrett, Department of Cell and Developmental Biology, University of North Carolina-Chapel Hill, Lineberger Comprehensive Cancer Center, Campus Box # 7295, Chapel Hill, North Carolina 27599, Tel. No.: 919-966-5783, Email address:
| | - Jaap D. Van Buul
- Department of Cell and Developmental Biology and Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, North Carolina 27599
- Department of Molecular Cell Biology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, The Netherlands
| | - Keith Burridge
- Department of Cell and Developmental Biology and Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, North Carolina 27599
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135
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136
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Schmitter T, Pils S, Sakk V, Frank R, Fischer KD, Hauck CR. The granulocyte receptor carcinoembryonic antigen-related cell adhesion molecule 3 (CEACAM3) directly associates with Vav to promote phagocytosis of human pathogens. THE JOURNAL OF IMMUNOLOGY 2007; 178:3797-805. [PMID: 17339478 DOI: 10.4049/jimmunol.178.6.3797] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The human granulocyte-specific receptor carcinoembryonic antigen-related cell adhesion molecule (CEACAM)3 is critically involved in the opsonin-independent recognition of several bacterial pathogens. CEACAM3-mediated phagocytosis depends on the integrity of an ITAM-like sequence within the cytoplasmic domain of CEACAM3 and is characterized by rapid stimulation of the GTPase Rac. By performing a functional screen with CEACAM3-expressing cells, we found that overexpression of a dominant-negative form of the guanine nucleotide exchange factor Vav, but not the dominant-negative versions SWAP70, Dock2, or ELMO1 interfered with CEACAM3-initiated phagocytosis. Moreover, small interfering RNA-mediated silencing of Vav reduced uptake and abrogated the stimulation of Rac in response to bacterial CEACAM3 engagement. In Vav1/Vav2-deficient cells, CEACAM3-mediated internalization was only observed after re-expression of Vav. Vav colocalized with CEACAM3 upon bacterial infection, coimmunoprecipitated in a complex with CEACAM3, and the Vav Src homology 2 domain directly associated with phosphorylated Tyr(230) of CEACAM3. In primary human granulocytes, TAT-mediated transduction of dominant-negative Vav, but not SWAP70, severely impaired the uptake of CEACAM3-binding bacteria. These data support the view that, different from canonical ITAM signaling, the CEACAM3 ITAM-like sequence short-wires bacterial recognition and Rac stimulation via a direct association with Vav to promote rapid phagocytosis and elimination of CEACAM-binding human pathogens.
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Affiliation(s)
- Tim Schmitter
- Zentrum für Infektionsforschung, Universität Würzburg, Würzburg, Germany
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137
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Brezski RJ, Monroe JG. BCR-linked factors in developmental fate decisions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 596:47-55. [PMID: 17338174 DOI: 10.1007/0-387-46530-8_4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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138
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Sahu SN, Nunez S, Bai G, Gupta A. Interaction of Pyk2 and PTP-PEST with leupaxin in prostate cancer cells. Am J Physiol Cell Physiol 2007; 292:C2288-96. [PMID: 17329398 DOI: 10.1152/ajpcell.00503.2006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have identified the presence of leupaxin (LPXN), which belongs to the paxillin extended family of focal adhesion-associated adaptor proteins, in prostate cancer cells. Previous studies have demonstrated that LPXN is a component of the podosomal signaling complex found in osteoclasts, where LPXN was found to associate with the protein tyrosine kinases Pyk2 and c-Src and the cytosolic protein tyrosine phosphatase-proline-, glutamate-, serine-, and threonine-rich sequence (PTP-PEST). In the current study, LPXN was detectable as a 50-kDa protein in PC-3 cells, a bone-derived metastatic prostate cancer cell line. In PC-3 cells, LPXN was also found to associate with Pyk2, c-Src, and PTP-PEST. A siRNA-mediated inhibition of LPXN resulted in decreased in vitro PC-3 cell migration. A recombinant adenoviral-mediated overexpression of LPXN resulted in an increased association of Pyk2 with LPXN, whereas a similar adenoviral-mediated overexpression of PTP-PEST resulted in decreased association of Pyk2 and c-Src with LPXN. The overexpression of LPXN in PC-3 cells resulted in increased migration, as assessed by in vitro Transwell migration assays. On the contrary, the overexpression of PTP-PEST in PC-3 cells resulted in decreased migration. The overexpression of LPXN resulted in increased activity of Rho GTPase, which was decreased in PTP-PEST-overexpressing cells. The increase in Rho GTPase activity following overexpression of LPXN was inhibited in the presence of Y27632, a selective inhibitor of Rho GTPase. In conclusion, our data demonstrate that LPXN forms a signaling complex with Pyk2, c-Src, and PTP-PEST to regulate migration of prostate cancer cells.
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Affiliation(s)
- Surasri Nandan Sahu
- Dept. of Biomedical Sciences, Dental School, University of Maryland, Baltimore, MD 21201, USA
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139
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Gazit R, Aker M, Elboim M, Achdout H, Katz G, Wolf DG, Katzav S, Mandelboim O. NK cytotoxicity mediated by CD16 but not by NKp30 is functional in Griscelli syndrome. Blood 2007; 109:4306-12. [PMID: 17255357 DOI: 10.1182/blood-2006-09-047159] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Abstract
Griscelli syndrome (GS) type 2 is an autosomal recessive disorder represented by pigment dilution and impaired cytotoxic T lymphocyte (CTL) activity. NK activity has been scarcely investigated in GS patients. Here, we describe a new patient, possessing a hemophagocytic syndrome with a homozygous Q118X nonsense RAB27A mutation. Single specific primer–polymerase chain reaction (SSP-PCR) was developed based on this mutation and is currently used in prenatal genetic analysis. As expected, CTLs in the patient are not functional and NK cytotoxicity against K562 or 721.221 cells is diminished. Surprisingly, however, we demonstrate that CD16-mediated killing is intact in this patient and is therefore RAB27A independent, whereas NKp30-mediated killing is impaired and is therefore RAB27A dependent. We further analyzed the signaling pathways of these 2 receptors and demonstrated phosphorylation of Vav1 after CD16 activation but not after NKp30 engagement. Thus, we identify a novel homozygous mutation in the RAB27A gene of a new GS patient, observe for the first time that some activating NK receptors function in GS patients, and demonstrate a functional dichotomy in the killing mediated by these human NK-activating receptors.
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Affiliation(s)
- Roi Gazit
- The Lautenberg Center for General and Tumor Immunology, Hadassah Medical School, Jerusalem, Israel
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140
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Borrego F, Masilamani M, Marusina AI, Tang X, Coligan JE. The CD94/NKG2 family of receptors: from molecules and cells to clinical relevance. Immunol Res 2007; 35:263-78. [PMID: 17172651 DOI: 10.1385/ir:35:3:263] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 12/21/2022]
Abstract
Immune responses must be tightly regulated to avoid hyporesponsiveness on one hand or excessive inflammation and the development of autoimmunity (hyperresponsiveness) on the other hand. This balance is attained through the throttling of activating signals by inhibitory signals that ideally leads to an adequate immune response against an invader without excessive and extended inflammatory signals that promote the development of autoimmunity. The CD94/NKG2 family of receptors is composed of members with activating or inhibitory potential. These receptors are expressed predominantly on NK cells and a subset of CD8+ T cells, and they have been shown to play an important role in regulating responses against infected and tumorigenic cells. In this review, we discuss the current knowledge about this family of receptors, including ligand and receptor interaction, signaling, membrane dynamics, regulation of gene expression and their roles in disease regulation, infections, and cancer, and bone marrow transplantation.
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Affiliation(s)
- Francisco Borrego
- Receptor Cell Biology Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
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141
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Sakai H, Chen Y, Itokawa T, Yu KP, Zhu ML, Insogna K. Activated c-Fms recruits Vav and Rac during CSF-1-induced cytoskeletal remodeling and spreading in osteoclasts. Bone 2006; 39:1290-301. [PMID: 16950670 DOI: 10.1016/j.bone.2006.06.012] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Revised: 05/30/2006] [Accepted: 06/17/2006] [Indexed: 12/13/2022]
Abstract
Colony-stimulating factor-1 (CSF-1) induces osteoclast spreading that requires activation of c-Src and phosphatidyl inositol 3-kinase (PI3-K), both of which are recruited to activated c-Fms, the CSF-1 receptor. The present report provides evidence that the hemopoietic guanine nucleotide exchange factor (GEF), Vav, and its target GTPase, Rac, lie downstream from this initial signaling complex. CSF-1 treatment of osteoclast-like cells induced translocation of Vav to the plasma membrane, an increase in its phosphotyrosine content, and a concomitant decline in the amount of phosphoinositol 4,5-bisphosphate bound to Vav, changes known to induce Vav's GEF activity. CSF-1 induced the association of Vav and Rac and increased Rac's GTPase activity. CSF-1 also induced rapid translocation of Rac to the periphery of spreading neonatal rat osteoclasts where it co-localized primarily with Vav3 and to a lesser extent with Vav1. Wortmannin, an inhibitor of PI3-K, blocked CSF-1-induced Rac translocation and prevented CSF-1-induced spreading and actin reorganization in osteoclasts. CSF-1-induced osteoclast spreading was not significantly reduced in osteoclasts isolated from Vav1 knock-out mice and Vav1 knock-out mice had normal bone density. Microinjection of constitutively active Rac, but not constitutively active Cdc42 or RhoA, induced lamellipodia formation and osteoclast spreading, mimicking the effects of CSF-1. Dominant-negative Rac blocked CSF-1-induced osteoclast spreading, whereas neither dominant-negative Cdc42 nor C3, an inhibitor of RhoA, affected the response to CSF-1. These data demonstrate that Vav and Rac lie downstream from activated PI3-K in CSF-1-treated osteoclasts and that Rac is required for CSF-1-induced cytoskeletal remodeling in these cells.
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Affiliation(s)
- Hiroaki Sakai
- Yale School of Medicine, TAC S-133, PO Box 208020, New Haven, CT 06520-8020, USA. hiro_yale.@yahoo.co.jp
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Masilamani M, Nguyen C, Kabat J, Borrego F, Coligan JE. CD94/NKG2A inhibits NK cell activation by disrupting the actin network at the immunological synapse. THE JOURNAL OF IMMUNOLOGY 2006; 177:3590-6. [PMID: 16951318 DOI: 10.4049/jimmunol.177.6.3590] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
An adequate immune response is the result of the fine balance between activation and inhibitory signals. The exact means by which inhibitory signals obviate activation signals in immune cells are not totally elucidated. Human CD94/NKG2A is an ITIM-containing inhibitory receptor expressed by NK cells and some CD8+ T cells that recognize HLA-E. We show that the engagement of this receptor prevents NK cell activation by disruption of the actin network and exclusion of lipid rafts at the point of contact with its ligand (inhibitory NK cell immunological synapse, iNKIS). CD94/NKG2A engagement leads to recruitment and activation of src homology 2 domain-bearing tyrosine phosphatase 1. This likely explains the observed dephosphorylation of guanine nucleotide exchange factor and regulator of actin, Vav1, as well as ezrin-radixin-moesin proteins that connect actin filaments to membrane structures. In contrast, NK cell activation by NKG2D induced Vav1 and ezrin-radixin-moesin phosphorylation. Thus, CD94/NKG2A prevents actin-dependent recruitment of raft-associated activation receptors complexes to the activating synapse. This was further substantiated by showing that inhibition of actin polymerization abolished lipid rafts exclusion at the iNKIS, whereas cholesterol depletion had no effect on actin disruption at the iNKIS. These data indicate that the lipid rafts exclusion at the iNKIS is an active process which requires an intact cytoskeleton to maintain lipid rafts outside the inhibitory synapse. The net effect is to maintain an inhibitory state in the proximity of the iNKIS, while allowing the formation of activation synapse at distal points within the same NK cell.
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Affiliation(s)
- Madhan Masilamani
- Receptor Cell Biology Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
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143
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Swaminathan G, Tsygankov AY. The Cbl family proteins: ring leaders in regulation of cell signaling. J Cell Physiol 2006; 209:21-43. [PMID: 16741904 DOI: 10.1002/jcp.20694] [Citation(s) in RCA: 228] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The proto-oncogenic protein c-Cbl was discovered as the cellular form of v-Cbl, a retroviral transforming protein. This was followed over the years by important discoveries, which identified c-Cbl and other Cbl-family proteins as key players in several signaling pathways. c-Cbl has donned the role of a multivalent adaptor protein, capable of interacting with a plethora of proteins, and has been shown to positively influence certain biological processes. The identity of c-Cbl as an E3 ubiquitin ligase unveiled the existence of an important negative regulatory pathway involved in maintaining homeostasis in protein tyrosine kinase (PTK) signaling. Recent years have also seen the emergence of novel regulators of Cbl, which have provided further insights into the complexity of Cbl-influenced pathways. This review will endeavor to provide a summary of current studies focused on the effects of Cbl proteins on various biological processes and the mechanism of these effects. The major sections of the review are as follows: Structure and genomic organization of Cbl proteins; Phosphorylation of Cbl; Interactions of Cbl; Localization of Cbl; Mechanism of effects of Cbl: (a) Ubiquitylation-dependent events: This section elucidates the mechanism of Cbl-mediated downregulation of EGFR and details the PTK and non-PTKs targeted by Cbl. In addition, it addresses the functional requirements for E3 Ubiquitin ligase activity of Cbl and negative regulation of Cbl-mediated downregulation of PTKs, (b) Adaptor functions: This section discusses the mechanisms of adaptor functions of Cbl in mitogen-activated protein kinase (MAPK) activation, insulin signaling, regulation of Ras-related protein 1 (Rap1), PI-3' kinase signaling, and regulation of Rho-family GTPases and cytoskeleton; Biological functions: This section gives an account of the diverse biological functions of Cbl and includes the role of Cbl in transformation, T-cell signaling and thymus development, B-cell signaling, mast-cell degranulation, macrophage functions, bone development, neurite growth, platelet activation, muscle degeneration, and bacterial invasion; Conclusions and perspectives.
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Affiliation(s)
- Gayathri Swaminathan
- Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
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144
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Schapira V, Lazer G, Katzav S. Osteopontin is an oncogenic Vav1- but not wild-type Vav1-responsive gene: implications for fibroblast transformation. Cancer Res 2006; 66:6183-91. [PMID: 16778192 DOI: 10.1158/0008-5472.can-05-3735] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Mammalian wild-type Vav1 (wtVav1) encodes a specific GDP/GTP nucleotide exchange factor that is exclusively expressed in the hematopoietic system. Despite numerous studies, the mechanism underlying transformation of fibroblasts by oncogenic Vav1 (oncVav1) is not well defined. We identified osteopontin, a marker for tumor aggressiveness, as an oncVav1-inducible gene. Osteopontin is highly expressed in oncVav1-transformed NIH3T3 cells (NIH/oncVav1) but is barely detected in NIH3T3 expressing wtVav1 (NIH/wtVav1) even following epidermal growth factor stimulation, which normally induces osteopontin. Depleting oncVav1 in NIH/oncVav1 using small interfering RNA led to a considerable decrease in osteopontin, whereas reducing osteopontin expression did not affect oncVav1 expression, suggesting that oncVav1 operates upstream of osteopontin. Vav1-depleted NIH/oncVav1 cells, but not osteopontin-depleted NIH/oncVav1 cells, exhibited impaired extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase phosphorylation. Inhibition of ERK phosphorylation in NIH/oncVav1 cells led to a decrease in osteopontin expression, implying that the elevated osteopontin expression in these cells is dependent on ERK phosphorylation. Vav1-depleted or osteopontin-depleted NIH/oncVav1 cells lost their tumorigenic properties as judged by the soft agar and invasion assays, although loss of osteopontin expression had a less dramatic effect. Suppression of Vav1 expression in NIH/oncVav1 cells led to reversion to "normal" morphology, whereas when only osteopontin expression was diminished cells retained their transformed morphology. This work strongly supports a role for oncVav1 as a master oncogene and provides clues to the molecular mechanism underlying oncVav1 transformation.
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Affiliation(s)
- Vered Schapira
- The Hubert H. Humphrey Center for Experimental Medicine and Cancer Research, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
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145
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Hunter SG, Zhuang G, Brantley-Sieders D, Swat W, Cowan CW, Chen J. Essential role of Vav family guanine nucleotide exchange factors in EphA receptor-mediated angiogenesis. Mol Cell Biol 2006; 26:4830-42. [PMID: 16782872 PMCID: PMC1489141 DOI: 10.1128/mcb.02215-05] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Angiogenesis, the process by which new blood vessels are formed from preexisting vasculature, is critical for vascular remodeling during development and contributes to the pathogenesis of diseases such as cancer. Prior studies from our laboratory demonstrate that the EphA2 receptor tyrosine kinase is a key regulator of angiogenesis in vivo. The EphA receptor-mediated angiogenic response is dependent on activation of Rho family GTPase Rac1 and is regulated by phosphatidylinositol 3-kinase. Here we report the identification of Vav2 and Vav3 as guanine nucleotide exchange factors (GEFs) that link the EphA2 receptor to Rho family GTPase activation and angiogenesis. Ephrin-A1 stimulation recruits the binding of Vav proteins to the activated EphA2 receptor. The induced association of EphA receptor and Vav proteins modulates the activity of Vav GEFs, leading to activation of Rac1 GTPase. Overexpression of either Vav2 or Vav3 in primary microvascular endothelial cells promotes Rac1 activation, cell migration, and assembly in response to ephrin-A1 stimulation. Conversely, loss of Vav2 and Vav3 GEFs inhibits Rac1 activation and ephrin-A1-induced angiogenic responses both in vitro and in vivo. In addition, embryonic fibroblasts derived from Vav2-/- Vav3-/- mice fail to spread on an ephrin-A1-coated surface and exhibit a significant decrease in the formation of ephrin-A1-induced lamellipodia and filopodia. These findings suggest that Vav GEFs serve as a molecular link between EphA2 receptors and the actin cytoskeleton and provide an important mechanism for EphA2-mediated angiogenesis.
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Affiliation(s)
- Sonja G Hunter
- Vanderbilt University School of Medicine, A-4323 MCN, 1161 21st Avenue South, Nashville, TN 37232-2363, USA
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146
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Wilsbacher JL, Moores SL, Brugge JS. An active form of Vav1 induces migration of mammary epithelial cells by stimulating secretion of an epidermal growth factor receptor ligand. Cell Commun Signal 2006; 4:5. [PMID: 16709244 PMCID: PMC1524963 DOI: 10.1186/1478-811x-4-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2006] [Accepted: 05/18/2006] [Indexed: 11/16/2022] Open
Abstract
Background Vav proteins are guanine nucleotide exchange factors (GEF) for Rho family GTPases and are activated following engagement of membrane receptors. Overexpression of Vav proteins enhances lamellipodium and ruffle formation, migration, and cell spreading, and augments activation of many downstream signaling proteins like Rac, ERK and Akt. Vav proteins are composed of multiple structural domains that mediate their GEF function and binding interactions with many cellular proteins. In this report we examine the mechanisms responsible for stimulation of cell migration by an activated variant of Vav1 and identify the domains of Vav1 required for this activity. Results We found that expression of an active form of Vav1, Vav1Y3F, in MCF-10A mammary epithelial cells increases cell migration in the absence or presence of EGF. Vav1Y3F was also able to drive Rac1 activation and PAK and ERK phosphorylation in MCF-10A cells in the absence of EGF stimulation. Mutations in the Dbl homology, pleckstrin homology, or cysteine-rich domains of Vav1Y3F abolished Rac1 or ERK activation in the absence of EGF and blocked the migration-promoting activity of Vav1Y3F. In contrast, mutations in the SH2 and C-SH3 domains did not affect Rac activation by Vav1Y3F, but reduced the ability of Vav1Y3F to induce EGF-independent migration and constitutive ERK phosphorylation. EGF-independent migration of MCF-10A cells expressing Vav1Y3F was abolished by treatment of cells with an antibody that prevents ligand binding to the EGF receptor. In addition, conditioned media collected from Vav1Y3F expressing cells stimulated migration of parental MCF-10A cells. Lastly, treatment of cells with the EGF receptor inhibitory antibody blocked the Vav1Y3F-induced, EGF-independent stimulation of ERK phosphorylation, but had no effect on Rac1 activation or PAK phosphorylation. Conclusion Our results indicate that increased migration of active Vav1 expressing cells is dependent on Vav1 GEF activity and secretion of an EGF receptor ligand. In addition, activation of ERK downstream of Vav1 is dependent on autocrine EGF receptor stimulation while active Vav1 can stimulate Rac1 and PAK activation independent of ligand binding to the EGF receptor. Thus, stimulation of migration by activated Vav1 involves both EGF receptor-dependent and independent activities induced through the Rho GEF domain of Vav1.
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Affiliation(s)
- Julie L Wilsbacher
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
- Current address : Cancer Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois 60064, USA
| | - Sheri L Moores
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
- Current address : GlaxoSmithKline, Oncology, Collegeville, PA 19426, USA
| | - Joan S Brugge
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
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147
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Chen Q, Coffey A, Bourgoin SG, Gadina M. Cytohesin binder and regulator augments T cell receptor-induced nuclear factor of activated T Cells.AP-1 activation through regulation of the JNK pathway. J Biol Chem 2006; 281:19985-94. [PMID: 16702224 DOI: 10.1074/jbc.m601629200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Cytohesin binder and regulator (Cybr; also known as CYTIP, CASP, and PSCDBP) is a cytokine-induced gene preferentially expressed in hematopoietic tissues and in T helper 1 cells. Cybr protein associates with members of the cytohesin family, which are known ADP-ribosylation factors-GDP/GTP exchange factors, and its functions appear to regulate lymphocyte adhesion and cell-cell contact. Here we show that Cybr mRNA and protein levels are increased upon T cell receptor engagement. Cybr expression then influences T cell receptor-dependent signaling events, such as nuclear factor of activated T cells and AP-1 transcriptional activity. In addition, expression of Cybr results in increased T cell receptor-mediated activation of the Rho/Rac exchange factor Vav and of the JNK-p38 MAPK signaling pathway. The effects of Cybr on nuclear factor of activated T cells and AP-1 are dependent on MAPK activation, and enhanced activation of this cascade results in cooperation between the two transcription factors in the regulation of gene expression. These findings provide the first evidence that the adaptor protein Cybr not only regulates lymphocyte adhesion and cell-cell interaction but also contributes to the regulation of the signaling cascade and of the genetic program downstream of the T cell receptor.
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Affiliation(s)
- Qian Chen
- Division of Infection and Immunity, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast BT9 7BL, UK
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Richards GR, Smith AJ, Cuddon P, Ma QP, Leveridge M, Kerby J, Roderick HL, Bootman MD, Simpson PB. The JAK3 inhibitor WHI-P154 prevents PDGF-evoked process outgrowth in human neural precursor cells. J Neurochem 2006; 97:201-10. [PMID: 16515549 DOI: 10.1111/j.1471-4159.2006.03723.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The prospect of manipulating endogenous neural stem cells to replace damaged tissue and correct functional deficits offers a novel mechanism for treating a variety of CNS disorders. The aim of this study was to investigate pathways controlling neurite outgrowth in human neural precursor cells, in particular in response to platelet-derived growth factor (PDGF). PDGF-AA, -AB and -BB were found to initiate calcium signalling and produce robust increases in neurite outgrowth. PDGF-induced outgrowth of Tuj1-positive precursors was abolished by the addition of EGTA, suggesting that calcium entry is a critical part of the signalling pathway. Wortmannin and PD098059 failed to inhibit PDGF-induced outgrowth. Clostridium Toxin B increased the amount of PDGF-induced neurite branching but had no effect on basal levels. In contrast, WHI-P154, an inhibitor of Janus protein tyrosine kinase (JAK3), Hck and Syk, prevented PDGF-induced neurite outgrowth. PDGF activates multiple signalling pathways with considerable potential for cross-talk. This study has highlighted the complexity of the pathways leading to neurite outgrowth in human neural precursors, and provided initial evidence to suggest that calcium entry is critical in producing the morphological changes observed.
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Affiliation(s)
- G R Richards
- The Neuroscience Research Centre, Merck Sharp and Dohme Research Laboratories, Harlow, Essex, UK.
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149
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Pello OM, Duthey B, García-Bernal D, Rodríguez-Frade JM, Stein JV, Teixido J, Martínez C, Mellado M. Opioids trigger alpha 5 beta 1 integrin-mediated monocyte adhesion. THE JOURNAL OF IMMUNOLOGY 2006; 176:1675-85. [PMID: 16424197 DOI: 10.4049/jimmunol.176.3.1675] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Inflammatory reactions involve a network of chemical and molecular signals that initiate and maintain host response. In inflamed tissue, immune system cells generate opioid peptides that contribute to potent analgesia by acting on specific peripheral sensory neurons. In this study, we show that opioids also modulate immune cell function in vitro and in vivo. By binding to its specific receptor, the opioid receptor-specific ligand DPDPE triggers monocyte adhesion. Integrins have a key role in this process, as adhesion is abrogated in cells treated with specific neutralizing anti-alpha5beta1 integrin mAb. We found that DPDPE-triggered monocyte adhesion requires PI3Kgamma activation and involves Src kinases, the guanine nucleotide exchange factor Vav-1, and the small GTPase Rac1. DPDPE also induces adhesion of pertussis toxin-treated cells, indicating involvement of G proteins other than Gi. These data show that opioids have important implications in regulating leukocyte trafficking, adding a new function to their known effects as immune response modulators.
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Affiliation(s)
- Oscar M Pello
- Department of Immunology and Oncology, Centro Nacional de Biotecnología/Consejo Superior de Investigaciones Científicas, Madrid, Spain
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150
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Amarasinghe GK, Rosen MK. Acidic region tyrosines provide access points for allosteric activation of the autoinhibited Vav1 Dbl homology domain. Biochemistry 2006; 44:15257-68. [PMID: 16285729 DOI: 10.1021/bi051126h] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Autoinhibited proteins serve key roles in many signal transduction pathways, and therefore proper regulation of these proteins is critical for normal cellular function. Proto-oncogene Vav1 is an autoinhibited guanine nucleotide exchange factor (GEF) for Rho family GTPases. The core autoinhibitory module of Vav1 consists of the catalytic Dbl homology (DH) domain bound through its active site to an alpha helix centered about Tyr174 in the Acidic (Ac) region of the protein. Phosphorylation of Tyr174 and two other tyrosines in the Ac region, Tyr142 and Tyr160, relieves autoinhibition and activates the catalytic DH domain. In this study, we use biochemical and structural analyses of the Vav1 Ac and DH domains to examine the kinetic and thermodynamic properties of Vav1 activation by the Src family kinase, Lck, and the role of the Lck SH2 domain in this process. We find that in the Ac-DH fragment of Vav1, Tyr174, but not Tyr142 or Tyr160, is protected from phosphorylation by interactions with the DH domain. Binding of the Lck SH2 domain to phosphorylated Tyr142 increases kcat/KM for Tyr174 by 4-fold, likely because the kinase domain can act on the substrate effectively in an intramolecular fashion. These studies of the autoinhibited Ac-DH module provide the foundation for a quantitative structural and thermodynamic understanding of the regulation of full length Vav1. Moreover, kinetic pathways involving initial interactions with exposed sites or "access points", as observed here for Vav1, may be generally important in the regulation of many autoinhibited proteins.
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Affiliation(s)
- Gaya K Amarasinghe
- Howard Hughes Medical Institute and Department of Biochemistry, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-8816, USA
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