title: Rac1 function is required for Src-induced transformation. Evidence of a role for Tiam1 and Vav2 in Rac activation by Src.
abstract: The proto-oncogene c-Src has been implicated in the development and progression of a number of human cancers including those of colon and breast. Accumulating evidence indicates that activated alleles of Src may induce cell transformation through Ras-ERK-dependent and -independent pathways. Here we show that Rac1 activity is strongly elevated in Src-transformed cells and that this small G protein is a critical component of the pathway connecting oncogenic Src with cell transformation. We further show that Vav2 and the ubiquitously expressed Rac1 guanine nucleotide exchange factor Tiam1 are phosphorylated in tyrosine residues in cells transfected with active and oncogenic Src. Moreover, phosphorylation of Tiam1 in cells treated with pervanadate, a potent inhibitor of tyrosine phosphatases, was partially inhibited by the Src inhibitor SU6656. Using truncated mutants of Tiam1, we demonstrate that multiple sites can be tyrosine-phosphorylated by Src. Furthermore, Tiam1 cooperated with Src to induce activation of Rac1 in vivo and the formation of membrane ruffles. Similarly, activation of JNK and the c-jun promoter by Src were also potently increased by Tiam1. Together, these results suggest that Vav2 and Tiam1 may act as downstream effectors of Src, thereby regulating Rac1-dependent pathways that participate in Src-induced cell transformation.
authors.affiliation: Oral and Pharyngeal Cancer Branch, National Institutes of Dental and Craniofacial Research, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892, USA.
authors.forename: Joan-Marc
authors.initials: JM
authors.lastname: Servitja
authors.forename: Maria Julia
authors.initials: MJ
authors.lastname: Marinissen
authors.forename: Akrit
authors.initials: A
authors.lastname: Sodhi
authors.forename: Xosé R
authors.initials: XR
authors.lastname: Bustelo
authors.forename: J Silvio
authors.initials: JS
authors.lastname: Gutkind
mesh_terms: D016475:3T3 Cells; D000483:Alleles; D000818:Animals; D001665:Binding Sites; D002384:Catalysis; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D004247:DNA / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000378:metabolism; D017930:Genes, Reporter; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D051379:Mice; D008856:Microscopy, Fluorescence; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009154:Mutation; D015513:Oncogene Proteins / Q000502:physiology*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000502:physiology*; D000090063:Proto-Oncogene Mas; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D051567:Proto-Oncogene Proteins c-vav; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; D013997:Time Factors; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology; D020830:rac1 GTP-Binding Protein / Q000378:metabolism* / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D020662:Guanine Nucleotide Exchange Factors; D007211:Indoles; C000715470:MAS1 protein, human; D015513:Oncogene Proteins; D011506:Proteins; D000090063:Proto-Oncogene Mas; D016755:Proto-Oncogene Proteins c-jun; D051567:Proto-Oncogene Proteins c-vav; C416927:SU 6656; D013449:Sulfonamides; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; C087334:TIAM1 protein, human; C513260:Tiam1 protein, mouse; C093651:VAV2 protein, human; C490565:Vav2 protein, mouse; C076715:pervanadate; D014638:Vanadates; D014443:Tyrosine; D004247:DNA; D016392:Proto-Oncogene Proteins pp60(c-src); D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D020558:GTP Phosphohydrolases; D020830:rac1 GTP-Binding Protein