title: Beta3 tyrosine phosphorylation and alphavbeta3-mediated adhesion are required for Vav1 association and Rho activation in leukocytes.
abstract: Integrin alpha(v)beta(3)-mediated adhesion of hematopoietic cells to vitronectin results in activation of the Rho GTPases. Mutation of beta(3) tyrosine residue 747, previously shown to disrupt cell adhesion, results in sustained activation of Cdc42 and diminished Rac and Rho activity. We investigated the role of the hematopoietically restricted guanine nucleotide exchange factor Vav1 in alpha(v)beta(3)-mediated adhesion. We find that Vav1, a guanine nucleotide exchange factor for Rac and Rho, associates with alpha(v)beta(3) upon cell adhesion to vitronectin and that this association requires beta(3) tyrosine phosphorylation. Expression of exogenous Vav1 demonstrates that Y160F, but not wild type or the Vav1Y174F mutant, inhibits Rac and Rho activation during alpha(v)beta(3)-mediated cell adhesion to vitronectin. Cells expressing Vav1Y160F exhibit a sustained Cdc42 activation similar to nonphosphorylatable beta(3) mutants. In addition, cytoskeletal reorganization and cell adhesion are severely suppressed in Vav1Y160F-transfected cells, and Vav1Y160F fails to associate with beta(3) integrins. Furthermore, Vav1 itself is selectively phosphorylated upon tyrosine 160 after alpha(v)beta(3)-mediated adhesion, and the association between Vav1 and beta(3) occurs in specific response to adhesion to substrate. These studies describe a phosphorylation-dependent association between beta(3) integrin and Vav1 which is essential for cell progression to a Rho-dominant phenotype during cell adhesion.
authors.affiliation: Department of Cell and Development Biology, State University of New York Upstate Medical University, Syracuse, New York 13210, USA.
authors.forename: Chunlei
authors.initials: C
authors.lastname: Gao
authors.forename: Erik
authors.initials: E
authors.lastname: Schaefer
authors.forename: Montaha
authors.initials: M
authors.lastname: Lakkis
authors.forename: Scott D
authors.initials: SD
authors.lastname: Blystone
mesh_terms: D002448:Cell Adhesion; D018797:Cell Cycle Proteins / Q000737:chemistry*; D003599:Cytoskeleton / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry; D006801:Humans; D047468:Immunoprecipitation; D039302:Integrin alphaVbeta3 / Q000737:chemistry* / Q000378:metabolism; D020014:K562 Cells; D007962:Leukocytes / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D009154:Mutation; D010641:Phenotype; D010766:Phosphorylation; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000737:chemistry*; D051567:Proto-Oncogene Proteins c-vav; D013997:Time Factors; D014443:Tyrosine / Q000737:chemistry*; D019096:Vitronectin / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D020662:Guanine Nucleotide Exchange Factors; D039302:Integrin alphaVbeta3; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; C496618:VAV1 protein, human; D019096:Vitronectin; D014443:Tyrosine; D005982:Glutathione Transferase; D020764:cdc42 GTP-Binding Protein; D020741:rho GTP-Binding Proteins