title: Structural determinants for the biological activity of Vav proteins.
abstract: We have used an extensive mutagenesis approach to study the specific role of the eight structural domains of Vav during both the activation and signaling steps of this Rac1 exchange factor. Our results indicate that several Vav domains (Dbl homology, pleckstrin homology, and zinc finger) are essential for all the biological activities tested, whereas others are required for discrete, cell type-specific biological effects. Interestingly, we have found that Vav domains have no unique functions. Thus, the calponin homology domain mediates the inhibition of Vav both in vitro and in vivo but, at the same time, exerts effector functions in lymphocytes upon receptor activation. The Vav SH2 and SH3 regions play regulatory roles in the activation of Vav in fibroblasts, mediating both its phosphorylation and translocation to the plasma membrane. In contrast, the Vav SH2 and SH3 regions act as scaffolding platforms in T-cells, ensuring the proper phosphorylation of Vav and the subsequent engagement of downstream effectors. We also provide evidence indicating that the zinc finger region exerts at least three different functional roles in Vav, aiding in the down-regulation of its basal activity, the engagement of substrates, and the induction of ancillary pathways required for cell transformation. Finally, the results obtained are consistent with a new regulatory model for Vav, in which the calponin homology region inhibits the basal activity of Vav through interactions with the zinc finger region.
authors.affiliation: Centro de Investigación del Cáncer and Instituto de Biologia Molecular y Celular del Cáncer, CSIC-University of Salamanca, Campus Unamuno, E-37007 Salamanca, Spain.
authors.forename: José L
authors.initials: JL
authors.lastname: Zugaza
authors.forename: Miguel A
authors.initials: MA
authors.lastname: López-Lago
authors.forename: María J
authors.initials: MJ
authors.lastname: Caloca
authors.forename: Mercedes
authors.initials: M
authors.lastname: Dosil
authors.forename: Nieves
authors.initials: N
authors.lastname: Movilla
authors.forename: Xosé R
authors.initials: XR
authors.lastname: Bustelo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000378:metabolism; D018797:Cell Cycle Proteins; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism; D017930:Genes, Reporter; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D051567:Proto-Oncogene Proteins c-vav; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013601:T-Lymphocytes / Q000378:metabolism; D016335:Zinc Fingers; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000906:Antibodies; D018797:Cell Cycle Proteins; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; D011993:Recombinant Fusion Proteins; C496618:VAV1 protein, human; C496619:Vav1 protein, mouse; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein