title: Association of Bcr-Abl with the proto-oncogene Vav is implicated in activation of the Rac-1 pathway.
abstract: Vav is a guanine nucleotide exchange factor for the Rho/Rac family predominantly expressed in hematopoietic cells and implicated in cell proliferation and cytoskeletal organization. The oncogenic tyrosine kinase Bcr-Abl has been shown to activate Rac-1, which is important for Bcr-Abl induced leukemogenesis. Previous studies by Matsuguchi et al. (Matsuguchi, T., Inhorn, R. C., Carlesso, N., Xu, G., Druker, B., and Griffin, J. D. (1995) EMBO J. 14, 257-265) describe enhanced phosphorylation of Vav in Bcr-Abl-expressing Mo7e cells yet fail to demonstrate association of the two proteins. Here, we report the identification of a direct complex between Vav and Bcr-Abl in yeast, in vitro and in vivo. Furthermore, we show tyrosine phosphorylation of Vav by Bcr-Abl. Mutational analysis revealed that the SH2 domain and the C-terminal SH3 domain as well as a tetraproline motif directly adjacent to the N-terminal SH3 domain of Vav are important for establishing this phosphotyrosine dependent interaction. Activation of Rac-1 by Bcr-Abl was abrogated by co-expression of the Vav C terminus encoding the SH3-SH2-SH3 domains as a dominant negative construct. Bcr-Abl transduced primary bone marrow from Vav knock-out mice showed reduced proliferation in a culture cell transformation assay compared with wild-type bone marrow. These results suggest, that Bcr-Abl utilizes Vav as a guanine nucleotide exchange factor to activate Rac-1 in a process that involves a folding mechanism of the Vav C terminus. Given the importance of Rac-1 activation for Bcr-Abl-mediated leukemogenesis, this mechanism may be crucial for the molecular pathogenesis of chronic myeloid leukemia and of importance for other signal transduction pathways leading to the activation of Rac-1.
authors.affiliation: Department of Internal Medicine III, Laboratory of Leukemogenesis, Technical University of Munich, 81675, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Bassermann
authors.forename: Thomas
authors.initials: T
authors.lastname: Jahn
authors.forename: Cornelius
authors.initials: C
authors.lastname: Miething
authors.forename: Petra
authors.initials: P
authors.lastname: Seipel
authors.forename: Ren-Yuan
authors.initials: RY
authors.lastname: Bai
authors.forename: Sunita
authors.initials: S
authors.lastname: Coutinho
authors.forename: Victor L
authors.initials: VL
authors.lastname: Tybulewicz
authors.forename: Christian
authors.initials: C
authors.lastname: Peschel
authors.forename: Justus
authors.initials: J
authors.lastname: Duyster
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism; D018797:Cell Cycle Proteins; D002460:Cell Line; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D016044:Fusion Proteins, bcr-abl / Q000737:chemistry* / Q000378:metabolism*; D005799:Genes, Dominant; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011392:Proline / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051567:Proto-Oncogene Proteins c-vav; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D015398:Signal Transduction; D013696:Temperature; D014162:Transfection; D020798:Two-Hybrid System Techniques; D014443:Tyrosine / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D018909:src Homology Domains
chemical_list: D018797:Cell Cycle Proteins; D018076:DNA, Complementary; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; D011993:Recombinant Fusion Proteins; C496618:VAV1 protein, human; C496619:Vav1 protein, mouse; D014443:Tyrosine; D011392:Proline; D005982:Glutathione Transferase; D016044:Fusion Proteins, bcr-abl; D020830:rac1 GTP-Binding Protein