Efficient Cellular Transformation by the Met Oncoprotein Requires a Functional Grb2 Binding Site and Correlates with Phosphorylation of the Grb2-associated Proteins, Cbl and Gab1

• Published in: The Journal of biological chemistry Vol. 272; no. 32; pp. 20167 - 20172
• Main Authors: Fixman, Elizabeth D., Holgado-Madruga, Marina, Nguyen, Linh, Kamikura, Darren M., Fournier, Tanya M., Wong, Albert J., Park, Morag
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 08.08.1997; American Society for Biochemistry and Molecular Biology
• Subjects: 3T3 Cells; Adaptor Proteins, Signal Transducing; Animals; Binding Sites; Cell Transformation, Neoplastic; ErbB Receptors - metabolism; GRB2 Adaptor Protein; Mice; Molecular Weight; Oncogene Protein v-cbl; Oncogene Proteins, Fusion - metabolism; Phosphoproteins - metabolism; Phosphorylation; Protein-Tyrosine Kinases - metabolism; Proteins - metabolism; Rats; Rats, Inbred F344; Retroviridae Proteins, Oncogenic - metabolism; Tyrosine - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.272.32.20167

The Tpr-Met oncoprotein consists of the catalytic kinase domain of the hepatocyte growth factor/scatter factor receptor tyrosine kinase (Met) fused downstream from sequences encoded by thetpr gene. Tpr-Met is a member of a family of tyrosine kinase oncoproteins generated following genomic rearrangement and has constitutive kinase activity. We have previously demonstrated that a single carboxyl-terminal tyrosine residue, Tyr489, is essential for efficient transformation of Fr3T3 fibroblasts by Tpr-Met and forms a multisubstrate binding site for Grb2, phosphatidylinositol 3′ kinase, phospholipase Cγ, SHP2, and an unknown protein of 110 kDa. A mutant Tpr-Met protein that selectively fails to bind Grb2 has reduced transforming activity, implicating pathways downstream of Grb2 in Tpr-Met mediated cell transformation. We show here that the 110-kDa Tpr-Met substrate corresponds to the recently identified Grb2-associated protein, Gab1. Moreover, we show that tyrosine phosphorylation of the Cbl protooncogene product as well as Gab1 required Tyr489 and correlated with the ability of Tpr-Met to associate with Grb2 and to transform cells, providing evidence that pathways downstream of Gab1 and/or Cbl may play a role in Tpr-Met-mediated cell transformation.