Pathways downstream of Shc and Grb2 are required for cell transformation by the tpr-Met oncoprotein

Abstract

The Tpr-Met oncoprotein, which is a member of a family of tyrosine kinase oncoproteins generated following genomic rearrangement, consists of the catalytic kinase domain of the hepatocyte growth factor/scatter factor receptor tyrosine kinase (Met) fused downstream from sequences encoded by the tpr gene. We have previously demonstrated that a single tyrosine residue in the carboxyl terminus, Tyr489, is highly phosphorylated and is essential for efficient transformation of Fr3T3 fibroblasts by Tpr-Met and for the association of Tpr-Met with the Grb2 adaptor protein and phosphatidylinositol 3'-kinase. We show here that Tyr489 is also required for association of Tpr-Met with phospholipase Cgamma and the tyrosine phosphatase, SHPTP2/Syp. To distinguish which of these substrates are required for cell transformation by the Tpr-Met oncoprotein, we generated a novel Tpr-Met mutant that selectively fails to associate with the Grb2 adaptor protein. Utilizing this mutant, together with additional Tpr-Met mutants containing Tyr to Phe substitutions, we have demonstrated that transformation of Fr3T3 fibroblasts by the Tpr-Met oncoprotein is dependent upon pathways downstream of Shc and Grb2 and that pathways downstream of phosphatidylinositol 3'-kinase, phospholipase Cgamma, and SHPTP2/Syp are insufficient for transformation.