PATHWAYS DOWNSTREAM OF SHC AND GRB2 ARE REQUIRED FOR CELL-TRANSFORMATION BY THE TPR-MET ONCOPROTEIN

The Tpr-Met oncoprotein, which is a member of a family of tyrosine kin ase oncoproteins generated following genomic rearrangement, consists o f 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, Tyr(489), is highly phosph orylated and is essential for efficient transformation of Fr3T3 fibrob lasts by Tpr-Met and for the association of Tpr-Met with the Grb2 adap tor protein and phosphatidylinositol 3'-kinase. We show here that Tyr( 489) is also required for association of Tpr-Met with phospholipase C gamma and the tyrosine phosphatase, SHPTP2/Syp. To distinguish which o f these substrates are required for cell transformation by the Tpr-Met oncoprotein, we generated a novel Tpr-Met mutant that selectively fai ls to associate with the Grb2 adaptor protein. Utilizing this mutant, together with additional Tpr-Met mutants containing Tyr to Phe substit utions, we have demonstrated that transformation of Fr3T3 fibroblasts by the Tpr-Met oncoprotein is dependent upon pathways downstream of Sh c and Grb2 and that pathways downstream of phosphatidylinositol 3'-kin ase, phospholipase G gamma, and SHPTP2/Syp are insufficient for transf ormation.