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.
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 the tpr 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 Cgamma, 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.
Fixman
E D
ED
Molecular Oncology Group, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada H3A 1A1.
Holgado-Madruga
M
M
Nguyen
L
L
Kamikura
D M
DM
Fournier
T M
TM
Wong
A J
AJ
Park
M
M
D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001665:Binding Sites; D002471:Cell Transformation, Neoplastic; D066246:ErbB Receptors / Q000378:metabolism*; D051380:GRB2 Adaptor Protein; D051379:Mice; D008970:Molecular Weight; D050722:Oncogene Protein v-cbl; D015514:Oncogene Proteins, Fusion / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D015682:Retroviridae Proteins, Oncogenic / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C490897:Gab1 protein, mouse; C490896:Gab1 protein, rat; C495949:Grb2 protein, mouse; C495950:Grb2 protein, rat; D050722:Oncogene Protein v-cbl; D015514:Oncogene Proteins, Fusion; D010750:Phosphoproteins; D011506:Proteins; D015682:Retroviridae Proteins, Oncogenic; D014443:Tyrosine; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases