Activation of the JNK pathway is essential for transformation by the Met oncogene.
The Met/Hepatocyte Growth Factor (HGF) receptor tyrosine kinase is oncogenically activated through a rearrangement that creates a hybrid gene Tpr-Met. The resultant chimeric p65(Tpr-Met) protein is constitutively phosphorylated on tyrosine residues in vivo and associates with a number of SH2-containing signaling molecules including the p85 subunit of PI-3 kinase and the Grb2 adaptor protein, which couples receptor tyrosine kinases to the Ras signaling pathway. Mutation of the binding site for Grb2 impairs the ability of Tpr-Met oncoprotein to transform fibroblasts, suggesting that the activation of the Ras/MAP kinase signaling pathway through Grb2 may be essential for cellular transformation. To test this hypothesis dominant-negative mutants of Grb2 with deletions of the SH3 domains were introduced into Tpr-Met transformed fibroblasts. Cells overexpressing the mutants were found to be morphologically reverted and exhibited reduced growth in soft agar. Surprisingly, the Grb2 mutants blocked activation of the JNK/SAPK but not MAP kinase activity induced by the Tpr-Met oncoprotein. Additionally, cells expressing dominant-negative Grb2 mutants had reduced PI-3-kinase activity and dominant-negative mutants of Rac1 blocked both Tpr-Met-induced transformation and activation of JNK. These experiments reveal a novel link between Met and the JNK pathway, which is essential for transformation by this oncogene.
Rodrigues
G A
GA
Department of Pharmacology, New York University Medical Center, New York 10016, USA.
Park
M
M
Schlessinger
J
J
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology; D051380:GRB2 Adaptor Protein; D019204:GTP-Binding Proteins / Q000235:genetics; D008565:Membrane Proteins / Q000378:metabolism; D009154:Mutation; D028861:Nuclear Pore Complex Proteins; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011485:Protein Binding; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019859:Proto-Oncogene Proteins c-met; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D017384:Sequence Deletion; D015398:Signal Transduction; D020664:Son of Sevenless Proteins; D020744:rac GTP-Binding Proteins; D018909:src Homology Domains / Q000235:genetics
D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495950:Grb2 protein, rat; D008565:Membrane Proteins; D028861:Nuclear Pore Complex Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D020664:Son of Sevenless Proteins; C073597:TPR protein, human; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D066246:ErbB Receptors; D019859:Proto-Oncogene Proteins c-met; D020794:Receptor Protein-Tyrosine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019204:GTP-Binding Proteins; D020744:rac GTP-Binding Proteins