Phosphorylation of GAP and GAP-associated proteins by transforming and mitogenic tyrosine kinases.
The critical pathways through which protein-tyrosine kinases induce cellular proliferation and malignant transformation are not well defined. As microinjection of antibodies against p21ras can block the biological effects of both normal and oncogenic tyrosine kinases, it is likely that they require functional p21ras to transmit their mitogenic signals. No biochemical link has been established, however, between tyrosine kinases and p21ras. We have identified a non-catalytic domain of cytoplasmic tyrosine kinases, SH2, that regulates the activity and specificity of the kinase domain. The presence of two adjacent SH2 domains in the p21ras GTPase-activating protein (GAP) indicates that GAP might interact directly with tyrosine kinases. Here we show that GAP, and two co-precipitating proteins of relative molecular masses 62,000 and 190,000 (p62 and p190) are phosphorylated on tyrosine in cells that have been transformed by cytoplasmic and receptor-like tyrosine kinases. The phosphorylation of these polypeptides correlates with transformation in cells expressing inducible forms of the v-src or v-fps encoded tyrosine kinases. Furthermore, GAP, p62 and p190 are also rapidly phosphorylated on tyrosine in fibroblasts stimulated with epidermal growth factor. Our results suggest a mechanism by which tyrosine kinases might modify p21ras function, and implicate GAP and its associated proteins as targets of both oncoproteins and normal growth factor receptors with tyrosine kinase activity. These data support the idea that SH2 sequences direct the interactions of cytoplasmic proteins involved in signal transduction.
Ellis
C
C
Division of Molecular and Developmental Biology, Mount Sinai Hospital Research Institute, Toronto, Ontario, Canada.
Moran
M
M
McCormick
F
F
Pawson
T
T
D000818:Animals; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic; D015681:Fusion Proteins, gag-onc / Q000235:genetics*; D020690:GTPase-Activating Proteins; D007163:Immunosorbent Techniques; D051379:Mice; D008938:Mitosis; D008970:Molecular Weight; D015689:Oncogene Protein p21(ras) / Q000378:metabolism; D015688:Oncogene Protein pp60(v-src) / Q000235:genetics; D009857:Oncogenes; D010766:Phosphorylation; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D012190:Retroviridae / Q000235:genetics; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D020703:ras GTPase-Activating Proteins
D015681:Fusion Proteins, gag-onc; D020690:GTPase-Activating Proteins; D011506:Proteins; D020703:ras GTPase-Activating Proteins; D019000:Phosphotyrosine; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D015688:Oncogene Protein pp60(v-src); D015689:Oncogene Protein p21(ras)