S.M. Thomas, M. DeMarco, G. D'Arcangelo, S. Halegoua, J.S. Brugge, "Ras is essential for nerve growth factor- and phorbol ester-induced tyrosine phosphorylation of MAP kinases,"Cell, 68:1031-40, 1992.
Joan S. Brugge (Ariad Pharmaceuticals Inc., Cambridge, Mass.): "Growth factor activation of receptor protein tyrosine kinases induces tyrosine phosphorylation of MAP kinases (MAPKs). MAPKs have been referred to as `switch' kinases, since they are activated by tyrosine phosphorylation but function as serine/threonine kinases. Our studies demonstrated that phosphorylation of MAPKs could be distinguished from other nerve growth factor (NGF)- induced tyrosine phosphorylation events by its dependence on Ras (smGTP binding protein).
"Tyrosine phosphorylation of MAPKs was inhibited in NGF- treated PC12 cells expressing a dominant-interfering vari- ant of Ras and stimulated in cells expressing oncogenic Ras. These results indicated that the tyrosine kinase re- sponsible for MAPK phosphorylation acts downstream from Ras, placing Ras between the NGF receptor and MAPK (see A below). ...
