Anti-phosphotyrosine immunoprecipitation of phosphatidylinositol 3' kinase activity in different cell types after exposure to epidermal growth factor.

In previous studies from this laboratory, it was shown that mouse epidermal growth factor (mEGF) or insulin increased the labeling of phosphaditylinositol-3,4-bisphosphate (PI-3,4-P2) in MA-10 cells prelabeled with different radioactive precursors (Pignataro, O.P., and Ascoli, M. (1990) J. Biol. Chem. 265, 1718-1723 and Mol. Endocrinol. (1990) 4, 758-765). In order to further characterize this phenomenon we sought to determine if we could use anti-phosphotyrosine antibodies to immunoprecipitate a phosphatidylinositol (PI) kinase activity from MA-10 cells treated with mEGF or insulin. Our data indicate that this is indeed the case, and that the PI kinase precipitated is a PI-3' kinase. A second cell type, A431 cells, in which we were unable to detect an increase in PI-3,4-P2 labeling when stimulated with mEGF or insulin, was also studied. It was found that, as in MA-10 cells, A431 cells also contain an immunoprecipitable PI-3' kinase activity that is increased in response to mEGF or insulin.