ASSOCIATION OF PHOSPHATIDYLINOSITOL 3-KINASE WITH SHC IN CHRONIC MYELOGENEOUS LEUKEMIA-CELLS

Expression of p210 BCR/abl oncoprotein transforms hematopoietic cells. P210 BCR/abl tyrosine kinase induces tyrosine phosphorylation of Shc, and activation of p21(ras) and PI 3-Kinase. Here we show that PI 3-Kinase associates with She in cells transformed by BCR/abl oncoprotein. Immunoprecipitation of Shc from cells expressing p210 BCR/abl had 7.5-fold increase in PI 3-Kinase activity compared to parental cells. Tyrosine phosphorylated She specifically bound to the C-SH2 domain of the p85 subunit of PI 3-Kinase. The p85 SH3 domain also interacted with She in cell lysates from parental and transformed cells. The binding of p85 SH3 domain to She was substantially higher in BCR/abl transformed than in parental cells. Phenylphosphate blocked p85 SH2 mediated association with She but enhanced the binding of the p85 SH3 domain to She. The N-terminal proline-rich region of She between A263 and N273 specifically blocked the interaction of p85 SH3 domain with She. Our results indicate that PI 3-Kinase interacts with She directly in hematopoietic cells which express p210 BCR/abl oncoprotein.