INSULIN-DEPENDENT PHOSPHATIDYLINOSITOL 3'-KINASE ACTIVITY CO-PRECIPITATES WITH INSULIN-RECEPTOR IN HUMAN CIRCULATING MONONUCLEAR-CELLS

In order to establish a working cellular model for the study of post-r eceptor signaling events, insulin-dependent phosphatidylinositol 3' (P tdIns 3')-kinase activity was investigated in circulating mononuclear cells from normal subjects. The p85 alpha regulatory subunit of PtdIns 3'-kinase co-precipitated with activated insulin receptor as revealed by immunoblotting. Whereas insulin receptor substrate-1 was weakly de tected, insulin increased 5.5+/-1.5-fold (mean+/-SD) PtdIns 3'-kinase activity in receptor immunoprecipitates. We conclude that insulin-stim ulated PtdIns 3'-kinase activity is measurable in circulating mononucl ear cells which may constitute an easily available cellular model for the detection of post-receptor defects in insulin-resistant states. (C ) 1995 Academic Press, Inc.