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-receptor signaling events, insulin-dependent phosphatidylinositol 3' (PtdIns 3')-kinase activity was investigated in circulating mononuclear cells from normal subjects. The p85α regulatory subunit of PtdIns 3'-kinase co-precipitated with activated insulin receptor as revealed by immunoblotting. Whereas insulin receptor substrate-1 was weakly detected, insulin increased 5.5±1.5-fold (mean±SD) PtdIns 3'-kinase activity in receptor immunoprecipitates. We conclude that insulin-stimulated PtdIns 3'-kinase activity is measurable in circulating mononuclear cells which may constitute an easily available cellular model for the detection of post-receptor defects in insulin-resistant states.Copyright 1995, 1999 Academic Press, Inc.