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Insulin-dependent phosphatidylinositol 3'-kinase activity co-precipitates with insulin receptor in human circulating
E Renard1, F Grigorescu, C Lavabre
1CRBM, INSERM U249/CNRS UPR 9008, University of Montpellier I, France.
Abstract:
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 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 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.