Fig. 5.

Effect of Serine Kinase Inhibitors on PMA-Stimulated IRS1 Phosphorylation on Ser24, Ser307, and Ser612

A, Serum-starved NIH/hIR cells ectopically expressing rIRS1-wt were pretreated with indicated inhibitors for 30 min and then stimulated with or without PMA (1 μm). IRS1 immunoprecipitates were collected and analyzed as described for Fig. 3. The inhibitors used selectively target MEK1 (PD098059, 50 μm), JNK (SP600125, 20 μm), p38 (SB203580, 10 μm), IKKβ (salicylic Acid, 5 mm), mTOR (rapamycin, 200 nm), GSK3 (LiCl₂, 25 mm), and P13K (LY294002, 20 μm). B, Schematic diagram illustrating PMA-stimulated serine kinases involved in site-specific serine phosphorylation of IRS1. Data are representative of at least three independent experiments.