Inhibitors of the PI3K/Akt signaling module do not inhibit the
activation of Akt by GIP. A, INS-1 cells were pretreated with
dimethyl sulfoxide (DMSO; control) or inhibitors of PI3K signaling (15
μm LY294002 or 5 μm Akt VIII) and then treated
with ±10 nm GIP or 10 nm IGF-I for 15 min.
Western analysis and Akt KA assays were performed on cell lysates with
indicated antibodies. IP, immunoprecipitate. B and
C, shown is the mean change ± S.E. in Akt activity
(P-GST-GSK3/Akt) relative to DMSO control (n = 4) for GIP-
(B) and IGF-I-treated (C) cells. #, p < 0.05
versus DMSO control; $, p < 0.05 versus IGF-I
without inhibitor. D, mouse islets were pretreated with DMSO
(control) or 15 μm LY294002 and then treated with ±10
nm GIP for 15 min. Western analysis and Akt KA assays were
performed with indicated antibodies. E, shown is the mean change
± S.E. in Akt activity relative to DMSO control (n = 3). #,
p < 0.05 versus DMSO control. Anti-β-actin and
anti-GST (GST-GSK3) blots were internal controls.