Insulin-feedback via PI3K-C2α activated PKBα/Akt1 is required for glucose-stimulated insulin secretion

Phosphatidylinositide 3-kinases (PI3Ks) play central roles in insulin signal transduction. While the contribution of class Ia PI3K members has been extensively studied, the role of class II members remains poorly understood. The diverse actions of class II PI3K-C2α have been attributed to its lipid product PI(3)P. By applying pharmacological inhibitors, transient overexpression and small-interfering RNA-based knockdown of PI3K and PKB/Akt isoforms, together with PI-lipid profiling and live-cell confocal and total internal reflection fluorescence microscopy, we now demonstrate that in response to insulin, PI3K-C2α generates PI(3,4)P2, which allows the selective activation of PKBα/Akt1. Knockdown of PI3K-C2α expression and subsequent reduction of PKBα/Akt1 activity in the pancreatic β-cell impaired glucose-stimulated insulin release, at least in part, due to reduced glucokinase expression and increased AS160 activity. Hence, our results identify signal transduction via PI3K-C2α as a novel pathway whereby in...