Description:
Atypical protein kinase C (aPKC) is a key modulator of insulin signaling that regulates glucose transport. Dysfunction of aPKC correlates with insulin‐resistant states in both mice and humans. Despite the engaged interest in this enzyme’s importance to type 2 diabetes, much less is known about the molecular mechanisms that govern its cellular functions than for the conventional and novel classes of PKCs. Here we examine the regulation of aPKC by phosphorylation and lipid binding in order to better define these mechanisms of activation in the context of insulin signaling pathways. Specifically, we show that key drivers of aPKC activity are 1) constitutive phosphorylation at the activation loop and turn motif phosphorylation sites and 2) that phospholipids regulate activity and susceptibility to dephosphorylation. Methods include in vitro kinase activity assays performed on recombinant aPKC purified from insect cells, using phospho‐resistant or phospho‐mimetic mutations placed at key phosphorylation sites. Additional biochemical activity studies were performed following dephosphorylation and in the presence of phospholipids. Our data are consistent with aPKCs sharing similar constitutive phosphorylation as conventional and novel PKCs, with dephosphorylation and activity accelerated by the presence of lipids.Grant Funding Source: This work was supported by P01 DK054441 to ACN and T32 GM007752 to IT