Intramolecular C2‐Kinase Domain Interactions Autoinhibit Conventional Protein Kinase

Abstract

The signaling output of protein kinase C (PKC) is exquisitely controlled, with its disruption resulting in pathophysiologies. Identifying the structural basis for autoinhibition is central to developing effective therapies for cancer, where PKC activity needs to be enhanced, or neurodegenerative diseases, where PKC activity should be inhibited. Here, we reinterpret a previously reported crystal structure of PKCβII and use docking and functional analysis to propose an alternative structure that is consistent with previous literature on PKC regulation. Mutagenesis of predicted contact residues establishes that the Ca2+‐sensing C2 domain interacts intramolecularly with the kinase domain and the carboxyl‐terminal tail, locking PKC in an inactive conformation. Applying a similar approach towards another conventional PKC isozyme, PKCα, confirmed C2 domain‐mediated autoinhibition as a shared mechanism among conventional PKC isozymes. Ca2+‐dependent bridging of the C2 domain to membranes provides the first step in activating PKC via conformational selection. Therefore, elucidation of the structural basis for autoinhibition of PKC unveils a unique direction for therapeutically targeting PKC activity.Support or Funding InformationThis work was supported by NIH grants GM43154 to A.C.N. and DK54441 to A.C.N. and S.S.T. C.E.A. was supported in part by the University of California, San Diego, Graduate Training Program in Cellular and Molecular Pharmacology (T32 GM007752) and the National Science Foundation Graduate Research Fellowship (DGE1144086).