Protein Kinase Cα (PKCα) Gain‐of‐Function Variant in Alzheimer's Disease Displays Enhanced Catalysis by a Mechanism that Evades Down‐Regulation

Abstract

The signaling output of protein kinase C (PKC) is precisely controlled through multiple mechanisms that balance its activity in order to maintain cellular homeostasis, with disruption of this balance resulting in pathophysiologies. In this vein, the cell has evolved mechanisms to maintain this balance by degrading constitutively active PKCα. We have previously shown that loss‐of‐function mutations in multiple PKC isozymes contribute to cancer, a disease of aberrant proliferation, and gain‐of‐function mutations in the conventional isozyme PKCα contribute to Alzheimer's Disease (AD), a disease of aberrant cell death. Here, we biochemically characterize one of the AD‐associated variants, PKCα‐M489V, in order to investigate the mechanism through which it confers enhanced signaling output without causing PKCα degradation. We use a combination of in vitro and in silico methods to demonstrate that this mutation effectively increases the specific activity of purified PKCα under activating conditions by increasing the molecular dynamics of the catalytic domain. Importantly, it does so without affecting the normal autoinhibition of basal signaling, thereby allowing for an enhanced signaling output that simultaneously evades the cell's homeostatic degradation of PKCα protein levels. Taken together, our results provide an in‐depth characterization of a disease‐associated gain‐of‐function PKC mutation, and for the first time report a mutation that enhances signaling output of PKCα while maintaining its stability in the cell.Support or Funding InformationThis work was supported by NIH R35 GM122523 and NIH GM43154 (ACN), the Cure Alzheimer's Fund (ACN), and Cancer Research UK (NS, JB). JC was supported by the UCSD Graduate Training Program in Cellular and Molecular Pharmacology (T32 GM007752).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.