PKGIα Leucine Zipper Domain Mediates a Novel Interaction with MLK3, a Potential Anti‐Remodeling Substrate in the Heart

Abstract

BackgroundHeart failure is a significant contributor to cardiovascular mortality. cGMP inhibits cardiac remodeling in part via cGMP‐dependent protein kinase G I α (PKGIα). Knock in mice with a mutant PKGIα Leucine Zipper (LZ) have both decreased cardiac function and JNK activity after transaortic constriction (TAC). JNK is regulated by MAPKs including mixed lineage kinase 3 (MLK3) which contains an LZ interacting motif. We hypothesized PKGIα interacts with MLK3 via the PKGIα LZ domain to regulate JNK.ResultsThe MLK3‐PKGIα interaction was observed in mouse heart by co‐immunoprecipitation of MLK3 and PKGIα (n=3). In Cos1 cells MLK3 co‐precipitated with PKGIα but was prevented by mutation of the PKGIα LZ domain (n=3). In cardiomyocytes JNK stimulation by 8‐Br‐cGMP was prevented in MLK3‐depleted cells (siRNA, n=3). The role of MLK3 in the heart was tested by subjecting MLK3 knockout mice (MLK3‐/‐) to TAC (7 days). Compared to WT littermates MLK3‐/‐ hearts had increased hypertrophy and LV end diastolic pressure indicating advanced cardiac dysfunction (n=8‐10)ConclusionThese data reveal a novel interaction between PKGIα‐MLK3 that requires the LZ domain. In cardiomyocytes MLK3 is necessary for cGMP dependent JNK activation. Loss of MLK3 in vivo promotes adverse cardiac remodeling.This work was supported by the NIH.