Phosphomimetic ‐mediated in vitro rescue of hypertrophic cardiomyopathy linked to R58Q mutation in myosin regulatory light chain

This study focuses on the arginine to glutamine (R58Q) substitution in the human ventricular RLC (MYL2 gene), linked to malignant hypertrophic cardiomyopathy in humans and causing severe functional abnormalities in transgenic R58Q mice, inclu ding inhibition of cardiac RLC phosphorylation. Using a phosphomimic recombinant RLC variant where the phosphorylation site Ser‐15 was substituted with an aspartic acid (S15D) and placed in the background of R58Q, we aimed to assess whether we could rescue/mitigate R58Q‐induced structural/functi onal abnormalitiesin vitro. We show rescue of several R58Q ‐exerted adverse phenotypes in S15D‐R58Q‐reconstituted porcine cardiac muscle preparations. A low level of maximal isometric force observed for R58Q‐ versus WT‐reconstituted fibers was restored by S15D‐R58Q. Significant beneficial effects were also observed on the Vmax of actin ‐activated myosin ATPase activity in S15D‐R58Q versus R58Q‐reconstituted myosin, along with its binding to fluorescently‐labeled actin. We also report that R58Q promotes the OFF state of myosin, both in reconstituted porcine fibers and in transgenic mouse papillary muscles, thereby stabilizi ng the super‐relaxed state (SRX) of myosin, characterized by a very low ATP turnover rate. Experiments in S15D‐R58Q‐reconstituted porcine fibers showed a mild destabilization of the SRX state, suggesting an S15D‐mediated shift in disordered‐relaxed (DRX)↔SRX equilibrium towards the DRX s tate...
Source: FEBS Journal - Category: Research Authors: Tags: Original Article Source Type: research