Post-translational modification patterns on β-myosin heavy chain are altered in ischemic and nonischemic human hearts

Phosphorylation and acetylation of sarcomeric proteins are important for fine-tuning myocardial contractility. Here, we used bottom-up proteomics and label-free quantification to identify novel post-translational modifications (PTMs) on beta-myosin heavy chain (beta-MHC) in normal and failing human heart tissues. We report six acetylated lysines and two phosphorylated residues: K34-Ac, K58-Ac, S210-P, K213-Ac, T215-P, K429-Ac, K951-Ac, and K1195-Ac. K951-Ac was significantly reduced in both ischemic and nonischemic failing hearts compared to nondiseased hearts. Molecular dynamics (MD) simulations show that K951-Ac may impact stability of thick filament tail interactions and ultimately myosin head positioning. K58-Ac altered the solvent-exposed SH3 domain surface - known for protein-protein interactions - but did not appreciably change motor domain conformation or dynamics under conditions studied. Together, K213-Ac/T215-P altered loop 1's structure and dynamics - known to regulate ADP-release, ATPase activity, and sliding velocity. Our study suggests that beta-MHC acetylation levels may be influenced more by the PTM location than the type of heart disease since less protected acetylation sites are reduced in both heart failure groups. Additionally, these PTMs have potential to modulate interactions between beta-MHC and other regulatory sarcomeric proteins, ADP-release rate of myosin, flexibility of the S2 region, and cardiac myofilament contractility in normal and failing hearts.

Automated summary

In this study, we identified novel post-translational modifications (PTMs) on beta-myosin heavy chain (beta-MHC) in normal and failing human heart tissues using proteomics and quantification methods. These PTMs, including acetylation and phosphorylation, were found to play crucial roles in regulating myocardial contractility. Our findings suggest that the location of PTMs on beta-MHC may have a greater impact on their acetylation levels than the type of heart disease. Furthermore, these modifications have the potential to modulate various cellular processes and protein interactions involved in cardiac muscle contraction.