Phosphorylation of Cardiac Myosin-Binding Protein-C Is a Critical Mediator of Diastolic Function

Background—Heart failure (HF) with preserved ejection fraction (HFpEF) accounts for ≈50% of all cases of HF and currently has no effective treatment. Diastolic dysfunction underlies HFpEF; therefore, elucidation of the mechanisms that mediate relaxation can provide new potential targets for treatment. Cardiac myosin-binding protein-C (cMyBP-C) is a thick filament protein that modulates cross-bridge cycling rates via alterations in its phosphorylation status. Thus, we hypothesize that phosphorylated cMyBP-C accelerates the rate of cross-bridge detachment, thereby enhancing relaxation to mediate diastolic function. Methods and Results—We compared mouse models expressing phosphorylation-deficient cMyBP-C(S273A/S282A/S302A)–cMyBP-C(t3SA), phosphomimetic cMyBP-C(S273D/S282D/S302D)–cMyBP-C(t3SD), and wild-type-control cMyBP-C(tWT) to elucidate the functional effects of cMyBP-C phosphorylation. Decreased voluntary running distances, increased lung/body weight ratios, and increased brain natriuretic peptide level...