Modulation of Myosin by Cardiac Myosin Binding Protein-C Peptides Improves Cardiac Contractility in Ex-Vivo Experimental Heart Failure Models

Abstract

Cardiac myosin binding protein-C (cMyBP-C) is an important regulator of sarcomeric function. Although reduced phosphorylation of cMyBP-C has been linked to compromised contractility in heart failure patients, direct modulation of cMyBP-C to myosin using small molecules or peptides has not been reported to improve cardiac performance. Here we used previously published cMyBP-C peptides 302A and 302S (surrogates to the regulatory phosphorylation site serine 302) as tool molecules to investigate the role of cMyBP-C in modulating cardiac contraction and relaxation in experimental heart failure (HF) models in vitro. cMyBP-C peptides 302A and 302S were able to increase contractility of papillary muscle fibers isolated from a cMyBP-C phospho-ablation (cMyBP-CAAA) mouse model. In addition, 302A was able to improve the force redevelopment rate (ktr) in papillary muscle fibers from cMyBP-CAAA mice. Consistent with above findings, cMyBP-C peptides 302A and 302S were able to increase the ATPase rates in myofibrils isolated from MI rats but not from sham rats. Furthermore, in cMyBP-CAAA mouse and myocardial infarction (MI) HF models, both cMyBP-C peptides 302A and 302S were able to improve ATPase hydrolysis rates. These changes were not observed in non-transgenic (NTG) mice or sham rats, indicating the specific effects of these peptides in regulating the reduced or unphosphorylated state of cMyBP-C only under pathological conditions of heart failure. Taken together, these studies demonstrate that modulation of cMyBP-C in a reduced phosphorylation or unphosphorylated state can be a therapeutic approach to improve myosin function, sarcomere contractility and relaxation. Therefore, targeting cMyBP-C can be a differentiated approach to improve overall cardiac performance on top of standard care drugs in HF patients.