Nitroxyl(HNO)-Mediated Disulfide Bond Formation Between Cardiac Myofilament Cysteines Enhances Contractile Function
Rationale: In the myocardium, redox/cysteine modification of proteins regulating Ca2+ cycling can affect contraction and may have therapeutic value. Nitroxyl (HNO), the one electron reduced form of nitric oxide, enhances cardiac function in a manner that suggests reversible cysteine modifications of the contractile machinery.
Objective: To determine the effects of HNO modification in cardiac myofilament proteins.
Methods and Results: The HNO-donor, 1-nitrosocyclohexyl acetate (NCA), was found to act directly on the myofilament proteins increasing maximum force (Fmax) and reducing the concentration of Ca2+ for 50% activation (Ca50) in intact and skinned cardiac muscles. The effects of NCA are reversible by reducing agents and distinct from those of another HNO-donor Angeli's salt (AS), which was previously reported to increase Fmax without affecting Ca50. Using a new mass spectrometry capture technique based on the biotin switch assay, we identified and characterized the formation by HNO of a disulfide linked actin-tropomyosin and myosin heavy chain (MHC)-myosin light chain 1 (MLC1). Comparison of the NCA and AS effects with the modifications induced by each donor indicated the actin-tropomyosin and MHC-MLC1 interactions independently correlated with increased Ca2+ sensitivity and force generation, respectively.
Conclusions: HNO exerts a direct effect on cardiac myofilament proteins increasing myofilament Ca2+ responsiveness by promoting disulfide bond formation between critical cysteine residues. These findings indicate a novel, redox-based modulation of the contractile apparatus which positively impacts myocardial function, providing further mechanistic insight for HNO as a therapeutic agent.
- Received April 4, 2012.
- Accepted July 31, 2012.
- Copyright © 2012, American Heart Association