HNO enhances SERCA2a activity and cardiomyocyte function by promoting redox-dependent phospholamban oligomerization.

Sivakumaran V, Stanley BA, Tocchetti CG, Ballin JD, Caceres V, Zhou L, Keceli G, Rainer PP, Lee DI, Huke S, Ziolo MT, Kranias EG, Toscano JP, Wilson GM, O'Rourke B, Kass DA, Mahaney JE, Paolocci N
Antioxid Redox Signal. 2013 19 (11): 1185-97

PMID: 23919584 · PMCID: PMC3785857 · DOI:10.1089/ars.2012.5057

AIMS - Nitroxyl (HNO) interacts with thiols to act as a redox-sensitive modulator of protein function. It enhances sarcoplasmic reticular Ca(2+) uptake and myofilament Ca(2+) sensitivity, improving cardiac contractility. This activity has led to clinical testing of HNO donors for heart failure. Here we tested whether HNO alters the inhibitory interaction between phospholamban (PLN) and the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a) in a redox-dependent manner, improving Ca(2+) handling in isolated myocytes/hearts.

RESULTS - Ventriculocytes, sarcoplasmic reticulum (SR) vesicles, and whole hearts were isolated from control (wildtype [WT]) or PLN knockout (pln(-/-)) mice. Compared to WT, pln(-/-) myocytes displayed enhanced resting sarcomere shortening, peak Ca(2+) transient, and blunted β-adrenergic responsiveness. HNO stimulated shortening, relaxation, and Ca(2+) transient in WT cardiomyocytes, and evoked positive inotropy/lusitropy in intact hearts. These changes were markedly blunted in pln(-/-) cells/hearts. HNO enhanced SR Ca(2+) uptake in WT but not pln(-/-) SR-vesicles. Spectroscopic studies in insect cell microsomes expressing SERCA2a±PLN showed that HNO increased Ca(2+)-dependent SERCA2a conformational flexibility but only when PLN was present. In cardiomyocytes, HNO achieved this effect by stabilizing PLN in an oligomeric disulfide bond-dependent configuration, decreasing the amount of free inhibitory monomeric PLN available.

INNOVATION - HNO-dependent redox changes in myocyte PLN oligomerization relieve PLN inhibition of SERCA2a.

CONCLUSIONS - PLN plays a central role in HNO-induced enhancement of SERCA2a activity, leading to increased inotropy/lusitropy in intact myocytes and hearts. PLN remains physically associated with SERCA2a; however, less monomeric PLN is available resulting in decreased inhibition of the enzyme. These findings offer new avenues to improve Ca(2+) handling in failing hearts.

MeSH Terms (25)

Adenosine Triphosphate Animals Antioxidants Calcium Calcium-Binding Proteins Calcium Signaling Cardiotonic Agents Cyclic AMP-Dependent Protein Kinases Disulfides Heart Ventricles In Vitro Techniques Mice Mice, Knockout Microsomes Myocytes, Cardiac Nitrogen Oxides Oxidation-Reduction Phosphorylation Protein Binding Protein Conformation Protein Interaction Domains and Motifs Protein Multimerization Protein Stability Sarcoplasmic Reticulum Sarcoplasmic Reticulum Calcium-Transporting ATPases

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