Ca2+-CaM Dependent Inactivation of RyR2 Underlies Ca2+ Alternans in Intact Heart. Issue 4 (19th February 2021)

• Record Type: Journal Article
• Authors: Wei, Jinhong; Yao, Jinjing; Belke, Darrell; Guo, Wenting; Zhong, Xiaowei; Sun, Bo; Wang, Ruiwu; Paul Estillore, John; Vallmitjana, Alexander; Benitez, Raul; Hove-Madsen, Leif; Alvarez-Lacalle, Enrique; Echebarria, Blas; Chen, S.R. Wayne
• Is Part Of: Circulation research. Volume 128:Issue 4(2021)
• Publication Date: 2021-02-19
• Subjects: calmodulin -- heart -- mutation -- ryanodine -- sarcoplasmic reticulum; Cardiovascular system -- Periodicals; Blood -- Circulation -- Periodicals; Blood Circulation; Cardiovascular System; Vascular Diseases; Sang -- Circulation -- Périodiques; Appareil cardiovasculaire -- Périodiques; 612.1
• DOI: 10.1161/CIRCRESAHA.120.318429
• Languages: English
• ISSNs: 0009-7330

Abstract

Abstract : Rationale: Ca 2+ alternans plays an essential role in cardiac alternans that can lead to ventricular fibrillation, but the mechanism underlying Ca 2+ alternans remains undefined. Increasing evidence suggests that Ca 2+ alternans results from alternations in the inactivation of cardiac RyR2 (ryanodine receptor 2). However, what inactivates RyR2 and how RyR2 inactivation leads to Ca 2+ alternans are unknown. Objective: To determine the role of CaM (calmodulin) on Ca 2+ alternans in intact working mouse hearts. Methods and Results: We used an in vivo local gene delivery approach to alter CaM function by directly injecting adenoviruses expressing CaM-wild type, a loss-of-function CaM mutation, CaM (1–4), and a gain-of-function mutation, CaM-M37Q, into the anterior wall of the left ventricle of RyR2 wild type or mutant mouse hearts. We monitored Ca 2+ transients in ventricular myocytes near the adenovirus-injection sites in Langendorff-perfused intact working hearts using confocal Ca 2+ imaging. We found that CaM-wild type and CaM-M37Q promoted Ca 2+ alternans and prolonged Ca 2+ transient recovery in intact RyR2 wild type and mutant hearts, whereas CaM (1–4) exerted opposite effects. Altered CaM function also affected the recovery from inactivation of the L-type Ca 2+ current but had no significant impact on sarcoplasmic reticulum Ca 2+ content. Furthermore, we developed a novel numerical myocyte model of Ca 2+ alternans that incorporates Ca 2+ -CaM-dependent regulation of RyR2 and the L-type Ca 2+ channel. Remarkably, the new model recapitulates the impact on Ca 2+ alternans of altered CaM and RyR2 functions under 9 different experimental conditions. Our simulations reveal that diastolic cytosolic Ca 2+ elevation as a result of rapid pacing triggers Ca 2+ -CaM dependent inactivation of RyR2. The resultant RyR2 inactivation diminishes sarcoplasmic reticulum Ca 2+ release, which, in turn, reduces diastolic cytosolic Ca 2+, leading to alternations in diastolic cytosolic Ca 2+, RyR2 inactivation, and sarcoplasmic reticulum Ca 2+ release (ie, Ca 2+ alternans). Conclusions: Our results demonstrate that inactivation of RyR2 by Ca 2+ -CaM is a major determinant of Ca 2+ alternans, making Ca 2+ -CaM dependent regulation of RyR2 an important therapeutic target for cardiac alternans. Abstract : Supplemental Digital Content is available in the text.