Phosphorylation of the ryanodine receptor mediates the cardiac fight or flight response in mice
Jian Shan, … , Peter J. Mohler, Andrew R. Marks
Jian Shan, … , Peter J. Mohler, Andrew R. Marks
Published November 22, 2010
Citation Information: J Clin Invest. 2010;120(12):4388-4398. https://doi.org/10.1172/JCI32726.
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Phosphorylation of the ryanodine receptor mediates the cardiac fight or flight response in mice

Abstract

During the classic “fight-or-flight” stress response, sympathetic nervous system activation leads to catecholamine release, which increases heart rate and contractility, resulting in enhanced cardiac output. Catecholamines bind to β-adrenergic receptors, causing cAMP generation and activation of PKA, which phosphorylates multiple targets in cardiac muscle, including the cardiac ryanodine receptor/calcium release channel (RyR2) required for muscle contraction. PKA phosphorylation of RyR2 enhances channel activity by sensitizing the channel to cytosolic calcium (Ca2+). Here, we found that mice harboring RyR2 channels that cannot be PKA phosphorylated (referred to herein as RyR2-S2808A+/+ mice) exhibited blunted heart rate and cardiac contractile responses to catecholamines (isoproterenol). The isoproterenol-induced enhancement of ventricular myocyte Ca2+ transients and fractional shortening (contraction) and the spontaneous beating rate of sinoatrial nodal cells were all blunted in RyR2-S2808A+/+ mice. The blunted cardiac response to catecholamines in RyR2-S2808A+/+ mice resulted in impaired exercise capacity. RyR2-S2808A+/+ mice were protected against chronic catecholaminergic-induced cardiac dysfunction. These studies identify what we believe to be new roles for PKA phosphorylation of RyR2 in both the heart rate and contractile responses to acute catecholaminergic stimulation.

Authors

Jian Shan, Alexander Kushnir, Matthew J. Betzenhauser, Steven Reiken, Jingdong Li, Stephan E. Lehnart, Nicolas Lindegger, Marco Mongillo, Peter J. Mohler, Andrew R. Marks

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Figure 2

Blunted cardiac response to acute β-adrenergic stimulation in RyR2-S2808A+/+ mice.

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Blunted cardiac response to acute β-adrenergic stimulation in RyR2-S2808...
(A–C) Pressure-volume loops before (black) and during (red) Iso (100 ng/kg/min i.v.) infusion. (A) The steeper and left-shifted Ees line indicates increased contractility as evidenced in WT, which is blunted in (B) RyR2-S2808A+/+ mice. (C) Treatment with Bay K 8644 (100 μg/kg i.p.) restored the inotropic response in RyR2-S2808A+/+ mice. Insets show representative examples of end-systolic pressure-volume relationships (ESPVRs) during β-adrenergic stimulation; Ees is determined by the slope of the automated end-systolic pressure-volume relationship regression analysis through a series of end-systolic points (black dots). (D) Ees response to gradually increasing Iso (0–100 ng/kg/min) and sigmoid regression analysis (n = 10 for each genotype; *P < 0.05 each versus WT). (E) dP/dtmax of WT and RyR2-S2808A+/+ mice prior to and after db-cAMP infusion (*P < 0.05). (F) dP/dtmax prior to and after treatment with Iso (100 ng/kg/min i.v.), according to genotype as indicated (calstabin2, referred to herein as CLN2–/–; phospholamban, Pln–/–; and crossed mouse strains as indicated) (*P < 0.05 versus baseline; #P < 0.05 versus WT baseline; **P < 0.05). (G) Ees change normalized to WT after treatment with inotropic agonists Bay K 8644 (100 μg/kg i.p.), Ca2+ (30 mg/kg/min i.v.), or ouabain (0.1 mg/kg/min i.v.) (P = NS versus WT; n = 5). (H) Heart rates in response to gradually increasing Iso concentrations (0–100 ng/kg/min) and sigmoid regression analysis from D (n = 10 for each genotype; *P < 0.05).