S-Nitrosylation of Calcium-Handling Proteins in Cardiac Adrenergic Signaling and Hypertrophy

Abstract

Rationale The regulation of calcium (Ca2+) homeostasis by beta-adrenergic receptor (βAR) activation provides the essential underpinnings of sympathetic regulation of myocardial function as well as a basis for understanding molecular events that result in hypertrophic signaling and heart failure. Sympathetic stimulation of the βAR not only induces protein phosphorylation but also activates nitric oxide (NO)-dependent signaling, which modulates cardiac contractility. Nonetheless, the role of NO in βAR-dependent regulation of Ca2+ handling has not yet been explicated fully. Objective To elucidate the role of protein S-nitrosylation, a major transducer of NO bioactivity, on βAR-dependent alterations in cardiomyocyte Ca2+ handling and hypertrophy. Methods and Results Using transgenic mice to titrate the levels of protein SNO, we uncovered major roles for protein S-nitrosylation generally, and for phospholamban (PLN) and cardiac troponin C (cTnC) S-nitrosylation in particular, in βAR-dependent regulation of Ca2+ homeostasis. Notably, S-nitrosylation of PLN consequent upon βAR stimulation is necessary for its inhibitory pentamerization of PLN, which activates sarcoplasmic reticulum Ca2+-ATPase (SERCA2a) and increases cytosolic Ca2+ transients. Coincident S-nitrosylation of cTnC decreases myocardial sensitivity to Ca2+. During chronic adrenergic stimulation, global reductions in cellular S-nitrosylation mitigate hypertrophic signaling resulting from Ca2+ overload. Conclusions S-nitrosylation operates in concert with phosphorylation to regulate many cardiac Ca2+-handling proteins, including PLN and cTnC, thereby playing an essential and previously unrecognized role in cardiac Ca2+ homeostasis. Manipulation of the S-nitrosylation level may prove therapeutic in heart failure.

Mesenchymal stem cells suppress cardiac alternans by activation of PI3K mediated nitroso-redox pathway

“…Yet, our results with GSNO and those reported by others [41] suggest that direct S-nitrosylation is associated with accelerated Ca ++ decay. Since models of nitrosoredox imbalance exhibit slower Ca ++ decay [42], and there is evidence that phosphorylation and S-nitrosylation of phospholamban are required for activation of SERCA2a [43], suggests an important role of S-nitrosylation and restoring nitroso-redox balance.…”

Adrenergic Fight-or-Flight

“…1 show that NOS works in concert with PKA at two of the main PKA targets (PLN and troponin) by a unique set of molecular mechanisms during β-AR induced cardiac inotropy. They use transgenic overexpression of S-nitrosoglutathione reductase (GSNOR) which causes protein denitrosylation.…”

“…1,4–7 β-AR-induced cAMP also activates Epac (exchange protein activated by cAMP) which can activate Ca-Calmodulin dependent protein kinase (CaMKII) to phosphorylate RyR and promote arrhythmogenic SR Ca 2+ leak. 8 β-AR stimulation can also activate CaMKII via a PKA-independent and NOS1-dependent pathway and promote RyR gating, 9–11 and we now know that cardiac CaMKIIδ can be directly nitrosylated at specific sites which either promote or inhibit CaMKIIδ activity.…”

“…1 demonstrate novel aspects of crosstalk downstream of β-adrenergic receptor (β-AR) between classical cAMP-dependent protein kinase (PKA) target proteins and nitric oxide synthase (NOS) signaling in cardiac myocytes. This study opens up intriguing new questions for this field.…”

How widespread is stable protein S-nitrosylation as an end-effector of protein regulation?

“…Many reviews ascribe S-nitrosothiols as end-effectors of NO signalling that contribute to homeostasis during health [6][7][8], with dysregulation of these processes contributing to disease pathogenesis. For example, hyper-or hypo-S-nitrosylation contributes to a range cardiovascular disease including type 1 and 2 diabetes [9], atherosclerosis [10], cardiac ischemic injury [11], hypertrophy [12] and sepsis [13].…”