Redox regulation of cardiac calcium channels and transporters

Abstract

Intracellular concentrations of redox-active molecules can significantly increase in the heart as a result of activation of specific signal transduction pathways or the development of certain pathophysiological conditions. Changes in the intracellular redox environment can affect many cellular processes, including the gating properties of ion channels and the activity of ion transporters. Because cardiac contraction is highly dependent on intracellular Ca²⁺ levels ([Ca²⁺]_i) and [Ca²⁺]_i regulation, redox modification of Ca²⁺ channels and transporters has a profound effect on cardiac function. The sarcoplasmic reticulum (SR) Ca²⁺ release channel, or ryanodine receptor (RyR), is one of the well-characterized redox-sensitive ion channels in the heart. The redox modulation of RyR activity is mediated by the redox modification of sulfhydryl groups of cysteine residues. Other key components of cardiac excitation–contraction (e–c) coupling such as the SR Ca²⁺ ATPase and L-type Ca²⁺ channel are subject to redox modulation. Redox-mediated alteration of the activity of ion channels and pumps is directly involved in cardiac pathologies such as ischemia–reperfusion injury. Significant bursts of reactive oxygen species (ROS) generation occur during reperfusion of the ischemic heart, and changes in the activity of the major components of [Ca²⁺]_i regulation, such as RyR, Na⁺–Ca²⁺ exchange and Ca²⁺ ATPases, are likely to play an important role in ischemia-related Ca²⁺ overload. This article summarizes recent findings on redox regulation of cardiac Ca²⁺ transport systems and discusses contributions of this redox regulation to normal and pathological cardiac function.