Ca 2+ Signaling Domains Responsible For Cardiac Hypertrophy and Arrhythmias

Abstract

See related articles, pages 514–521 and 522–530 Ca2+ activates and regulates multiple processes in every cell type. In the mammalian heart, cyclic fluctuations in cytosolic [Ca2+] induce and regulate the strength of cardiac contraction (termed “contractile” [Ca2+]). In addition, changes in Ca2+ appear to be centrally involved in normal and pathological signaling (termed “signaling” [Ca2+]) that regulates myocyte growth, hypertrophy, apoptosis, and necrosis.1 Whether or not contractile and signaling [Ca2+] are derived from common or distinct sources and are constrained to unique cellular microdomains is not established.2 What is clear is that cardiovascular diseases including hypertension and myocardial infarction are associated with alterations in contractile and possibly signaling [Ca2+] that are centrally involved in pathological cardiac hypertrophy, heart failure progression,1 and lethal cardiac arrhythmias.3 Defining the sources of signaling Ca2+ involved in the induction of pathological hypertrophy and the bases of dysregulated contractile [Ca2+] in cardiovascular disease should identify novel ways to treat heart disease. In this issue of Circulation Research , 2 independent reports address fundamental aspects of alterations in signaling and contractile [Ca2+]. Chiang et al4 have studied the idea that Ca2+ influx through voltage operated α1H (CaV3.2) T-type Ca2+ channels (TTCCs) is the source of the signaling [Ca2+] that activates the calcineurin (Cn)-NFAT (nuclear factor of activated T cells) signaling cascade and induces pathological cardiac hypertrophy in pressure overload. In a separate report, Terentyev et al5 explore the idea that microRNA (miR)-1, a muscle-specific microRNA that increases in abundance in cardiac disease,6 causes dysregulated contractile [Ca2+] and induces single cell arrhythmias. These 2 reports are provocative and, if independently confirmed, will have identified novel …