Calmodulin: a gatekeeper for ryanodine receptor function in the myocardium

This editorial refers to ‘Dissociation of calmodulin from cardiac ryanodine receptor causes aberrant Ca2+ release in heart failure’, by M. Ono et al. , pp. 609–617, this issue. The ryanodine receptor (RyR) releases intracellular Ca2+ from the sarcoplasmic reticulum (SR) of beating cardiomyocytes following Ca2+ influx via the voltage-dependent sarcolemmal Ca2+ channel. This crucial cellular event, named ‘Ca2+-induced Ca2+ release' and discovered three decades ago by Fabiato and Fabiato,1 is mandatory for the rhythmic contraction as well as for maintaining the force–frequency relationship of the myocardium. RyR type 1 (RyR1), cardiac RyR2, and RyR3 have been the subject of intensive investigation for many years. More recently, Ikemoto and Yamamoto provided evidence of structure–function relationships in the RyRs. They reported that the N-terminal and central domains of RyRs form an interacting domain pair. Unzipping and zipping actions of such a domain pair determines the opening and closing probabilities of the RyR Ca2+ channel, respectively.2 A dysregulation of this domain pair leads to a defect in heart function. Unzipping the N-terminal from the central domain leads to RyR2 hyperactivation and Ca2+ leak from the SR, … *Corresponding author. Tel: +33 160 878 923; fax: +33 160 878 999, Email: michel.puceat{at}inserm.fr