Regulation of Cardiac Cav1.2 Channels by Calmodulin

Cav1.2 Ca(2+) channels, a type of voltage-gated L-type Ca(2+) channel, are ubiquitously expressed, and the predominant Ca(2+) channel type, in working cardiac myocytes. Cav1.2 channels are regulated by the direct interactions with calmodulin (CaM), a Ca(2+)-binding protein that causes Ca(2+)-dependent facilitation (CDF) and inactivation (CDI). Ca(2+)-free CaM (apoCaM) also contributes to the regulation of Cav1.2 channels. Furthermore, CaM indirectly affects channel activity by activating CaM-dependent enzymes, such as CaM-dependent protein kinase II and calcineurin (a CaM-dependent protein phosphatase). In this article, we review the recent progress in identifying the role of apoCaM in the channel ‘rundown’ phenomena and related repriming of channels, and CDF, as well as the role of Ca(2+)/CaM in CDI. In addition, the role of CaM in channel clustering is reviewed.