0151 : Role a calcium/calmodulin-dependent serine protein kinase on Cav1.2 channel regulation

Abstract

Voltage-dependent calcium channels (Cav) constitute a major pathway for the entry of calcium into excitable cells. The long list of cardiac pathologies highlights the key role played by Cav1.2 channels in cardiac physiology. A calcium/calmodulin-dependent serine protein kinase (CASK) has been recently identified as a potent new protein interacting with Cav1.2 channel. Nevertheless, despite the fact that CASK is expressed in cardiac cells, to this date, no functional experiments have been performed to investigate the role of CASK on Cav1.2 channels regulation. Full length or the C-terminal truncated (2024stop) Cavα1c subunit, both expressed in cardiac cells, was coexpressed with Cavβ2 and Cavα2-δ1 subunits in TsA-201 cells. In addition scramble or silencer of CASK protein was co-transfected with Cav1.2 channels. Barium currents (IBa) and calcium current (ICa) were recorded under voltage-clamp conditions using the whole-cell configuration. After 72 hours post-transfection, the cells silenced for CASK, expressing either the full length or 2024stop Cavα1c subunits, show an increase of ICa. In contrast, in similar condition of transfection, the IBa current is only increased in the condition with the C-terminal truncated Cavα1c subunit suggesting that the C-terminal part of Cavα1c subunit counteracts the CASK silencing effect. Interestingly, the C-terminal part of Cavα1c subunit masks an interacting motif for the calcium-dependent serine-threonine phosphatase: calcineurin. One hour incubation with cyclosporin A, a specific inhibitor of calcineurin phosphatase, blunts the CASK silencing effect on IBa with the C-terminal truncated part of Cavα1c subunit bringing out the key role of calcineurin in the mechanism of Cav1.2 channels regulation by CASK. In the present study, we highlight CASK protein as a novel regulator of voltage-gated calcium channel Cav1.2 via the calcineurin.