Regulation of voltage-gated L-type Ca²⁺ channel current by calcium/calmodulin-dependent kinase

Abstract

Voltage-gated L-type Ca²⁺ channel current (I_Ca) can be enhanced by preceding strong depolarization. Although this phenomenon is well recognized as voltage-dependent facilitation, its fundamental mechanisms are still unknown. Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) has been reported to play a key role in this process. Therefore we aimed to further clarify these regulation using the whole-cell mode of patch-clamp technique in HEK 293 cells expressing Ca_V1.2_b, β2 and CaMKII. Voltage-dependent facilitation was Ca²⁺-dependent, and was prevented by CaMKII-inhibitor KN93 and autocamtide-2-related inhibitory peptide. Sixteen putative phosphorylation sites in Ca_V1.2_b and β2 subunits according to the consensus sequences which were previously reported. Ca_V1.2_b subunit truncated at amino acid 1728 did not affect voltage-dependent facilitation of I_Ca. Replacement of Ser¹⁵¹² and/or Ser¹⁵⁷⁰ in Ca_V1.2_b subunit by Ala markedly attenuated the voltage-dependent facilitation of I_Ca, while other mutants had no effects. These results indicate that voltage-dependent facilitation of I_Ca is CaMKII-dependent and is generated by phosphorylation of Ca_V1.2_b at Ser¹⁵¹² and/or Ser¹⁵⁷⁰. [J Physiol Sci. 2007;57 Suppl:S233]