Molecular mechanism of Ca^<2+> channel activation by phosphorylation : functional regulation by phosphorylation of channel subunit CACNA1C

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Background : Ca^<2+> channel & beta ; subunit plays an important role in an enhancement of the channel function. A possibility of a gene therapy using & beta ; subunit for the failing heart is postulated. The purpose of this study was to clarify the functional interaction of & beta ; subunit with pore forming & alpha;1c subunit. Methods : Calcium channel alpha 1c (0.5 ng) subunit with selected concentrations of beta 2a subunit were cotransfected into BHK cells : & beta;2a/ & alpha;1c=0/5,1/5,5/1(mole concentration ratio). The expressed Ca^<2+> channels currents were recorded using the whole-cell patch clamp method with 40mM Ba^<2+>. cAMP (1 mM) was added in the pipette solution to observe the cAMP-PKA-mediated phosphorylation. Results and conclusion : 1)current enhancement with beta 2a subunit was dose-dependent, 2)activation kinetics shift toward negative potential with beta 2a, 3)steady-state inactivation kinetics were not affected with beta 2a, 4)no significant enhancement of the current by cAMP was observed in the cells over expressing beta 2a. Our data indicate that calcium channel beta 2a subunit regulates activation gate of alpha 1c and modulates the cAMP-PKA-mediated regulation.