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

背景：钙通道β亚基在增强通道功能中起着重要作用。使用β亚基对衰竭的心脏进行基因治疗的可能性是被假定的。本研究的目的是阐明β亚基与孔道形成α1c亚基之间的功能相互作用。方法：将钙通道α1c亚基(0.5 ng)与选定浓度的β2a亚基共转染入BHK细胞：β2a/α；1c=0/5，1/5，5/1(摩尔浓度比)。用40 mM钙离子膜片钳全细胞膜片钳技术记录钙通道电流。在吸管溶液中加入cAMP(1 MM)，观察cAMP-PKA介导的磷酸化。结果与结论：1)β2a亚基的电流增强呈剂量依赖性，2)β2a激活动力学向负电位移动，3)稳态失活动力学不受β2a的影响，4)在高表达β2a的细胞中，cAMP对电流的增强作用不明显。我们的数据表明，钙通道β2a亚单位调节α1c的激活门，并调节cAMP-PKA介导的调节。

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.