Nafzger Sabine, Rougier Jean-Sebastien
Department of Clinical Research, University of Bern, Bern CH-3008, Switzerland.
Department of Clinical Research, University of Bern, Bern CH-3008, Switzerland.
Cell Calcium. 2017 Jan;61:10-21. doi: 10.1016/j.ceca.2016.10.001. Epub 2016 Oct 5.
The L-type voltage-gated calcium channel Ca1.2 mediates the calcium influx into cells upon membrane depolarization. The list of cardiopathies associated to Ca1.2 dysfunctions highlights the importance of this channel in cardiac physiology. Calcium/calmodulin-dependent serine protein kinase (CASK), expressed in cardiac cells, has been identified as a regulator of Ca2.2 channels in neurons, but no experiments have been performed to investigate its role in Ca1.2 regulation.
Full length or the distal C-terminal truncated of the pore-forming Ca1.2 channel (Ca1.2α1c), both present in cardiac cells, were expressed in TsA-201 cells. In addition, a shRNA silencer, or scramble as negative control, of CASK was co-transfected in order to silence CASK endogenously expressed. Three days post-transfection, the barium current was increased only for the truncated form without alteration of the steady state activation and inactivation biophysical properties. The calcium current, however, was increased after CASK silencing with both types of Ca1.2α1c subunits suggesting that, in absence of calcium, the distal C-terminal counteracts the CASK effect. Biochemistry experiments did not reveals neither an alteration of Ca1.2 channel protein expression after CASK silencing nor an interaction between Ca1.2α1c subunits and CASK. Nevertheless, after CASK silencing, single calcium channel recordings have shown an increase of the voltage-gated calcium channel Ca1.2 open probability explaining the increase of the whole-cell current.
This study suggests CASK as a novel regulator of Ca1.2 via a modulation of the voltage-gated calcium channel Ca1.2 open probability.
L型电压门控钙通道Ca1.2在细胞膜去极化时介导钙离子流入细胞。与Ca1.2功能障碍相关的一系列心脏病凸显了该通道在心脏生理学中的重要性。在心脏细胞中表达的钙/钙调蛋白依赖性丝氨酸蛋白激酶（CASK）已被确定为神经元中Ca2.2通道的调节剂，但尚未进行实验来研究其在Ca1.2调节中的作用。
在TsA-201细胞中表达了心脏细胞中存在的全长或孔形成Ca1.2通道（Ca1.2α1c）的远端C末端截短形式。此外，共转染了CASK的shRNA沉默剂或作为阴性对照的乱序序列，以内源性沉默CASK。转染后三天，仅截短形式的钡电流增加，而稳态激活和失活生物物理特性未改变。然而，在用两种类型的Ca1.2α1c亚基沉默CASK后，钙电流增加，这表明在没有钙的情况下，远端C末端抵消了CASK的作用。生物化学实验既未揭示CASK沉默后Ca1.2通道蛋白表达的改变，也未揭示Ca1.2α1c亚基与CASK之间的相互作用。尽管如此，在CASK沉默后，单通道钙记录显示电压门控钙通道Ca1.2的开放概率增加，这解释了全细胞电流的增加。
本研究表明CASK是Ca1.2的一种新型调节剂，通过调节电压门控钙通道Ca1.2的开放概率发挥作用。
