Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, PO Box 1627, Neulaniementie 2, FI-70211 Kuopio, Finland.
J Physiol. 2011 Jun 1;589(Pt 11):2669-86. doi: 10.1113/jphysiol.2010.201400. Epub 2011 Mar 28.
Recent studies have demonstrated that changes in the activity of calcium-calmodulin-dependent protein kinase II (CaMKII) induce a unique cardiomyocyte phenotype through the regulation of specific genes involved in excitation-contraction (E-C)-coupling. To explain the transcriptional effects of CaMKII we identified a novel CaMKII-dependent pathway for controlling the expression of the pore-forming α-subunit (Cav1.2) of the L-type calcium channel (LTCC) in cardiac myocytes. We show that overexpression of either cytosolic (δC) or nuclear (δB) CaMKII isoforms selectively downregulate the expression of the Cav1.2. Pharmacological inhibition of CaMKII activity induced measurable changes in LTCC current density and subsequent changes in cardiomyocyte calcium signalling in less than 24 h. The effect of CaMKII on the α1C-subunit gene (Cacna1c) promoter was abolished by deletion of the downstream regulatory element (DRE), which binds transcriptional repressor DREAM/calsenilin/KChIP3. Imaging DREAM-GFP (green fluorescent protein)-expressing cardiomyocytes showed that CaMKII potentiates the calcium-induced nuclear translocation of DREAM. Thereby CaMKII increases DREAM binding to the DRE consensus sequence of the endogenous Cacna1c gene. By mathematical modelling we demonstrate that the LTCC downregulation through the Ca2+-CaMKII-DREAM cascade constitutes a physiological feedback mechanism enabling cardiomyocytes to adjust the calcium intrusion through LTCCs to the amount of intracellular calcium detected by CaMKII.
最近的研究表明，钙调蛋白依赖性蛋白激酶 II（CaMKII）活性的变化通过调节兴奋-收缩（E-C）偶联中涉及的特定基因，诱导心肌细胞出现独特的表型。为了解释 CaMKII 的转录效应，我们确定了一种新的 CaMKII 依赖性途径，用于控制心肌细胞中 L 型钙通道（LTCC）的孔形成α亚基（Cav1.2）的表达。我们发现，细胞质（δC）或核（δB）CaMKII 同工型的过表达选择性地下调 Cav1.2 的表达。CaMKII 活性的药理学抑制在不到 24 小时内诱导 LTCC 电流密度的可测量变化，随后诱导心肌细胞钙信号的变化。通过删除下游调节元件（DRE），即与转录抑制因子 DREAM/calsenilin/KChIP3 结合的元件，CaMKII 对α1C 亚基基因（Cacna1c）启动子的作用被消除。对表达 DREAM-GFP（绿色荧光蛋白）的心肌细胞进行成像显示，CaMKII 增强了钙诱导的 DREAM 核易位。因此，CaMKII 增加了 DREAM 与内源性 Cacna1c 基因的 DRE 共有序列的结合。通过数学建模，我们证明了通过 Ca2+-CaMKII-DREAM 级联下调 LTCC 构成了一种生理反馈机制，使心肌细胞能够根据 CaMKII 检测到的细胞内钙的量来调节通过 LTCC 的钙入侵。
