Arrhythmogenic Calmodulin Mutations Affect the Activation and Termination of Cardiac Ryanodine Receptor-mediated Ca2+ Release
Arrhythmogenic Calmodulin Mutations Affect the Activation and Termination of Cardiac Ryanodine Receptor-mediated Ca2+ Release
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DOI：
10.1074/jbc.m115.676627
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发表时间：
2015-10-23
影响因子：
4.8
通讯作者：
Overgaard, Michael T.
中科院分区：
文献类型：
--
作者：
Sondergaard, Mads T.;Tian, Xixi;Overgaard, Michael T.
细胞内Ca 2+传感器钙调素（CaM）调节心脏Ca 2+释放通道/RyR 2（RyR 2），CaM突变可导致心律失常，如儿茶酚胺能性多形性室性心动过速（CPVT）和长QT综合征。在这里，我们研究了导致CPVT（N53 I），长QT综合征（D95 V和D129 G）或两者（CaM N97 S）的CaM突变对RyR 2介导的Ca 2+释放的影响。所有的突变增加了Ca 2+的释放，并使RyR 2更容易受到存储过载诱导的Ca 2+释放（SOICR），通过降低阈值的存储Ca 2+含量在SOICR发生和SOICR终止的阈值。为了获得机理见解，我们研究了在存在与RyR 2的CaM结合结构域对应的肽的情况下CaM的N-和C-末端结构域（N-和C-结构域）的Ca 2+结合。相对于CaM WT，N53 I突变降低了Ca 2+与CaM N结构域结合的亲和力，但不影响C结构域。相反，突变N97 S、D95 V和D129 G对Ca 2+与N结构域的结合几乎没有影响，但显著降低了C结构域对Ca 2+的亲和力。这些结果表明，突变D95 V，N97 S和D129 G改变CaM和CaMBD之间的相互作用，从而RyR 2调节。由于N53 I突变对Ca 2+与C结构域结合的影响最小，因此它必须通过不同的机制引起异常调节。这些结果支持异常RyR 2调节作为与CaM突变相关的CPVT的疾病机制，并表明与CPVT无关的CaM突变也可影响RyR 2。提出了CaM-RyR 2相互作用的模型，其中Ca 2+饱和的C-结构域组成性地结合到RyR 2，并且N-结构域感测Ca 2+浓度增加。
The intracellular Ca2+ sensor calmodulin (CaM) regulates the cardiac Ca2+ release channel/ryanodine receptor 2 (RyR2), and mutations in CaM cause arrhythmias such as catecholaminergic polymorphic ventricular tachycardia (CPVT) and long QT syndrome. Here, we investigated the effect of CaM mutations causing CPVT (N53I), long QT syndrome (D95V and D129G), or both (CaM N97S) on RyR2-mediated Ca2+ release. All mutations increased Ca2+ release and rendered RyR2 more susceptible to store overload-induced Ca2+ release (SOICR) by lowering the threshold of store Ca2+ content at which SOICR occurred and the threshold at which SOICR terminated. To obtain mechanistic insights, we investigated the Ca2+ binding of the N- and C-terminal domains (N-and C-domain) of CaM in the presence of a peptide corresponding to the CaM-binding domain of RyR2. The N53I mutation decreased the affinity of Ca2+ binding to the N-domain of CaM, relative to CaM WT, but did not affect the C-domain. Conversely, mutations N97S, D95V, and D129G had little or no effect on Ca2+ binding to the N-domain but markedly decreased the affinity of the C-domain for Ca2+. These results suggest that mutations D95V, N97S, and D129G alter the interaction between CaM and the CaMBD and thus RyR2 regulation. Because the N53I mutation minimally affected Ca2+ binding to the C-domain, it must cause aberrant regulation via a different mechanism. These results support aberrant RyR2 regulation as the disease mechanism for CPVT associated with CaM mutations and shows that CaM mutations not associated with CPVT can also affect RyR2. A model for the CaM-RyR2 interaction, where the Ca2+-saturated C-domain is constitutively bound to RyR2 and the N-domain senses increases in Ca2+ concentration, is proposed.