Liu Yingjie, Wei Jinhong, Wong King Yuen Siobhan M, Sun Bo, Tang Yijun, Wang Ruiwu, Van Petegem Filip, Chen S R Wayne
Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada.
Department of Biochemistry and Molecular Biology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, Canada.
PLoS One. 2017 Sep 29;12(9):e0184177. doi: 10.1371/journal.pone.0184177. eCollection 2017.
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is one of the most lethal inherited cardiac arrhythmias mostly linked to cardiac ryanodine receptor (RyR2) mutations with high disease penetrance. Interestingly, a novel RyR2 mutation G357S discovered in a large family of more than 1400 individuals has reduced penetrance. The molecular basis for the incomplete disease penetrance in this family is unknown. To gain insights into the variable disease expression in this family, we determined the impact of the G357S mutation on RyR2 function and expression. We assessed spontaneous Ca2+ release in HEK293 cells expressing RyR2 wildtype and the G357S mutant during store Ca2+ overload, also known as store overload induced Ca2+ release (SOICR). We found that the G357S mutation reduced the percentage of RyR2-expressing cells that showed SOICR. However, in cells that displayed SOICR, G357S reduced the thresholds for the activation and termination of SOICR. Furthermore, G357S decreased the thermal stability of the N-terminal domain of RyR2, and markedly reduced the protein expression of the full-length RyR2. On the other hand, the G357S mutation did not alter the Ca2+ activation of [3H]ryanodine binding or the Ca2+ induced release of Ca2+ from the intracellular stores in HEK293 cells. These data indicate that the CPVT-associated G357S mutation enhances the arrhythmogenic SOICR and reduces RyR2 protein expression, which may be attributable to the incomplete penetrance of CPVT in this family.
儿茶酚胺能多形性室性心动过速（CPVT）是最致命的遗传性心律失常之一，主要与疾病外显率高的心脏雷诺丁受体（RyR2）突变有关。有趣的是，在一个超过1400人的大家族中发现的一种新的RyR2突变G357S具有降低的外显率。该家族中疾病不完全外显的分子基础尚不清楚。为了深入了解该家族中可变的疾病表现，我们确定了G357S突变对RyR2功能和表达的影响。我们评估了在表达RyR2野生型和G357S突变体的HEK293细胞中，在储存Ca2+过载期间（也称为储存过载诱导的Ca2+释放，SOICR）的自发Ca2+释放。我们发现G357S突变降低了显示SOICR的RyR2表达细胞的百分比。然而，在显示SOICR的细胞中，G357S降低了SOICR激活和终止的阈值。此外，G357S降低了RyR2 N端结构域的热稳定性，并显著降低了全长RyR2的蛋白表达。另一方面，G357S突变并未改变HEK293细胞中[3H]雷诺丁结合的Ca2+激活或细胞内储存中Ca2+诱导的Ca2+释放。这些数据表明，与CPVT相关的G357S突变增强了致心律失常的SOICR并降低了RyR2蛋白表达，这可能归因于该家族中CPVT的不完全外显率。
