过表达Junctate蛋白对小鼠心肌细胞肌浆网Ca^(2+)浓度调节的影响

Effects of Junctate Protein Overexpression on Regulation of Ca^(2+) Concentration in Cardiomyocytes Sarcoplasmic Reticulum of Mice

目的:探讨过表达junctate蛋白后,小鼠心肌细胞肌浆网上钙通道对细胞内钙离子浓度调节的影响。方法:以正常表达junctate蛋白的小鼠(wild-type mice,WT)心肌细胞为WT组,以过表达junctate蛋白的转基因小鼠(transgenic mice,TG)心肌细胞为TG组,用离子荧光测定仪测定两组小鼠心肌细胞静息状态下的钙离子浓度,后再分别测定两组小鼠在给予咖啡因及氯化钾刺激后,心肌细胞内的钙离子浓度的变化情况,并测定咖啡因引起钙瞬变后的恢复时间。结果:静息状态下,TG组心肌细胞[Ca^(2+)]i为(77.6!8.8)nmol·L-1,显著低于WT组(144.2!10.6)nmol·L-1,(P<0.01);加入咖啡因后,TG组细胞内钙瞬变幅度显著低于WT组,且TG组钙瞬变后自峰值恢复到基础水平的时间较WT组明显延长(P<0.01);加入KCl后,两组细胞内[Ca^(2+)]i均瞬间增高,TG组心肌细胞内钙瞬变幅度明显大于WT组(P<0.01)。结论:过表达junctate蛋白会影响肌浆网对细胞内钙离子浓度的调节,其机制可能是过表达junctate蛋白会导致兰尼碱受体(Ryanodine receptor,RyR)功能上调、肌浆网Ca^(2+)-ATP酶(Sarcoplasmic-endoplasmic-reticulum Ca^(2+)-ATPase,SERCA)功能下调,并使肌浆网钙库储存量减少,最终导致静息状态及去极化状态下细胞内钙离子浓度异常。

Objective To investigate the influence of overexpression junctate protein on regulating Ca2＋ concentration （ [ Ca2＋ ] i） ,through Ca2＋ channel in sarcoplasmic reticulum of cardiomyocytes.Methods The cardiomyocytes from wild-type mice and transgenic mice with normal and over junctate expression were selected as control group（ group WT） and observa- tion group（ group TG）, respectively.The [ Ca2＋]i of cardiomyocytes under resting states was determined by ion fluorescence spectrometer.The changes of [ Ca2＋]i was monitored after inducing with caffeine and KC1 in both groups, and the recovery time of calcium transient induced by caffeine was recorded.Results The [ Ca2＋] i in myocardial cells of mice in group TG was （77.6 ±8.8） nmol · L^-1 ,which was significantly lower than that of group WT（ 144.2 ±10.6） nmol · L^-1, （P〈0.01）. After inducing with caffeine, the range of calcium transient in group TG was obviously bigger than that of group WT, and the recovery time that from peak value to basal level in group TG was longer than that of group WT（ P〈0.01 ）iAfter inducing with KCl,the [ Ca2＋] i were both transiently increased in two groups, while the range of group TG was obviously bigger than that of group WT, （P〈0.01）.Conclusion The overexpression of junctate protein may affect the regulation of [ Ca2＋ ] i in sar-coplasmic reticulum through upregulating ryanodine receptor, downregulating sarcoplasmic-endoplasmic reticulum Ca2＋ -AT- Pase,reducing the storage of calcium and finally leading a abnormal [ Ca2＋ ]i under resting and depolarization states.