长QT综合征相关基因新突变R863X-HERG的功能研究

目的 R863X是在国人长QT综合征家系中发现的一个新的HERG基因无义突变,本研究旨在探讨R863X-HERG的功能。方法 采用PCR方法制备突变体R863X-HERG,并克隆到真核细胞表达载体中;用CHO细胞表达系统及全细胞膜片钳电生理技术研究突变体的功能。结果 实验表明R863-HERG基因单独表达时不能形成有功能的离子通道,而突变体R863X同野生型HERG共表达时,通道的电流密度降低约30％,且HERG WT／R863X通道的电压依赖性失活过程加速。结论突变体R863X亚基自身不能装配成有功能的通道,但可和野生型HERG亚基形成有功能的HERG通道异聚体,改变通道的门控特性。HERG蛋白C末端可能在通道装配中发挥一定的作用。

Electrophysiological characterization of a novel mutation R863X in HERG C-terminus associated with long QT syndrome

Objective Molecular mechanism underlying long QT syndrome (LQTS) by mutations in C-terminus of HERG has not been fully characterized. We found a novel nonsense mutation in HERG in a four generation Chinese family with LQTS, the molecular mechanism of the mutation was investigated in vitro. Methods The mutation was constructed by PCR. Whole cell patch clamp studies were conducted in CHO cells by transfecting wild type and /or the mutant R863X HERG. Results In the cell transfected with R863X HERG, no time-dependent current was recorded. Whereas coexpression of wild-type HERG with R863X HERG significantly reduced the amplitude of HERG currents and resulted in currents with altered voltage-dependent inactivation. Conclusions Functional analysis suggests that the single mutation can not form the functional channel, but it can coassemble with the wild-type HERG and change its kinetics. These functional alterations may contribute to a prolongation of QT intervals and arrhythmias.