KCNE2对Kv4.3通道功能的调节作用

KCNE2 modulates the function of Kv4.3 channel

目的研究KCNE2对人类心肌细胞瞬间外向钾电流的主要α亚基-Kv4.3功能的调节。方法通过基因转染技术将Kv4.3或Kv4.3与KCNE2cDNA转入COS-7细胞株,采用膜片钳全细胞记录方式记录通道电流。结果KCNE2对Kv4.3功能有明显调控作用:减小Kv4.3通道电流密度;Kv4.3单独表达组通道电流密度为375.13±112.87pA/pF(n=11),KCNE2与Kv4.3共表达组电流密度为152.96±33.71pA/pF(n=16);减慢Kv4.3通道激活和衰减,在+60mV电压刺激下通道激活达峰值的时间由4.82±0.32ms(n=11)延长至20.41±2.13ms(n=16),P<0.05;通道电压依赖性失活发生正向移位,半数失活电压由-53.62±1.24mV(n=8)移至-46.58±1.6mV(n=10);通道从失活中恢复的速度加快,恢复时间常数由193.43±17.98ms缩短137.71±18.29ms,(n=7,P<0.05)。结论KCNE2可能作为人类心肌细胞膜Kv4.3钾离子通道一个重要的辅助亚基-β亚基参与Ito通道功能的调节。

Objective To understand the role of KCNE2 in functional regulation of Kv4.3, the major α subunit of transient outward current （Ito） in human heart. Methods The cDNAs of Kv4.3 or Kv4.3 plus KCNE2 were transfected into COS-7 cells and 24-36 h after the transfection, the channel proteins were expressed in the surface membrane of the cells and the channel currents were recorded with patch-clamp technique in whole-cell mode. Results KCNE2 played an important role in modulating the channel function. The recorded current density was decreased in cells co-expressing KCNE2 and Kv4.3 to 152.96±33.71 pA/pF （n=16） as compared with Kv4.3-expressing cells with a mean current density of375.13±112,87 pA/pF （n=11）. At the recording voltage of 60 mV, KCNE2 increased the time to peak （TTP） of the current. TTP in only Kv4. 3-expressing cells was 4.82±0.32 ms （n= 11）, significantly shorter than the TTP of 20.41 ±2.13 ms （n=16） in cells co-expressing Kv4.3 and KCNE2 （P〈0.05）. In the presence of KCNE2, the voltage-dependent inactivation of Kv4,3 showed a positive shift. The voltage of half maximum inactivation （V0s） was decreased significantly from -53.62±1.24 mV （n=8） in Kv4.3 group to -46.58±1.6 mV （n=10） in KCNE2 co-expression group （P〈0.05）. KCNE2 accelerated the recovery of the channel from inactivation, reducing the recovery time constant （r） from 193.43±17.98 ms to 137.71 ±18.29 ms. Conclusion KCNE2 might serve as an important 13 subunit and play a role in the regulation of Ito function in human heart.