Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA; Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA.
Department of Chemistry, Indiana University, Bloomington, Indiana, USA.
J Biol Chem. 2021 Jan-Jun;296:100423. doi: 10.1016/j.jbc.2021.100423. Epub 2021 Feb 16.
Gain-of-function (GOF) mutations in the voltage-gated potassium channel subfamily Q member 1 (KCNQ1) can induce cardiac arrhythmia. In this study, it was tested whether any of the known human GOF disease mutations in KCNQ1 act by increasing the amount of KCNQ1 that reaches the cell surface-"supertrafficking." Seven of the 15 GOF mutants tested were seen to surface traffic more efficiently than the WT channel. Among these, we found that the levels of R231C KCNQ1 in the plasma membrane were fivefold higher than the WT channel. This was shown to arise from the combined effects of enhanced efficiency of translocon-mediated membrane integration of the S4 voltage-sensor helix and from enhanced post-translational folding/trafficking related to the energetic linkage of C231 with the V129 and F166 side chains. Whole-cell electrophysiology recordings confirmed that R231C KCNQ1 in complex with the voltage-gated potassium channel-regulatory subfamily E member 1 not only exhibited constitutive conductance but also revealed that the single-channel activity of this mutant is only 20% that of WT. The GOF phenotype associated with R231C therefore reflects the effects of supertrafficking and constitutive channel activation, which together offset reduced channel activity. These investigations show that membrane protein supertrafficking can contribute to human disease.
电压门控钾通道亚家族 Q 成员 1（KCNQ1）中的功能获得性（GOF）突变可诱导心律失常。在这项研究中，测试了 KCNQ1 中的任何已知人类 GOF 疾病突变是否通过增加到达细胞表面的 KCNQ1 量而起作用——“超运输”。在测试的 15 个 GOF 突变体中，有 7 个显示出比 WT 通道更高的表面运输效率。在这些突变体中，我们发现 R231C KCNQ1 的质膜水平比 WT 通道高五倍。这是由于 S4 电压传感器螺旋的易位介导的膜整合效率提高以及与 C231 与 V129 和 F166 侧链的能量连接相关的翻译后折叠/运输增强的综合作用所致。全细胞电生理学记录证实，与电压门控钾通道调节亚家族 E 成员 1 形成复合物的 R231C KCNQ1 不仅表现出组成型电导，而且还表明该突变体的单通道活性仅为 WT 的 20%。因此，与 R231C 相关的 GOF 表型反映了超运输和组成型通道激活的影响，这两者共同抵消了通道活性的降低。这些研究表明，膜蛋白的超运输可能导致人类疾病。
