Liu Nan, Liu Yuxia, Yang Yaxiong, Liu Xiaodong
a Department of Biomedical Engineering , School of Medicine, Tsinghua University , Beijing , China.
b School of Life Sciences, Tsinghua University , Beijing , China.
Channels (Austin). 2017 Jan 2;11(1):34-45. doi: 10.1080/19336950.2016.1207023. Epub 2016 Jun 30.
Extracellular S3-S4 linkers of domain IV (IVS3-S4) of L-type Ca channels (Ca1) are subject to alternative splicing, resulting into distinct gating profiles serving for diverse physiological roles. However, it has remained elusive what would be the determining factor of IVS3-S4 effects on Ca1 channels. In this study, we systematically compared IVS3-S4 variants from Ca1.1-1.4, and discover that the flexibility of the linker plays a prominent role in gating characteristics. Chimeric analysis and mutagenesis demonstrated that changes in half activation voltage (V) or activation time constant (τ) are positively correlated with the numbers of flexible glycine residues within the linker. Moreover, antibodies that reduce IVS3-S4 flexibility negatively shifted V, emerging as a new category of Ca1 enhancers. In summary, our results suggest that the flexibility or rigidity of IVS3-S4 linker underlies its modulations on Ca1 activation (V and τ), paving the way to dissect the core mechanisms and to develop innovative perturbations pertaining to voltage-sensing S4 and its vicinities.
L型钙通道（Ca1）结构域IV的细胞外S3-S4连接区（IVS3-S4）存在可变剪接，产生不同的门控特征，以发挥多种生理作用。然而，IVS3-S4对Ca1通道影响的决定因素仍不清楚。在本研究中，我们系统比较了Ca1.1 - 1.4的IVS3-S4变体，发现连接区的柔韧性在门控特性中起重要作用。嵌合分析和诱变表明，半激活电压（V）或激活时间常数（τ）的变化与连接区内柔性甘氨酸残基的数量呈正相关。此外，降低IVS3-S4柔韧性的抗体使V负向偏移，成为一类新的Ca1增强剂。总之，我们的结果表明IVS3-S4连接区的柔韧性或刚性是其对Ca1激活（V和τ）进行调节的基础，为剖析核心机制和开发与电压感应S4及其附近区域相关的创新干扰方法铺平了道路。
