Wu Dong-Mei, Lai Ling-Ping, Zhang Mei, Wang Hui-Liang, Jiang Min, Liu Xian-Sheng, Tseng Gea-Ny
Department of Physiology, Virginia Commonwealth University, Richmond, 23298, USA.
Heart Rhythm. 2006 Sep;3(9):1031-40. doi: 10.1016/j.hrthm.2006.05.022. Epub 2006 May 25.
Y81C is a new long QT-5 (LQT5)-related KCNE1 mutation, which is located in the post-transmembrane domain (post-TMD) region in close proximity to three other LQT5 mutations (S74L, D76N, and W87R).
We examine the effects of Y81C on the function and drug sensitivity of the slow delayed rectifier channel (I(Ks)) formed by KCNE1 with pore-forming KCNQ1 subunits. We also infer a structural basis for the detrimental effects of Y81C on I(Ks) function.
Wild-type (WT) and mutant (harboring Y81C) I(Ks) channels are expressed in oocytes or COS-7 cells. Channel function and KCNQ1 protein expression/subcellular distribution are studied by techniques of electrophysiology, biochemistry, and immunocytochemistry. Ab initio structure predictions of KCNE1 cytoplasmic domain are performed by the Robetta server.
Relative to WT KCNE1, Y81C reduces I(Ks) current amplitude and shifts the voltage range of activation to a more positive range. Y81C does not reduce whole-cell KCNQ1 protein level or interfere with KCNQ1 trafficking to cell surface. Thus, its effects are mediated by altered KCNQ1/KCNE1 interactions in cell surface channels. Importantly, Y81C potentiates the effects of an I(Ks) activator. Preserving the aromatic or hydroxyl side chain at position 81 (Y81F or Y81T) does not prevent the detrimental effects of Y81C. Structure predictions suggest that the post-TMD region of KCNE1 may adopt a helical secondary structure.
We propose that the post-TMD region of KCNE1 interacts with the KCNQ1 channel to modulate I(Ks) current amplitude and gating kinetics. Other LQT5 mutations in this region share the Y81C phenotype and probably affect the I(Ks) channel function by a similar mechanism.
Y81C是一种新的与长QT-5（LQT5）相关的KCNE1突变，它位于跨膜后结构域（post-TMD）区域，与其他三个LQT5突变（S74L、D76N和W87R）位置相近。
我们研究Y81C对由KCNE1与成孔KCNQ1亚基形成的缓慢延迟整流通道（I(Ks)）的功能和药物敏感性的影响。我们还推断Y81C对I(Ks)功能产生有害影响的结构基础。
野生型（WT）和携带Y81C的突变型I(Ks)通道在卵母细胞或COS-7细胞中表达。通过电生理学、生物化学和免疫细胞化学技术研究通道功能以及KCNQ1蛋白表达/亚细胞分布。利用Robetta服务器对KCNE1胞质结构域进行从头结构预测。
相对于野生型KCNE1，Y81C降低I(Ks)电流幅度，并将激活电压范围向更正的范围移动。Y81C不会降低全细胞KCNQ1蛋白水平，也不会干扰KCNQ1转运到细胞表面。因此，其作用是由细胞表面通道中KCNQ1/KCNE1相互作用的改变介导的。重要的是，Y81C增强了I(Ks)激活剂的作用。在第81位保留芳香族或羟基侧链（Y81F或Y81T）并不能阻止Y81C的有害影响。结构预测表明，KCNE1的post-TMD区域可能采用螺旋二级结构。
我们提出，KCNE1的post-TMD区域与KCNQ1通道相互作用，以调节I(Ks)电流幅度和门控动力学。该区域的其他LQT5突变具有与Y81C相似的表型，可能通过类似机制影响I(Ks)通道功能。
