Altered conductance and permeability of Cx40 mutations associated with atrial fibrillation.
Altered conductance and permeability of Cx40 mutations associated with atrial fibrillation.
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DOI：
10.1085/jgp.201511475
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发表时间：
2015-11
期刊：
影响因子：
--
通讯作者：
Valiunas V
中科院分区：
文献类型：
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作者：
Santa Cruz A;Meşe G;Valiuniene L;Brink PR;White TW;Valiunas V
突变型心房连接蛋白的通透性和电导的改变可能导致折返性心律失常。缝隙连接确保动作电位在整个心肌中快速传播。连接蛋白40的三种突变形式（Cx40; A96 S、M163 V和G38 D）是心房缝隙连接通道的主要组分，与心房颤动相关并保留形成功能通道的能力。我们确定了这些突变的间隙连接在瞬时转染的HeLa和N2 A细胞的生物物理特性。所有三个突变体显示宏观交界电导在0.5至40 nS的范围内，和电压依赖性的野生型（WT）Cx40。然而，G38 D通道的单位电导比WT Cx 40通道的单位电导高1.6倍（1.220 pS对1.135 pS），而A96 S和M163 V突变体的单位电导与WT Cx 40的单位电导相似。此外，与WT Cx 40相比，M163 V和G38 D通道对阴离子染料荧光黄（LY）的渗透性相对于K+（LY/K+）高约2倍和约5倍，而A96 S LY转移与WT相似（G38 D> M163 V> A96 S LY转移Cx 40 WT）。相比之下，G38 D通道几乎不渗透阳离子溴化乙锭（EtBr），表明G38 D改变通道选择性。相反，A96 S和M163 V通道显示相对于WT Cx40增强的EtBr渗透性，具有以下渗透性顺序：M163 V> A96 S> Cx40 WT> G38 D。突变通道的导电性和渗透性的改变表明Cx40介导的生化和电耦合在心脏组织中的重要作用。三个单碱基替换突变体的改变的性质可能在折返性心律失常的机制中发挥作用。
Alterations in the permeability and conductance of mutant atrial connexins may contribute to reentry arrhythmias. Gap junctions ensure the rapid propagation of the action potential throughout the myocardium. Three mutant forms of connexin40 (Cx40; A96S, M163V, and G38D), the primary component of the atrial gap junction channel, are associated with atrial fibrillation and retain the ability to form functional channels. We determined the biophysical properties of these mutant gap junctions in transiently transfected HeLa and N2A cells. All three mutants showed macroscopic junctional conductances over the range of 0.5 to 40 nS, and voltage dependences comparable to those of wild-type (WT) Cx40. However, the unitary conductance of G38D channels was ∼1.6-fold higher than that of WT Cx40 channels (∼220 vs. ∼135 pS), whereas the unitary conductances of the A96S and M163V mutants were similar to that of WT Cx40. Furthermore, the M163V and G38D channels exhibited approximately two- and approximately fivefold higher permeability to the anionic dye Lucifer yellow (LY) relative to K+ (LY/K+) compared with that of WT Cx40, whereas A96S LY transfer was similar to that of WT (G38D > M163V > A96S ≈ Cx40WT). In contrast, G38D channels were almost impermeable to cationic ethidium bromide (EtBr), suggesting that G38D alters channel selectivity. Conversely, A96S and M163V channels showed enhanced EtBr permeability relative to WT Cx40, with the following permeability order: M163V > A96S > Cx40WT > G38D. Altered conductive and permeability properties of mutant channels suggest an essential role for Cx40-mediated biochemical and electrical coupling in cardiac tissues. The altered properties of the three single-base substitution mutants may play a role in mechanisms of reentry arrhythmias.