Connexin 46 and connexin 50 gap junction channel properties are shaped by structural and dynamic features of their N-terminal domains.
Connexin 46 and connexin 50 gap junction channel properties are shaped by structural and dynamic features of their N-terminal domains.
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DOI：
10.1113/jp281339
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发表时间：
2021-07
期刊：
影响因子：
--
通讯作者：
Bai D
中科院分区：
文献类型：
--
作者：
Yue B;Haddad BG;Khan U;Chen H;Atalla M;Zhang Z;Zuckerman DM;Reichow SL;Bai D
连接蛋白形成细胞间通讯通道，称为间隙连接（GJ），促进各种生理作用，从长距离电和化学耦合到协调发育和营养交换。由不同的连接蛋白亚型形成的GJ具有独特的通道特性，其机制尚未完全确定。最近的结构研究Cx46和Cx 50定义了一种新的和稳定的开放状态，并牵连的氨基末端（NT）域的主要贡献者之间的异构体特异性功能差异密切相关的透镜连接蛋白。为了更好地理解这些差异，我们构建了对应于野生型Cx 50和Cx46 GJ、NT结构域交换嵌合体和第9个残基的点变体的模型，用于比较MD模拟和电生理学研究。所有构建体形成功能性GJ通道，除了嵌合Cx46- 50 NT变体，其与通过MD模拟观察到的NT结构域的引入的空间冲突和增加的动力学行为（不稳定性）相关。单通道电导与MD预测的自由能景观相关，但结果令人惊讶地更大程度的影响。此外，我们观察到对由设计的NT结构域变体诱导的跨连接电压依赖性门控（Vj-门控）和/或开放状态停留时间的显著影响。总之，这些研究表明，涉及Cx46和Cx 50的NT结构域内的疏水和带电残基的亚基内和亚基间相互作用在定义GJ开放状态稳定性和单通道电导中起重要作用，建立开放状态的Cx46/50结构模型，作为结构-功能研究的原型，旨在阐明GJ通道机制和白内障的分子基础。连接蛋白变体。
Connexins form intercellular communication channels, known as gap junctions (GJs), that facilitate diverse physiological roles, from long-range electrical and chemical coupling to coordinating development and nutrient exchange. GJs formed by different connexin isoforms harbor unique channel properties that have not been fully defined mechanistically. Recent structural studies on Cx46 and Cx50 defined a novel and stable open state and implicated the amino-terminal (NT) domain as major contributor for isoform-specific functional differences between these closely related lens connexins. To better understand these differences, we constructed models corresponding to wildtype Cx50 and Cx46 GJs, NT domain swapped chimeras, and point variants at the 9th residue for comparative MD simulation and electrophysiology studies. All constructs formed functional GJ channels, except the chimeric Cx46-50NT variant, which correlated with an introduced steric clash and increased dynamical behavior (instability) of the NT domain observed by MD simulation. Single channel conductance correlated well with free-energy landscapes predicted by MD, but resulted in a surprisingly greater degree of effect. Additionally, we observed significant effects on transjunctional voltage-dependent gating (Vj-gating) and/or open state dwell times induced by the designed NT domain variants. Together, these studies indicate intra- and inter-subunit interactions involving both hydrophobic and charged residues within the NT domains of Cx46 and Cx50 play important roles in defining GJ open state stability and single channel conductance, and establish the open state Cx46/50 structural models as archetypes for structure-function studies targeted at elucidating GJ channel mechanism and the molecular basis of cataract-linked connexin variants.