Sun Yiguo, Hills Matthew D, Ye Willy G, Tong Xiaoling, Bai Donglin
Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada.
PLoS One. 2014 Apr 14;9(4):e95125. doi: 10.1371/journal.pone.0095125. eCollection 2014.
Mutations in GJA5 encoding the gap junction protein connexin40 (Cx40) have been linked to lone atrial fibrillation. Some of these mutants result in impaired gap junction function due to either abnormal connexin localization or impaired gap junction channels, which may play a role in promoting atrial fibrillation. However, the effects of the atrial fibrillation-linked Cx40 mutants on hemichannel function have not been studied. Here we investigated two atrial fibrillation-linked germline Cx40 mutants, V85I and L221I. These two mutants formed putative gap junction plaques at cell-cell interfaces, with similar gap junction coupling conductance as that of wild-type Cx40. Connexin deficient HeLa cells expressing either one of these two mutants displayed prominent propidium iodide-uptake distinct from cells expressing wild-type Cx40 or other atrial fibrillation-linked Cx40 mutants, I75F, L229M, and Q49X. Propidium iodide-uptake was sensitive to [Ca2+]o and the hemichannel blockers, carbenoxolone, flufenamic acid and mefloquine, but was not affected by the pannexin 1 channel blocking agent, probenecid, indicating that uptake is most likely mediated via connexin hemichannels. A gain-of-hemichannel function in these two atrial fibrillation-linked Cx40 mutants may provide a novel mechanism underlying the etiology of atrial fibrillation.
编码间隙连接蛋白连接蛋白40（Cx40）的GJA5基因突变与孤立性心房颤动有关。其中一些突变体由于连接蛋白定位异常或间隙连接通道受损而导致间隙连接功能受损，这可能在促进心房颤动中起作用。然而，与心房颤动相关的Cx40突变体对半通道功能的影响尚未得到研究。在这里，我们研究了两种与心房颤动相关的种系Cx40突变体，V85I和L221I。这两种突变体在细胞间界面形成了假定的间隙连接斑块，其间隙连接耦合电导与野生型Cx40相似。表达这两种突变体之一的连接蛋白缺陷型HeLa细胞表现出明显的碘化丙啶摄取，这与表达野生型Cx40或其他与心房颤动相关的Cx40突变体I75F、L229M和Q49X的细胞不同。碘化丙啶摄取对细胞外[Ca2+]和半通道阻滞剂羧苄青霉素、氟芬那酸和甲氟喹敏感，但不受泛连接蛋白1通道阻断剂丙磺舒的影响，表明摄取最有可能通过连接蛋白半通道介导。这两种与心房颤动相关的Cx40突变体的半通道功能增强可能为心房颤动的病因提供一种新机制。
