Press Eric R, Shao Qing, Kelly John J, Chin Katrina, Alaga Anton, Laird Dale W
Physiology and Pharmacology, University of Western Ontario, London, Ontario N6A 5C1, Canada.
From the Departments of Anatomy and Cell Biology and.
J Biol Chem. 2017 Jun 9;292(23):9721-9732. doi: 10.1074/jbc.M116.770917. Epub 2017 Apr 20.
Connexin26 (Cx26) is a gap junction protein that oligomerizes in the cell to form hexameric transmembrane channels called connexons. Cell surface connexons dock between adjacent cells to allow for gap junctional intercellular communication. Numerous autosomal dominant mutations in the Cx26-encoding gene lead to many skin disorders and sensorineural hearing loss. Although some insights have been gained into the pathogenesis of these diseases, it is not fully understood how distinct mutations result in hearing loss alone or in skin pathologies with comorbid hearing loss. Here we investigated five autosomal dominant Cx26 mutants (N14K, D50N, N54K, M163V, and S183F) linked to various syndromic or nonsyndromic diseases to uncover the molecular mechanisms underpinning these disease links. We demonstrated that when gap junction-deficient HeLa cells expressed the N14K and D50N mutants, they undergo cell death. The N54K mutant was retained primarily within intracellular compartments and displayed dominant or transdominant properties on wild-type Cx26 and coexpressed Cx30 and Cx43. The S183F mutant formed some gap junction plaques but was largely retained within the cell and exhibited only a mild transdominant reduction in gap junction communication when co-expressed with Cx30. The M163V mutant, which causes only hearing loss, exhibited impaired gap junction function and showed no transdominant interactions. These findings suggest that Cx26 mutants that promote cell death or exert transdominant effects on other connexins in keratinocytes will lead to skin diseases and hearing loss, whereas mutants having reduced channel function but exhibiting no aberrant effects on coexpressed connexins cause only hearing loss. Moreover, cell death-inducing mutations lead to more severe syndromic disease.
连接蛋白26（Cx26）是一种间隙连接蛋白，在细胞内寡聚形成称为连接子的六聚体跨膜通道。细胞表面的连接子在相邻细胞之间对接，以实现间隙连接介导的细胞间通讯。编码Cx26的基因中存在许多常染色体显性突变，可导致多种皮肤疾病和感音神经性听力损失。尽管对这些疾病的发病机制已有一些了解，但尚不完全清楚不同的突变如何单独导致听力损失，或导致伴有听力损失的皮肤病变。在此，我们研究了与各种综合征性或非综合征性疾病相关的5种常染色体显性Cx26突变体（N14K、D50N、N54K、M163V和S183F），以揭示这些疾病关联背后的分子机制。我们证明，当缺乏间隙连接的HeLa细胞表达N14K和D50N突变体时，它们会发生细胞死亡。N54K突变体主要保留在细胞内区室中，并对野生型Cx26以及共表达的Cx30和Cx43表现出显性或反式显性特性。S183F突变体形成了一些间隙连接斑，但大部分保留在细胞内，与Cx30共表达时，在间隙连接通讯中仅表现出轻微的反式显性降低。仅导致听力损失的M163V突变体表现出间隙连接功能受损，且未显示反式显性相互作用。这些发现表明，促进细胞死亡或对角质形成细胞中的其他连接蛋白发挥反式显性作用的Cx26突变体将导致皮肤疾病和听力损失，而通道功能降低但对共表达的连接蛋白无异常影响的突变体仅导致听力损失。此外，诱导细胞死亡的突变会导致更严重的综合征性疾病。
