The Role of Connexin32 in the Pathogenesis of CMTX

描述(申请人提供)：连接蛋白32(Cx32)属于一个基因 至少有15个成员的家族(在哺乳动物中)，所有这些成员都编码缝隙连接 蛋白质。六个连接蛋白齐聚形成半通道(或连接蛋白)，这 当与相邻膜上的另一个半通道相对时形成通道。 缝隙结允许离子和小分子的扩散，通常是通过 分子质量小于1000Da。单个半通道可以由以下部分组成 不止一个连接蛋白(异型连接蛋白)，以及由 不同的连接蛋白也可以形成通道(异型缝隙连接)。在一个 一系列论文中，我和我的同事们研究了基因突变是如何 人类Cx32基因导致X连锁的夏科-玛丽-图斯病(CMTX)。 这是第二种最常见的遗传性脱髓鞘神经病(CMT 类型1)，这是一个基因异质性群体，总体上是 常见的遗传性神经疾病。我们最先证明了这一点 突变导致CMTX，即Cx32定位于切牙和偏执 (雪旺细胞(SC)髓鞘的区域由 非致密髓鞘)，SC髓鞘含有功能性间隙 交汇点。与这笔赠款特别相关的是，一些突变会导致损失 或者改变运输方式，使突变的蛋白质不会到达 细胞膜。在到达细胞膜的突变体中，有些未能 形成功能性缝隙连接(沟通能力不强)，而其他 善于沟通。我们已经制造出了表达野生型或 两个不同的突变体Cx32等位基因发现这两个突变体的贩运 蛋白质表达水平与转基因细胞相似。其中一个变种人， Arg142Trp对野生型Cx32具有显性-负性效应：不仅 突变蛋白在高尔基体中挂起，它也导致野生型蛋白 在那里也要积累起来。这次竞争性更新的目标如下：(1) 为了确定CMTX突变的影响是否自主于 髓鞘雪旺细胞；(2)确定Cx32突变体如何形成间隙 体外连接阻断髓鞘干细胞的功能；(3)确定 髓鞘SC是否表达其他连接蛋白以及其他连接蛋白是否可以 在髓鞘干细胞中替代Cx32。结果将阐明差距是如何 连接蛋白被组装并在髓鞘SC中发挥作用，提供 关于CMTX分子病理生理学的基本信息，以及 说明其他缝隙连接蛋白的突变如何导致疾病。

DESCRIPTION (provided by the applicant): Connexin 32 (Cx32) belongs to a gene family of at least 15 members (in mammals), all of which encode gap junction proteins. Six connexins oligomerize to form a hemi-channel (or connexon), which forms a channel when apposed to another hemi-channel on an adjacent membrane. Gap junctions allow the diffusion of ions and small molecules, typically with a molecular mass less than 1000 Da. Individual hemichannels can be composed of more than one connexin (heterotypic connexons), and hemichannels composed of different connexins can also form channels (heterotypic gap junctions). In a series of papers, my colleagues and I have investigated how mutations in the human Cx32 gene cause the X-linked form of Charcot-Marie-Tooth disease (CMTX). This is the second most common form of inherited demyelinating neuropathy (CMT type 1), a genetically heterogenous group that collectively is among the most common inherited neurological diseases. We were the first to show that mutations cause CMTX, that Cx32 is localized to incisures and paranodes (regions of the Schwann cell (SC) myelin sheath that are composed on non-compact myelin) and that the SC myelin sheath contains functional gap junctions. Of particular relevance to this grant, some mutations result in loss of the protein, or alter trafficking so that the mutant protein does not reach the cell membrane. Of the mutants that reach the cell membrane, some fail to form functional gap junctions (communication-incompetent), whereas others are communication-competent. We have made transgenic mice that express wild type or two different mutant Cx32 alleles and found that trafficking of the two mutant proteins was similar to that in transfected cells. One of the mutants, Arg142Trp, has a dominant-negative effect on wild type Cx32: not only does the mutant protein "hang up" in the Golgi, it also causes the wild type protein to accumulate there, too. The goals of this competing renewal are as follows: (1) to determine whether the effects of CMTX mutations are autonomous to myelinating Schwann cells; (2) to determine how Cx32 mutants that form gap junctions in vitro disrupt the function of myelinating SC; (3) to determine whether myelinating SC express other connexins and whether other connnexins can substitute for Cx32 in myelinating SC. The results will elucidate how gap junction proteins are assembled and function in myelinating SC, provide fundamental information on the molecular pathophysiology of CMTX, and illuminate how mutations in other gap junction proteins cause disease.