Bortolozzi Mario
Department of Physics and Astronomy G. Galilei, University of Padua, Padua, Italy.
Venetian Institute of Molecular Medicine (VIMM), Padua, Italy.
Front Mol Neurosci. 2018 Jul 10;11:227. doi: 10.3389/fnmol.2018.00227. eCollection 2018.
Connexin 32 (Cx32) is a fundamental protein in the peripheral nervous system (PNS) as its mutations cause the X-linked form of Charcot-Marie-Tooth disease (CMT1X), the second most common form of hereditary motor and sensory neuropathy and a demyelinating disease for which there is no effective therapy. Since mutations of the gene encoding Cx32 were first reported in 1993, over 450 different mutations associated with CMT1X including missense, frameshift, deletion and non-sense ones have been identified. Despite the availability of a sizable number of studies focusing on normal and mutated Cx32 channel properties, the crucial role played by Cx32 in the PNS has not yet been elucidated, as well as the molecular pathogenesis of CMT1X. Is Cx32 fundamental during a particular phase of Schwann cell (SC) life? Are Cx32 paired (gap junction, GJ) channels in myelinated SCs important for peripheral nerve homeostasis? The attractive hypothesis that short coupling of adjacent myelin layers by Cx32 GJs is required for efficient diffusion of K and signaling molecules is still debated, while a growing body of evidence is supporting other possible functions of Cx32 in the PNS, mainly related to Cx32 unpaired channels (hemichannels), which could be involved in a purinergic-dependent pathway controlling myelination. Here we review the intriguing puzzle of findings about Cx32 function and dysfunction, discussing possible directions for future investigation.
连接蛋白32(Cx32)是周围神经系统(PNS)中的一种重要蛋白质,因为其突变会导致X连锁型夏科-马里-图斯病(CMT1X),这是遗传性运动和感觉神经病的第二常见类型,也是一种尚无有效治疗方法的脱髓鞘疾病。自1993年首次报道编码Cx32的基因突变以来,已鉴定出超过450种与CMT1X相关的不同突变,包括错义突变、移码突变、缺失突变和无义突变。尽管有大量研究关注正常和突变的Cx32通道特性,但Cx32在PNS中所起的关键作用以及CMT1X的分子发病机制尚未阐明。Cx32在雪旺细胞(SC)生命的特定阶段是否至关重要?有髓SC中的Cx32配对(间隙连接,GJ)通道对周围神经稳态是否重要?关于相邻髓鞘层通过Cx32 GJs进行短耦合对于K和信号分子的有效扩散是必需的这一引人注目的假设仍存在争议,而越来越多的证据支持Cx32在PNS中的其他可能功能,主要与Cx32未配对通道(半通道)有关,其可能参与控制髓鞘形成的嘌呤能依赖性途径。在这里,我们回顾了关于Cx32功能和功能障碍的有趣研究谜团,并讨论了未来研究的可能方向。