Gap junctions (GJ)s are formed by the assembly of constituent transmembrane proteins called connexins (Cxs). Aberrations in this assembly of Cxs are observed in several genetic diseases as well as in cancers. Hence it becomes imperative to understand the molecular mechanisms underlying such assembly defect. The polarized cells in the epithelia express Connexin32 (Cx32). The carboxyl-terminal tail (CT) of Cx32 orchestrates several aspects of GJ dynamics, function and growth. The study here was aimed at determining if post-translational modifications, specifically, palmitoylation of cysteine residues, present in the CT of Cx32, has any effect on GJ assembly. The CT of Cx32 was found to harbor three cysteine residues, which are likely to be modified by palmitoylation. The study here has revealed for the first time that Cx32 is palmitoylated at cysteine 217 (C217). However, it was found that mutating C217 to alanine affected neither the trafficking nor the ability of Cx32 to assemble into GJs. Intriguingly, it was discovered that mutating cysteine 280 and 283 in combination, blocked the transport of Cx32 from the Golgi to the cell surface. Overall, the findings reveal the importance of the two terminal cysteine residues of Cx32 in regulating its trafficking and stability and hence is ability to assemble into GJs, possibly as being part of a CAAX motif in its CT.

中文翻译：

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连接蛋白32 C末端尾半胱氨酸残基调节其运输

间隙连接（GJ）由称为连接蛋白（Cxs）的跨膜蛋白组成。在几种遗传疾病以及癌症中都观察到了这种Cxs组装的异常。因此，必须了解这种组装缺陷的分子机制。上皮细胞中的极化细胞表达连接蛋白32（Cx32）。Cx32的羧基末端尾巴（CT）协调了GJ动力学，功能和生长的几个方面。此处的研究旨在确定Cx32 CT中存在的翻译后修饰，特别是半胱氨酸残基的棕榈酰化是否对GJ组装有影响。发现Cx32的CT包含三个半胱氨酸残基，很可能被棕榈酰化修饰。此处的研究首次揭示了Cx32在半胱氨酸217（C217）处被棕榈酰化。但是，发现将C217突变为丙氨酸既不会影响运输，也不会影响Cx32组装成GJ的能力。有趣的是，发现结合突变半胱氨酸280和283可以阻止Cx32从高尔基体到细胞表面的转运。总的来说，这些发现揭示了Cx32的两个末端半胱氨酸残基在调节其运输和稳定性方面的重要性，因此具有组装成GJ的能力，可能是其CT的CAAX基序的一部分。阻止了Cx32从高尔基体到细胞表面的运输。总的来说，这些发现揭示了Cx32的两个末端半胱氨酸残基在调节其运输和稳定性方面的重要性，因此具有组装成GJ的能力，可能是其CT的CAAX基序的一部分。阻止了Cx32从高尔基体到细胞表面的运输。总的来说，这些发现揭示了Cx32的两个末端半胱氨酸残基在调节其运输和稳定性方面的重要性，因此具有组装成GJ的能力，可能是其CT的CAAX基序的一部分。