Modulation of Cx46 hemichannels by nitric oxide.
Modulation of Cx46 hemichannels by nitric oxide.
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DOI：
10.1152/ajpcell.00054.2009
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发表时间：
2009-06
期刊：
影响因子：
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通讯作者：
M. Retamal;Shengyong Yin;G. Altenberg;L. Reuss
中科院分区：
文献类型：
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作者：
M. Retamal;Shengyong Yin;G. Altenberg;L. Reuss
间隙连接半通道由六个蛋白质亚基（连接蛋白）组成。未对接的半通道有助于生理性自分泌/旁分泌细胞信号传导，包括信号传导分子的释放、细胞体积调节和葡萄糖摄取。此外，半通道可通过去磷酸化和细胞膜去极化而病理性激活。这样的半通道打开可以诱导和/或加速细胞死亡。已经表明连接蛋白43（Cx43）半通道对氧化还原电位变化敏感，并且一个或多个细胞内半胱氨酸对于该过程是重要的。Cx46在透镜中表达，其功能障碍诱导白内障形成。它在细胞外环中含有六个半胱氨酸，一个在第四跨膜螺旋中，两个在COOH末端结构域中。后者可能易受一氧化氮（NO）的氧化，这可能通过半胱氨酸S-亚硝基化参与白内障的形成。在这里，我们报告的NO供体S-亚硝基谷胱甘肽（GSNO）的电特性和荧光染料的渗透性野生型Cx46和突变体半通道表达非洲爪蟾卵母细胞的影响的研究。GSNO增强了Cx46和Cx46-CT 43（Cx46突变体，其中Cx43的COOH末端被替换）的半通道电压敏感性，增加了尾电流幅度，并改变了Cx46和Cx46-CT 43的激活和关闭动力学，但在Cx46-C3 A（Cx46，其中细胞内和跨膜螺旋4半胱氨酸突变为丙氨酸）中没有。我们的结论是，Cx46半通道是敏感的NO和NO的影响是由一个或多个细胞内半胱氨酸的修改介导的。然而，由于半通道激活，NO不太可能诱导白内障形成，因为在正常静息电位下，NO对Cx46半通道通透性没有重大影响。
Gap-junction hemichannels are composed of six protein subunits (connexins). Undocked hemichannels contribute to physiological autocrine/paracrine cell signaling, including release of signaling molecules, cell-volume regulation, and glucose uptake. In addition, hemichannels may be pathologically activated by dephosphorylation and cell-membrane depolarization. Such hemichannel opening may induce and/or accelerate cell death. It has been suggested that connexin43 (Cx43) hemichannels are sensitive to redox potential changes and that one or more intracellular cysteines is/are important for this process. Cx46 is expressed in the lens, and its dysfunction induces cataract formation. It contains six cysteines in the extracellular loops, one in the fourth transmembrane helix, and two in the COOH-terminal domain. The latter may be susceptible to oxidation by nitric oxide (NO), which could be involved in cataract formation through cysteine S-nitrosylation. Here we report studies of the effects of the NO donor S-nitrosoglutathione (GSNO) on the electrical properties and fluorescent-dye permeability of wild-type Cx46 and mutant hemichannels expressed in Xenopus laevis oocytes. GSNO enhanced hemichannel voltage sensitivity, increased tail-current amplitude, and changed activation and closing kinetics in Cx46 and Cx46-CT43 (Cx46 mutant in which the COOH terminus was replaced with that of Cx43), but not in Cx46-C3A (Cx46 in which the intracellular and transmembrane helix 4 cysteines were mutated to alanine). We conclude that Cx46 hemichannels are sensitive to NO and that the NO effects are mediated by modification of one or more intracellular cysteines. However, it is unlikely that NO induces cataract formation due to the hemichannel activation, because at normal resting potential, NO had no major effects on Cx46 hemichannel permeability.