Institute of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland.
Pharmacol Res. 2012 May;65(5):546-52. doi: 10.1016/j.phrs.2012.02.002. Epub 2012 Feb 21.
Connexin mimetic peptides corresponding to short conserved extracellular loop sequences of connexins have been used widely as reversible inhibitors of gap junctional intercellular communication. These peptides also block movement of ATP and Ca(2+) across connexin hemichannels, i.e. hexameric channels yet to dock with partners in aligned cells and to generate the gap junction cell-cell conduit. By means of electrophysiology, we compared the effects of Gap26, a mimetic peptide corresponding to a short linear sequence in the first extracellular loop of connexin43, on connexin channel function in HeLa cells expressing connexin43. We demonstrate that Gap26 inhibited electrical coupling in cell pairs mediated by gap junctions after exposure for 30min. In contrast, Gap26 applied to single cells, inhibited hemichannel currents evoked in low Ca(2+) solution with a response time of less than 5min. The results further support the view that the likely primary and direct inhibitory effect of Gap26 is on connexin hemichannels, with gap junctions becoming inhibited later. The mechanism of action of Gap26 in blocking hemichannels and gap junction channels is discussed in the context of their different functions and locations.
连接蛋白模拟肽对应连接蛋白短保守细胞外环序列已被广泛用作缝隙连接细胞间通讯的可逆抑制剂。这些肽还阻断了 ATP 和 Ca(2+) 通过连接蛋白半通道的运动，即尚未与对齐细胞中的伴侣对接并产生缝隙连接细胞-细胞通道的六聚体通道。通过电生理学，我们比较了 Gap26 的作用，Gap26 是对应连接蛋白 43 第一细胞外环短线性序列的模拟肽，在表达连接蛋白 43 的 HeLa 细胞中对连接蛋白通道功能的影响。我们证明 Gap26 在 30 分钟暴露后抑制了由缝隙连接介导的细胞对之间的电偶联。相比之下，应用于单个细胞的 Gap26 抑制了低 Ca(2+)溶液中半通道电流的激发，其反应时间小于 5 分钟。结果进一步支持这样的观点，即 Gap26 的可能主要和直接抑制作用是在连接蛋白半通道上，随后才抑制缝隙连接。在讨论 Gap26 在阻断半通道和缝隙连接通道中的作用机制时，考虑了它们不同的功能和位置。
