Contreras Jorge E, Sáez Juan C, Bukauskas Feliksas F, Bennett Michael V L
Department of Neuroscience, Albert Einstein College of Medicine, NY 10461, USA.
Cell Commun Adhes. 2003 Jul-Dec;10(4-6):245-9. doi: 10.1080/cac.10.4-6.245.249.
It has been suggested that the opening of non-junctional connexin 43 (Cx43) hemichannels may play a role in cell physiology, but some workers doubt the reality of hemichannel openings. Here we show data on unitary conductance and voltage gating properties demonstrating that Cx43 hemichannels can open. Membrane depolarization > +60 mV induced single hemichannel currents in HeLa cells expressing Cx43 or Cx43 with enhanced green fluorescent protein attached to the carboxy terminal (Cx43-EGFP). The conductance of single hemichannels was approximately 220 pS, about twice that of the cell-cell channels. Cx43 and Cx43-EGFP hemichannels exhibited slow transitions (>5 ms) between closed and fully open states. Cx43 hemichannels also exhibited fast transitions (<1 ms) between the fully open state and a substate of approximately 75 pS. Similar gating was described for their respective cell-cell channels. No comparable single channel activity was detected in the parental (nontransfected cells) or HeLa cells expressing Cx43 fused at the amino terminal with EGFP (EGFP-Cx43). The latter chimera was inserted into the surface and formed plaques, but did not express functional hemichannels or cell-cell channels. These data convincingly demonstrate the opening of Cx43 hemichannels.
有人提出，非连接性连接蛋白43（Cx43）半通道的开放可能在细胞生理学中发挥作用，但一些研究人员对半通道开放的真实性表示怀疑。在此，我们展示了关于单通道电导和电压门控特性的数据，证明Cx43半通道可以开放。膜去极化> +60 mV可在表达Cx43或羧基末端连接增强型绿色荧光蛋白的Cx43（Cx43-EGFP）的HeLa细胞中诱导单一半通道电流。单一半通道的电导约为220 pS，约为细胞间通道的两倍。Cx43和Cx43-EGFP半通道在关闭状态和完全开放状态之间表现出缓慢转变（>5毫秒）。Cx43半通道在完全开放状态和大约75 pS的亚状态之间也表现出快速转变（<1毫秒）。其各自的细胞间通道也有类似的门控现象。在亲本（未转染细胞）或氨基末端与EGFP融合的Cx43（EGFP-Cx43）表达的HeLa细胞中未检测到类似的单通道活性。后一种嵌合体插入到表面并形成斑块，但不表达功能性半通道或细胞间通道。这些数据令人信服地证明了Cx43半通道的开放。
