Stout Charles E, Costantin James L, Naus Christian C G, Charles Andrew C
Loma Linda University School of Medicine, Loma Linda, California 92350, USA.
J Biol Chem. 2002 Mar 22;277(12):10482-8. doi: 10.1074/jbc.M109902200. Epub 2002 Jan 14.
Astrocytes are capable of widespread intercellular communication via propagated increases in intracellular Ca(2+) concentration. We have used patch clamp, dye flux, ATP assay, and Ca(2+) imaging techniques to show that one mechanism for this intercellular Ca(2+) signaling in astrocytes is the release of ATP through connexin channels ("hemichannels") in individual cells. Astrocytes showed low Ca(2+)-activated whole-cell currents consistent with connexin hemichannel currents that were inhibited by the connexin channel inhibitor flufenamic acid (FFA). Astrocytes also showed molecular weight-specific influx and release of dyes, consistent with flux through connexin hemichannels. Transmembrane dye flux evoked by mechanical stimulation was potentiated by low Ca(2+) and was inhibited by FFA and Gd(3+). Mechanical stimulation also evoked release of ATP that was potentiated by low Ca(2+) and inhibited by FFA and Gd(3+). Similar whole-cell currents, transmembrane dye flux, and ATP release were observed in C6 glioma cells expressing connexin43 but were not observed in parent C6 cells. The connexin hemichannel activator quinine evoked ATP release and Ca(2+) signaling in astrocytes and in C6 cells expressing connexin43. The propagation of intercellular Ca(2+) waves in astrocytes was also potentiated by quinine and inhibited by FFA and Gd(3+). Release of ATP through connexin hemichannels represents a novel signaling pathway for intercellular communication in astrocytes and other non-excitable cells.
星形胶质细胞能够通过细胞内钙离子（Ca(2+)）浓度的传播性增加进行广泛的细胞间通讯。我们运用膜片钳、染料通量、ATP检测以及Ca(2+)成像技术，证明星形胶质细胞中这种细胞间Ca(2+)信号传导的一种机制是通过单个细胞中的连接蛋白通道（“半通道”）释放ATP。星形胶质细胞表现出低Ca(2+)激活的全细胞电流，这与连接蛋白半通道电流一致，且该电流被连接蛋白通道抑制剂氟芬那酸（FFA）所抑制。星形胶质细胞还表现出分子量特异性的染料流入和释放，这与通过连接蛋白半通道的通量一致。机械刺激引起的跨膜染料通量在低Ca(2+)条件下增强，并被FFA和Gd(3+)抑制。机械刺激还引发了ATP的释放，该释放也在低Ca(2+)条件下增强，并被FFA和Gd(3+)抑制。在表达连接蛋白43的C6胶质瘤细胞中观察到了类似的全细胞电流、跨膜染料通量和ATP释放，但在亲本C6细胞中未观察到。连接蛋白半通道激活剂奎宁在星形胶质细胞和表达连接蛋白43的C6细胞中引发了ATP释放和Ca(2+)信号传导。奎宁还增强了星形胶质细胞中细胞间Ca(2+)波的传播，并被FFA和Gd(3+)抑制。通过连接蛋白半通道释放ATP代表了星形胶质细胞和其他非兴奋性细胞中细胞间通讯的一种新的信号通路。
