Iglesias Rodolfo, Dahl Gerhard, Qiu Feng, Spray David C, Scemes Eliana
The Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
J Neurosci. 2009 May 27;29(21):7092-7. doi: 10.1523/JNEUROSCI.6062-08.2009.
Purinergic signaling plays distinct and important roles in the CNS, including the transmission of calcium signals between astrocytes. Gap junction hemichannels are among the mechanisms proposed by which astrocytes might release ATP; however, whether the gap junction protein connexin43 (Cx43) forms these "hemichannels" remains controversial. Recently, a new group of proteins, the pannexins, have been shown to form nonselective, high-conductance plasmalemmal channels permeable to ATP, thereby offering an alternative for the hemichannel protein. Here, we provide strong evidence that, in cultured astrocytes, pannexin1 (Panx1) but not Cx43 forms hemichannels. Electrophysiological and fluorescence microscope recordings performed in wild-type and Cx43-null astrocytes did not reveal any differences in hemichannel activity, which was mostly eliminated by treating Cx43-null astrocytes with Panx1-short interfering RNA [Panx1-knockdown (Panx1-KD)]. Moreover, quantification of the amount of ATP released from wild-type, Cx43-null, and Panx1-KD astrocytes indicates that downregulation of Panx1, but not of Cx43, prevented ATP release from these cells.
嘌呤能信号传导在中枢神经系统中发挥着独特而重要的作用，包括在星形胶质细胞之间传递钙信号。间隙连接半通道是星形胶质细胞可能释放ATP的机制之一；然而，间隙连接蛋白连接蛋白43（Cx43）是否形成这些“半通道”仍存在争议。最近，一组新的蛋白质，即泛连接蛋白，已被证明可形成对ATP通透的非选择性、高电导质膜通道，从而为半通道蛋白提供了一种替代物。在此，我们提供了强有力的证据表明，在培养的星形胶质细胞中，是泛连接蛋白1（Panx1）而非Cx43形成半通道。在野生型和Cx43基因敲除的星形胶质细胞中进行的电生理和荧光显微镜记录未显示半通道活性有任何差异，而用Panx1短发夹RNA [Panx1敲低（Panx1-KD）]处理Cx43基因敲除的星形胶质细胞后，半通道活性大多被消除。此外，对野生型、Cx43基因敲除型和Panx1-KD星形胶质细胞释放的ATP量进行定量分析表明，Panx1的下调而非Cx43的下调可阻止这些细胞释放ATP。
