Gap junctional hemichannel-mediated ATP release and hearing controls in the inner ear
Gap junctional hemichannel-mediated ATP release and hearing controls in the inner ear
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DOI：
10.1073/pnas.0506481102
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发表时间：
2005-12-20
影响因子：
11.1
通讯作者：
Fleming, CR
中科院分区：
文献类型：
--
作者：
Zhao, HB;Yu, N;Fleming, CR
连接蛋白缝隙连接在听力功能中起着重要作用，但其作用机制尚不清楚。连接蛋白仅在支持细胞中表达，而在听觉毛细胞中不表达。缝隙连接通道由两个半槽形成。在这里，我们表明，在耳蜗液中测得的亚微摩尔浓度的水平上，耳蜗组织中的连接蛋白半通道可以释放出ATP。细胞外钙离子的减少或膜压力的增加可使细胞释放增加3-5倍，并可被缝隙连接阻滞剂阻断。我们还证明了亚微摩尔水平的细胞外ATP明显影响外毛细胞(OHC)的电动，这是一种决定哺乳动物耳蜗声刺激敏感性的主动耳蜗放大器。ATP降低了OHC的电动势和电压依赖的斜率系数，并移动了工作点以降低有源放大器的增益。ATP还减少了失真产品的产生。免疫荧光染色显示，嘌呤能受体P2X2和P2X7分布在OHC表面。阻断P2受体可消除三磷酸腺苷对OHC电活动的影响。这些数据表明，耳蜗内支持细胞和毛细胞之间存在一条半通道介导的嘌呤能细胞间信号通路，以控制听力敏感性。这些数据还显示了耳蜗中ATP的一个潜在来源。
Connexin gap junctions play an important role in hearing function, but the mechanism by which this contribution occurs is unknown. Connexins in the cochlea are expressed only in supporting cells; no connexin expression occurs in auditory sensory hair cells. A gap junctional channel is formed by two hemichannels. Here, we show that connexin hemichannels in the cochlea can release ATP at levels that account for the submicromolar concentrations measured in the cochlear fluids in vivo. The release could be increased 3- to 5-fold by a reduction of extracellular Ca2+ or an increase in membrane stress, and blocked by gap junctional blockers. We also demonstrated that extracellular ATP at submicromolar levels apparently affected outer hair cell (OHC) electromotility, which is an active cochlear amplifier determining cochlear sensitivity to sound stimulation in mammals. ATP reduced OHC electromotility and the slope factor of the voltage dependence and shifted the operating point to reduce the active amplifier gain. ATP also reduced the generation of distortion products. Immunofluorescent staining showed that purinergic receptors P2x2 and P2x7 were distributed on the OHC surface. Blockage of P2 receptors eliminated the effect of ATP on the OHC electromotility. The data revealed that there is a hemichannel-mediated, purinergic intercellular signaling pathway between supporting cells and hair cells in the cochlea to control hearing sensitivity. The data also demonstrated a potential source of ATP in the cochlea.