Proton signaling mediated by voltagegated proton channels

我们研究了电压门控质子（H^+）通道如何调节破骨细胞、小胶质细胞和骨髓源性肥大细胞（BMMC）中的H^+信号。电导的Q值<10>&gt; 2.0，门控参数的Q值为3 - 6。这些高Q<10>值在小胶质细胞和BMMC中均得到很好的保持，这表明通道的高温度依赖性存在于通道本身。然而<10>，电导的Q值在高温或肿胀的细胞中经常降低，因此，表明H^+通道的激活状态是不均匀的。为了阐明H^+通道在完整细胞中的作用，我们在内源性pH缓冲液中，通过穿孔全细胞记录，检测了响应于各种类型细胞酸中毒的通道活性。在破骨细胞中，蛋白激酶C激活剂PMA可诱导细胞酸中毒和H^+通道激活。逆转电位作为一个实时监测细胞pH值的变化，在夹紧的细胞。在小胶质细胞中，H^+通道被激活，伴随着急性或长期的细胞酸中毒。由于H^+排出，酸中毒消除后，通道激活终止。然而，一部分活化被Δ pH非依赖性过程修饰。此外，有时细胞内Ca^2+或CL^-（H^+的抗衡离子）流量的增加也与酸中毒有关。因此，H^+信号与其他离子信号的协同作用密切相关。本研究提供的证据表明，H^+可以通过感知pH扰动的微小变化来维持细胞内pH的稳态，同时也会将H^+触发到周围的细胞。

We have investigated how the voltage-gated proton (H^+) channels regulate H^+ signaling in osteoclasts, microglia and bone-marrow-derived mast cells (BMMC). The Q_<10> value was > 2.0 for conductance and 3 -6 for gating parameters. These high Q_<10> values were preserved well in both microglia and BMMC, which differed in the expression rate of the channel, implying that the high temperature dependence resides in the channel itself. The Q_<10> value for the conductance was, however, often decreased at high temperature or in swollen cells, thus, indicating that the activation status of the H^+ channel is heterogeneous. To clarify actions of the H^+ channel in intact cells, the channel activity in response to various types of cell acidosis was examined in the perforated-whole cell recordings under intrinsic pH buffers. In osteoclasts, an activator for protein kinase C, PMA, induced cell acidosis and activation of the H^+ channel. The reversal potential was served as a real-time monitor for changes in cellular pH in clamped cells. In microglia, the H^+ channel was activated accompanying either acute or prolonged cell acidosis. The channel activation terminated upon removal of the acidosis due to the H^+ extrusion. A part of the activation was, however, modified by ΔpH-independent processes. In addition, sometimes increases in intracellular Ca^<2+> or flux of CL^-, a counter ion for H^+, were associated with the acidosis. Thus H^+ signaling is intimately related to synergistic actions of other ion signals. This study has provided evidences that the H^+ can maintain cellular pH homeostasis by sensing minor changes in pH disturbances and, simultaneously, would trigger H^+ to the surrounding cells.