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。Q_&lt；10&gt；值为电导为&gt；2.0，门控参数为3-6。这些高Q值在小胶质细胞和BMMC中都保存得很好，这两种细胞的通道表达速率不同，这意味着高温依赖存在于通道本身。然而，在高温或肿胀的细胞中，电导的Q_10&gt；值往往降低，从而表明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，在固有的pH缓冲液中，在穿孔全细胞记录中检测了不同类型细胞酸化时的通道活性。在破骨细胞中，蛋白激酶C的激活剂PMA诱导细胞酸化和H^+通道的激活。反转电位被用作钳制细胞中细胞pH变化的实时监测。在小胶质细胞中，H^+通道被激活，并伴有急性或长期的细胞酸中毒。由于H^+的挤出，当酸中毒消除时，通道激活终止。然而，部分激活被Δ不依赖于pH的过程修饰。此外，有时细胞内Ca~(2+)和Gt~(2+)或H~(2+)的拮抗剂CL~(-)流量的增加与酸中毒有关。因此，H^+信号与其他离子信号的协同作用密切相关。这项研究提供了证据，表明H~(++)可以通过感知pH扰动的微小变化来维持细胞的pH动态平衡，同时也会触发H~(++)到周围细胞。

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.