Department of Basic Medical Science, School of Medicine, University of Missouri-Kansas City, 2411 Holmes Street, Kansas City, MO 64108, USA.
Neuroscience. 2010 Aug 25;169(2):574-83. doi: 10.1016/j.neuroscience.2010.05.043. Epub 2010 May 24.
Acid-sensing ion channel 3 (ASIC3) is a proton-gated, voltage-insensitive Na(+) channel that is expressed primarily in peripheral sensory neurons and plays an important role in pain perception, particularly as a pH sensor following cardiac ischemia. We previously reported that ASIC3 currents are not affected by zinc at nanomolar concentrations. In this study, we examined the potential role of micromolar zinc in the regulation of ASIC3. In CHO cells expressing ASIC3, we found that ASIC3 currents triggered by dropping the pH from 7.4 to 6.0 were inhibited by pretreatment with zinc in a concentration-dependent manner; the half-maximum inhibitory concentration of zinc was 61 muM. ASIC currents activated by a relatively small drop in pH from 7.4 to 7.2 or 7.0 were also subject to inhibition by zinc. The inhibition was fast and pH independent, and occurred within a relatively narrow range of zinc concentrations between 30 and 300 muM. Further, increasing extracellular Ca(2+) concentrations from 2 to 10 mM failed to affect inhibition of ASIC3 currents by zinc. Experimentally elevating intracellular zinc levels did not affect the inhibition of ASIC3 currents by equal concentrations of extracellular zinc, and modification of cysteine or histidine residues had no effect on the inhibition of ASIC3 currents by zinc. These collective results suggest that zinc is an important regulator of ASIC3 at physiological concentrations, that zinc inhibits ASIC3 in a pH- and Ca(2+)-independent manner, and that inhibition of ASIC3 currents is dependent upon the interaction of zinc with extracellular domain(s) of ASIC3.
酸敏离子通道 3（ASIC3）是一种质子门控、电压不敏感的 Na(+)通道，主要表达于外周感觉神经元，在痛觉感知中发挥重要作用，尤其作为心脏缺血后的 pH 感受器。我们之前报道过，锌在纳摩尔浓度下不会影响 ASIC3 电流。在这项研究中，我们研究了微摩尔锌在 ASIC3 调节中的潜在作用。在表达 ASIC3 的 CHO 细胞中，我们发现通过将 pH 从 7.4 降低至 6.0 来触发 ASIC3 电流时，锌预处理以浓度依赖的方式抑制 ASIC3 电流；锌的半抑制浓度为 61 μM。pH 从 7.4 降低至 7.2 或 7.0 时，相对较小的 pH 下降也会激活的 ASIC 电流也会受到锌的抑制。这种抑制作用快速且与 pH 无关，发生在锌浓度在 30 至 300 μM 之间的相对较窄范围内。此外，将细胞外 Ca(2+)浓度从 2 增加到 10 mM 并不能影响锌对 ASIC3 电流的抑制作用。实验性地升高细胞内锌水平不会影响细胞外锌浓度相等时对 ASIC3 电流的抑制作用，而且半胱氨酸或组氨酸残基的修饰对锌对 ASIC3 电流的抑制作用没有影响。这些综合结果表明，锌在生理浓度下是 ASIC3 的重要调节剂，锌以 pH 和 Ca(2+) 独立的方式抑制 ASIC3，而 ASIC3 电流的抑制取决于锌与 ASIC3 细胞外结构域（s）的相互作用。
