Chu Xiang-Ping, Close Natasha, Saugstad Julie A, Xiong Zhi-Gang
Robert S. Dow Neurobiology Laboratories, Legacy Research, Portland, Oregon 97232, USA.
J Neurosci. 2006 May 17;26(20):5329-39. doi: 10.1523/JNEUROSCI.0938-06.2006.
Acid-sensing ion channel (ASIC)-1a, the major ASIC subunit with Ca2+ permeability, is highly expressed in the neurons of CNS. Activation of these channels with resultant intracellular Ca2+ accumulation plays a critical role in normal synaptic plasticity, learning/memory, and in acidosis-mediated glutamate receptor-independent neuronal injury. Here we demonstrate that the activities of ASICs in CNS neurons are tightly regulated by the redox state of the channels and that the modulation is ASIC1a subunit dependent. In cultured mouse cortical neurons, application of the reducing agents dramatically potentiated, whereas the oxidizing agents inhibited the ASIC currents. However, in neurons from the ASIC1 knock-out mice, neither oxidizing agents nor reducing reagents had any effect on the acid-activated current. In Chinese Hamster Ovary cells, redox-modifying agents only affected the current mediated by homomeric ASIC1a, but not homomeric ASIC1b, ASIC2a, or ASIC3. In current-clamp recordings and Ca(2+)-imaging experiments, the reducing agents increased but the oxidizing agents decreased acid-induced membrane depolarization and the intracellular Ca2+ accumulation. Site-directed mutagenesis studies identified involvement of cysteine 61 and lysine 133, located in the extracellular domain of the ASIC1a subunit, in the modulation of ASICs by oxidizing and reducing agents, respectively. Our results suggest that redox state of the ASIC1a subunit is an important factor in determining the overall physiological function and the pathological role of ASICs in the CNS.
酸敏感离子通道（ASIC）-1a是具有Ca2+通透性的主要ASIC亚基，在中枢神经系统（CNS）的神经元中高度表达。这些通道的激活以及由此导致的细胞内Ca2+积累在正常突触可塑性、学习/记忆以及酸中毒介导的不依赖谷氨酸受体的神经元损伤中起关键作用。在此，我们证明中枢神经系统神经元中ASIC的活性受到通道氧化还原状态的严格调控，且这种调节依赖于ASIC1a亚基。在培养的小鼠皮质神经元中，还原剂的应用显著增强了ASIC电流，而氧化剂则抑制了该电流。然而，在来自ASIC1基因敲除小鼠的神经元中，氧化剂和还原剂对酸激活电流均无任何影响。在中国仓鼠卵巢细胞中，氧化还原修饰剂仅影响由同聚体ASIC1a介导的电流，而不影响同聚体ASIC1b、ASIC2a或ASIC3介导的电流。在电流钳记录和Ca(2+)成像实验中，还原剂增加了酸诱导的膜去极化和细胞内Ca2+积累，而氧化剂则降低了这些效应。定点诱变研究分别确定了位于ASIC1a亚基胞外结构域的半胱氨酸61和赖氨酸133参与了氧化剂和还原剂对ASIC的调节。我们的结果表明，ASIC1a亚基的氧化还原状态是决定ASIC在中枢神经系统中的整体生理功能和病理作用的一个重要因素。
