The effect of anions on the human P2X7 receptor
The effect of anions on the human P2X7 receptor
复制标题
DOI：
10.1016/j.bbamem.2011.08.017
复制
发表时间：
2011-12-01
影响因子：
3.4
通讯作者：
Markwardt, Fritz
中科院分区：
文献类型：
--
作者：
Kubick, Christoph;Schmalzing, Guenther;Markwardt, Fritz
P2 X7受体（P2 X7 Rs）是非选择性阳离子通道，其通过细胞外ATP的结合而打开，并且参与调节上皮分泌、炎症和伤害感受。在这里，我们研究了细胞外阴离子对非洲爪蟾卵母细胞中表达的人P2 X7 Rs（hP 2X 7 Rs）的通道门控和渗透的影响。双微电极电压钳记录表明，ATP诱导的hP 2X 7 R介导的电流增加时，细胞外氯离子被取代的有机阴离子谷氨酸或天冬氨酸和减少时，氯离子被取代的无机阴离子硝酸盐，硫酸盐或碘。ATP浓度-反应比较显示，谷氨酸盐取代氯降低激动剂的效力，而碘取代增加激动剂的效力在高ATP浓度。同时，ATP效力保持不变。在低ATP浓度下通过高亲和力ATP效应位点激活hP 2X 7 R不受谷氨酸盐或碘化物取代氯离子的影响。为了在单分子水平上分析阴离子对hP 2X 7 R的影响，我们使用膜片钳技术在外向配置下进行单通道电流测量。氯离子取代不影响单通道电导，但P2 X7 R通道开放的可能性增加时，氯离子被谷氨酸盐取代，并降低时，氯离子被碘离子取代。这种效应是由于阴离子对hP 2X 7 R通道的平均关闭时间的影响。我们的结论是，hP 2X 7 R通道是不阴离子渗透生理Na+为基础的媒体和外部阴离子变构影响离子通道开放的完全ATP（4）-配体的P2 X7 R通过细胞外阴离子结合位点。(C)2011 Elsevier B. V.保留所有权利。
P2X7 receptors (P2X7Rs) are nonselective cation channels that are opened by the binding of extracellular ATP and are involved in the modulation of epithelial secretion, inflammation and nociception. Here, we investigated the effect of extracellular anions on channel gating and permeation of human P2X7Rs (hP2X7Rs) expressed in Xenopus laevis oocytes. Two-microelectrode voltage-clamp recordings showed that ATP-induced hP2X7R-mediated currents increased when extracellular chloride was substituted by the organic anions glutamate or aspartate and decreased when chloride was replaced by the inorganic anions nitrate, sulfate or iodide. ATP concentration-response comparisons revealed that substitution of chloride by glutamate decreased agonist efficacy, while substitution by iodide increased agonist efficacy at high ATP concentrations. Meanwhile, the ATP potency remained unchanged. Activation of the hP2X7R at low ATP concentrations via the high-affinity ATP effector site was not affected by the replacement of chloride by glutamate or iodide. To analyze the anion effect on the hP2X7R at the single-molecule level, we performed single-channel current measurements using the patch-clamp technique in the outside-out configuration. Chloride substitution did not affect the single-channel conductance, but the probability that the P2X7R channel was open increased when chloride was replaced by glutamate and decreased when chloride was replaced by iodide. This effect was due to an influence of the anions on the mean closed times of the hP2X7R channel. We conclude that hP2X7R channels are not anion-permeable in physiological Na+-based media and that external anions allosterically affect ion channel opening in the fully ATP(4)-liganded P2X7R through an extracellular anion binding site. (C) 2011 Elsevier B.V. All rights reserved.