Chloride/proton antiporter activity of mammalian CLC proteins ClC-4 and ClC-5
Chloride/proton antiporter activity of mammalian CLC proteins ClC-4 and ClC-5
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DOI：
10.1038/nature03720
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发表时间：
2005-07-21
期刊：
影响因子：
64.8
通讯作者：
Pusch, M
中科院分区：
文献类型：
--
作者：
Picollo, A;Pusch, M
ClC-4和ClC-5是CLC基因家族的成员（1），其中ClC-5在登特氏病（Dent's disease）中突变（2），登特氏病是一种与低分子量蛋白尿和最终肾衰竭相关的肾病。已提出ClC-5是早期内体中的电分流Cl-通道，促进管腔内酸化（3，4）。由于发现某些细菌CLC蛋白是二级活性Cl-/H+反向转运蛋白（5），我们假设哺乳动物CLC蛋白可能不是经典的Cl-离子通道，但可能表现出Cl-偶联质子转运活性。在这里，我们报告说，ClC-4和ClC-5携带大量的质子跨质膜时，激活的正电压，所揭示的pH值接近细胞表面的测量。这两种蛋白质都能够挤出质子对他们的电化学梯度，证明二级主动运输。H+，但不是Cl-，运输被废除时，孔谷氨酸突变为丙氨酸（E211 A）。ClC-0、ClC-2和ClC-Ka蛋白没有显示出显著的质子转运。肌肉通道ClC-1表现出一个小的H+运输，可能是生理相关的。对于ClC-5，我们估计，Cl-和H+运输贡献约相等的总电荷运动，提高耦合Cl-/H+运输的ClC-4和ClC-5的可能性是显着的幅度在体内。
ClC-4 and ClC-5 are members of the CLC gene family(1), with ClC-5 mutated in Dent's disease(2), a nephropathy associated with low-molecular-mass proteinuria and eventual renal failure. ClC-5 has been proposed to be an electrically shunting Cl- channel in early endosomes, facilitating intraluminal acidification(3,4). Motivated by the discovery that certain bacterial CLC proteins are secondary active Cl-/H+ antiporters(5), we hypothesized that mammalian CLC proteins might not be classical Cl- ion channels but might exhibit Cl-- coupled proton transport activity. Here we report that ClC-4 and ClC-5 carry a substantial amount of protons across the plasma membrane when activated by positive voltages, as revealed by measurements of pH close to the cell surface. Both proteins are able to extrude protons against their electrochemical gradient, demonstrating secondary active transport. H+, but not Cl-, transport was abolished when a pore glutamate was mutated to alanine (E211A). ClC-0, ClC-2 and ClC-Ka proteins showed no significant proton transport. The muscle channel ClC-1 exhibited a small H+ transport that might be physiologically relevant. For ClC-5, we estimated that Cl- and H+ transport contribute about equally to the total charge movement, raising the possibility that the coupled Cl-/H+ transport of ClC-4 and ClC-5 is of significant magnitude in vivo.