Weylandt K H, Valverde M A, Nobles M, Raguz S, Amey J S, Diaz M, Nastrucci C, Higgins C F, Sardini A
Medical Research Council Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Rd., London W12 0NN, United Kingdom.
J Biol Chem. 2001 May 18;276(20):17461-7. doi: 10.1074/jbc.M011667200. Epub 2001 Feb 22.
Volume regulation is essential for normal cell function. A key component of the cells' response to volume changes is the activation of a channel, which elicits characteristic chloride currents (I(Cl, Swell)). The molecular identity of this channel has been controversial. Most recently, ClC-3, a protein highly homologous to the ClC-4 and ClC-5 channel proteins, has been proposed as being responsible for I(Cl, Swell). Subsequently, however, other reports have suggested that ClC-3 may generate chloride currents with characteristics clearly distinct from I(Cl, Swell). Significantly different tissue distributions for ClC-3 have also been reported, and it has been suggested that two isoforms of ClC-3 may be expressed with differing functions. In this study we generated a series of cell lines expressing variants of ClC-3 to rigorously address the question of whether or not ClC-3 is responsible for I(Cl, Swell). The data demonstrate that ClC-3 is not responsible for I(Cl, Swell) and has no role in regulatory volume decrease, furthermore, ClC-3 is not activated by intracellular calcium and fails to elicit chloride currents under any conditions tested. Expression of ClC-3 was shown to be relatively tissue-specific, with high levels in the central nervous system and kidney, and in contrast to previous reports, is essentially absent from heart. This distribution is also inconsistent with the previous proposed role in cell volume regulation.
容积调节对于正常细胞功能至关重要。细胞对容积变化做出反应的一个关键组成部分是通道的激活，该通道会引发特征性的氯离子电流（I(Cl, Swell)）。该通道的分子身份一直存在争议。最近，ClC-3，一种与ClC-4和ClC-5通道蛋白高度同源的蛋白质，被认为是I(Cl, Swell)的产生原因。然而，随后其他报告表明，ClC-3可能产生与I(Cl, Swell)特征明显不同的氯离子电流。也有报告称ClC-3的组织分布存在显著差异，并且有人提出ClC-3的两种同工型可能具有不同的功能。在本研究中，我们构建了一系列表达ClC-3变体的细胞系，以严格解决ClC-3是否是I(Cl, Swell)产生原因的问题。数据表明，ClC-3不是I(Cl, Swell)的产生原因，在调节性容积减小中不起作用，此外，ClC-3不会被细胞内钙激活，并且在任何测试条件下都不会引发氯离子电流。研究表明，ClC-3的表达具有相对的组织特异性，在中枢神经系统和肾脏中水平较高，与之前的报告不同，心脏中基本不存在。这种分布也与之前提出的在细胞容积调节中的作用不一致。
