作者:Antonella Liantonio、Alessandra Picollo、Elena Babini、Giuseppe Carbonara、Giuseppe Fracchiolla、Fulvio Loiodice、Vincenzo Tortorella、Michael Pusch、Diana Conte Camerino
DOI:10.1124/mol.105.017384
日期:2006.1
CLC-K Cl– channels are selectively expressed in kidney and ear, where they are pivotal for salt homeostasis, and loss-of-function mutations of CLC-Kb produce Bartter's syndrome type III. The only ligand known for CLC-K channels is a derivative of the 2- p -chlorophenoxypropionic acid (CPP), 3-phenyl-CPP, which blocks CLC-Ka, but not CLC-Kb. Here we show that in addition to this blocking site, CLC-K channels bear an activating binding site that controls channel opening. Using the voltage-clamp technique on channels expressed in Xenopus laevis oocytes, we found that niflumic acid (NFA) increases CLC-Ka and CLC-Kb currents in the 10 to 1000 μM range. Flufenamic acid (FFA) derivatives or high doses of NFA produced instead an inhibitory effect on CLC-Ka, but not on CLC-Kb, and on blocker-insensitive CLC-Ka mutants, indicating that the activating binding site is distinct from the blocker site. Evaluation of the sensitivity of CLC-Ka to derivatives of NFA and FFA together with a modeling study of these ligands allow us to conclude that one major characteristic of activating compounds is the coplanarity of the two rings of the molecules, whereas block requires a noncoplanar configuration. These molecules provide a starting point for identification of diuretics or drugs useful in the treatment of Bartter's syndrome.
CLC-K Cl– 渠道在肾脏和耳朵中特异性表达,它们对盐的稳态至关重要,CLC-Kb 的功能缺失突变可导致 III 型巴特综合征。目前已知的 CLC-K 渠道唯一配体是 2- p -氯苯氧丙酸 (CPP) 的衍生物 3-苯基-CPP,它可以阻断 CLC-Ka,但不影响 CLC-Kb。在这里,我们展示了除了该阻断位点外,CLC-K 渠道还具有一个激活结合位点,该位点控制通道的开启。通过对表达在非洲爪蛙卵母细胞中的通道使用电压夹持技术,我们发现氟尼辛酸 (NFA) 在 10 至 1000 μM 范围内增加了 CLC-Ka 和 CLC-Kb 的电流。氟芬那酸 (FFA) 的衍生物或高剂量的 NFA 对 CLC-Ka 产生了抑制作用,而对 CLC-Kb 则没有,并且在对阻断剂不敏感的 CLC-Ka 突变体上同样显示出该作用,表明激活结合位点与阻断位点是不同的。对 CLC-Ka 对 NFA 和 FFA 衍生物的敏感性评估,以及对这些配体的建模研究,让我们得出结论:激活化合物的一个主要特征是分子两个环的共平面性,而阻断则需要非共平面构型。这些分子为识别利尿剂或在治疗巴特综合征方面有用的药物提供了起点。