Two SUR1-specific histidine residues mandatory for zinc-induced activation of the rat KATP channel
Two SUR1-specific histidine residues mandatory for zinc-induced activation of the rat KATP channel
复制标题
DOI：
10.1074/jbc.m413426200
复制
发表时间：
2005-03-11
影响因子：
4.8
通讯作者：
Bloc, A
中科院分区：
文献类型：
--
作者：
Bancila, V;Cens, T;Bloc, A
微摩尔浓度的锌通过激活atp敏感钾通道（K-ATP）使大鼠胰腺β细胞和脑神经末梢超极化。使用胰岛素瘤细胞系和转染野生型或突变K-ATP亚基的细胞分析了这种效应的分子决定因素。锌在共表达大鼠Kir6.2和SUR1亚基的细胞中激活K-ATP，如在胰岛素瘤细胞系中。相反，锌对含有sur2a的细胞有抑制作用。因此，锌的激活作用也依赖于细胞外pH值，并被焦碳酸二乙酯阻断，这表明组氨酸参与其中。五个sur1特异性的细胞外组氨酸残基被提交到定点突变。其中，两种组氨酸（His-326和His-332）被发现对锌活化K-ATP至关重要，这被双重突变H326A/H332A所证实。总之，锌通过与细胞外的SUR1亚基的His-326和His-332结合来激活K-ATP。由此可见，锌对胰腺β细胞和α细胞的细胞兴奋性和分泌过程具有负向调控作用。事实上，我们最近已经证明，这种机制发生在海马苔藓纤维中，这是一个大脑区域，像胰腺一样，以锌的重要积累和含有sur1的K-ATP的高密度为特征。
Zinc at micromolar concentrations hyperpolarizes rat pancreatic beta-cells and brain nerve terminals by activating ATP-sensitive potassium channels (K-ATP). The molecular determinants of this effect were analyzed using insulinoma cell lines and cells transfected with either wild type or mutated K-ATP subunits. Zinc activated K-ATP in cells coexpressing rat Kir6.2 and SUR1 subunits, as in insulinoma cell lines. In contrast, zinc exerted an inhibitory action on SUR2A-containing cells. Therefore, SUR1 expression is required for the activating action of zinc, which also depended on extracellular pH and was blocked by diethyl pyrocarbonate, suggesting histidine involvement. The five SUR1-specific extracellular histidine residues were submitted to site-directed mutagenesis. Of them, two histidines (His-326 and His-332) were found to be critical for the activation of K-ATP by zinc, as confirmed by the double mutation H326A/H332A. In conclusion, zinc activates K-ATP by binding itself to extracellular His-326 and His-332 of the SUR1 subunit. Thereby zinc could exert a negative control on cell excitability and secretion process of pancreatic beta-and alpha-cells. In fact, we have recently shown that such a mechanism occurs in hippocampal mossy fibers, a brain region characterized, like the pancreas, by an important accumulation of zinc and a high density of SUR1-containing K-ATP.