SLC26A7 is a Cl- channel regulated by intracellular pH
SLC26A7 is a Cl- channel regulated by intracellular pH
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DOI：
10.1074/jbc.m409162200
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发表时间：
2005-02-25
影响因子：
4.8
通讯作者：
Muallem, S
中科院分区：
文献类型：
--
作者：
Kim, KH;Shcheynikov, N;Muallem, S
SLC26转运蛋白家族成员在多种上皮功能中发挥重要作用，这是由该家族成员的突变相关疾病所揭示的。一些成员被证明是Cl-和HCO3-转运蛋白，可能在上皮Cl-吸收和HCO3-分泌中起重要作用。然而，大多数转运蛋白的作用机制尚不清楚。SLC26A7是SLC26转运蛋白家族的一员，据报道，SLC26A7在皮质集管基底外膜和顶壁细胞中表达，并作为Cl-/HCO3-偶联交换剂发挥作用。在本工作中，我们研究了SLC26A7的输运性质，以确定其输运特性和电致性。我们发现，当在爪蟾卵母细胞或HEK293细胞中表达时，SLC26A7作为pH(i)调节的Cl-通道，具有最小的OH-/HCO3-通透性。SLC26A7在卵母细胞或HEK293细胞中的表达产生具有线性in的Cl-电流和与电压和时间无关的瞬时电流。通过对逆转电位的测量，SLC26A7对NO3-的选择性远高于Cl- = Br- = I- > SO42- = Glu(-)，尽管I-对电流有部分抑制作用。用HCO3-或丁酸盐孵育细胞可使细胞质酸化，提高SLC26A7对Cl-的选择性。膜电位和pH(i)的测量表明，当细胞在含氯或无氯培养基中孵育时，SLC26A7对OH-和HCO3-的运输很少。SLC26A7的活性被所测试的所有阴离子转运体抑制剂，4,4'-二异硫氰二苯乙烯-2,2'-二磺酸，二苯胺-2-羧酸和格列苯脲抑制。这些发现表明SLC26A7是一个独特的Cl-通道，受细胞内H+调节。
Members of the SLC26 transporter family play an essential role in several epithelial functions, as revealed by diseases associated with mutations in members of the family. Several members were shown to function as Cl- and HCO3- transporters that likely play an important role in epithelial Cl- absorption and HCO3- secretion. However, the mechanism of most transporters is not well understood. SLC26A7 is a member of the SLC26 transporter family reported to be expressed in the basolateral membrane of the cortical collecting duct and parietal cells and functions as a coupled Cl-/HCO3- exchanger. In the present work we examined the transport properties of SLC26A7 to determine its transport characteristics and electrogenicity. We found that when expressed in Xenopus oocytes or HEK293 cells SLC26A7 functions as a pH(i)-regulated Cl- channel with minimal OH-/HCO3- permeability. Expression of SLC26A7 in oocytes or HEK293 cells generated a Cl- current with linear IN and an instantaneous current that was voltage- and time-independent. Based on measurement of reversal potential the selectivity of SLC26A7 is NO3- much greater than Cl- = Br- = I- > SO42- = Glu(-), although I- partially inhibited the current. Incubating the cells with HCO3- or butyrate acidified the cytosol and increased the selectivity of SLC26A7 for Cl-. Measurement of membrane potential and pH(i) showed minimal OH- and HCO3- transport by SLC26A7 when the cells were incubated in Cl--containing or Cl--firee media. The activity of SLC26A7 was inhibited by all inhibitors of anion transporters tested, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, diphenylamine-2-carboxylic acid, and glybenclamide. These findings reveal that SLC26A7 functions as a unique Cl- channel that is regulated by intracellular H+.