An electroneutral sodium/bicarbonate cotransporter NBCn1 and associated sodium channel
An electroneutral sodium/bicarbonate cotransporter NBCn1 and associated sodium channel
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DOI：
10.1038/35014615
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发表时间：
2000-06-01
期刊：
影响因子：
64.8
通讯作者：
Boron, WF
中科院分区：
文献类型：
--
作者：
Choi, I;Aalkjaer, C;Boron, WF
两种电中性的 Na+ 驱动的 HCO3- 转运蛋白（Na+ 驱动的 Cl-/HCO3- 交换器和电中性的 Na+/HCO3- 协同转运蛋白）在调节多种细胞的细胞内 pH 值方面发挥着至关重要的作用，包括心肌细胞 (1,2)、血管平滑肌 (3,4)、神经元 (5) 和 成纤维细胞(6);然而，在哺乳动物细胞中很难区分它们的 CT 依赖性。在这里，我们报告了从大鼠平滑肌中克隆出电中性 Na+/HCO3- 协同转运蛋白 NBCn1 的三种变体。它们与人类骨骼肌克隆的同一性为 89-92% (7)，与生电 NBC 的同一性为 55-57%，与阴离子交换剂的同一性为 33-43% (8)。当在非洲爪蟾卵母细胞中表达时，NBCn1-B（编码 1,218 个氨基酸）呈电中性、Na+ 依赖性和 HCO3 依赖性，但不依赖于 Cl 。注射低水平 NBCn1-B 互补 RNA 的卵母细胞表现出 Na+ 电导，4,4-diisothiocyanatostilbene-2,2'-disulfonate 会缓慢且不可逆地刺激。
Two electroneutral, Na+-driven HCO3- transporters, the Na+-driven Cl-/HCO3- exchanger and the electroneutral Na+/HCO3- cotransporter, have crucial roles in regulating intracellular pH in a variety of cells, including cardiac myocytes(1,2), vascular smooth-muscle(3,4), neurons(5) and fibroblasts(6); however, it is difficult to distinguish their CT dependence in mammalian cells. Here we report the cloning of three variants of an electroneutral Na+/HCO3- cotransporter, NBCn1, from rat smooth muscle. They are 89-92% identical to a human skeletal muscle clone(7), 55-57% identical to the electrogenic NBCs and 33-43% identical to the anion exchangers(8). When expressed in Xenopus oocytes, NBCn1-B (which encodes 1,218 amino acids) is electroneutral, Na+-dependent and HCO3--dependent, but not Cl--dependent. Oocytes injected with low levels of NBCn1-B complementary RNA exhibit a Na+ conductance that 4,4-diisothiocyanatostilbene-2,2'-disulphonate stimulates slowly and irreversibly.