Functional characterization of nonsynonymous single nucleotide polymorphisms in the electrogenic Na^+-HCO_3^- cotransporter NBCe1A
Functional characterization of nonsynonymous single nucleotide polymorphisms in the electrogenic Na^+-HCO_3^- cotransporter NBCe1A
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产电Na^-HCO_3^-协同转运蛋白NBCe1A中非同义单核苷酸多态性的功能表征
DOI：
10.1007/s00424-010-0918-x
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
Fujita T
中科院分区：
文献类型：
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作者：
Yamazaki O;Yamada H;Suzuki M;Horita S;Shirai A;Nakamura M;Seki G;Fujita T
SLC 4A 4编码的产电Na+-HCO 3 −协同转运蛋白NBCe 1在细胞内/细胞外pH的调节中起重要作用。NBCe 1的纯合突变引起与眼部异常相关的近端肾小管酸中毒。在本研究中，我们试图进行功能特性的四个非同义单核苷酸多态性（SNPs），E122 G，S356 Y，K558 R，和N640 I在NBCe 1A。在异种卵母细胞中的功能分析显示，虽然K558 R变体具有显著降低的转运活性，相当于野生型活性的47%，但其余变体E122 G、S356 Y和N640 I没有改变NBCe 1A活性。K558 R的表观Na+亲和力与野生型NBCe 1A的表观Na+亲和力没有差异。在HEK 293细胞和MDCK细胞中的免疫组织化学分析表明，这些SNPs都没有改变NBCe 1A的运输行为。在HEK 293细胞中的功能分析还揭示，仅K558 R变体具有降低的转运活性，对应于野生型活性的41-47%。从这些结果中，我们得出结论，在四个SNP中，只有K558 R变体，它被预测为位于跨膜片段5，显着降低NBCe 1A活性，而不改变运输行为或表观细胞外Na+亲和力。
The electrogenic Na+–HCO3−cotransporter NBCe1 encoded bySLC4A4plays essential roles in the regulation of intracellular/extracellular pH. Homozygous mutations in NBCe1 cause proximal renal tubular acidosis associated with ocular abnormalities. In the present study, we tried to perform functional characterization of the four nonsynonymous single nucleotide polymorphisms (SNPs), E122G, S356Y, K558R, and N640I in NBCe1A. Functional analysis inXenopusoocytes revealed that while the K558R variant had a significantly reduced transport activity corresponding to 47% of the wild-type activity, the remaining variants E122G, S356Y, and N640I did not change the NBCe1A activity. Apparent Na+affinity of K558R was not different from that of wild-type NBCe1A. Immunohistological analyses in HEK293 cells and MDCK cells indicated that none of these SNPs changed the trafficking behaviors of NBCe1A. Functional analysis in HEK293 cells also revealed that only the K558R variant had a reduced transport activity, corresponding to 41–47% of the wild-type activity. From these results, we conclude that among four SNPs, only the K558R variant, which is predicted to lie in transmembrane segment 5, significantly reduces the NBCe1A activity without changing the trafficking behavior or the apparent extracellular Na+affinity.