The electrogenic Na+-HCO3- cotransporter NBCe1 encoded by SLC4A4 plays 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 I tried to perform functional characterization of the 4 nonsynonymous single nucleotide polymorphisms (SNPs), E122G, S356Y, K558R, and N640I in NBCe1A. Functional analysis in Xenopus oocytes 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 I conclude that among 4 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.
発行年
2011-03-24
日本十進分類法
490
学位名
博士(医学)
学位
doctoral
学位分野
Medical Science(医学)
学位授与機関
University of Tokyo (東京大学)
研究科・専攻
Department of Internal Medicine, Graduate School of Medicine (医学系研究科内科学専攻)
学位授与年月日
2011-03-24
学位授与番号
甲第27070号
学位記番号
博医第3680号
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Functional analysis of SNP mutations leading to single amino acid substitution in NBCe1
h22_yamazaki.pdf
(2.07MB)
