Cloning and functional characterization of human SMCT2 (SLC5A12) and expression pattern of the transporter in kidney
Cloning and functional characterization of human SMCT2 (SLC5A12) and expression pattern of the transporter in kidney
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DOI：
10.1016/j.bbamem.2007.06.031
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发表时间：
2007-11-01
影响因子：
3.4
通讯作者：
Prasad, P. D.
中科院分区：
文献类型：
--
作者：
Gopal, E.;Umapathy, N. S.;Prasad, P. D.
最近，我们从小鼠肾脏中克隆了两个Na+偶联乳酸转运蛋白，一个高亲和力转运蛋白（SMCT 1或slc5a8）和一个低亲和力转运蛋白（SMCT 2或slc5a12）。本文报道了人SMCT 2（SLC5A12）的克隆和功能鉴定，并比较了SLC5A12和SLC5A8在小鼠肾脏中的免疫定位模式。人SMCT2 cDNA编码由618个氨基酸组成的蛋白质。当在哺乳动物细胞或非洲爪蟾卵母细胞中表达时，人SMCT2介导乳酸、丙酮酸和烟酸的Na+偶联转运。转运蛋白对这些底物的亲和力低于对人SMCT1的亲和力。几种非甾体抗炎药抑制人SMCT 2介导的烟酸转运，表明NSAID与转运蛋白相互作用，就像它们与人SMCT 1相互作用一样。用SMCT 2特异性抗体对小鼠肾脏切片进行免疫荧光显微镜检查，结果显示转运蛋白主要在皮质中表达。使用抗SMCT1抗体的类似研究表明，SMCT1也主要在皮质中表达。用4F2hc（CD98）（肾单位S1和S2段近端肾小管细胞基底外侧膜的标记物）对SMCT1和SMCT2进行双标记，表明SMCT1和SMCT2均在肾小管细胞的顶膜中表达。这些研究还表明，虽然SMCT 2沿着整个近端小管长度（S1/S2/S3段）广泛表达，但SMCT I的表达主要限于S3段。这些研究表明，低亲和力转运蛋白SMCT 2在近端小管的早期部分启动乳酸盐吸收，随后高亲和力转运蛋白SMCT 1在近端小管的后期部分参与。(c)2007 Elsevier B.V.保留所有权利。
Recently, we cloned two Na+-coupled lactate transporters from mouse kidney, a high-affinity transporter (SMCT 1 or slc5a8) and a low-affinity transporter (SMCT2 or slc5a12). Here we report on the cloning and functional characterization of human SMCT2 (SLC5A12) and compare the immunolocalization patterns of slc5a12 and slc5a8 in mouse kidney. The human SMCT2 cDNA codes for a protein consisting of 618 amino acids. When expressed in mammalian cells or Xenopus oocytes, human SMCT2 mediates Na+-coupled transport of lactate, pyruvate and nicotinate. The affinities of the transporter for these substrates are lower than those reported for human SMCT1. Several non-steroidal anti-inflammatory drugs inhibit human SMCT2-mediated nicotinate transport, suggesting that NSAIDs interact with the transporter as they do with human SMCT1 Immunofluorescence microscopy of mouse kidney sections with an antibody specific for SMCT2 shows that the transporter is expressed predominantly in the cortex. Similar studies with an anti-SMCT1 antibody demonstrate that SMCT1 is also expressed mostly in the cortex. Dual-labeling of SMCT1 and SMCT2 with 4F2hc (CD98), a marker for basolateral membrane of proximal tubular cells in the S1 and S2 segments of the nephron, shows that both SMCT1 and SMCT2 are expressed in the apical membrane of the tubular cells. These studies also show that while SMCT2 is broadly expressed along the entire length of the proximal tubule (S1/S2/S3 segments), the expression of SMCT I is mostly limited to the S3 segment. These studies suggest that the low-affinity transporter SMCT2 initiates lactate absorption in the early parts of the proximal tubule followed by the participation of the high-affinity transporter SMCT1 in the latter parts of the proximal tubule. (c) 2007 Elsevier B.V. All rights reserved.