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标题：Evolution of substrate specificity for the bile salt transporter ASBT (SLC10A2)
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作者：Daniël A. Lionarons ; James L. Boyer ; Shi-Ying Cai 等
期刊名称：JLR Papers In Press
印刷版ISSN：0022-2275
电子版ISSN：1539-7262
出版年度：2012
卷号：53
期号：8
页码：1535-1542
DOI：10.1194/jlr.M025726
语种：English
出版社：American Society for Biochemistry and Molecular Biology
摘要：The apical Na⁺-dependent bile salt transporter (ASBT/SLC10A2) is essential for maintaining the enterohepatic circulation of bile salts. It is not known when Slc10a2 evolved as a bile salt transporter or how it adapted to substantial changes in bile salt structure during evolution. We characterized ASBT orthologs from two primitive vertebrates, the lamprey that utilizes early 5α-bile alcohols and the skate that utilizes structurally different 5β-bile alcohols, and compared substrate specificity with ASBT from humans who utilize modern 5β-bile acids. Everted gut sacs of skate but not the more primitive lamprey transported ³H-taurocholic acid (TCA), a modern 5β-bile acid. However, molecular cloning identified ASBT orthologs from both species. Cell-based assays using recombinant ASBT/Asbt's indicate that lamprey Asbt has high affinity for 5α-bile alcohols, low affinity for 5β-bile alcohols, and lacks affinity for TCA, whereas skate Asbt showed high affinity for 5α- and 5β-bile alcohols but low affinity for TCA. In contrast, human ASBT demonstrated high affinity for all three bile salt types. These findings suggest that ASBT evolved from the earliest vertebrates by gaining affinity for modern bile salts while retaining affinity for older bile salts. Also, our results indicate that the bile salt enterohepatic circulation is conserved throughout vertebrate evolution.
关键词：sodium-dependent transporter ; enterohepatic circulation ; bile acids ; bile alcohols ; taurocholic acid ; lamprey ; petromyzon marinus ; skate ; leucoraja erinacea