Functional and molecular characterization of the shark renal Na-K-Cl cotransporter:: novel aspects
Functional and molecular characterization of the shark renal Na-K-Cl cotransporter:: novel aspects
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DOI：
10.1152/ajprenal.00107.2002
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发表时间：
2002-11-01
影响因子：
4.2
通讯作者：
Isenring, P
中科院分区：
文献类型：
--
作者：
Gagnon, É;Forbush, B;Isenring, P
Na-K-Cl协同转运蛋白亚型1（NKCC 1）已从几个物种中分离出来，包括棘角鲨。第二种肾脏特异性亚型（NKCC 2）主要从高等脊椎动物中克隆出来。在这里，我们已经分离出S。发现它至少产生四种剪接变体（saNKCC 2A、saNKCC 2F、saNKCC 2AF和saNKCC 2AFno 8），其相似性为1，090个残基。这些成绩单在非洲爪蟾卵母细胞中的表达表明，只有A和F的变体是功能性的，并且它们在低氯或高渗介质中孵育后更活跃。暴露于这些介质后的激活率异常迅速，首次证明NKCC 2本身是Cl调节的重要位点，并且涉及胞外结构域。这项研究中另一个值得注意的发现是未能鉴定出NKCC 2B，这是一种在高等脊椎动物肾脏中发现的变体，并在致密斑细胞中特异性表达。这一结果，结合鲨鱼肾脏缺乏发育良好的肾小球器官的事实，表明B外显子进化作为选择压力的结果（可能是通过外显子复制），NKCC 2 B和致密斑之间存在限制性关系。
The Na-K-Cl cotransporter isoform 1 (NKCC1) has been isolated from several species, including Squalus acanthias. A second kidney-specific isoform (NKCC2) has been cloned mainly from higher vertebrates. Here, we have isolated the S. acanthias NKCC2 and found that it is produced in at least four spliced variants (saNKCC2A, saNKCC2F, saNKCC2AF, and saNKCC2AFno8) of similar to1,090 residues. Expression of these transcripts in Xenopus laevis oocytes revealed that only the A and F variants are functional and that they are more active after incubation in low-Cl or hyperosmolar media. Rates of activation after exposure to these media were exceptionally rapid, demonstrating for the first time that the NKCC2 itself represents an important site of regulation by Cl and that extracellular domains are involved. Another remarkable finding in this study was the failure to identify NKCC2B, a variant found in the kidney of higher vertebrates and expressed specifically in macula densa cells. This result, in conjunction with the fact that the shark kidney lacks a well-developed juxtaglomerular apparatus, suggests that the B exon evolved as a result of selective pressure (presumably by exon duplication) and that a restricted relationship exists between NKCC2B and macula densa.