Euryhaline pufferfish NBCe1 differs from nonmarine species NBCe1 physiology
Euryhaline pufferfish NBCe1 differs from nonmarine species NBCe1 physiology
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DOI：
10.1152/ajpcell.00233.2011
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发表时间：
2012-04-01
影响因子：
5.5
通讯作者：
Romero, Michael F.
中科院分区：
文献类型：
--
作者：
Chang, Min-Hwang;Plata, Consuelo;Romero, Michael F.
张 MH、普拉塔 C、栗田 Y、加藤 A、广濑 S、罗梅罗 MF。广盐河豚 NBCe1 与非海洋物种 NBCe1 生理学不同。 Am J Physiol Cell Physiol 302：C1083-C1095，2012。首次发表于 2011 年 12 月 7 日； doi:10.1152/ajpcell.00233.2011.-海洋鱼类饮用海水，并通过鳃和肠道上皮细胞主动运输盐分来消除多余的盐分。广盐河豚 (Takifugu obscurus, mefugu) 进入海水后会在肠腔表面形成 CaCO3 沉淀。肠上皮细胞基底外侧膜的 NBCe1 (Slc4a4) 在跨上皮肠 HCO3- 分泌中起主要作用，对于 mefugu 适应海水至关重要。我们检测了爪蟾卵母细胞表达系统中的河豚-NBCe1 (fNBCe1) 活性。与其他物种中发现的 NBCe1 类似，fNBCe1 是一种产电 Na+/HCO3 协同转运蛋白，对二苯乙烯抑制剂 DIDS 敏感。然而，我们的实验揭示了哺乳动物或其他硬骨鱼NBCe1直系同源物中未发现的几种独特且可区分的fNBCe1转运特征：生电Li+/nHCO(3)(-)共转运； HCO3- 独立、DIDS 不敏感的运输；并增加基础细胞内 Na+ 积累。 fNBCe1 是一种电压依赖性 Na+/nHCO(3)(-) 协同转运蛋白，可独立于细胞外 Na+ 或 HCO3- 浓度进行约 -60 mV 的整流。 Na+ 去除（0Na(+) 预脉冲）对于产生真正的 HCO3- 引发电流是必要的。 HCO3-的添加导致巨大的外向电流和快速的电流衰减。 HCO3-电流的动力学分析表明，在生理范围（膜电位 = -80 mV；[HCO3-] = 10 mM）内，fNBCe1 比人肾 NBCe1 (hkNBCe1) 具有更高的转运能力（更高的最大电流）和更低的亲和力（更高的 K-m）。在这种状态下，fNBCe1 有利于作为跨上皮 HCO3- 分泌，与 hkNBCe1 相反，从血液到管腔侧。因此，fugu-NBCe1 代表了第一个基于直系同源物的工具，用于研究 NBCe1 中的氨基酸取代以及这些取代如何改变离子和电压依赖性。
Chang MH, Plata C, Kurita Y, Kato A, Hirose S, Romero MF. Euryhaline pufferfish NBCe1 differs from nonmarine species NBCe1 physiology. Am J Physiol Cell Physiol 302: C1083-C1095, 2012. First published December 7, 2011; doi:10.1152/ajpcell.00233.2011.-Marine fish drink seawater and eliminate excess salt by active salt transport across gill and gut epithelia. Euryhaline pufferfish (Takifugu obscurus, mefugu) forms a CaCO3 precipitate on the luminal gut surface after transitioning to seawater. NBCe1 (Slc4a4) at the basolateral membrane of intestinal epithelial cell plays a major role in transepithelial intestinal HCO3- secretion and is critical for mefugu acclimation to seawater. We assayed fugu-NBCe1 (fNBCe1) activity in the Xenopus oocyte expression system. Similar to NBCe1 found in other species, fNBCe1 is an electrogenic Na+/HCO3 cotransporter and sensitive to the stilbene inhibitor DIDS. However, our experiments revealed several unique and distinguishable fNBCe1 transport characteristics not found in mammalian or other teleost NBCe1-orthologs: electrogenic Li+/nHCO(3)(-) cotransport; HCO3- independent, DIDS-insensitive transport; and increased basal intracellular Na+ accumulation. fNBCe1 is a voltage-dependent Na+/nHCO(3)(-) cotransporter that rectifies, independently from the extracellular Na+ or HCO3- concentration, around -60 mV. Na+ removal (0Na(+) pre-pulse) is necessary to produce the true HCO3--elicited current. HCO3- addition results in huge outward currents with quick current decay. Kinetic analysis of HCO3- currents reveals that fNBCe1 has a much higher transport capacity (higher maximum current) and lower affinity (higher K-m) than human kidney NBCe1 (hkNBCe1) does in the physiological range (membrane potential = -80 mV; [HCO3-] = 10 mM). In this state, fNBCe1 is in favor of operating as transepithelial HCO3- secretion, opposite of hkNBCe1, from blood to the luminal side. Thus, fugu-NBCe1 represents the first ortholog-based tool to study amino acid substitutions in NBCe1 and how those change ion and voltage dependence.