Sodium-coupled electrogenic transport of pyroglutamate (5-oxoproline) via SLC5A8, a monocarboxylate transporter
Sodium-coupled electrogenic transport of pyroglutamate (5-oxoproline) via SLC5A8, a monocarboxylate transporter
复制标题
DOI：
10.1016/j.bbamem.2010.03.002
复制
发表时间：
2010-06-01
影响因子：
3.4
通讯作者：
Prasad, Puttur D.
中科院分区：
文献类型：
--
作者：
Miyauchi, Seiji;Gopal, Elangovan;Prasad, Puttur D.
焦谷氨酸，也称为5-氧代脯氨酸，是脯氨酸的结构类似物。这种氨基酸衍生物是谷胱甘肽代谢的副产物，通过Na+偶联转运机制在肾脏中被有效重吸收。以前的研究集中在氨基酸转运系统在肾脏重吸收这种化合物的潜在参与。在这里，我们表明，它不是氨基酸转运系统，而是Na+ -偶联的单羧酸转运蛋白SLC 5A 8在这个重吸收过程中发挥了主导作用。克隆的人和小鼠SLC 5A 8在哺乳动物细胞中的表达诱导了可被各种SLC 5A 8底物替代的焦谷氨酸的Na+依赖性转运。SLC 5A 8介导的焦谷氨酸转运是饱和的，米氏常数为0.36 +/- 0.04 mM。Na+ -转运过程的活化表现出S形动力学，希尔系数为1.8 +/- 0.4，表明活化过程中涉及一种以上的Na+。SLC 5A 8在非洲爪蟾卵母细胞中的表达在电压钳条件下在焦谷氨酸存在下诱导Na+依赖性内向电流。诱导半最大电流所需的焦谷氨酸盐浓度为0.19 +/- 0.01 mM。Na+激活动力学呈S形，希尔系数为2.3 +/- 0.2。Icline是一种SLC 5A 8的阻断剂，可抑制表达SLC 5A 8的卵母细胞中焦谷氨酸诱导的电流;引起半数最大抑制所需的阻断剂浓度为14 +/- 1 μ M。SLC 5A 8的参与可以在兔肾刷状缘膜囊泡中通过显示这些囊泡中焦谷氨酸盐的Na+依赖性摄取可通过已知的SLC 5A 8底物来证实。Na+梯度驱动的焦谷氨酸摄取被缬氨霉素诱导的内部负K扩散电位刺激，表明摄取过程是产电的。(C)2010 Elsevier BV保留所有权利。
Pyroglutamate, also known as 5-oxoproline, is a structural analog of proline. This amino acid derivative is a byproduct of glutathione metabolism, and is reabsorbed efficiently in kidney by Na+ -coupled transport mechanisms. Previous studies have focused on potential participation of amino acid transport systems in renal reabsorption of this compound. Here we show that it is not the amino acid transport systems but instead the Na+ -coupled monocarboxylate transporter SLC5A8 that plays a predominant role in this reabsorptive process. Expression of cloned human and mouse SLC5A8 in mammalian cells induces Na+ -dependent transport of pyroglutamate that is inhibitable by various SLC5A8 substrates. SLC5A8-mediated transport of pyroglutamate is saturable with a Michaelis constant of 0.36 +/- 0.04 mM. Na+ -activation of the transport process exhibits sigmoidal kinetics with a Hill coefficient of 1.8 +/- 0.4, indicating involvement of more than one Na+ in the activation process. Expression of SLC5A8 in Xenopus laevis oocytes induces Na+ -dependent inward currents in the presence of pyroglutamate under voltage-clamp conditions. The concentration of pyroglutamate necessary for induction of half-maximal current is 0.19 +/- 0.01 mM. The Na+ -activation kinetics is sigmoidal with a Hill coefficient of 2.3 +/- 0.2. Ibuprofen, a blocker of SLC5A8, suppressed pyroglutamate-induced currents in SLC5A8-expressing oocytes; the concentration of the blocker necessary for causing half-maximal inhibition is 14 +/- 1 mu M. The involvement of SLC5A8 can be demonstrated in rabbit renal brush border membrane vesicles by showing that the Na+ -dependent uptake of pyroglutamate in these vesicles is inhibitable by known substrates of SLC5A8. The Na+ gradient-driven pyroglutamate uptake was stimulated by an inside-negative K diffusion potential induced by valinomycin, showing that the uptake process is electrogenic.(C) 2010 Elsevier B.V. All rights reserved.