Contributions of system A subtypes to α-methylaminoisobutyric acid uptake by placental microvillous membranes of human and rat.
Contributions of system A subtypes to α-methylaminoisobutyric acid uptake by placental microvillous membranes of human and rat.
复制标题
系统 A 亚型对人和大鼠胎盘微绒毛膜吸收 α-甲基氨基异丁酸的贡献。
DOI：
10.1007/s00726-017-2384-7
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Nakashima E
中科院分区：
文献类型：
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作者：
Takahashi Y;Nishimura T;Maruyama T;Tomi M;Nakashima E
系统A由三种亚型组成，钠偶联中性氨基酸转运蛋白1（SNAT 1），SNAT 2和SNAT 4，它们都在胎盘中表达。本研究的目的是评估三种亚型中的每一种对人类和大鼠胎盘MVM中总系统A介导的摄取的贡献，分别使用甜菜碱和l-精氨酸作为SNAT 2和SNAT 4的亚型选择性抑制剂。确定了在SNAT过表达细胞中用于亚型选择性抑制的甜菜碱和l-精氨酸的适当浓度。发现10 mM甜菜碱特异性且几乎完全抑制人和大鼠SNAT 2介导的[14 C]α-甲基氨基异丁酸（[14 C]MeAIB）摄取，而5 mM精氨酸特异性且完全抑制通过人SNAT 4的[3 H]甘氨酸摄取以及通过大鼠SNAT 4的[14 C]MeAIB摄取。在人和大鼠胎盘MVM囊泡中，20 mM未标记的MeAIB几乎完全抑制了[14 C]MeAIB的钠依赖性摄取。L-精氨酸（5 mM）部分抑制了人的摄取，但几乎不影响大鼠的摄取。甜菜碱（10 mM）部分抑制大鼠的摄取，但几乎不影响它在人类。这些结果表明，SNAT 1是最有可能的主要贡献者系统A介导的MeAIB摄取的人类和大鼠的MVM囊泡，其余的摄取主要是由SNAT 4在人类和SNAT 2在大鼠介导。因此，使用甜菜碱和l-精氨酸的抑制研究是有用的，以表征系统A介导的运输的分子机制。
System A consists of three subtypes, sodium-coupled neutral amino acid transporter 1 (SNAT1), SNAT2, and SNAT4, which are all expressed in the placenta. The aim of this study was to evaluate the contributions of each of the three subtypes to total system A-mediated uptake in placental MVM of human and rat, using betaine andl-arginine as subtype-selective inhibitors of SNAT2 and SNAT4, respectively. Appropriate concentrations of betaine andl-arginine for subtype-selective inhibition in SNAT-overexpressing cells were identified. It was found that 10 mM betaine specifically and almost completely inhibited human and rat SNAT2-mediated [14C]α-methylaminoisobutyric acid ([14C]MeAIB) uptake, while 5 mMl-arginine specifically and completely inhibited [3H]glycine uptake via human SNAT4, as well as [14C]MeAIB uptake via rat SNAT4. In both human and rat placental MVM vesicles, sodium-dependent uptake of [14C]MeAIB was almost completely inhibited by 20 mM unlabeled MeAIB.l-Arginine (5 mM) partly inhibited the uptake in humans, but hardly affected that in rats. Betaine (10 mM) partly inhibited the uptake in rats, but hardly affected it in humans. These results suggest that SNAT1 is most likely the major contributor to system A-mediated MeAIB uptake by human and rat MVM vesicles and that the remaining uptake is mainly mediated by SNAT4 in humans and SNAT2 in rats. Thus, inhibition studies using betaine andl-arginine are useful to characterize the molecular mechanisms of system A-mediated transport.