Expression and regulation of the neutral amino acid transporter B0AT1 in rat small intestine
Expression and regulation of the neutral amino acid transporter B0AT1 in rat small intestine
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DOI：
10.1371/journal.pone.0184845
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发表时间：
2017-09-15
期刊：
影响因子：
3.7
通讯作者：
Verrey, Francois
中科院分区：
文献类型：
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作者：
Jando, Julia;Camargo, Simone M. R.;Verrey, Francois
肠上皮细胞对中性氨基酸的吸收是由广泛的中性氨基酸转运蛋白B(0)AT1(SLC6A19)介导的。它的肠道表达依赖于膜锚定的肽酶血管紧张素转换酶2(ACE2)的共表达，并被氨基肽酶N(CD13)增强。本研究探讨了B(0)AT1及其辅助性多肽酶的表达及其在大鼠小肠中的转运功能。此外，我们还测试了饮食蛋白质和氨基酸对其可能的短期和长期调节作用。免疫荧光显示B(0)AT1、ACE2和CD13共定位于小肠绒毛的管腔膜上，Western blotting显示它们的蛋白表达沿远端方向增加。此外，我们观察到与非活动期相比，夜间活动期中性氨基酸L-异亮氨酸的转运活性增加。灌胃氨基酸鸡尾酒可以延迟胃排空，但我们没有观察到急性饮食对B(0)AT1蛋白表达和L-异亮氨酸转运的调节。对不同饲料对B(0)AT1、ACE2和CD13的慢性饲料调节的研究表明，在添加氨基酸的饲料中，B(0)AT1蛋白的表达在近端增加，而在远端没有增加，而ACE2的蛋白表达则相反。饮食对CD13蛋白表达的调节不像对其他两种蛋白质那样明显。环摄取实验表明，添加氨基酸的饲料对L-异亮氨酸的吸收有增加的趋势，而在体内，高蛋白和氨基酸的饲料对L-异亮氨酸的吸收更有效。此外，在高蛋白和氨基酸饮食下，血浆支链氨基酸水平升高。综上所述，我们的实验没有揭示急性氨基酸诱导的B(0)AT1的调节，但揭示了一种主要局限于小肠近端的慢性饮食适应。
Absorption of neutral amino acids across the luminal membrane of intestinal enterocytes is mediated by the broad neutral amino acid transporter B(0)AT1 (SLC6A19). Its intestinal expression depends on co-expression of the membrane-anchored peptidase angiotensin converting enzyme 2 (ACE2) and is additionally enhanced by aminopeptidase N (CD13). We investigated in this study the expression of B(0)AT1 and its auxiliary peptidases as well as its transport function along the rat small intestine. Additionally, we tested its possible short-and long-term regulation by dietary proteins and amino acids. We showed by immunofluorescence that B(0)AT1, ACE2 and CD13 co-localize on the luminal membrane of small intestinal villi and by Western blotting that their protein expression increases in distal direction. Furthermore, we observed an elevated transport activity of the neutral amino acid L-isoleucine during the nocturnal active phase compared to the inactive one. Gastric emptying was delayed by intragastric application of an amino acid cocktail but we observed no acute dietary regulation of B(0)AT1 protein expression and L-isoleucine transport. Investigation of the chronic dietary regulation of B(0)AT1, ACE2 and CD13 by different diets revealed an increased B(0)AT1 protein expression under amino acid-supplemented diet in the proximal section but not in the distal one and for ACE2 protein expression a reverse localization of the effect. Dietary regulation for CD13 protein expression was not as distinct as for the two other proteins. Ring uptake experiments showed a tendency for increased L-isoleucine uptake under amino acid-supplemented diet and in vivo L-isoleucine absorption was more efficient under high protein and amino acid-supplemented diet. Additionally, plasma levels of branched-chain amino acids were elevated under high protein and amino acid diet. Taken together, our experiments did not reveal an acute amino acid-induced regulation of B(0)AT1 but revealed a chronic dietary adaptation mainly restricted to the proximal segment of the small intestine.