Na^+-依赖性谷氨酰胺载体ASCT2的生物学功能及表皮生长因子的调控作用  

The biological function of Na^+-dependent glutamine transporter ASCT2 and regulatory effect of epidermal growth factor

作　　者：黄骞[1] 李宁[1] 朱维铭[1] 李秋荣[1] 王斌[1] 石斌[1] 黎介寿[1] 

机构地区：[1]第二军医大学南京临床学院(南京军区南京总医院)解放军普通外科研究所,江苏南京210002

出　　处：《肠外与肠内营养》2006年第6期329-334,341,共7页Parenteral & Enteral Nutrition

基　　金：国家自然科学基金课题(批准号:30371392);第二军医大学博士创新性研究资助

摘　　要：目的:Na+-依赖性中性氨基酸载体ASCT2,是一种广谱的氨基酸载体,它的生理功能主要是转运肠腔内谷氨酰胺、丙氨酸、丝氨酸和半胱氨酸等中性氨基酸。本研究拟对ASCT2载体转运特性及表皮生长因子对其的调控机制作一探讨。方法:体外培养Caco-2细胞,观察ASCT2对核素标记谷氨酰胺的转运特性、动力学特征及底物特异性;利用ASCT2多克隆抗体及TaqMan实时定量PCR方法,研究表皮生长因子对ASCT2功能的调控作用。结果:Caco-2细胞中Na+-依赖性3H-L-谷氨酰胺(50μmol)的转运速率为(635±80.1)pmol/(mgprotein·min),大部分中性氨基酸如丙氨酸、丝氨酸、半胱氨酸等可对其产生竞争性抑制;在表皮生长因子(100μg/L)孵育下,可以提高其转运活性约100%(P<0.01),Western-blot及real-timePCR显示其蛋白及mRNA表达增高。结论:谷氨酰胺载体ASCT2对核素标记谷氨酰胺具有强大的转运活性,对中性氨基酸底物具有亲和特异性;表皮生长因子对其转运活性、蛋白表达、mRNA丰度具有上调作用。Objective ：The amino acid transporter of intestinal epithelial cells plays a vital role in nutrient uptake of human body. The Na^＋-dependent neutral amino acid transporter ASCT2 is a broad-scope amino acid transporter, which transports most of neutral amino acids such as glutamine, alanine, serine, and eystine. The study was designed to investigate the functional characteristics of Na^＋-dependent glutamine transporter ASCT2 and regulatory effect of epidermal growth factor. Methods ： Using human intestinal epithelial cell line Caco-2, we investigated the transport and kinetic characteristics of 3 H-L-glutamine, and substrate specialty of transporter ASCT2. Furthermore, we explored the regulatory action of EGF on ASCT2 using the ASCT2 polyclonal antibody and TaqMan real-time PCR methods. Results：The velocity of Na^＋-dependent glutamine uptake in Caco-2 cell lines was （635±80.1 ） pmol/mg protein/min. Most of neutral amino acids such as alanine, serine, and cystine could competitively inhibit the glutamine uptake. Epidermal growth factor （100μg/L） could increase 100 percent of the Na^＋-dependent glutamine uptake （P 〈 0.01 ）. The results of western-blot and real-time PCR indicated that EGF increased the expression of ASCT2 protein and mRNA. Conclusion：The Na^＋-dependent neutral amino acid transporter ASCT2 has strong transport activity of L-glutamine. ASCT2 also displays its dermal growth factor can up-regulate the transport activity substrate specialty of neutral amino acids. Epiand expression of ASCT2 protein and mRNA.

关 键 词：肠上皮细胞 谷氨酰胺载体 ASCT2 表皮生艮因子 

分 类 号：R346[医药卫生—基础医学]