Expression and regulation of the taurine transporter in cultured cell lines of human origin.
Expression and regulation of the taurine transporter in cultured cell lines of human origin.
复制标题
牛磺酸转运蛋白在人源培养细胞系中的表达和调节。
DOI：
10.1007/978-1-4899-1471-2_6
复制
发表时间：
1994
影响因子：
--
通讯作者：
Leibach,FH
中科院分区：
文献类型：
--
作者：
Ganapathy,V;Leibach,FH
牛磺酸是多种组织中最丰富的游离氨基酸 (5,9,28)。组织积累牛磺酸的能力主要取决于牛磺酸和其他 3-氨基酸特异性转运蛋白的活性。某些组织可以将牛磺酸浓缩至高达 40-50 mM 的水平，而牛磺酸的血浆水平仅在 50-80 μM 范围内，这一发现表明转运蛋白在其浓缩能力方面具有独特性。三种不同的驱动力，即 Na+ 梯度、CI 梯度和膜电位，为运输系统提供能量。 Na+: Cl-: 牛磺酸的化学计量为 2: 1: 1。该转运蛋白最近从 MDCK (Madin-Darby 犬肾) 细胞 (32)、大鼠脑 (27)、小鼠脑 (15)、人 FRTL-5 甲状腺细胞 (10) 和人胎盘 (21, 25) 中克隆。牛磺酸转运蛋白 cDNA 的核苷酸序列与其他克隆转运蛋白的核苷酸序列的比较表明，牛磺酸转运蛋白属于编码 Na+- 和 Cl- 偶联转运蛋白的基因家族 (2, 3)。人类对牛磺酸的营养需求部分通过膳食来源满足，部分通过蛋氨酸和半胱氨酸的生物合成来满足。然而，生物合成能力表现出有趣的发展模式。它在胎儿和新生儿阶段不存在或非常低，并随着年龄的增长逐渐增加，达到成人水平 (1, 8, 30)。与此形成鲜明对比的是，牛磺酸的组织水平随着年龄的增长而降低，在胎儿期最高，在成年期最低 (1, 26, 29)。因此，牛磺酸似乎很可能在人类胎儿和新生儿发育中发挥重要作用 (28)。然而矛盾的是，人类胎儿和新生儿内源产生这种氨基酸的能力最低。牛奶中含有高浓度的牛磺酸，肠道吸收牛磺酸是新生儿获得这种氨基酸的主要途径。肠粘膜细胞的刷状缘膜表达 Na+ 和 CI 偶联的牛磺酸转运蛋白，负责从饮食中吸收牛磺酸 (18)。满足胎儿生命中牛磺酸营养需求的唯一可用机制是来自母亲的胎盘转移。人类胎盘面向母体的刷状缘膜
Taurine is the most abundant free amino acid in several tissues (5, 9, 28). The ability of tissues to accumulate taurine is primarily determined by the activity of a transporter that is specific for taurine and other {3-amino acids. The findings that certain tissues can concentrate taurine to levels as high as 40-50 mM with the plasma levels of taurine being in the range of only 50-80 IlM point to the uniqueness of the transporter in terms of its concentrative ability. Three different driving forces, namely a Na+ gradient, a CI-gradient, and membrane potential, energize the transport system. The Na+: Cl-: taurine stoichiometry is 2: 1: 1. The transporter has been recently cloned from MDCK (Madin-Darby Canine Kidney) cells (32), rat brain (27), mouse brain (15), human FRTL-5 thyroid cells (10) and human placenta (21, 25). A comparison of nucleotide sequences of the taurine transporter cDNAs with those of the other cloned transporters indicates that the taurine transporter belongs to a gene family which encodes Na+-and Cl--coupled transporters (2, 3). The nutritional requirements for taurine in man are met partly by dietary sources and partly by biosynthesis from methionine and cysteine. The biosynthetic capacity, however, exhibits an interesting developmental pattern. It is nonexistent or very low at fetal and neonatal stages, and progressively increases with age to reach adult levels (1, 8, 30). In marked contrast, the tissue levels of taurine decrease with age, being highest in fetal life and lowest in adult life (1, 26, 29). Therefore, it seems very likely that taurine plays an important role in fetal and neonatal development in man (28). Paradoxically however, the human fetus and the newborn have the least ability to produce this amino acid endogenously. Milk contains high concentrations of taurine, and intestinal absorption from this source is the primary route by which the newborn obtains this amino acid. The brush border membrane of the intestinal mucosal cells expresses the Na+-and CI--coupled taurine transporter that is responsible for absorption of taurine from dietary sources (18). The only mechanism available for meeting the nutritional requirements for taurine in fetal life is the placental transfer from mother. The maternal-facing brush border membrane of the human placenta