Borden L A, Smith K E, Gustafson E L, Branchek T A, Weinshank R L
Department of Pharmacology, Synaptic Pharmaceutical Corporation, Paramus, New Jersey 07652.
J Neurochem. 1995 Mar;64(3):977-84. doi: 10.1046/j.1471-4159.1995.64030977.x.
A cDNA clone encoding a human gamma-aminobutyric acid (GABA) transporter has been isolated from a brain cDNA library, and its functional properties have been examined in mammalian cells. The nucleotide sequence predicts a transporter with 614 amino acids and 12 putative transmembrane domains. The highest degree of amino acid identity is with a betaine/GABA transporter originally cloned from the dog termed BGT-1 (91%) and a related transporter from mouse brain (87%). These identities are similar to those for species homologues of other neurotransmitter transporters and suggest that the new clone represents the human homologue of BGT-1. The transporter displays high affinity for GABA (IC50 of 30 microM) and is also sensitive to phloretin, L-2,4-diaminobutyric acid, and hypotaurine (IC50 values of approximately 150-400 microM). The osmolyte betaine is approximately 25-fold weaker than GABA, displaying an IC50 of approximately 1 mM. The relative potencies of these inhibitors at human BGT-1 differ from those of mouse and dog BGT-1. Northern blot analysis reveals that BGT-1 mRNA is widely distributed throughout the human brain. The cloning of the human homologue of BGT-1 will further our understanding of the roles of GABA and betaine in neural function.
一个编码人类γ-氨基丁酸（GABA）转运体的cDNA克隆已从大脑cDNA文库中分离出来，并且其功能特性已在哺乳动物细胞中进行了检测。核苷酸序列预测该转运体有614个氨基酸和12个假定的跨膜结构域。氨基酸同源性最高的是最初从狗中克隆的甜菜碱/GABA转运体，称为BGT-1（91%），以及来自小鼠大脑的相关转运体（87%）。这些同源性与其他神经递质转运体的物种同源物相似，表明新克隆代表了BGT-1的人类同源物。该转运体对GABA具有高亲和力（IC50为30微摩尔），并且对根皮素、L-2,4-二氨基丁酸和亚牛磺酸也敏感（IC50值约为150 - 400微摩尔）。渗透溶质甜菜碱的亲和力比GABA弱约25倍，IC50约为1毫摩尔。这些抑制剂在人类BGT-1上的相对效力与小鼠和狗的BGT-1不同。Northern印迹分析显示BGT-1 mRNA广泛分布于整个人脑中。BGT-1人类同源物的克隆将进一步加深我们对GABA和甜菜碱在神经功能中作用的理解。
