Kambayashi Y, Takahashi K, Bardhan S, Inagami T
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee.
Kidney Int. 1994 Dec;46(6):1502-4. doi: 10.1038/ki.1994.430.
More than two isoforms have been identified for angiotensin receptors based on their ligand selectivity. The objective of this study is to determine the molecular structure of angiotensin type 2 receptor (AT2), whose physiological functions are still an enigma despite extensive studies on its distribution in fetal tissues. We expression-cloned a cDNA of an affinity-purified AT2 from rat pheochromocytoma cells (PC12w). The AT2 cDNA clone comprises 2,868 nucleotides and encodes a 363 amino acid protein with seven putative transmembrane domains. The dissociation constant for its binding to 125I-CGP42112A, an AT2-specific ligand, was 0.11 +/- 0.01 nM. Its binding to 0.5 nM 125I-[Sar1,Ile8]-Ang II was not inhibited by Dup 753 but by PD123319 (IC50 = 1.7 +/- 0.2 nM). These binding features are characteristic of angiotensin type 2 receptor. The amino acid sequence analysis of the purified AT2 corroborated the amino terminus of the deduced primary structure of AT2. Angiotensin type 1 receptor (AT1) is the most closely related to AT2 but with only 32% amino acid sequence identity. Angiotensin II attenuated membrane-associated protein tyrosine phosphatase activity in the COS-7 cells stably expressing AT2 through a pertussis toxin-sensitive G protein. However, the physiological function of AT2 in the fetal kidney is still unresolved.
根据配体选择性，已鉴定出两种以上的血管紧张素受体亚型。本研究的目的是确定2型血管紧张素受体（AT2）的分子结构，尽管对其在胎儿组织中的分布进行了广泛研究，但其生理功能仍是一个谜。我们从大鼠嗜铬细胞瘤细胞（PC12w）中表达克隆了亲和纯化的AT2的cDNA。AT2 cDNA克隆包含2868个核苷酸，编码一个具有7个推定跨膜结构域的363个氨基酸的蛋白质。其与AT2特异性配体125I-CGP42112A结合的解离常数为0.11±0.01 nM。其与0.5 nM 125I-[Sar1，Ile8]-血管紧张素II的结合不受Dup 753抑制，但受PD123319抑制（IC50 = 1.7±0.2 nM）。这些结合特征是2型血管紧张素受体的特征。纯化的AT2的氨基酸序列分析证实了AT2推导的一级结构的氨基末端。1型血管紧张素受体（AT1）与AT2关系最为密切，但氨基酸序列同一性仅为32%。血管紧张素II通过百日咳毒素敏感的G蛋白减弱了稳定表达AT2的COS-7细胞中膜相关蛋白酪氨酸磷酸酶的活性。然而，AT2在胎儿肾脏中的生理功能仍未解决。
