Vu T K, Hung D T, Wheaton V I, Coughlin S R
Department of Medicine, University of California, San Francisco 94143-0524.
Cell. 1991 Mar 22;64(6):1057-68. doi: 10.1016/0092-8674(91)90261-v.
We isolated a cDNA encoding a functional human thrombin receptor by direct expression cloning in Xenopus oocytes. mRNA encoding this receptor was detected in human platelets and vascular endothelial cells. The deduced amino acid sequence revealed a new member of the seven transmembrane domain receptor family with a large amino-terminal extracellular extension containing a remarkable feature. A putative thrombin cleavage site (LDPR/S) resembling the activation cleavage site in the zymogen protein C (LDPR/I) was noted 41 amino acids carboxyl to the receptor's start methionine. A peptide mimicking the new amino terminus created by cleavage at R41 was a potent agonist for both thrombin receptor activation and platelet activation. "Uncleavable" mutant thrombin receptors failed to respond to thrombin but were responsive to the new amino-terminal peptide. These data reveal a novel signaling mechanism in which thrombin cleaves its receptor's amino-terminal extension to create a new receptor amino terminus that functions as a tethered ligand and activates the receptor.
我们通过在非洲爪蟾卵母细胞中进行直接表达克隆，分离出了一个编码功能性人凝血酶受体的cDNA。在人血小板和血管内皮细胞中检测到了编码该受体的mRNA。推导的氨基酸序列显示，它是七跨膜结构域受体家族的一个新成员，其氨基末端有一个大的细胞外延伸区，具有一个显著特征。在受体起始甲硫氨酸羧基端41个氨基酸处，发现了一个类似于酶原蛋白C激活切割位点（LDPR/I）的假定凝血酶切割位点（LDPR/S）。模拟在R41处切割产生的新氨基末端的肽，是凝血酶受体激活和血小板激活的有效激动剂。“不可切割”的突变凝血酶受体对凝血酶无反应，但对新的氨基末端肽有反应。这些数据揭示了一种新的信号传导机制，即凝血酶切割其受体的氨基末端延伸区，产生一个新的受体氨基末端，作为一种拴系配体发挥作用并激活受体。
