Xu W F, Andersen H, Whitmore T E, Presnell S R, Yee D P, Ching A, Gilbert T, Davie E W, Foster D C
Department of Biochemistry, University of Washington, Box 357350, Seattle, WA 98195-7350, USA.
Proc Natl Acad Sci U S A. 1998 Jun 9;95(12):6642-6. doi: 10.1073/pnas.95.12.6642.
Protease-activated receptors 1-3 (PAR1, PAR2, and PAR3) are members of a unique G protein-coupled receptor family. They are characterized by a tethered peptide ligand at the extracellular amino terminus that is generated by minor proteolysis. A partial cDNA sequence of a fourth member of this family (PAR4) was identified in an expressed sequence tag database, and the full-length cDNA clone has been isolated from a lymphoma Daudi cell cDNA library. The ORF codes for a seven transmembrane domain protein of 385 amino acids with 33% amino acid sequence identity with PAR1, PAR2, and PAR3. A putative protease cleavage site (Arg-47/Gly-48) was identified within the extracellular amino terminus. COS cells transiently transfected with PAR4 resulted in the formation of intracellular inositol triphosphate when treated with either thrombin or trypsin. A PAR4 mutant in which the Arg-47 was replaced with Ala did not respond to thrombin or trypsin. A hexapeptide (GYPGQV) representing the newly exposed tethered ligand from the amino terminus of PAR4 after proteolysis by thrombin activated COS cells transfected with either wild-type or the mutant PAR4. Northern blot showed that PAR4 mRNA was expressed in a number of human tissues, with high levels being present in lung, pancreas, thyroid, testis, and small intestine. By fluorescence in situ hybridization, the human PAR4 gene was mapped to chromosome 19p12.
蛋白酶激活受体1 - 3（PAR1、PAR2和PAR3）是独特的G蛋白偶联受体家族的成员。它们的特征是在细胞外氨基末端有一个通过轻微蛋白水解产生的拴系肽配体。在一个表达序列标签数据库中鉴定出了该家族第四个成员（PAR4）的部分cDNA序列，并从淋巴瘤Daudi细胞cDNA文库中分离出了全长cDNA克隆。该开放阅读框编码一个由385个氨基酸组成的七跨膜结构域蛋白，与PAR1、PAR2和PAR3具有33%的氨基酸序列同一性。在细胞外氨基末端鉴定出一个假定的蛋白酶切割位点（Arg - 47/Gly - 48）。用PAR4瞬时转染的COS细胞在用凝血酶或胰蛋白酶处理时会导致细胞内三磷酸肌醇的形成。将Arg - 47替换为Ala的PAR4突变体对凝血酶或胰蛋白酶无反应。一种代表PAR4氨基末端经凝血酶蛋白水解后新暴露的拴系配体的六肽（GYPGQV）激活了用野生型或突变型PAR4转染的COS细胞。Northern印迹显示PAR4 mRNA在多种人类组织中表达，在肺、胰腺、甲状腺、睾丸和小肠中含量较高。通过荧光原位杂交，将人类PAR4基因定位于19号染色体p12区域。
