Cloning of prostaglandin E receptor cDNAs and molecular mechanisms of activation

前列腺素（PG） E_2通过遍布全身的PGE受体发挥血管舒张、免疫抑制、发热等多种生理药理作用。PGE受体分为EP1、EP2和EP3三个亚型，分别偶联于磷酸肌苷代谢、刺激和抑制腺苷酸环化酶。前列腺素是一组含有环戊烷环的C_<20>羧酸。除PGE_2外，PDG_2、PGF_<2alpha>和PGI_2均通过各自的受体产生活性。由于很少有激动剂和拮抗剂能够识别各自的PG受体，因此并不总是清楚给定的PG通过哪个受体引起作用。为了解决这一问题，我们开展了PG受体的鉴定、克隆和信号转导分析的研究，得到了以下结果：1)用合成的稳定的PGI_2类似物进行光亲和标记，鉴定PGI_2受体蛋白。2)克隆了PGE受体EP1亚型，该亚型可在不刺激磷酸肌苷代谢的情况下提高细胞内Ca^<2+>。3) EP3受体在牛肾上腺髓质中存在4种亚型，它们通过不同的gtp结合蛋白偶联不同的信号转导。4)我们成功地从牛卵巢黄体中克隆了PGF_<2alpha>受体，并在转染cdna的中国仓鼠细胞中证实了该受体与G_q的偶联。5) PGE_2和PGF_<2alpha>均通过谷氨酸受体参与疼痛传递。近年来，PGE受体亚型EP1、EP2、EP3和PGF_<2alpha>受体相继被克隆为血栓素A_2受体cDNA作为探针。在不久的将来，我们可以期望将PG受体蛋白激活的官能团分配给效应物，从而产生信息传递。

Prostaglandin (PG) E_2 exerts diverse physiological and pharmacological actions such as vasodilatation, immunosuppression, and fever through PGE receptors ubiquitously distributed in the whole body. The PGE receptor is subdivided into three subtypes, EP1, EP2, and EP3, which are coupled to phosphoinositide metabolism, stimulation and inhibition of adenylate cyclase, respectively. Prostaglandins are a group of C_<20> carboxylic acids containing a cyclopentane ring. In addition to PGE_2, PDG_2, PGF_<2alpha>, and PGI_2 are known to produce their activities through their respective receptors. Because there are few agonists and antagonists which recognize the respective PG receptor, it is not always clear through which receptor a given PG elicits an action. To solve this problem, we carried out studies on identification and cloning of PG receptors and analysis of signal transduction and obtained following results. 1) PGI_2 receptor protein was identified by photoaffinity labeling with a synthetic stable PGI_2 analogue. 2) We cloned PGE receptor subtype EP1, which elevates the intracellular Ca^<2+> without stimulation of phosphoinositide metabolism. 3) Four isoforms of EP3 receptor exist in bovine adrenal medulla and they couple to different signal transduction through different GTP-binding proteins. 4) We succeeded in the cloning of PGF_<2alpha> receptor from bovine corpus luteum of the ovary and demonstrated the coupling of the receptor with G_q in cDNA-transfected Chinese hamster cells. 5) Both PGE_2 and PGF_<2alpha> involve pain transmission through glutamate receptors.Recently, PGE receptor subtypes EP1, EP2, and EP3 and PGF_<2alpha> receptor have been successively cloned as thromboxane A_2 receptor cDNA as probe. We can expect to assign functional groups of PGs to activation of PG receptor proteins which produces information transfer to the effector in the near future.