Cloning of prostaglandin E receptor cDNAs and molecular mechanisms of activation

前列腺素E_2（PG E_2）通过广泛分布于全身的PGE受体发挥多种生理和药理作用，如扩张血管、抑制免疫、发热等。前列腺素E受体分为三种亚型，EP1、EP2和EP3，分别与磷酸肌醇代谢、腺苷酸环化酶的刺激和抑制偶联。前列腺素是一组<20>含有环戊烷环的C_6羧酸。除PGE_2外，已知PDG_2、PGF_2<2alpha>和PGI_2通过其各自的受体产生其活性。因为几乎没有识别各自PG受体的激动剂和拮抗剂，所以并不总是清楚给定PG通过哪种受体发挥作用。为了解决这一问题，我们进行了PG受体的鉴定、克隆和信号转导分析的研究，取得了以下结果。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)我们克隆了前列腺素E受体亚型EP 1，它能升高细胞内Ca^2+浓度而不刺激磷酸肌醇代谢。3)牛肾上腺髓质存在四种EP 3受体亚型，它们通过不同的GTP结合蛋白参与不同的信号转导。4)我们成功地<2alpha>从牛卵巢黄体中克隆了PGF_2受体，并在cDNA转染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_2均<2alpha>通过谷氨酸受体参与痛觉传递，近年来，PGE受体亚型EP_1、EP_2和EP_3以及<2alpha>PGF_2受体相继被克隆为血栓素A_2受体cDNA探针。我们可以预期在不久的将来将PG的功能基团分配给PG受体蛋白的激活，从而产生向效应器的信息传递。

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.