Takeuchi K, Takahashi N, Abe T, Ito O, Tsutsumi E, Taniyama Y, Abe K
Second Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Biochem Biophys Res Commun. 1994 Sep 30;203(3):1897-903. doi: 10.1006/bbrc.1994.2409.
We have cloned two isoforms of rat kidney prostaglandin E2 receptor EP3 subtype (rEP3A and rEP3B), which differ only in their cytosolic carboxyl-terminal tails (30 and 29 amino acids, respectively). The aim is to clarify the functional difference between two rEP3 receptor isoforms by examining formation of adenosine 3',5'-monophosphate (cAMP) and change in cytosolic free calcium ([Ca2+]i) in cultured cells transiently transfected with cloned rEP3A or rEP3B receptor cDNA. In immortalized renal distal tubule cells (TKC2), vasopressin (VP) stimulated cAMP formation, and the cAMP formation was significantly attenuated by a non-peptide VP receptor antagonist, OPC-31260. The VP-induced increase in cAMP formation was also attenuated by over-expression of rEP3A receptor but not that of rEP3B receptor. On the other hand, in COS-7 cells transfected with rEP3B receptor cDNA, PGE2 induced an increase in [Ca2+]i, but no increase in [Ca2+]i was observed in the cells transfected with rEP3A cDNA. In conclusion, rEP3A receptor is suggested to antagonize VP (V2) receptor by inhibiting cAMP formation, whereas rEP3B receptor is linked with Ca2+ messenger system.
我们克隆了大鼠肾脏前列腺素E2受体EP3亚型的两种同工型（rEP3A和rEP3B），它们仅在胞质羧基末端尾巴上有所不同（分别为30和29个氨基酸）。目的是通过检测用克隆的rEP3A或rEP3B受体cDNA瞬时转染的培养细胞中3',5'-单磷酸腺苷（cAMP）的形成以及胞质游离钙（[Ca2+]i）的变化，来阐明两种rEP3受体同工型之间的功能差异。在永生化肾远端小管细胞（TKC2）中，血管加压素（VP）刺激cAMP形成，并且非肽VP受体拮抗剂OPC-31260可显著减弱cAMP的形成。rEP3A受体的过表达也减弱了VP诱导的cAMP形成增加，但rEP3B受体的过表达则没有这种作用。另一方面，在用rEP3B受体cDNA转染的COS-7细胞中，前列腺素E2（PGE2）诱导[Ca2+]i增加，但在用rEP3A cDNA转染的细胞中未观察到[Ca2+]i增加。总之，rEP3A受体被认为通过抑制cAMP形成来拮抗VP（V2）受体，而rEP3B受体与Ca2+信使系统相关。
