Wu H, Turner J T, Halenda S P
Department of Pharmacology, School of Medicine, University of Missouri-Columbia.
J Pharmacol Exp Ther. 1991 Aug;258(2):607-12.
Phospholipase D (PLD) can be activated by a variety of receptor agonists in different cell types. However, an effect of prostaglandins (PGs) on the activity of this enzyme has not been demonstrated previously. In this study, we found that PGE1 could stimulate PLD in human erythroleukemia cells, as measured by phosphatidylethanol formation, with an ED50 of 3.5 x 10(-7) M. PGE2 was also active, but other PGs including prostacyclin, PGD2 and PGF2, had no effect. PGE1 also elicited cyclic AMP production over the same concentration range that activated PLD. However, it is unlikely that cyclic AMP per se is responsible for PGE-induced PLD activation, because PLD could be substantially activated by PGE2 at concentrations (0.1-1 microM) which did not stimulate cyclic AMP production. Furthermore, no increase of phosphatidylethanol formation could be observed when cells were treated with other adenylyl cyclase-activating agents such as prostacyclin, forskolin and vasoactive intestinal peptide. In Ca+(+)-free medium, PLD activation by PGE1 and PGE2 was greatly reduced, indicating that their effect was through a Ca+(+)-dependent pathway. Pretreatment of cells with pertussis toxin abolished PGE1- and PGE2-stimulated PLD activity, implying the involvement of a G protein in the PGE-mediated signal transduction pathway. Our results not only indicate that E-series PGs may initiate some of their cellular effects through a novel pathway, activation of PLD, but also suggest that PGE-stimulated PLD activity in human erythroleukemia cells is Ca+(+)-dependent and is regulated via a pertussis toxin-sensitive G protein.
磷脂酶D（PLD）可被不同细胞类型中的多种受体激动剂激活。然而，前列腺素（PGs）对该酶活性的影响此前尚未得到证实。在本研究中，我们发现PGE1可刺激人红白血病细胞中的PLD，通过磷脂酰乙醇的形成来衡量，其半数有效剂量（ED50）为3.5×10^(-7)M。PGE2也有活性，但包括前列环素、PGD2和PGF2在内的其他PGs则无作用。PGE1在激活PLD的相同浓度范围内也能引发环磷酸腺苷（cAMP）的产生。然而，cAMP本身不太可能是PGE诱导的PLD激活的原因，因为在不刺激cAMP产生的浓度（0.1 - 1微摩尔）下，PGE2能显著激活PLD。此外，当用其他腺苷酸环化酶激活剂如前列环素、福斯高林和血管活性肠肽处理细胞时，未观察到磷脂酰乙醇形成的增加。在无钙离子的培养基中，PGE1和PGE2对PLD的激活作用大大降低，表明它们的作用是通过钙离子依赖途径。用百日咳毒素预处理细胞可消除PGE1和PGE2刺激的PLD活性，这意味着G蛋白参与了PGE介导的信号转导途径。我们的结果不仅表明E系列PGs可能通过一种新的途径，即激活PLD来启动它们的一些细胞效应，还表明PGE刺激的人红白血病细胞中的PLD活性是钙离子依赖的，并通过一种对百日咳毒素敏感的G蛋白进行调节。
