Nakashima Karin, Ueno Noriko, Kamei Daisuke, Tanioka Toshihiro, Nakatani Yoshihito, Murakami Makoto, Kudo Ichiro
Department of Health Chemistry, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
Biochim Biophys Acta. 2003 Jul 21;1633(2):96-105. doi: 10.1016/s1388-1981(03)00092-1.
Distinct functional coupling between cyclooxygenases (COXs) and specific terminal prostanoid synthases leads to phase-specific production of particular prostaglandins (PGs). In this study, we examined the coupling between COX isozymes and PGF synthase (PGFS). Co-transfection of COXs with PGFS-I belonging to the aldo-keto reductase family into HEK293 cells resulted in increased production of PGF(2alpha) only when a high concentration of exogenous arachidonic acid (AA) was supplied. However, this enzyme failed to produce PGF(2alpha) from endogenous AA, even though significant increase in PGF(2alpha) production occurred in cells transfected with COX-2 alone. This poor COX/PGFS-I coupling was likely to arise from their distinct subcellular localization. Measurement of PGF(2alpha)-synthetic enzyme activity in homogenates of several cells revealed another type of PGFS activity that was membrane-bound, glutathione (GSH)-activated, and stimulus-inducible. In vivo, membrane-bound PGFS activity was elevated in the lung of lipopolysaccharide-treated mice. Taken together, our results suggest the presence of a novel, membrane-associated form of PGFS that is stimulus-inducible and is likely to be preferentially coupled with COX-2.
环氧化酶（COXs）与特定的末端前列腺素合成酶之间独特的功能偶联导致特定前列腺素（PGs）的阶段特异性产生。在本研究中，我们检测了COX同工酶与前列腺素F合成酶（PGFS）之间的偶联。将属于醛酮还原酶家族的PGFS-I与COXs共转染至人胚肾293细胞（HEK293）中，仅在提供高浓度外源性花生四烯酸（AA）时，才会导致前列腺素F2α（PGF(2α)）产量增加。然而，即使单独转染COX-2的细胞中PGF(2α)产量显著增加，该酶也无法从内源性AA产生PGF(2α)。这种较差的COX/PGFS-I偶联可能源于它们不同的亚细胞定位。对几种细胞匀浆中PGF(2α)合成酶活性的测定揭示了另一种类型的PGFS活性，其为膜结合型、谷胱甘肽（GSH）激活型且可被刺激诱导。在体内，脂多糖处理小鼠肺中的膜结合型PGFS活性升高。综上所述，我们的结果表明存在一种新型的、与膜相关的PGFS形式，其可被刺激诱导，并且可能优先与COX-2偶联。
