Analysis of prostaglandin E2 synthases

本研究的目的是对两种前列腺素E2合成酶（PGESs）进行生化表征，并阐明其生理和病理功能。胞质PGES （cPGES）是一种23 kda的胞质蛋白，广泛存在于多种细胞和组织中。这种酶与p23相同，p23与分子伴侣Hsp9O相关。cPGES与环氧化酶(COX)-1功能偶联，促进PGE2的立即生成。hsp9o结合的cPGES是一种活性形式，在A23187激活细胞后，这种复合物的形成立即得到促进。Hsp9O抑制剂，如格尔达霉素，以及糖皮质激素可以阻止Hsp9O/cPGES复合物的形成，从而减弱pge2的生物合成反应。细胞活化后，cPGES从细胞质转移到内质网，在内质网与COX-1共定位。cPGES经历磷酸化，尽管其生物学意义尚不清楚。最后，cPGES至少有四种可选择的剪接变体，每种变体都具有不同的组织分布，并且对底物PGH2具有不同的动力学参数（Km和Vmax）。微粒体PGES （mPGES）是一种核周18 kda蛋白，在促炎刺激后在各种细胞和组织中被强烈诱导。这种酶属于微粒体谷胱甘肽转移酶家族。mPGES与COX-2的功能偶联明显优于COX-1，以促进延迟PGE2的产生和启动立即PGE2的产生。将COX-2和mPGES共转染HEK293细胞，可导致细胞的侵袭性生长和形态学改变。此外，共转染物在软琼脂中生长形成大菌落，并在裸鼠中具有致瘤性。结肠癌细胞系（HCA-7）的生长依赖于COX-2，也表达mPGES，这两种酶都在核周区域共定位。人体组织免疫组化染色显示COX-2和mPGES在结肠肿瘤、类风湿关节炎、缺血性心脏、c型肝炎和脑内皮细胞中均有表达。少

The aims of this study are to perform biochemical characterization of two prostaglandin E2 synthases (PGESs) and to clarify their physilogical and pathological functions.Cytosolic PGES (cPGES) is a cytosolic 23-kDa protein that is expressed ubiuitously and constitutively in a wide variety of cells and tissues. This enzyme is identical to p23, which is associated with the molecular chaperone Hsp9O. cPGES is functionally coupled with cyclooxygenase (COX)-1 to promote immediate PGE2 production. The Hsp9O-bound cPGES is an active form, and the formation of this complex is facilitated immediately after cell activation with A23187. Hsp9O inhibitors, such as geldanamycin, as well as glucocorticoid prevents the formation of the Hsp9O/cPGES complex, thereby attenuating the PGE2biosynthetic response. After cell activation, cPGES translocates from the cytosol to the endoplasmic reticulum, where it is colocalized with COX-1. cPGES undergoes phosphorylation, although its biological significance rem … More ains elusive. Finally, there are at least four alternative spliced variants of cPGES, each of which exhibited distinct tissue distribution and showed different kinetic parameters (Km and Vmax) for the substrate PGH2.Microsomal PGES (mPGES) is a perinuclear 18-kDa protein that is strongly induced in various cells and tissues following proinflamamtory stimuli. This enzyme belongs to the class microsomal glutathione-Stransferase family. mPGES is functionally coupled with COX-2 in marked preference to COX-1 to promote delayed PGE2 production and primed immediate PGE2 production. Cotransfection of COX-2 and mPGES into HEK293 cells results in aggressive growth and morphological change in culture. Furthermore, the cotransfectants grow in soft agar to form large colonies and are tumorigenic in nude mice. A colon carcinoma cell line (HCA-7), the growth of which depends on COX-2, also expresses mPGES, where both enzymes are colocalized in the perinuclear reagion. Immunohistochemical staining of human tissues reveal that both COX-2 and mPGES are expressed in colon tumors, rheumatoid arthritis, ischemic hearts, C-type hepatitis, and brain endothelial cells. Less