Identification of human prostaglandin E synthase: A microsomal, glutathione-dependent, inducible enzyme, constituting a potential novel drug target

Human prostaglandin (PG) E synthase (EC 5.3.99.3) is a member of a recently recognized protein superfamily consisting of membrane associated proteins involved in eicosanoid and glutathione metabolism (the MAPEG family). Previ ous designations of the protein are PIG12 and MGST1-L1. PGE synthase was ex pressed in Escherichia coli, and both cytosolic and membrane fractions were prepared. Western blot analysis specifically detected a 15- to 16-kDa prot ein in the membrane fraction. Both fractions were incubated with prostaglan din H-2 in the presence or absence of reduced glutathione, The membrane but not the cytosolic fraction was found to possess high glutathione-dependent PGE synthase activity (0.25 mu mol/min/mg). The human tissue distribution was analyzed by Northern blot analysis. High expression of PGE synthase mRN A was detected in A549 and HeLa cancer cell lines. Intermediate level of ex pression was demonstrated in placenta, prostate, testis, mammary gland, and bladder whereas lon mRNA expression was observed in several other tissues. A549 cells have been used as a model system to study cyclooxygenase-2 indu ction by IL-1 beta, If A549 cells were grown in the presence of IL-1 beta, a significant induction of the PGE synthase was observed by Western blot an alysis. Also, Western blot analysis specifically detected a 16-kDa protein in sheep seminal vesicles. In summary, we have identified a human membrane bound PGE synthase. The enzyme activity is glutathione-dependent, and the p rotein expression is induced by the proinflammatory cytokine IL-1 beta, PGE synthase is a potential novel target for drug development.