Induction of prostaglandin endoperoxide synthase-2 by serine-threonine phosphatase inhibition.
Regulation of prostaglandin endoperoxide synthase-2 (PGHS-2) mRNA levels by serine-threonine phosphatases was examined in murine fibrosarcoma methylcholanthrene-101 cells. Okadaic acid (OA), a serine-threonine phosphatase inhibitor, induced PGE2 production and a significant increase in PGHS-2 immunoreactive protein. A specific PGHS-2 inhibitor, N-(2-cyclohexyloxy-4-nitrophenyl) methanesulphonamide, completely abolished the OA-mediated increase in PGE2 production, which suggests that the PGE2 formed in response to OA was derived from PGHS-2. OA-mediated PGHS-2 mRNA accumulation was observed at 1 hr, remained elevated for 24 hr and was blocked by actinomycin D, which indicates that OA increases PGHS-2 gene transcription. A significant post-transcriptional mechanism also contributed to the increased PGHS-2 mRNA accumulation, because the mRNA half-life was approximately 4 to 5 h in OA-stimulated cells. Tumor necrosis factor-alpha, but not OA, activated transcription factor nuclear factor-kappaB in methylcholanthrene-101 cells, as demonstrated by translocation of the nuclear factor-kappaB complex to the nucleus and disappearance of the cytoplasmic inhibitory protein, IkappaB-alpha. We conclude that inhibition of serine-threonine phosphatases contributes to the up-regulation of PGHS-2 expression in an NF-kappaB-independent manner.
Mahboubi
K
K
Department of Pharmacology, New York Medical College, Valhalla 10595, USA.
Young
W
W
Ferreri
N R
NR
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction; D005260:Female; D007527:Isoenzymes / Q000096:biosynthesis*; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000378:metabolism; D019319:Okadaic Acid / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000502:physiology*; D010766:Phosphorylation; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D012694:Serine / Q000378:metabolism; D013912:Threonine / Q000378:metabolism; D051841:Transcription Factor RelB; D014157:Transcription Factors
D007527:Isoenzymes; D016328:NF-kappa B; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; C497594:Relb protein, mouse; D014157:Transcription Factors; D051841:Transcription Factor RelB; D019319:Okadaic Acid; D013912:Threonine; D012694:Serine; D011451:Prostaglandin-Endoperoxide Synthases; D010749:Phosphoprotein Phosphatases