title: Ubiquitin-proteasomal degradation of COX-2 in TGF-β stimulated human endometrial cells is mediated through endoplasmic reticulum mannosidase I.
abstract: Cyclooxygenase (COX)-2 is a key regulatory enzyme in the production of prostaglandins (PG) during various physiological processes. Mechanisms of COX-2 regulation in human endometrial stromal cells (human endometrial stromal cells) are not fully understood. In this study, we investigate the role of TGF-β in the regulation of COX-2 in human uterine stromal cells. Each TGF-β isoform decreases COX-2 protein level in human uterine stromal cells in Smad2/3-dependent manner. The decrease in COX-2 is accompanied by a decrease in PG synthesis. Knockdown of Smad4 using specific small interfering RNA prevents the decrease in COX-2 protein, confirming that Smad pathway is implicated in the regulation of COX-2 expression in human endometrial stromal cells. Pretreatment with 26S proteasome inhibitor, MG132, significantly restores COX-2 protein and PG synthesis, indicating that COX-2 undergoes proteasomal degradation in the presence of TGF-β. In addition, each TGF-β isoform up-regulates endoplasmic reticulum (ER)-mannosidase I (ERManI) implying that COX-2 degradation is mediated through ER-associated degradation pathway in these cells. Furthermore, inhibition of ERManI activity using the mannosidase inhibitor (kifunensine), or small interfering RNA-mediated knockdown of ERManI, prevents TGF-β-induced COX-2 degradation. Taken together, these studies suggest that TGF-β promotes COX-2 degradation in a Smad-dependent manner by up-regulating the expression of ERManI and thereby enhancing ER-associated degradation and proteasomal degradation pathways.
authors: Department of Chemistry-Biology, University of Québec at Trois-Rivières, 3351 Boulevard des Forges, Trois-Rivières, Québec, Canada.
authors: Mohan
authors: M
authors: Singh
authors: Parvesh
authors: P
authors: Chaudhry
authors: Sophie
authors: S
authors: Parent
authors: Eric
authors: E
authors: Asselin
mesh_terms: D001483:Base Sequence; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D004717:Endometrium / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D060746:Endoplasmic Reticulum-Associated Degradation / Q000187:drug effects; D005260:Female; D055785:Gene Knockdown Techniques; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D008361:Mannosidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D011453:Prostaglandins / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D034741:RNA, Small Interfering / Q000235:genetics; D051901:Smad4 Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D017154:Stromal Cells / Q000187:drug effects / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism / Q000494:pharmacology*; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D017931:DNA Primers; D007976:Leupeptins; D011453:Prostaglandins; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D034741:RNA, Small Interfering; C497796:SMAD4 protein, human; D051901:Smad4 Protein; D016212:Transforming Growth Factor beta; D025801:Ubiquitin; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D008361:Mannosidases; C046090:mannosyl-oligosaccharide 1,2-alpha-mannosidase; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde