title: Proteasome-dependent degradation of ERalpha but not ERbeta in cultured mouse aorta smooth muscle cells.
abstract: Here we investigate ERalpha and ERbeta expression and regulation in vascular smooth muscle cells from mouse aorta. Immunocytochemistry showed nuclear staining for both ERalpha and ERbeta. Double stainings revealed co-expression of ERalpha and ERbeta in vascular smooth muscle cells. ERalpha (66 kDa) and ERbeta (54 kDa) expression determined by Western blotting was unchanged within 7 h after inhibition of protein synthesis with cycloheximide in the absence of 17beta-estradiol (E(2)), showing that both proteins are stable without ligand-binding. Treatment with 10 nM E(2) for 7 h in the presence of cycloheximide increased ERalpha, suggesting that E(2) causes a conformational change in the ERalpha protein. The ERbeta was not affected by E(2). Treatment with the proteasome inhibitor epoxomicin (100 nM) for 3 days caused a prominent upregulation of ERalpha both in the absence and in the presence of E(2), while ERbeta was unaffected, suggesting that ERalpha but not ERbeta is degraded by ubiquitin-proteasome system in vascular smooth muscle cells. In summary, we disclose a short-term regulation of ERalpha protein by estrogen and that ERalpha but not ERbeta is degraded via the ubiquitin-proteasome pathway in vascular smooth muscle cells.
authors.affiliation: Department of Physiological Sciences, Lund University, BMC F12, SE-221 84 Lund, Sweden. min.liang@mphy.lu.se
authors.forename: Min
authors.initials: M
authors.lastname: Liang
authors.forename: Bengt-Olof
authors.initials: BO
authors.lastname: Nilsson
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000032:analysis / Q000378:metabolism*; D047629:Estrogen Receptor beta / Q000032:analysis / Q000378:metabolism*; D005260:Female; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000201:enzymology* / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000502:physiology*
chemical_list: D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D009842:Oligopeptides; D004958:Estradiol; D046988:Proteasome Endopeptidase Complex; C078846:epoxomicin