Min Liang, and Bengt-Olof Nilsson
Department of Physiological Sciences, Lund University, BMC F12, SE-221 84 Lund, Sweden
Molecular and Cellular Endocrinology, 2004, 224: 65-71
Abstract
Here we investigate ERa and ERb expression and regulation in vascular smooth muscle cells from mouse aorta. Immunocytochemistry showed nuclear staining for both ERa and ERb. Double stainings revealed co-expression of ERa and ERb in vascular smooth muscle cells. ERa (66 kDa) and ERb (54 kDa) expression determined by Western blotting was unchanged within 7 h after inhibition of protein synthesis with cycloheximide in the absence of 17b-estradiol (E2), showing that both proteins are stable without ligand-binding. Treatment with 10 nM E2 for 7 h in the presence of cycloheximide increased ERa, suggesting that E2 causes a conformational change in the ERa protein. The ERb was not affected by E2. Treatment with the proteasome inhibitor epoxomicin (100 nM) for 3 days caused a prominent upregulation of ERa both in the absence and in the presence of E2, while ERb was unaffected, suggesting that ERa but not ERb is degraded by ubiquitin-proteasome system in vascular smooth muscle cells. In summary, we disclose a short-term regulation of ERa protein by estrogen and that ERa but not ERb is degraded via the ubiquitin-proteasome pathway in vascular smooth muscle cells.
Keywords: Estrogen; Estrogen receptor a and b; Immunocytochemistry; Vascular smooth muscle cells; Western blotting
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