INVESTIGATION OF MECHANISM OF PREVENTION OF ATHEROSCLEROSIS BY SELECTIVE ESTROGEN RECEPTOR MODULATORS (SERM)

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1) We screened Estrogen Receptor α (ERα)-interacting proteins using yeast two hybrid system from a human heart cDNA library. We successfully identified LIM-only-domain containing factor FHL2 and Sumoylation enzymes Ubc9 and PIAS1 as ERα-interacting proteins in an estradiol-sensitive manner. FHL2 is highly expressed in cardiac muscle specifically, and reported that it interacts with several transcription factors, such as Androgen Receptor, AP-1, CREB and CREM. This is the first report of FHL2 as ERα interacting protein. FHL2 interacts with ERα in the presence of 17β-estradiol, but there was no significant influence on transcriptional activity through ERα by transient transfection assay using an ERE-E 1b-Luciferase reporter. Given the fact that FHL2 is specifically highly expressed in the cardiac muscle, FHL2 is likely to be involved in the pathophysiology of cardiac hypertrophy.2) We have previously identified SUMOylation enzymes Ubc9 and PIAS1 as COUP-TFI interacting proteins. In the present project, we also identified them as ERα-interacting proteins. We investigated the role of these proteins in ER-mediated transcription, and found that they function as transcriptional coactivators of ERα. Since a recent report showed that COUP-TFI activates ERα through phospholylation of Ser118 of ERα, it is conceivable that Ubc9, PIAS1 and COUP-TFI form ternary complex to modulate ERα transcriptional activities.