ERα/E2 signaling suppresses the expression of steroidogenic enzyme genes via cross-talk with orphan nuclear receptor Nur77 in the testes

► ERα/E2 signaling inhibited the promoter activity of steroidogenic enzyme genes. ► ERα/E2 signaling down-regulated the transactivation and protein level of Nur77. ► ERαflox/floxCyp17iCre mice showed an increase in testicular testosterone levels. Estrogen receptor alpha (ERα) has been reported to affect steroidogenesis in testicular Leydig cells, but its molecular mechanism remains unclear. Here, we investigate the effect of estrogen and ERα on Nur77, a major transcription factor that regulates the expression of steroidogenic enzyme genes. In MA-10 Leydig cells, estradiol (E2) treatment, and interestingly ERα overexpression, suppressed the cAMP-induced and Nur77-activated promoter activity of steroidogenic enzyme genes via the suppression of Nur77 transactivation. ERα physically interacted with Nur77 and inhibited its DNA binding activity. In addition, ERα/E2 signaling decreased Nur77 protein levels. Consistent with the above results, the testicular testosterone level was higher in Leydig cell-specific ERα knock-out mice (ERαflox/floxCyp17iCre) than in wild-type mice (ERαflox/flox). Taken together, these results suggest that ERα/E2 signaling controls the Nur77-mediated expression of steroidogenic enzyme genes in Leydig cells. These findings may provide a mechanistic explanation for the local regulation of testicular steroidogenesis by estrogenic compounds and ERα.