CREBZF regulates testosterone production in mouse Leydig cells

CREBZF, including the two isoforms SMILE (long isoform of CREBZF) and Zhangfei (short isoform of CREBZF), has been identified as a novel transcriptional coregulator of a variety of nuclear receptors. Our previous studies found that SMILE is expressed in the mouse uterine luminal and glandular epithelium and is upregulated by estrogen. In the present study, CREBZF was age‐dependently and ‐specifically expressed in mouse interstitial Leydig cells during sexual maturation. The expression pattern of CREBZF exhibited an age‐related increase, and SMILE was the dominant isoform in the mouse testis. Although hCG did not affect CREBZF expression, CREBZF silencing significantly inhibited hCG‐stimulated testosterone production in primary Leydig cells and MLTC‐1 cells. Meanwhile, the serum concentration of testosterone was significantly decreased after microinjection of lentiviral‐mediated shRNA‐CREBZF into the mature mouse testis. In addition, CREBZF silencing markedly decreased P450c17, 17β‐HSD, and 3β‐HSD expression following hCG stimulation in primary Leydig cells, and this inhibitory effect was obviously reversed by overexpression of CREBZF. Furthermore, CREBZF significantly upregulated the mRNA levels of Nr4a1 and Nr5a1, which are the essential orphan nuclear receptors for steroidogenic gene expression. Together our data indicate that CREBZF promotes hCG‐induced testosterone production in mouse Leydig cells by affecting Nr4a1 and Nr5a1 expression levels and subsequently increasing the expression of steroidogenic genes such as 3β‐HSD, 17β‐HSD, and P450c17, suggesting a potential important role of CREBZF in testicular testosterone synthesis. CREBZF is specifically localized in mouse Leydig cells and can promote hCG‐stimulated testosterone biosynthesis. The promoting effect may be mediated, in part, by increasing expression of Nr4a1 and Nr5a1, hence resulting in increased expression of steroidogenic genes, including P450c17, 17β‐HSD, and 3β‐HSD.