CCAAT/enhancer-binding protein beta (C/EBPß) is an important mediator of 1,25 dihydroxyvitamin D3 (1,25D3)-induced receptor activator of nuclear factor kappa-B ligand (RANKL) expression in osteoblasts.

ABSTRACT

Receptor activator of nuclear factor kappa B ligand (RANKL) expression in osteoblasts is regulated by 1,25-dihydroxyvitamin D3 (1,25D3). CCAAT/enhancer-binding protein beta (C/EBPß) has been proposed to function as a transcription factor and upregulate RANKL expression, but it is still uncertain how C/EBPß is involved in 1,25D3-induced RANKL expression of osteoblasts. 1,25D3 stimulation increased the expression of RANKL and C/EPBß genes in osteoblasts and enhanced phosphorylation and stability of these proteins. Moreover, induction of RANKL expression by 1,25D3 in osteoblasts was downregulated upon knockdown of C/EBPß. In contrast, C/EBPß overexpression directly upregulated RANKL promoter activity and exhibited a synergistic effect on 1,25D3-induced RANKL expression. In particular, 1,25D3 treatment of osteoblasts increased C/EBPß protein binding to the RANKL promoter. In conclusion, C/EBPß is required for induction of RANKL by 1,25D3. [BMB Reports 2019; 52(6) 391-396].