C/EBPα transcription factor is regulated by the RANK cytoplasmic 535IVVY538 motif and stimulates osteoclastogenesis more strongly than c-Fos
Year: 2017
Type: article
Abstract: Binding of receptor activator of NF-κB ligand (RANKL) to its receptor RANK on osteoclast (OC) precursors up-regulates c-Fos and CCAAT/enhancer–binding protein-α (C/EBPα), two critical OC transcription factors. However, the effects of c-Fos and C/EBPα on osteoclastogenesis have not been compared. Herein, we demonstrate that overexpression of c-Fos or C/EBPα in OC precursors up-regulates OC genes and initiates osteoclastogenesis independently of RANKL. However, although C/EBPα up-regulated c-Fos, c-Fos failed to up-regulate C/EBPα in OC precursors. Consistently, C/EBPα overexpression more strongly promoted OC differentiation than did c-Fos overexpression. RANK has a cytoplasmic 535 IVVY 538 (IVVY) motif that is essential for osteoclastogenesis, and we found that mutation of the IVVY motif blocked OC differentiation by partly inhibiting expression of C/EBPα but not expression of c-Fos. We therefore hypothesized that C/EBPα overexpression might rescue osteoclastogenesis in cells expressing the mutated IVVY motif. However, overexpression of C/EBPα or c-Fos failed to stimulate osteoclastogenesis in the mutant cells. Notably, the IVVY motif mutation abrogated OC gene expression compared with a vector control, suggesting that the IVVY motif might counteract OC inhibitors during osteoclastogenesis. Consistently, the IVVY motif mutant triggered up-regulation of recombinant recognition sequence–binding protein at the Jκ site (RBP-J) protein, a potent OC inhibitor. Mechanistically, C/EBPα or c-Fos overexpression in the mutant cells failed to control the up-regulated RBP-J expression, leading to suppression of OC genes. Accordingly, RBP-J silencing in the mutant cells rescued osteoclastogenesis with C/EBPα or c-Fos overexpression with C/EBPα exhibiting a stronger osteoclastogenic effect. Collectively, our findings indicate that C/EBPα is a stronger inducer of OC differentiation than c-Fos, partly via C/EBPα regulation by the RANK 535 IVVY 538 motif.
Source: Journal of Biological Chemistry
Authors: Joel Jules, Wei Chen, Xu Feng, Yi-Ping Li
Institutions: University of Alabama, University of Alabama at Birmingham
Language: English
Topic: Bone Metabolism and Diseases
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
Awards: UAB Core Center for Basic Skeletal Research (CCBSR), RANK Signaling in Osteoclast Differentiation and Function, Cbfβ mediates articular cartilage regeneration and repair in aging, G3494759633, Characterizing the mechanism by which endogenous negative regulators of osteoclasts control bone homeostasis under physiological and pathological conditions in mouse models, Transcriptional Regulation of Osteoclast Lineage Commitment and Differentiation, G9000018974
OpenAlex ID: W2767366342