BMP-2 Induction of Dlx3 Expression Is Mediated by p38/Smad5 Signaling Pathway in Osteoblastic MC3T3-E1 Cells

Abstract

Dlx3 is essential for osteoblast differentiation and bone formation, and its expression is regulated by bone morphogenetic protein-2 (BMP-2). However, the intimate mechanism of BMP-2 regulation of Dlx3 transcription in osteoblasts is still unknown. Considering the important roles of Smad5 and p38 in osteoblast differentiation, we hypothesized that Smad5 and p38 mediated BMP-2-induced Dlx3 transcription in osteoblasts. We found activation of Smad5 and p38 increased the expression of Dlx3, whereas knocking down Smad5 or inactivation of p38 inhibited BMP-2-induced Dlx3 expression. Both Smad5 and p38 were able to activate Dlx3 promoter activity and p38/Smad5 response elements were located from -698 to -368 in Dlx3 promoter. Two Smad5 binding sites (SBEI and SBEII, TGTCT box) were identified in this region by EMSA and ChIP assay. Deletions and mutagenesis study of the Dlx3 promoter region indicated that the TGTCT boxes are crucial for p38/Smad5-induced Dlx3 promoter activity. At last, we found a cross-talk between p38 and Smad5, and that activation of p38 is necessary for BMP-2-induced Smad5 phosphorylation and nuclear translocation. Overall, we provide a novel insight that BMP-2-induced Dlx3 expression is regulated by p38/Smad5 signaling pathway in osteoblasts.

KDM5A controls bone morphogenic protein 2-induced osteogenic differentiation of bone mesenchymal stem cells during osteoporosis

“…5, 21 Thus, we investigated whether KDM5A inhibits BMP2-induced osteoblastic differentiation through altering the BMP2-SMAD1/5/8 pathway in the KDM5A overexpressed MSCs. The results showed that phosphorylated SMAD1/5/8 was obviously increased after BMP2 treatment for 4 h in normal MSCs, which were not significantly changed by KDM5A overexpression (Figure 5a).…”

Icariin Enhances Bone Repair in Rabbits with Bone Infection during Post-infection Treatment and Prevents Inhibition of Osteoblasts by Vancomycin

“…In short, Osteoblasts and osteoblastic lineage cells modulate the formation and activity of osteoclasts by expressing RANKL and OPG, which induce and inhibit osteoclastogenesis, respectively ( Krum et al, 2010 ). On the other hand, BMPs, belong to the transforming growth factor β (TGF-β) superfamily, which have been identified as inducers of ectopic bone and cartilage formation ( Yang et al, 2014 ). BMP2 is one of the most important cytokines playing important roles in bone development and fracture repair ( Jang et al, 2012 ).…”

p38 MAPK Signaling in Osteoblast Differentiation

“…Another DLX member, Dlx3 , is also induced by BMP-2. In this case, it occurs through cooperation between SMAD5 and pp38 as they translocate to the nucleus and exert their function on the Dlx3 promoter (Yang et al, 2014 ). These p38-activated osteogenic events continue with the phosphorylation of Osterix at serines Ser77 and Ser33.…”