Transcriptional Regulation of BMP2 Expression by the PTH-CREB Signaling Pathway in Osteoblasts

Abstract

Intermittent application of parathyroid hormone (PTH) has well established anabolic effects on bone mass in rodents and humans. Although transcriptional mechanisms responsible for these effects are not fully understood, it is recognized that transcriptional factor cAMP response element binding protein (CREB) mediates PTH signaling in osteoblasts, and that there is a communication between the PTH-CREB pathway and the BMP2 signaling pathway, which is important for osteoblast differentiation and bone formations. These findings, in conjunction with putative cAMP response elements (CREs) in the BMP2 promoter, led us to hypothesize that the PTH-CREB pathway could be a positive regulator of BMP2 transcription in osteoblasts. To test this hypothesis, we first demonstrated that PTH signaling activated CREB by phosphorylation in osteoblasts, and that both PTH and CREB were capable of promoting osteoblastic differentiation of primary mouse osteoblast cells and multiple rodent osteoblast cell lines. Importantly, we found that the PTH-CREB signaling pathway functioned as an effective activator of BMP2 expression, as pharmacologic and genetic modulation of PTH-CREB activity significantly affected BMP2 expression levels in these cells. Lastly, through multiple promoter assays, including promoter reporter deletion, mutation, chromatin immunoprecipitation (ChIP), and electrophoretic mobility shift assay (EMSA), we identified a specific CRE in the BMP2 promoter which is responsible for CREB transactivation of the BMP2 gene in osteoblasts. Together, these results demonstrate that the anabolic function of PTH signaling in bone is mediated, at least in part, by CREB transactivation of BMP2 expression in osteoblasts.

Estrogen-Related Receptor γ Plays a Key Role in Vascular Calcification Through the Upregulation of BMP2 Expression

“…However, ERRγ-induced Bmp2 promoter activation was still detected after deletion of 2 put-ERRE motifs or mutation of put-ERRE1, suggesting that an indirect mechanism may contribute to promoter stimulation by ERRγ. CREB is known to transacitvate BMP2 through CRE in the BMP2 promoter, 20 and we found a putative CREB-binding site on D2 −195 BMP2 promoter. Therefore, we checked whether CRE contributes to ERRγ-stimulated BMP2 promoter activation after deletion of both ERRE1 and ERRE2.…”

Melatonin regulates human bone sialoprotein gene transcription

“…Activation of PKA may induce CREB1 phosphorylation, and phospho-CREB1 can bind firmly to CRE, thereby inducing gene transcription (51). HA, U0126 and LY294002 have been shown to inhibit the increased binding activities of transcription factors to the FRE and HOX elements in the rat BSP gene promoter (35).…”

Administration of BMP2/7 in utero partially reverses Rubinstein-Taybi syndrome–like skeletal defects induced by Pdk1 or Cbp mutations in mice

“…Spontaneous bone fractures observed in Pdk1 osx neonates and compound Pdk1 and Runx2 heterozygotes resemble the fractures resulting from limb-specific deletion of BMP2 (47). Additionally, recent in vitro analyses have suggested that BMP2 is a target of activated CREB in osteoblasts (48). To explore whether the PDK1 pathway is linked to the regulation of Bmp2 expression, human mesenchymal stem cells (hMSCs) or CalvObs were cultured under osteoblast differentiation conditions and treated with either PDK1 or PI3K inhibitors (Supplemental Figure 10A).…”

“…Luciferase activity showed a dose-dependent increase with expression of either WT CREB or the constitutively active mutant VP16/CREB (Supplemental Figure 10C, top, and ref. 50). In addition, CREB activity was further increased in the presence of CBP, suggesting that CREB functions along with its coactivator CBP to upregulate Bmp2 expression (Supplemental Figure 10C, bottom).…”