| First Author | Pellicelli M | Year | 2018 |
| Journal | Biochim Biophys Acta | Volume | 1861 |
| Issue | 2 | Pages | 61-71 |
| PubMed ID | 29413898 | Mgi Jnum | J:257534 |
| Mgi Id | MGI:6119155 | Doi | 10.1016/j.bbagrm.2018.01.008 |
| Citation | Pellicelli M, et al. (2018) Lrp6 is a target of the PTH-activated alphaNAC transcriptional coregulator. Biochim Biophys Acta 1861(2):61-71 |
| abstractText | In the nucleus of differentiated osteoblasts, the alpha chain of nascent polypeptide associated complex (alphaNAC) interacts with cJUN transcription factors to regulate the expression of target genes, including Osteocalcin (Bglap2). PTH induces the phosphorylation of alphaNAC on serine 99 through a Galphas-PKA dependent pathway. This leads to activation of alphaNAC and expression of Bglap2. To identify additional target genes regulated by PTH-activated alphaNAC, we performed ChIP-Seq against alphaNAC in PTH-treated MC3T3-E1 cells. This identified Low density lipoprotein receptor-Related Protein 6 (Lrp6) as a potential alphaNAC target. LRP6 acts as a co-receptor for the PTH receptor to allow optimal activation of PTH signaling. PTH increased Lrp6 mRNA levels in primary osteoblasts. Conventional quantitative ChIP confirmed the ChIP-Seq results. To assess whether alphaNAC plays a critical role in PTH-stimulated Lrp6 expression, we knocked-down Naca expression in MC3T3-E1 cells. Reduction of alphaNAC levels decreased basal expression of Lrp6 by 30% and blocked the stimulation of Lrp6 expression by PTH. We cloned the proximal mouse Lrp6 promoter (-2523/+120bp) upstream of the luciferase reporter. Deletion and point mutations analysis in electrophoretic mobility shift assays and transient transfections identified a functional alphaNAC binding site centered around -343bp. ChIP and ChIP-reChIP against JUND and alphaNAC showed that they cohabit on the proximal Lrp6 promoter. Luciferase assays confirmed that PTH-activated alphaNAC potentiated JUND-mediated Lrp6 transcription and Jund knockdown abolished this response. This study identified a novel alphaNAC target gene induced downstream of PTH signaling and represents the first characterization of the regulation of Lrp6 transcription in osteoblasts. |
