Cooperative Role of NF-κB and Poly(ADP-ribose) Polymerase 1 (PARP-1) in the TNF-induced Inhibition of PHEX Expression in Osteoblasts
Cooperative Role of NF-κB and Poly(ADP-ribose) Polymerase 1 (PARP-1) in the TNF-induced Inhibition of PHEX Expression in Osteoblasts
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DOI：
10.1074/jbc.m110.152868
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发表时间：
2010-11-05
影响因子：
4.8
通讯作者：
Ghishan, Fayez K.
中科院分区：
文献类型：
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作者：
Majewski, Pawel M.;Thurston, Robert D.;Ghishan, Fayez K.
骨量减少是慢性炎症性疾病的常见并发症，尽管其机制尚不完全清楚。PHEX基因编码成骨细胞中表达的锌内肽酶，并有助于骨矿化。本研究的目的是确定参与TNF介导的Phex基因转录下调的分子机制。我们证明了在两种结肠炎模型中Phex基因的下调：幼稚T细胞转移和gnotobiotic IL-10（-/-）小鼠。在体外，TNF降低UMR 106细胞中Phex的表达，并且不需要从头合成反式阻遏物。用一系列Phex启动子近端缺失构建体转染UMR-106细胞，鉴定了位于~ 74个核苷酸内的含有NF-κ B和AP-1结合位点的区域。TNF处理后，RelA/p50 NF-κ B复合物与近端Phex启动子中-70/-66和-29/-25位核苷酸的两个顺式元件相互作用。NF-κ B信号的抑制增加了Phex转录的基础水平，并消除了TNF的作用，而RelA的过表达模拟了TNF的作用。我们鉴定了聚（ADP-核糖）聚合酶1（PARP-1）结合在NF-κ B B位点的上游，并表明当与Phex启动子结合时，TNF诱导RelA的聚（ADP-核糖基）化。TNF介导的Phex下调在体外通过PARP-1抑制剂和聚（ADP-核糖）葡萄糖水解酶（PARG）的过表达以及在PARP-1（-/-）小鼠体内完全消除。我们的研究结果表明，NF-κ B B信号和PARP-1酶活性协同有助于Phex的组成性和诱导性抑制。所描述的现象可能有助于慢性炎性疾病（例如炎性肠病）中的骨质量密度损失。
Reduced bone mass is a common complication in chronic inflammatory diseases, although the mechanisms are not completely understood. The PHEX gene encodes a zinc endopeptidase expressed in osteoblasts and contributes to bone mineralization. The aim of this study was to determine the molecular mechanism involved in TNF-mediated down-regulation of Phex gene transcription. We demonstrate down-regulation of the Phex gene in two models of colitis: naive T-cell transfer and in gnotobiotic IL-10(-/-) mice. In vitro, TNF decreased expression of Phex in UMR106 cells and did not require de novo synthesis of a transrepressor. Transfecting UMR-106 cells with a series of deletion constructs of the proximal Phex promoter identified a region located within -74 nucleotides containing NF-kappa B and AP-1 binding sites. After TNF treatment, the RelA/p50 NF-kappa B complex interacted with two cis-elements at positions -70/-66 and -29/-25 nucleotides in the proximal Phex promoter. Inhibition of NF-kappa B signaling increased the basal level of Phex transcription and abrogated the effects of TNF, whereas overexpression of RelA mimicked the effect of TNF. We identified poly(ADP-ribose) polymerase 1 (PARP-1) binding immediately upstream of the NF-kappa B sites and showed that TNF induced poly( ADP-ribosyl)ation of RelA when bound to the Phex promoter. TNF-mediated Phex down-regulation was completely abrogated in vitro by PARP-1 inhibitor and overexpression of poly( ADP-ribose) glucohydrolase (PARG) and in vivo in PARP-1(-/-) mice. Our results suggest that NF-kappa B signaling and PARP-1 enzymatic activity cooperatively contribute to the constitutive and inducible suppression of Phex. The described phenomenon likely contributes to the loss of bone mass density in chronic inflammatory diseases, such as inflammatory bowel disease.