Regulation of the osterix (Osx, Sp7) promoter by osterix and its inhibition by parathyroid hormone.
Regulation of the osterix (Osx, Sp7) promoter by osterix and its inhibition by parathyroid hormone.
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DOI：
10.1530/jme-12-0251
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发表时间：
2013
影响因子：
3.5
通讯作者：
Mitchell J
中科院分区：
文献类型：
--
作者：
Barbuto R;Mitchell J
Osterix（Osx，Sp7）是一种锌指转录因子，属于特异性蛋白（Sp）家族，在发育中的骨骼成骨细胞谱系细胞中表达，调节许多成骨基因的表达。我们先前报道了成骨细胞中甲状旁腺激素（PTH）刺激cAMP抑制osterix mRNA和蛋白。我们在这里表明，Osx在成骨细胞中的表达是由Sp蛋白质的光神霉素A抑制Osx mRNA和OSX蛋白水平所证明的。Osx启动子内假定的转录因子结合位点的突变证明了一个串联重复序列，该序列选择性结合OSX，但不结合成骨细胞中表达的其他Sp因子（Sp1、Sp3或Tieg（Klf10））。一个或两个重复序列的突变抑制90%的启动子活性，也废除了一些PTH介导的抑制的启动子。以前的研究表明，生长因子通过MAPK蛋白调节Osx的表达，特别是p38磷酸化的OSX，增加其转录活性。成骨细胞的PTH刺激抑制MAPK组分（ERK、JNK和p38），但PTH对Osx mRNA和蛋白表达的抑制被p38抑制选择性地模仿，并且组成性活性MKK6的表达（其刺激p38）阻断PTH对OSX的抑制。总之，我们的研究表明，OSX自动调节是成骨细胞的主要机制，PTH刺激通过抑制OSX的p38 MAPK调节来抑制osterix。
Osterix (Osx, Sp7) is a zinc-finger transcription factor belonging to the specificity protein (Sp) family expressed in cells of the osteoblast lineage in the developing skeleton where it regulates expression of a number of osteoblastic genes. We previously reported inhibition of osterix mRNA and protein by parathyroid hormone (PTH) stimulation of cAMP in osteoblasts. We here show that Osx expression in osteoblasts is regulated by Sp proteins as demonstrated by mithramycin A inhibition of Osx mRNA and OSX protein levels. Mutation of putative transcription factor binding sites within the Osx promoter demonstrated a tandem repeat sequence that selectively binds OSX but not other Sp factors expressed in osteoblasts (Sp1, Sp3, or Tieg (Klf10)). Mutation of either or both the repeat sequences inhibited 90% of the promoter activity and also abrogated some of the PTH-mediated inhibition of the promoter. Previous studies have shown growth factor regulation of Osx expression by MAPK proteins, particularly p38 phosphorylation of OSX that increases its transcriptional activity. PTH stimulation of osteoblasts inhibits MAPK components (ERK, JNK, and p38) but inhibition of Osx mRNA and protein expression by PTH was selectively mimicked by p38 inhibition and expression of constitutively active MKK6, which stimulates p38, blocked PTH inhibition of OSX. Together, our studies suggest that OSX autoregulation is a major mechanism in osteoblasts and that PTH stimulation inhibits osterix by inhibition of p38 MAPK regulation of OSX.