Parathyroid hormone induces E4bp4 messenger ribonucleic acid expression primarily through cyclic adenosine 3′,5′-monophosphate signaling in osteoblasts
Parathyroid hormone induces E4bp4 messenger ribonucleic acid expression primarily through cyclic adenosine 3′,5′-monophosphate signaling in osteoblasts
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DOI：
10.1210/en.2003-1436
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发表时间：
2004-08-01
期刊：
影响因子：
4.8
通讯作者：
Tetradis, S
中科院分区：
文献类型：
--
作者：
Ozkurt, IC;Pirih, FQ;Tetradis, S
PTH与其受体结合激活蛋白激酶A（PKA）、蛋白激酶C（PKC）和钙信号传导以诱导成骨细胞中初级应答基因的转录。IL-3调控的腺病毒E4启动子结合蛋白/核因子（E4 BP 4/NFIL 3）是一种转录抑制因子，是PTH诱导的小鼠成骨细胞（MOBs）的主要反应基因。在这里，我们研究了导致PTH诱导E4 bp 4 mRNA表达的信号通路。10和100 nM PTH诱导MOB中E4 bp 4的最大表达。佛司可林（FSK），腺苷酸环化酶诱导剂，8-溴-cAMP，cAMP类似物，和佛波醇肉豆蔻酸乙酸酯，PKC激活剂，增加E4 bp 4 mRNA水平，而离子霉素，钙离子载体，没有影响。用PKA抑制剂30 μ M H89预处理细胞，强烈抑制PTH和FSK诱导的E4 bp 4表达。相反，用1 μ M佛波醇肉豆蔻酸酯醋酸酯过夜预处理以下调PKC信号传导并不改变PTH和FSK效应。此外，不激活cAMP信号传导的PTH（3-34）不增加E4 bp 4表达。前列腺素E-2通过cAMP发出信号，在所有剂量下均可增加E4 bp 4 mRNA，而主要激活PKC和钙信号的前列腺素F-2 α仅在高剂量下诱导E4 bp 4，而仅激活PKC和钙信号的氟前列醇无影响。最后，80 μ g/kg PTH（1-34）ip注射在1 h诱导小鼠E4 bp 4 mRNA表达。相比之下，80 μ g/kg PTH（3-34）没有影响。我们的数据表明，PTH诱导的E4 bp 4 mRNA表达主要是通过cAMP-PKA信号在体外和体内介导。结合我们以前的报道，我们假设E4 bp 4减弱了具有E4 bp 4启动子结合位点的成骨细胞基因的转录。
PTH binding to its receptor activates protein kinase A (PKA), protein kinase C (PKC), and calcium signaling to induce transcription of primary response genes in osteoblasts. Adenovirus E4 promoter-binding protein/nuclear factor regulated by IL-3 (E4BP4/NFIL3), a transcriptional repressor, is a PTH-induced primary response gene in primary mouse osteoblasts (MOBs). Here we investigate the signaling pathway(s) that lead to PTH induction of E4bp4 mRNA expression. Ten and 100 nM PTH induced maximum E4bp4 expression in MOBs. Forskolin (FSK), an adenylate cyclase inducer, 8-bromo-cAMP, a cAMP analog, and phorbol myristate acetate, a PKC activator, increased E4bp4 mRNA levels, whereas ionomycin, a calcium ionophore, had no effect. Pretreatment of cells with 30 muM H89, a PKA inhibitor, strongly inhibited PTH- and FSK-induced E4bp4 expression. In contrast, overnight pretreatment with 1 muM phorbol myristate acetate to down-regulate PKC signaling did not alter PTH and FSK effects. Moreover, PTH (3-34) that does not activate cAMP signaling did not increase E4bp4 expression. Prostaglandin E-2, which signals through cAMP, increased E4bp4 mRNA at all doses, whereas prostaglandin F-2alpha that primarily activates PKC and calcium signaling, induced E4bp4 only at high doses and fluprostenol that only activates PKC and calcium signaling, had no effect. Finally, 80 mug/kg PTH(1-34) ip injection induced E4bp4 mRNA expression at 1 h in mice. In contrast, 80 mug/kg PTH (3-34) had no effect. Our data suggest that PTH-induced E4bp4 mRNA expression is mediated primarily through cAMP-PKA signaling in vitro and in vivo. In conjunction with our previous report, we hypothesize that E4bp4 attenuates transcription of osteoblastic genes possessing E4bp4 promoter binding sites.