Regulation of intracellular signal transmission for osteogenesis

成骨细胞内信号传递的调节

基本信息

批准号：
15591595
负责人：
KOIKE Tatsuya
金额：
$ 2.24万
依托单位：
Osaka City University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

Bone morphogenetic proteins (BMPs) belong to the transforming growth factor (TGF)-〓 super-family, and some display potent osteogenic activity both in vivo and in vitro. The BMP signaling cascade involving BMP receptors at the cell membrane and intracellular messengers (Smads) has been elucidated, but the regulatory mechanisms of BMP signaling have not been clarified. We previously found that pentoxifylline (PeTx), a nonspecific inhibitor of phosphodiesterase (PDE), and rolipram, a PDE-4-specific inhibitor, enhance BMP-4-induced osteogenic differentiation of mesenchymal cells, probably through the elevation of intracellular cyclic adenosine monophosphate (cAMP) accumulation and modulation of BMP signaling pathways, as enhanced BMP-4 action was reproduced by addition of dibutylyl-cAMP (dbcAMP). However, the precise mechanisms underlying the enhancing effects of those agents on BMP signaling were not completely revealed. As already reported, BMPs utilize a specific intracellular signaling … More cascade to target genes via R-Smads (Smad1,5,8), Co-Smad (Smad4) and I-Smads (Smad6,7). One possibility for cAMP-mediated effects on BMP signaling might be suppression of I-Smads expression, since these proteins form a negative feedback loop in BMP signaling. To examine this possibility, changes in I-Smad (Smad6) expression on addition of dbcAMP or PeTx were examined in a bone marrow-derived osteogenic cell line (ST2). Alkaline phosphatase activity in ST2 cells was consistently induced by BMP-4 treatment (300 ng/ml), and Smad6 mRNA expression was also induced by BMP-4 treatment. Although, concurrent treatment of ST2 cells with BMP-4 and dbcAMP elicited further activation of alkaline phosphatase, addition of dbcAMP reduced BMP-4 induced-Smad6 expression in a dose-dependent manner. Furthermore, detection of phosphorylated Smad1/5/8 on Western blotting analysis was prolonged, suggesting prolonged kinase activity of BMP receptors through suppressed expression of Smad6. Elevated intracellular cAMP might thus enhance BMP signaling by suppressing Smad6 induction and prolonging intracellular BMP signaling. Less

骨形态发生蛋白（BMP）属于转化生长因子（TGF） - 超家族，某些在体内和体外都显示出潜在的成骨活性。 BMP信号传导级联反应涉及细胞膜和细胞内信使（SMADS）的BMP受体，但尚未阐明BMP信号传导的调节机制。我们先前发现，五氧化酯（PETX）是磷酸二酯酶（PDE）的非特异性抑制剂（PDE）和PDE-4特异性抑制剂Rolipram，增强了BMP-4特异性的抑制剂，可以通过内质细胞的甲基化元素和模型元素（可能通过培养基）的甲基化元素（甲基化元素）促成BMP-4诱导的细胞的骨化细胞（通过添加双脂酰训练营（DBCAMP）再现了作为增强的BMP-4作用的途径。但是，尚未完全揭示这些药物对BMP信号传导增强作用的确切机制。如前所述，BMP利用特定的细胞内信号传导……通过R-SMADS（SMAD1,5,8），Co-SMAD（SMAD4）和I-SMADS（SMAD6,7），更多地级联到靶基因。 CAMP介导的对BMP信号传导影响的一种可能性可能是抑制I-SMADS表达，因为这些蛋白质在BMP信号中形成负反馈回路。为了检查这种可能性，在骨髓衍生的成骨细胞系（ST2）中检查了I-SMAD（SMAD6）表达的变化（SMAD6）表达。 BMP-4处理（300 ng/mL）始终诱导ST2细胞中的碱性磷酸酶活性，并且BMP-4处理也诱导SMAD6 mRNA表达。尽管，与BMP-4和DBCAMP一起对ST2细胞的同时治疗引起了酒精磷酸酶的进一步激活，但添加DBCAMP以剂量依赖性方式降低了BMP-4诱导的SMAD6表达。此外，在蛋白质印迹分析中检测磷酸化的SMAD1/5/8的检测延长了，表明通过抑制SMAD6的表达，BMP受体的激酶活性延长。因此，细胞内cAMP升高可能会通过抑制SMAD6诱导并延长细胞内BMP信号传导来增强BMP信号传导。较少的