Activation of osteocalcin transcription involves interaction of protein kinase A- and protein kinase C-dependent pathways
Activation of osteocalcin transcription involves interaction of protein kinase A- and protein kinase C-dependent pathways
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DOI：
10.1074/jbc.275.2.999
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发表时间：
2000-01-14
影响因子：
4.8
通讯作者：
Chandrasekhar, S
中科院分区：
文献类型：
--
作者：
Boguslawski, G;Hale, LV;Chandrasekhar, S
骨钙素是骨细胞外基质的主要非胶原蛋白组分，仅由成熟晚期的成骨细胞合成和分泌，并且被认为是成骨细胞分化的指标。骨钙素的表达受甲状旁腺激素（PTH）和多种其他因素的调节。cAMP依赖性蛋白激酶通路在PTH信号传导和骨钙素表达调控中起重要作用。为了确定其他途径也可能参与骨钙素表达的程度，我们使用大鼠和人成骨细胞样细胞系来产生稳定转染的克隆，其中骨钙素启动子与荧光素酶报告基因融合。检查这些克隆对已知激活或干扰蛋白激酶A（PKA）和蛋白激酶C（PKC）依赖性途径的试剂的反应性。我们已经发现，毛喉素，cAMP和PTH，以及胰岛素样生长因子I（IGF-I）和碱性成纤维细胞生长因子，都是有效的激活骨钙素启动子。佛波醇12-肉豆蔻酸酯13-乙酸酯（PIMA）也是该启动子的强诱导剂，表明PKC在骨钙素的表达中起作用。在与PTH或毛喉素的组合中，PMA的作用是相加的协同作用。Calphostin C，PRC的选择性抑制剂，以剂量依赖性方式降低PMA，PTH和IGF-I诱导的荧光素酶活性; PKA抑制剂H-89，也阻断了PTH和IGF-I的诱导，但不阻断PMA。我们的结论是，调节骨钙素转录介导的PKA依赖和PKC依赖的机制和相应的激酶驻留在一个线性或收敛的途径。
Osteocalcin is a major noncollagenous protein component of bone extracellular matrix, synthesized and secreted exclusively by osteoblastic cells in the late stage of maturation, and is considered indicator of osteoblast differentiation. Osteocalcin expression is modulated by parathyroid hormone (PTH) and a variety of other factors. The cAMP-dependent protein kinase pathway has been shown previously to have an essential role in PTH signaling and regulation of osteocalcin expression. To determine the extent to which other pathways may also participate in osteocalcin expression, we used rat and human osteoblast-like cell lines to generate stably transfected clones in which the osteocalcin promoter was fused to a luciferase reporter gene. These clones were examined for their responsiveness to agents known to activate or interfere with protein kinase A (PKA)- and protein kinase C (PKC)-dependent pathways. We have found that forskolin, cAMP, and PTH, as well as insulin-like growth factor I (IGF-I) and basic fibroblast growth factor, all were effective in activating the osteocalcin promoter. Phorbol 12-myristate 13-acetate (PIMA) was also a strong inducer of the promoter, indicating that PKC plays a role in expression of osteocalcin. In combination with PTH or forskolin, the effect of PMA was additive to synergistic. Calphostin C, a selective inhibitor of PRC, decreased the PMA-, PTH-, and IGF-I-induced luciferase activity in a dose-dependent manner; a PKA inhibitor, H-89, also blocked the induction by PTH and IGF-I but not by PMA. We conclude that regulation of osteocalcin transcription is mediated by both PKA-dependent and PKC-dependent mechanisms and that the respective kinases reside on a linear or convergent pathway.