Kawa-uchi T, Nifuji A, Mataga N, Olson E N, Bonaventure J, Shinomiya K, Liu Y, Noda M
Department of Molecular Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Japan.
J Cell Biochem. 1998 Sep 15;70(4):468-77. doi: 10.1002/(sici)1097-4644(19980915)70:4<468::aid-jcb4>3.0.co;2-h.
Scleraxis is a basic helix-loop-helix-type transcription factor that is expressed in sclerotome. Fibroblast growth factor (FGF) is one of the cytokines produced by the cells in skeletal tissues and is a potent modulator of skeletogenesis. The aim of this study was to examine the effects of FGF on the expression of scleraxis in chondrocyte-like cells, TC6. In these cells, scleraxis mRNA was constitutively expressed as a 1 .2 kb message at a high level in contrast to its low levels of expression in fibroblast-like cells or osteoblast-like cells. Upon treatment with FGF, scleraxis mRNA level was decreased within 12 h. This effect was at its nadir at 24 h and the scleraxis mRNA level returned to its base line level by 48 h. The FGF effect was maximal at 1 ng/ml. FGF effects on scleraxis were blocked by actinomycin D but not by cycloheximide, suggesting the involvement of transcriptional events that do not require new protein synthesis. The FGF effects on scleraxis were blocked by genistein, suggesting the involvement of tyrosine kinase in the post-receptor signaling. TGFbeta treatment of TC6 cells enhanced scleraxis mRNA expression; however, combination of the saturation doses of FGF and TGFbeta resulted in suppression of scleraxis mRNA level. BMP2 also suppressed scleraxis mRNA expression in TC6 cells and no further suppression was observed in combination with FGF. These results indicate that scleraxis is expressed in chondrocyte-like TC6 cells and it is one of the targets of FGF action in these cells.
硬骨素是一种在生骨节中表达的碱性螺旋-环-螺旋型转录因子。成纤维细胞生长因子（FGF）是骨骼组织细胞产生的细胞因子之一，是骨生成的有效调节因子。本研究的目的是检测FGF对软骨样细胞TC6中硬骨素表达的影响。在这些细胞中，硬骨素mRNA以1.2 kb的转录本持续高水平表达，这与其在成纤维样细胞或成骨样细胞中的低表达水平形成对比。用FGF处理后，硬骨素mRNA水平在12小时内下降。这种效应在24小时时达到最低点，硬骨素mRNA水平在48小时时恢复到基线水平。FGF的效应在1 ng/ml时最大。FGF对硬骨素的作用被放线菌素D阻断，但不被环己酰亚胺阻断，这表明涉及不需要新蛋白质合成的转录事件。FGF对硬骨素的作用被金雀异黄素阻断，这表明酪氨酸激酶参与了受体后信号传导。TGFβ处理TC6细胞可增强硬骨素mRNA表达；然而，饱和剂量的FGF和TGFβ联合使用会导致硬骨素mRNA水平受到抑制。BMP2也可抑制TC6细胞中硬骨素mRNA表达，与FGF联合使用时未观察到进一步的抑制作用。这些结果表明，硬骨素在软骨样TC6细胞中表达，并且它是这些细胞中FGF作用的靶点之一。
