模拟微重力效应通过微丝骨架调控成骨细胞BMP2-Smad信号

Simulated Microgravity Regulates Osteoblast BMP2-Smad Signaling via Actin Microfilament

细胞微丝骨架在力信号传导和基因表达调控中起重要作用。为了研究微丝骨架在模拟微重力效应调控成骨细胞BMP2-Smad信号中的作用,作者通过构建反映Smad活性的报告基因载体转染MC3T3-E1细胞,并通过报告基因活性分析、Western blot等方法检测了微丝骨架解聚剂和回转模拟微重力效应对BMP2诱导Samd磷酸化、核质分布和转录活性的作用。结果显示,构建的报告基因载体在成骨细胞中正确表达并响应BMP2;破坏微丝骨架会抑制BMP2诱导的Smad1/5/8蛋白磷酸化、入核及转录活性;回转抑制Smad1/5/8磷酸化、入核及其转录活性,而微丝骨架稳定剂可对抗回转的抑制作用。因此,认为回转模拟微重力效应可通过解聚微丝骨架抑制BMP2-Smad信号传导。

The actin microfilament plays important roles in the regulation of mechanotransduction and gene expression. To study the effects of dynamic microfilament induced by simulated microgravity on activity of osteoblast Smad induced by BMP2, a plasmJd p3BRE-90CoIX-Luc was constructed and transfected into MC3T3-E1 cell to detect effects of depolymerizing agent and clinorotation on activity of Smadl/5/8 via luciferase reporter. The phosphorylation and its subcellular location of Smadl/5/8 were detected by Western blot. Results showed that reporter vector was constructed correctly. MC3T3-E1 cell transfected with the vector expressed luciferase activity and responded to BMP2. Cytochalasin B which can depolymerize actin microfilament inhibited phosphorylation, nucleus translocation and activity of Smadl/5/8. Consistently, clinorotation inhibited phosphorylation, nucleus translocation and activity of Smadll518, and the inhibition effect was partly reversed by microfilament stabilizer Jasplakinolide. Therefore, these results suggest that the simulated microgravity could inhibits BMP2-Smad signaling via depolymerizing actin microfilament.