The Transcriptional Activity of Sox9 in Chondrocytes Is Regulated by RhoA Signaling and Actin Polymerization
The Transcriptional Activity of Sox9 in Chondrocytes Is Regulated by RhoA Signaling and Actin Polymerization
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DOI：
10.1128/mcb.01779-08
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发表时间：
2009-08-01
影响因子：
5.3
通讯作者：
Lassar, Andrew B.
中科院分区：
文献类型：
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作者：
Kumar, Deepak;Lassar, Andrew B.
在这项研究中，我们证明了圆的原代软骨细胞去分化成纤维细胞形态与RhoA蛋白和应力纤维的深刻诱导相关。藻酸盐凝胶中去分化软骨细胞的培养诱导RhoA蛋白的急剧损失和应力纤维的损失，伴随着软骨细胞分化程序的重新表达。我们已经发现，软骨形成在肢芽微团文化同样需要损失的RhoA蛋白和显性负RhoA在这种文化中的表达可以显着增强软骨形成。与这些结果一致，Rho拮抗剂C3转移酶的表达可以恢复在塑料上生长的去分化软骨细胞中的软骨细胞基因表达。用阻断肌动蛋白聚合的试剂转染细胞增强外源Sox 9或Gal 4 DBD-Sox 9融合蛋白激活基因表达的能力。有趣的是，通过肌动蛋白解聚来增强Sox 9功能需要蛋白激酶A（PKA）活性和Sox 9（S181）中的PKA磷酸化位点，已知该位点增强Sox 9转录活性。最后，我们证明了RhoA介导的肌动蛋白聚合调节Sox 9激活软骨细胞特异性标志物并通过正反馈回路维持其自身在软骨细胞中表达的能力。
In this study, we demonstrate that dedifferentiation of round primary chondrocytes into a fibroblast morphology correlates with a profound induction of RhoA protein and stress fibers. Culture of dedifferentiated chondrocytes in alginate gel induces a precipitous loss of RhoA protein and a loss of stress fibers concomitant with the reexpression of the chondrocyte differentiation program. We have found that chondrogenesis in limb bud micromass cultures similarly entails a loss of RhoA protein and that expression of dominant negative RhoA in such cultures can markedly enhance chondrogenesis. Consistent with these results, expression of the Rho antagonist C3 transferase can restore chondrocyte gene expression in dedifferentiated chondrocytes grown on plastic. Transfection of cells with agents that block actin polymerization enhance the ability of either exogenous Sox9 or a Gal4 DBD-Sox9 fusion protein to activate gene expression. Interestingly, the enhancement of Sox9 function by actin depolymerization requires both protein kinase A (PKA) activity and a PKA phosphorylation site in Sox9 (S181) that is known to enhance Sox9 transcriptional activity. Lastly, we demonstrate that RhoA-mediated modulation of actin polymerization regulates the ability of Sox9 to both activate chondrocyte-specific markers and maintain its own expression in chondrocytes via a positive feedback loop.