Rac1 signaling stimulates N-cadherin expression, mesenchymal condensation, and chondrogenesis
Rac1 signaling stimulates N-cadherin expression, mesenchymal condensation, and chondrogenesis
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DOI：
10.1074/jbc.m700680200
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发表时间：
2007-08-10
影响因子：
4.8
通讯作者：
Beier, Frank
中科院分区：
文献类型：
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作者：
Woods, Anita;Wang, Guoyan;Beier, Frank
控制间充质前体细胞分化为软骨细胞(软骨形成)的分子机制尚不完全清楚。我们最近发现，小分子GTP酶RhoA可以抑制这一过程。在这里，我们证明了一个不同的Rho GTP酶家族成员，rac1，促进软骨形成。在微团培养中药物抑制rac1的表达导致软骨标志物II型胶原和聚集素的mRNA水平降低，糖胺聚糖的积累减少。重要的成软骨转录因子Sox9、Sox5和Sox6的表达也在Rac1信号通路被抑制后减少。相反，在软骨源性ATDC5细胞系中，rac1的过表达增加了Sox9、5和6、II型胶原和聚集素的mRNA转录。抑制rac1导致细胞凝集的数量、大小和组织减少，N-钙粘附素的表达减少。Rac1过表达导致N-钙粘附素表达水平升高。此外，在原代微团培养中，对rac1基因的去除导致软骨形成标志物的表达减少。此外，我们还提供了Cdc42也促进软骨形成的证据。在ATDC5细胞中过表达CDC42导致Sox5、Sox9和II型胶原的表达增加，而不是Sox6、aggrecan或N-钙粘素的表达。因此，我们证明了rac1和cdc42是软骨形成的正调控因子，但至少部分通过不同的细胞和分子机制发挥作用。
The molecular mechanisms controlling differentiation of mesenchymal precursor cells into chondrocytes (chondrogenesis) are not completely understood. We have recently shown that the small GTPase RhoA inhibits this process. Here we demonstrate that a different Rho GTPase family member, Rac1, promotes chondrogenesis. Pharmacological inhibition of Rac1 expression in micromass culture resulted in reduced mRNA levels of the chondrogenic markers collagen II and aggrecan, and decreased accumulation of glycosaminoglycans. Expression of the essential chondrogenic transcription factors Sox9, Sox5, and Sox6 was also reduced upon inhibition of Rac1 signaling. In contrast, overexpression of Rac1 in the chondrogenic ATDC5 cell line increased mRNA transcripts of Sox9, 5, and 6, collagen II, and aggrecan. Inhibition of Rac1 resulted in a reduction in the number, size, and organization of cellular condensations and decreased expression of N-cadherin. Overexpression of Rac1 resulted in an increase in N-cadherin expression levels. Furthermore, genetic ablation of Rac1 in primary micromass cultures resulted in reduced expression of chondrogenic markers. Additionally, we provide evidence that Cdc42 also promotes chondrogenesis. Overexpression of Cdc42 in ATDC5 cells resulted in increased expression of Sox5, Sox9, and collagen II but not Sox6, aggrecan, or N-cadherin. Therefore, we demonstrate that Rac1 and Cdc42 are positive regulators of chondrogenesis, but act at least in part through different cellular and molecular mechanisms.