Cdc42-mTOR Signaling Pathway Controls Hes5 and Pax6 Expression in Retinoic Acid-dependent Neural Differentiation
Cdc42-mTOR Signaling Pathway Controls Hes5 and Pax6 Expression in Retinoic Acid-dependent Neural Differentiation
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DOI：
10.1074/jbc.m807745200
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发表时间：
2009-02-20
影响因子：
4.8
通讯作者：
Cerione, Richard A.
中科院分区：
文献类型：
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作者：
Endo, Makoto;Antonyak, Marc A.;Cerione, Richard A.
小鼠端脑中神经上皮(NE)和放射状胶质(RG)细胞的小GTP酶CDc42的条件性敲除被证明对脑发育有重要影响，因为这些神经前体细胞从心尖/脑室表面分离并失去细胞特性。这归因于在建立适当的顶端/基底端细胞极性和细胞-细胞粘连时需要CDC42。在本研究中，我们以小鼠胚胎癌细胞系P19为模型系统，对CDC42在维持神经前体细胞中所起的作用提供了新的见解。我们发现，在维甲酸(RA)处理后，P19细胞经历从Oct3/4阳性的未分化状态到微管相关蛋白2阳性神经元和胶质纤维酸性蛋白阳性星形胶质细胞的能力，需要在神经细胞谱系指定阶段由RA诱导CDc42的激活。使用化学抑制剂和RNA干扰的实验表明，CDC42的作用是通过信号通路介导的，这些信号通路始于成纤维细胞生长因子和Delta/Notch蛋白，导致CDc42依赖的mTOR激活，最终上调对NE和RG细胞维持至关重要的两种转录因子Hes5和Pax6的表达。即使在没有RA处理的情况下，CDC42(F28L)突变体也足以上调P19细胞中Hes5和Pax6的表达，最终促进它们向神经前体细胞的转变。异位表达的CDC42还显著增强了这些转录因子的RA依赖上调，导致P19细胞保持其神经前体状态，但不能进行终末分化。这些发现揭示了CDC42如何通过调节基因表达来影响神经前体细胞的命运。
The conditional knockout of the small GTPase Cdc42 from neuroepithelial (NE) and radial glial (RG) cells in the mouse telencephalon has been shown to have a significant impact on brain development by causing these neural progenitor cells to detach from the apical/ventricular surface and to lose their cell identity. This has been attributed to the requirement for Cdc42 in establishing properapical/basal cell polarity and cell-cell adhesions. In the present study, we provide new insights into the role played by Cdc42 in the maintenance of neural progenitor cells, using the mouse embryonal carcinoma P19 cell line as a model system. We show that the ability of P19 cells to undergo the transition from an Oct3/4-positive, undifferentiated status to microtubule-associated protein 2-positive neurons and glial fibrillary acidic protein-positive astrocytes, upon treatment with retinoic acid (RA), requires RA-induced activation of Cdc42 during the neural cell lineage specification phase. Experiments using chemical inhibitors and RNA interference suggest that the actions of Cdc42 are mediated through signaling pathways that start with fibroblast growth factors and Delta/Notch proteins and lead to Cdc42-dependent mTOR activation, culminating in the up-regulation of Hes5 and Pax6, two transcription factors that are essential for the maintenance of NE and RG cells. The constitutively active Cdc42(F28L) mutant was sufficient to up-regulate Hes5 and Pax6 in P19 cells, even in the absence of RA treatment, ultimately promoting their transition to neural progenitor cells. The ectopic Cdc42 expression also significantly augmented the RA-dependent up-regulation of these transcription factors, resulting in P19 cells maintaining their neural progenitor status but being unable to undergo terminal differentiation. These findings shed new light on how Cdc42 influences neural progenitor cell fate by regulating gene expression.