Adhesion-regulated G1 cell cycle arrest in epithelial cells requires the downregulation of c-Myc
Adhesion-regulated G1 cell cycle arrest in epithelial cells requires the downregulation of c-Myc
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DOI：
10.1038/sj.onc.1204609
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发表时间：
2001-07-27
期刊：
影响因子：
8
通讯作者：
Dickson, RB
中科院分区：
文献类型：
--
作者：
Benaud, CM;Dickson, RB
细胞周期蛋白-细胞周期蛋白依赖性激酶（CDK）复合物的表达和活化以及非转化细胞的G1期进展需要粘附到细胞外基质。然而，在非粘附细胞中，尚未提出p27细胞周期蛋白依赖性激酶抑制剂（CKI）的细胞粘附依赖性上调以及细胞周期蛋白E-CDK 2的相关抑制的分子机制。我们现在发现，在上皮细胞中，c-Myc的表达受到细胞-基质粘附的严格调控。当被剥夺的粘附，两个独立的乳腺上皮细胞系，184 AlN 4和MCF-10A，迅速降低其c-Myc mRNA和蛋白质的水平。c-Myc水平的降低与G1期阻滞相关，如pRb的低磷酸化和细胞周期蛋白E-CDK 2复合物活性的抑制所示。在184 AlN 4细胞中，细胞-基质粘附是抑制p27和诱导细胞周期蛋白E，E2 F-1所必需的，但不是细胞周期蛋白D1和D3。c-Myc在非粘附184 AIN 4和MCF-10A细胞中的增强表达逆转了细胞周期进程的粘附依赖性抑制。在非贴壁细胞中c-Myc的恢复诱导E2 F-1的表达，以及响应EGF处理的pRb的过度磷酸化。此外，c-Myc的表达导致CDK 2复合物的锚定非依赖性激活，相关的细胞周期蛋白E的上调，以及通过泛素-蛋白酶体途径的p27的不稳定和降解。因此，我们的研究表明，c-Myc是细胞粘附和调节p27和细胞周期蛋白ECDK 2之间的联系。此外，我们描述了c-Myc在粘附介导的E2 F-1调节中的作用。
Adhesion to the extracellular matrix is required for the expression and activation of the cyclin-cyclin-dependent kinase (CDK) complexes, and for G1 phase progression of non-transformed cells. However, in non-adherent cells no molecular mechanism has yet been proposed for the cell adhesion-dependent up-regulation of the p27 cyclin-dependent kinase inhibitor (CKI), and the associated inhibition of cyclin E-CDK2. We now show that in epithelial cells the expression of c-Myc is tightly regulated by cell-substrate adhesion. When deprived of adhesion, two independently derived mammary epithelial cell lines, 184AlN4 and MCF-10A, rapidly decrease their level of c-Myc mRNA and protein. This decrease in levels of c-Myc correlates with G1 phase arrest, as indicated by hypophosphorylation of pRb and inhibition of the activity of the cyclin E-CDK2 complex. In 184AlN4 cells, cell-substrate adhesion is required for the suppression of p27, and induction of cyclin E, E2F-1, but not cyclins D1 and D3. Enforced expression of c-Myc in non-adherent 184AIN4 and MCF-10A cells reverses the adhesion-dependent inhibition of cell cycle progression. Restoration of c-Myc in non-adherent cells induces the expression of E2F-1, and hyperphosphorylation of pRb in response to EGF treatment. In addition, expression of c-Myc results in the anchorage-independent activation of the CDK2 complex, the associated upregulation of cyclin E, and the destabilization and degradation of p27 by the ubiquitin-proteasome pathway. Our study thus suggests that c-Myc is the link between cell adhesion and the regulation of p27 and cyclin ECDK2. Furthermore, we describe a role for c-Myc in adhesion-mediated regulation of E2F-1.