†Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del IPN, México.
‡Department of Pharmacological Sciences, State University of New York at Stony Brook, NY, U.S.A.
ASN Neuro. 2013 Dec 23;5(5):e00130. doi: 10.1042/AN20130023.
The Notch pathway is a highly conserved signaling system essential for modulating neurogenesis and promoting astrogenesis. Similarly, the cAMP signaling cascade can promote astrocytic commitment in several cell culture models, such as the C6 glioma cell line. These cells have the capacity to differentiate into oligodendrocytes or astrocytes, characteristics that allow their use as a glial progenitor model. In this context, we explore here the plausible involvement of cAMP in Notch-dependent signal transactions. The exposure of C6 cells to a non-hydrolysable cAMP analogue resulted in a sustained augmentation of Notch activity, as detected by nuclear translocation of its intracellular domain portion (NICD) and transcriptional activity. The cAMP effect is mediated through the activation of the γ-secretase complex, responsible for Notch cleavage and is sensitive to inhibitors of the cAMP-dependent protein kinase, PKA. As expected, Notch cleavage and nuclear translocation resulted in the up-regulation of the mRNA levels of one of its target genes, the transcription factor Hair and enhancer of split 5. Moreover, the glutamate uptake activity, as well as the expression of astrocytic markers such as glial fibrillary acidic protein, S100β protein and GLAST was also enhanced in cAMP-exposed cells. Our results clearly suggest that during the process of C6 astrocytic differentiation, cAMP activates the PKA/γ-secretase/NICD/RBPJ(κ) pathway and Notch1 expression, leading to transcriptional activation of the genes responsible for glial progenitor cell fate decision.
Notch 通路是一个高度保守的信号系统，对于调节神经发生和促进星形胶质细胞发生至关重要。同样，cAMP 信号级联在几种细胞培养模型中也可以促进星形胶质细胞的分化，例如 C6 神经胶质瘤细胞系。这些细胞具有分化为少突胶质细胞或星形胶质细胞的能力，其特征允许它们作为神经胶质祖细胞模型使用。在这种情况下，我们在这里探讨 cAMP 在 Notch 依赖性信号转导中的可能作用。将 C6 细胞暴露于非水解型 cAMP 类似物中会导致 Notch 活性持续增强，这可以通过其细胞内结构域部分（NICD）的核转位和转录活性来检测。cAMP 的作用是通过激活 γ-分泌酶复合物介导的，该复合物负责 Notch 的切割，并且对 cAMP 依赖性蛋白激酶 PKA 的抑制剂敏感。如预期的那样， Notch 的切割和核转位导致其靶基因之一的 mRNA 水平上调，即转录因子 Hair 和 Split 5 的增强子。此外，cAMP 暴露的细胞中的谷氨酸摄取活性以及星形胶质细胞标志物如胶质纤维酸性蛋白、S100β 蛋白和 GLAST 的表达也增强了。我们的结果清楚地表明，在 C6 星形胶质细胞分化过程中，cAMP 激活 PKA/γ-分泌酶/NICD/RBPJ(κ)途径和 Notch1 表达，导致负责神经胶质祖细胞命运决定的基因的转录激活。
