University of Ottawa, Department of Cellular and Molecular Medicine, Ottawa, ON, Canada.
University of Ottawa, Department of Cellular and Molecular Medicine, Ottawa, ON, Canada; University of Ottawa Heart Institute, Ottawa, ON, Canada.
Cell Signal. 2017 Dec;40:230-238. doi: 10.1016/j.cellsig.2017.09.022. Epub 2017 Sep 28.
The E2F/Rb pathway regulates cell growth, differentiation, and death. In particular, E2F1 promotes apoptosis in all cells including those of the heart. E2F6, which represses E2F activity, was found to induce dilated cardiomyopathy in the absence of apoptosis in murine post-natal heart. Here we evaluate the anti-apoptotic potential of E2F6 in neonatal cardiomyocytes (NCM) from E2F6-Tg hearts which showed significantly less caspase-3 cleavage, a lower Bax/Bcl2 ratio, and improved cell viability in response to CoCl exposure. This correlated with a decrease in the pro-apoptotic E2F3 protein levels. In contrast, no difference in apoptotic markers or cell viability was observed in response to Doxorubicin (Dox) treatment between Wt and Tg-NCM. Dox caused a rapid and dramatic loss of the E2F6 protein in Tg-NCM within 6h and was undetectable after 12h. The level of e2f6 transcript was unchanged in Wt NCM, but was dramatically decreased in Tg cells in response to both Dox and CoCl. This was related to an impact of the drugs on the α-myosin heavy chain promoter used to drive the E2F6 transgene. By comparison in HeLa, Dox induced apoptosis through upregulation of endogenous E2F1 involving post-transcriptional mechanisms, while E2F6 was down regulated with induction of the Checkpoint kinase-1 and proteasome degradation. These data imply that E2F6 serves to modulate E2F activity and protect cells including cardiomyocytes from apoptosis and improve survival. Strategies to modulate E2F6 levels may be therapeutically useful to mitigate cell death associated disorders.
E2F/Rb 通路调节细胞生长、分化和死亡。特别是，E2F1 促进所有细胞包括心脏细胞的凋亡。E2F6 抑制 E2F 活性，被发现可在没有凋亡的情况下诱导鼠产后心脏扩张型心肌病。在这里，我们评估了 E2F6-Tg 心脏来源的新生心肌细胞（NCM）中的抗凋亡潜力，E2F6-Tg 心脏中的 E2F6-Tg 心脏中的 caspase-3 切割明显减少，Bax/Bcl2 比值降低，对 CoCl 暴露的细胞活力提高。这与促凋亡 E2F3 蛋白水平降低有关。相比之下，在 Wt 和 Tg-NCM 中，Dox 处理对凋亡标志物或细胞活力无差异。Dox 在 6 小时内迅速且显著地导致 Tg-NCM 中 E2F6 蛋白丢失，12 小时后无法检测到。在 Wt NCM 中，e2f6 转录本水平不变，但在 Tg 细胞中，无论是 Dox 还是 CoCl 处理，都明显降低。这与药物对用于驱动 E2F6 转基因的α肌球蛋白重链启动子的影响有关。相比之下，在 HeLa 细胞中，Dox 通过涉及转录后机制的内源性 E2F1 的上调诱导凋亡，而 E2F6 则随着细胞周期检查点激酶-1 的诱导和蛋白酶体降解而下调。这些数据表明，E2F6 可调节 E2F 活性，保护包括心肌细胞在内的细胞免受凋亡并提高存活率。调节 E2F6 水平的策略可能在治疗上有助于减轻与细胞死亡相关的疾病。
