Zhang Wei, Liu Meng-Wei, Li Ming, Xiao Wei, Zhang Xue-Wen, He Hao-Juan, Chen Ya-Bin, Ding Lei, Luo Kai-Jun
School of Life Sciences, Yunnan University, Kunming, P.R. China.
Key Laboratory for Biochemistry and Molecular Biology of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China.
Arch Insect Biochem Physiol. 2018 Sep;99(1):e21473. doi: 10.1002/arch.21473. Epub 2018 Jun 3.
Little is known about how mammalian cells respond to the expression of innexins (Inxs), which are known to mediate cell-to-cell communication that causes apoptosis in the cells of the insect Spodoptera litura. The mammalian expression system, p3xFLAG tag protein, containing the CMV promoter, allowed us to construct two C-terminally elongated innexins (Cte-Inxs), SpliInx2 (Inx2-FLAG), and SpliInx3 (Inx3-FLAG), which were predicted to have the same secondary topological structures as the native SpliInx2 and SpliInx3. Here, we found that only the mRNAs of the two Cte-Inxs were expressed under the control of the CMV promoter in HeLa cells. Unexpectedly, mRNA expression of the two Cte-Inxs enhanced apoptosis of HeLa cells. The two Cte-Inx mRNAs were associated with a significant decrease in Akt phosphorylation in HeLa cells undergoing apoptosis. Furthermore, Inx3-FLAG mRNA expression in nonapoptotic HCT116 cells was also associated with a significant decrease in the levels of phosphorylated Akt. Intriguingly, expression of the mRNAs of the two Cte-Inxs did not activate caspase 3, but it markedly reduced Bid levels in HeLa cells undergoing apoptosis. These results suggest that mRNA expression of the two Cte-Inxs may activate a Bid-dependent apoptotic pathway in HeLa cells. Our study demonstrates that invertebrate gap junction mRNAs can function in vertebrate cancer cells as tumor suppressors.
关于哺乳动物细胞如何响应连接蛋白（Inxs）的表达知之甚少，已知连接蛋白介导细胞间通讯，可导致昆虫斜纹夜蛾细胞凋亡。含有巨细胞病毒（CMV）启动子的哺乳动物表达系统p3xFLAG标签蛋白，使我们能够构建两种C末端延长的连接蛋白（Cte-Inxs），即斜纹夜蛾连接蛋白2（Inx2-FLAG）和斜纹夜蛾连接蛋白3（Inx3-FLAG），预计它们具有与天然斜纹夜蛾连接蛋白2和斜纹夜蛾连接蛋白3相同的二级拓扑结构。在此，我们发现只有这两种Cte-Inxs的mRNA在CMV启动子的控制下在HeLa细胞中表达。出乎意料的是，这两种Cte-Inxs的mRNA表达增强了HeLa细胞的凋亡。这两种Cte-Inx mRNA与凋亡HeLa细胞中Akt磷酸化的显著降低有关。此外，非凋亡HCT116细胞中Inx3-FLAG mRNA的表达也与磷酸化Akt水平的显著降低有关。有趣的是，这两种Cte-Inxs的mRNA表达并未激活半胱天冬酶3，但它显著降低了凋亡HeLa细胞中的Bid水平。这些结果表明，这两种Cte-Inxs的mRNA表达可能在HeLa细胞中激活了一条Bid依赖性凋亡途径。我们的研究表明，无脊椎动物间隙连接mRNA可以在脊椎动物癌细胞中作为肿瘤抑制因子发挥作用。
