Institute of Genomic Medicine, College of Pharmacy, Jinan University, Guangzhou, 510632, China.
Guangdong Provincial Key Laboratory of Pharmacodynamics Constituents of TCM and New Drugs Research, Jinan University, Guangzhou, 510632, China.
Cell Biol Int. 2018 Aug;42(8):1030-1040. doi: 10.1002/cbin.10972. Epub 2018 May 8.
Growing evidences have demonstrated alternative splicing makes great contribution to tumor metastasis since multiple protein isoforms from a single gene that often display different functions in the cell. Human manganese superoxide dismutase (hMnSOD) was revealed dysregulation in progress of tumor metastasis, while the effect of hMnSOD isoforms on metastasis remained unclear. In this study, we showed a novel truncated hMnSOD isoform hMnSOD183, which lacked 39 amino acids compared with hMnSOD222. We expressed two hMnSOD protein isoforms in Escherichia coli, respectively, and found that the MnSOD activity of truncated hMnSOD isoform was especially weaker. In 95-D cells, mRNA levels of hMnSOD variants and MnSOD activity were significantly increased than that in A549 cells. Furthermore, the hMnSODc exhibited lower mRNA level than hMnSODa/b in A549 and 95-D cells. Additionally, the effects of two isoforms were assessed about cell invasion, overexpression of hMnSOD222 but not hMnSOD183 promoted 95-D cells metastasis, and hMnSOD knockdown significantly reduced cells invasive behavior. Overexpression of hMnSOD isoforms also caused changes of metastasis associated proteins, such as up-regulation of MMPs, VEGF and Vimentin and down-regulation of E-cadherin. Moreover, overexpression of hMnSOD183 had weaker effect on metastasis related signaling proteins, such as Akt, JNK and IKKβ, compared to hMnSOD222. In conclusion, our study identified that hMnSOD isoforms induced lung cancer cells invasion through Akt-JNK-IKKβ signaling pathways and the hMnSOD183 isoform played a weaker role than hMnSOD222. Characterization of hMnSOD isoforms is useful for future investigation on metastasis of lung cancer cells.
越来越多的证据表明，选择性剪接对肿瘤转移有很大贡献，因为一个基因可以产生多种蛋白质异构体，这些异构体在细胞中通常具有不同的功能。人类锰超氧化物歧化酶（hMnSOD）在肿瘤转移过程中被发现失调，而 hMnSOD 异构体对转移的影响尚不清楚。在这项研究中，我们展示了一种新型的截断 hMnSOD 异构体 hMnSOD183，它与 hMnSOD222 相比缺失了 39 个氨基酸。我们分别在大肠杆菌中表达了两种 hMnSOD 蛋白异构体，发现截断 hMnSOD 异构体的 MnSOD 活性特别弱。在 95-D 细胞中，hMnSOD 变体的 mRNA 水平和 MnSOD 活性明显高于 A549 细胞。此外，hMnSODc 在 A549 和 95-D 细胞中的 mRNA 水平低于 hMnSODa/b。此外，还评估了两种异构体对细胞侵袭的影响，过表达 hMnSOD222 而不是 hMnSOD183 促进 95-D 细胞转移，hMnSOD 敲低显著降低了细胞侵袭行为。过表达 hMnSOD 异构体也导致了与转移相关的蛋白的变化，如 MMPs、VEGF 和 Vimentin 的上调和 E-cadherin 的下调。此外，与 hMnSOD222 相比，hMnSOD183 对转移相关信号蛋白（如 Akt、JNK 和 IKKβ）的上调作用较弱。综上所述，我们的研究表明，hMnSOD 异构体通过 Akt-JNK-IKKβ 信号通路诱导肺癌细胞侵袭，hMnSOD183 异构体的作用弱于 hMnSOD222。对 hMnSOD 异构体的特征描述有助于对肺癌细胞转移的进一步研究。
