Department of Odontology, Fukuoka Dental College, Fukuoka 814-0193, Japan.
Biochem Biophys Res Commun. 2013 Jan 11;430(2):810-5. doi: 10.1016/j.bbrc.2012.11.064. Epub 2012 Nov 29.
When DNA is damaged by alkylating agents, apoptosis is induced to exclude cells carrying DNA lesions in order to prevent mutations and cancer. MAPO1, identified as a component involved in the induction of apoptosis, interacts with AMP-activated protein kinase (AMPK) and folliculin (FLCN). We herein report that MAPO1 is stabilized during the course of apoptosis, triggered by alkylation-induced O(6)-methylguanine in DNA. An immunoblotting analysis revealed that the amount of MAPO1 increased gradually after treatment with N-methyl-N-nitrosourea (MNU), although the level of mRNA for MAPO1 was unchanged. When cells were exposed to a proteasome inhibitor, MG132, the MAPO1 level significantly increased. On the other hand, application of a protein synthesis inhibitor, cycloheximide, caused a decrease in the MAPO1 content, implying that proteasome-mediated degradation is involved. In FLCN-knockdown cells, the MAPO1 level decreased, and no increases occurred even after MNU treatment. In contrast, stabilization of MAPO1 occurred in AMPKα-knockdown cells even without MNU treatment. While MAPO1 retains its ability to stably bind to FLCN, it dissociates gradually from AMPK after exposure to MNU. It seems that the proapoptotic function of MAPO1 may be regulated by AMPK and FLCN through stabilization of MAPO1 itself.
当 DNA 受到烷化剂的损伤时，会诱导细胞凋亡以排除携带 DNA 损伤的细胞，从而防止突变和癌症的发生。MAPO1 被鉴定为参与细胞凋亡诱导的一个组成部分，它与 AMP 激活的蛋白激酶 (AMPK) 和滤泡素 (FLCN) 相互作用。我们在此报告，在由 DNA 中烷化诱导的 O(6)-甲基鸟嘌呤引起的细胞凋亡过程中，MAPO1 被稳定。免疫印迹分析显示，在用 N-甲基-N-亚硝基脲 (MNU) 处理后，MAPO1 的量逐渐增加，尽管 MAPO1 的 mRNA 水平保持不变。当细胞暴露于蛋白酶体抑制剂 MG132 时，MAPO1 水平显著增加。另一方面，应用蛋白质合成抑制剂环己酰亚胺会导致 MAPO1 含量减少，这表明蛋白酶体介导的降解参与其中。在 FLCN 敲低细胞中，MAPO1 水平降低，即使在用 MNU 处理后也没有增加。相比之下，即使没有 MNU 处理，AMPKα 敲低细胞中 MAPO1 的稳定也会发生。虽然 MAPO1 仍然能够稳定地与 FLCN 结合，但在用 MNU 处理后，它会逐渐从 AMPK 上解离。MAPO1 的促凋亡功能似乎可以通过稳定 MAPO1 本身来被 AMPK 和 FLCN 调节。
