Molecular Mechanisms Of Mitochondrial FOXM1-Mediated Cellular Senescence

Cellular senescence is an important risk factor for many diseases,including neurodegenerative diseases,cancer and metabolic diseases such as type II diabetes.As the energy production center of cells,mitochondria are closely related to aging and regulate cell senescence from many aspects,such as chronic inflammation,mitophagy,and mitochondrial unfolded protein response(mt UPR).FOXM1 is a key nuclear transcription factor in cells that regulates G1/S,G2/M transitions and M-phase progression in the cell cycle and plays a critical role in suppressing cellular senescence.It has been found that FOXM1 is localized in the nucleus as well as in mitochondria,however,the functions of FOXM1 in mitochondria are poorly studied.In order to explore the function of FOXM1 in mitochondria and its role in cellular senescence.With the whole gene synthesis technology,we created a construct expressing mitochondrial-specific FOXM1(mito-FOXM1)by adding mitochondrial localization sequence of cytochrome C oxidase VIII subunit(COX VIII)to the Nterminus of wild-type FOXM1.EGFP was included to the C-terminus Wild-type FOXM1(WT-FOXM1)was also constructed as a control.By analyzing EGFP fluorescence of the cells overexpressing mito-FOXM1.we found mito-FOXM1 was specifically overexpressed in mitochondria.The cells expressing mito-FOXM1 were tested for the cell respiration and ROS production.We found that mito-FOXM1 promoted cell respiration as well as intracellular ROS production.In in vivo experiments,we examined the total FOXM1 protein levels and mitochondrial-specific FOXM1 protein levels from mouse tissues at the different ages.We found that as the mice aging,the total protein level of FOXM1 decreased,however,while the liver mitochondrial FOXM1 protein increased.To further investigate if the mitochondrial FOXM1 is associated with cellular senescence,we overexpressed mito-FOXM1 and WT-FOXM1 in mouse embryonic fibroblast(MEFs)using a lentiviral system and subsequently examined the senescence indicators Gal of MEFs at different passage.We found that FOXM1 accelerated the senescence of MEFs.Taken together,our results showed mitochondrial-specific FOXM1 contributes to the cellular aging independent of its nuclear function.Our study is very first to associate the mitochondrial FOXM1 plays a role cellular senescence,providing potential new mechnisms of aging and the novel therapeutic targets for aging and age-related diseases.