The human ΔNp53 isoform triggers metabolic and gene expression changes that activate mTOR and alter mitochondrial function

Summary A naturally occurring p53 isoform that lacks 39 residues at the N-terminus (denoted Delta Np53), when expressed with wild-type p53 (WTp53), forms mixed Delta Np53:WTp53 tetramers and causes accelerated aging in mice. Cellular alterations specific to Delta Np53:WTp53 have been difficult to assess because Delta Np53 and WTp53 coexpression results in tetramer heterogeneity, including formation of contaminating WTp53 tetramers. Based on the p53 tetramer structure, we expressed Delta Np53 and WTp53 as a single transcript that maintained tetramer architecture, ensuring a 2:2 Delta Np53:WTp53 stoichiometry. As expected, Delta Np53:WTp53 tetramers were stable and transcriptionally active in vitro and in cells, largely mimicking the function of WTp53 tetramers. Microarray analyses, however, revealed about 80 genes whose expression was altered twofold or more in Delta Np53:WTp53 cells. Moreover, global metabolomic profiling quantitated hundreds of biochemicals across different experiments (WTp53, Delta Np53:WTp53, plus controls). When evaluated collectively, these data suggested altered mTOR signaling and mitochondrial function-each canonical regulators of longevity-in cells expressing Delta Np53:WTp53 vs. WTp53. Increased levels of free amino acids, increased expression of IRS-1, and decreased expression of INPP5D/SHIP-1 suggested activated mTOR signaling in Delta Np53:WTp53 cells; this was confirmed upon comparative analyses of several mTOR pathway intermediates. We also observed changes in mitochondrial function in Delta Np53:WTp53 cells, which correlated with increased MARS2 expression and increased levels of carnitine, acetyl CoA, ATP, and Krebs cycle intermediates. Finally, increased levels of succinate and 2-hydroxyglutarate indicate potential epigenetic means to propagate Delta Np53:WTp53-induced gene expression changes to cell progeny. This may be especially important for aging, as biological effects manifest over time.