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

Abstract

Summary A naturally occurring p53 isoform that lacks 39 residues at the N-terminus (denoted ΔNp53), when expressed with wild-type p53 (WTp53), forms mixed ΔNp53:WTp53 tetramers and causes accelerated aging in mice. Cellular alterations specific to ΔNp53:WTp53 have been difficult to assess because ΔNp53 and WTp53 co-expression results in tetramer heterogeneity, including formation of contaminating WTp53 tetramers. Based upon the p53 tetramer structure, we expressed ΔNp53 and WTp53 as a single transcript that maintained tetramer architecture, ensuring a 2:2 ΔNp53:WTp53 stoichiometry. As expected, ΔNp53: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 2-fold or more in ΔNp53:WTp53 cells. Moreover, global metabolomic profiling quantitated hundreds of biochemicals across different experiments (WTp53, ΔNp53:WTp53, plus controls). When evaluated collectively, these data suggested altered mTOR signaling and mitochondrial function—each canonical regulators of longevity—in cells expressing ΔNp53: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 ΔNp53:WTp53 cells; this was confirmed upon comparative analyses of several mTOR pathway intermediates. We also observed changes in mitochondrial function in ΔNp53:WTp53 cells, which correlated with increased MARS2 expression and elevated levels of carnitine, acetyl CoA, ATP, and Krebs cycle intermediates. Finally, elevated levels of succinate and 2-hydroxyglutarate indicate potential epigenetic means to propagate ΔNp53:WTp53-induced gene expression changes to cell progeny. This may be especially important for aging, as biological effects manifest over time.

Post-translational regulation of p53 function through 20S proteasome-mediated cleavage

“…Results are a representative experiment of at least three independent experiments diverse cellular conditions, as was shown in response to DNA damage or proteotoxic stress. 19,23,34 Therefore, we conclude that the balance between Δ40p53 and FLp53 has an impact on the expression pattern of p53-inducible genes. Whether recruitment of diverse co-activators and chromatin remodeling factors, or different affinities toward DNA (as shown in Figure 1c) dictate Δ40p53 effect, remains elusive.…”

“…18 The Δ40p53 isoform has been shown to impact p53 activity, when expressed together with the wild-type (WT) p53 protein, especially in imposing a dominant negative effect. 18,[22][23][24] Altogether, it seems that Δ40p53 expression can affect cancer formation and, therefore, it is important to uncover the molecular mechanisms that coordinate its cellular levels and function.…”

Endoplasmic reticulum stress sensitizes cells to DNA damage-induced apoptosis through p53-dependent suppression of p21CDKN1A

“…p53/47 forms oligomers more easily as compared with p53 FL and relatively small changes in p53/47 levels during ER stress impose a dominant phenotype 23 . Genomic profiling has implicated p53/47 in differentiating p53 transactivation and more recent data have, in addition to cell cycle control, linked p53/47 activity to the mammalian target of rapamycin metabolic pathway and mitochondria 16,23,26 . Recent studies also identified p53/47 expression in glioblastoma and suggested a role for p53/47 in ageing and stem cell pluripotency 27,28 .…”

Identification of significantly different modules between permanent and deciduous teeth by network and pathway analyses

“…Moreover, the roles of TMEM229A, LEPREL1, and GAD1 have been validated in our research. Transmembrane protein 229A (TMEM229A) plays a major role in the binding of zona pellucida and participates in Ca 2+ signaling-associated acrosomal exocytosis (Lin et al, 2013a). Glutamate decarboxylase 1 (GAD1) encodes a glutamic acid decarboxylase that catalyzes the production of gamma-aminobutyric acid from l-glutamic acid (Lin et al, 2013b).…”