Serine 392 phosphorylation modulates p53 mitochondrial translocation and transcription-independent apoptosis

Abstract

The tumor suppressor p53 is a key regulator of apoptosis induced by various cellular stresses. p53 can induce apoptosis by two mechanisms. First, p53 acts as a transcription factor inducing and repressing pro-apoptotic and anti-apoptotic targets genes, respectively. Second, p53 is able to translocate to the mitochondria, where it interacts with BCL-2 family members to induce membrane permeabilization and cytochrome c release. p53 transcriptional activity is regulated by a set of post-translational modifications that have been well documented. However, how these modifications impact the direct mitochondrial pathway of death remain poorly understood. In this study, we focused on the role of serine 392 phosphorylation in the control of p53-dependent apoptosis. We used CRISPR/Cas9 genome editing to substitute serine 392 by a non-phosphorylatable alanine in HCT-116 colon carcinoma cells. The S392A mutant displayed normal transcriptional activity following genotoxic stress, but markedly impaired ability to localize to mitochondria. The decreased mitochondrial localization of the S392A mutant correlated with a lower ability to induce apoptosis. Confirmatory observations were made following enforced expression of the S392A p53 mutant or a phospho-mimetic S392E mutant in H1299 lung carcinoma cells. Our observations support the premise that serine 392 phosphorylation of p53 influences its mitochondrial translocation and transcription-independent apoptotic function.

Control of metabolism by p53 – Cancer and beyond

“…Modifications of p53 can also enhance its apoptotic functions. For example, Pin-1 catalyses the cis-trans interconversion of p53 proline 47 to enhance p53 dependent Bax activation [ 23 ], while serine 392 phosphorylation is necessary for p53 to relocate to the mitochondria where it binds to Bax and Bak to trigger apoptosis [ 24 ]. p53 can also prime cells to undergo apoptosis in response to extracellular adenosine - which accumulates under conditions of metabolic stress - by activating the receptor Adora2B [ 25 ].…”

How the Other Half Lives: What p53 Does When It Is Not Being a Transcription Factor

“…With the advent of easily accessible gene editing, p53 can be mutated endogenously to avoid issues with overexpressing non-physiological levels of the potent tumor suppressor. Castrogiovanni et al used CRISPR/Cas9 to introduce mutations to serine 392, a phosphorylation site that is important for mitochondrial translocation following genotoxic stress [109]. While the S392A phospho-incompetent mutant retains the ability to activate key p53 genes, including p21, PUMA, and BAX, it is unable to translocate the mitochondria following camptothecin treatment, and as a result the cells are deficient in inducing apoptosis compared to cells expressing wildtype p53.…”

BH3-only sensors Bad, Noxa and Puma are Key Regulators of Tacaribe virus-induced Apoptosis

“…While phosphorylation at Ser15 has been shown to be essential for transcriptional activation by p53, this appears to require only basal levels of modification and is not necessarily inducible in response to any given apoptotic stimulus [ 54 ], as also appears to be the case for TCRV-induced p53 activation. However, modification of Ser392 alone may not be sufficient to explain the strong nuclear accumulation of p53 observed during TCRV-induced apoptosis, as phospho-Ser392 p53 has been reported to be only weakly translocated compared to other phosphorylated forms of p53 [ 55 ]. As such, this suggests that other modifications contributing to p53 stabilization and nuclear localization remain to be identified.…”