Decrease of mitochondrial p53 during late apoptosis is linked to its dephosphorylation on serine 20

Abstract

Following a genotoxic stress, the tumor suppressor p53 translocates to mitochondria to take part in direct induction of apoptosis, via interaction with BCL-2 family members such as BAK and BAX. We determined the kinetics of the mitochondrial translocation of p53 in HCT-116 and PA-1 cells exposed to different genotoxic stresses (doxorubicin, camptothecin, UVB). This analysis revealed an early escalation in the amount of mitochondrial p53, followed by a peak amount and a decrease of mitochondrial p53 at later time points. We show that the serine 20 phosphorylated form of p53 is present at the mitochondria and that the decrease of p53 mitochondrial level during late apoptosis correlates with a decrease of Ser-20 phosphorylation. Moreover, the S20A p53 mutant translocates well to mitochondria after a genotoxic stress but its mitochondrial localization is very low during late apoptosis when compared to wt p53. The S20A mutant also appears to be compromised for interaction with BAK. We propose here that the level of serine 20 phosphorylation is influential on p53 mitochondrial localization during late apoptosis. Additionally, we report the presence of a new '45 kDa caspase-cleaved fragment of p53 in the cytosolic and mitochondrial fractions of apoptotic cells.

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

“…36 We previously showed that S20 phosphorylation is influential on the p53-BAK interaction and modulates p53 mitochondrial level during late apoptosis. 49 More recently, Zhang et al 50 showed that ubiquitination of cytosolic p53 on K24 by the TRAF6 E3 ligase inhibits its mitochondrial translocation and interaction with the BAK-MCL1 complex. 50 We show here in two different cell models that failure to phosphorylate S392 markedly reduces p53 mitochondrial translocation after exposure to an apoptotic stimulus.…”

“…A growing body of evidence now indicates that several PTMs regulate p53 proapoptotic mitochondrial activity through modulating its interaction with protein partners, as described above. 4,[49][50][51][52][53] Targeting such interactions may constitute an effective strategy to trigger p53 mitochondrial localization and hence apoptosis in cancer cells. Figure 8 S392 phosphorylation of p53 increases in cells exposed to a genotoxic stress, promoting its mitochondrial localization and apoptosis.…”

p53 modifications: exquisite decorations of the powerful guardian

“…Polo-like kinase 1 can also regulate cell cycle re-entry by activating Cdc25C and later will dephosphorylate p53 at S15 to abolish its cell cycle arrest effect (Chen et al, 2006). Moreover, an unknown phosphatase dephosphorylates p53 at S20 to decrease p53 mitochondrial localization during late apoptosis, leading to the attenuation of mitochondrial p53-mediated cell apoptosis (Castrogiovanni et al, 2015).…”

Combination therapy of canine osteosarcoma with canine bone marrow stem cells, bone morphogenetic protein and carboplatin in an in vivo model

“…In this way, there is an early peak of mitochondrial p53, followed by a plateau phase and then a marked decrease of p53 during late apoptosis . After apoptotic stimulus, p53 acts as a transcription factor and induces the expression of pro‐apoptotic proteins of the Bcl‐2 family (Bax and BAK) . These proteins induce changes in the mitochondrial membrane, leading to activation of cytochrome c in the presence of ATP, with apoptosome formation and caspase 9 active, which in turn effector caspases 3, 6 and 7, finally triggering apoptosis via the intrinsic pathway .…”

“…23 After apoptotic stimulus, p53 acts as a transcription factor and induces the expression of pro-apoptotic proteins of the Bcl-2 family (Bax and BAK). 24 as breast cancer, head, neck, larynx and lung tumours, and parathyroid adenoma and carcinoma. 29 All treatment modalities in this study led to decreased expression of cyclin D1 compared to the control group, with a more significant decrease in groups treated with MSCs.…”