Ischemia-associated oxidative damage leading to necrosis is a major cause of catastrophic tissue loss, and elucidating its signaling mechanism is therefore of paramount importance. p53 is a central ...stress sensor responding to multiple insults, including oxidative stress to orchestrate apoptotic and autophagic cell death. Whether p53 can also activate oxidative stress-induced necrosis is, however, unknown. Here, we uncover a role for p53 in activating necrosis. In response to oxidative stress, p53 accumulates in the mitochondrial matrix and triggers mitochondrial permeability transition pore (PTP) opening and necrosis by physical interaction with the PTP regulator cyclophilin D (CypD). Intriguingly, a robust p53-CypD complex forms during brain ischemia/reperfusion injury. In contrast, reduction of p53 levels or cyclosporine A pretreatment of mice prevents this complex and is associated with effective stroke protection. Our study identifies the mitochondrial p53-CypD axis as an important contributor to oxidative stress-induced necrosis and implicates this axis in stroke pathology.
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► Necrosis in oxidative stress and ischemia depends on mitochondrial PTP pore opening ► PTP opening is triggered by p53 interaction with CypD in the mitochondrial matrix ► A p53-CypD complex is formed in necrotic brain tissue in a stroke model in mice ► Blocking formation of the p53-CypD complex is associated with stroke protection
In addition to regulating apoptosis and autophagic cell death, p53 also promotes necrosis. During ischemic stroke, p53 accumulates in the neuronal mitochondrial matrix and opens the permeability transition pore by binding CypD, causing mitochondria to swell and rupture.
p53 missense mutant alleles are present in nearly 40% of all human tumors. Such mutated alleles generate aberrant proteins that not only lose their tumor-suppressive functions but also frequently act ...as driver oncogenes, which promote malignant progression, invasion, metastasis, and chemoresistance, leading to reduced survival in patients and mice. Notably, these oncogenic gain-of-function (GOF) missense mutant p53 proteins (mutp53) are constitutively and tumor-specific stabilised. This stabilisation is one key pre-requisite for their GOF and is largely due to mutp53 protection from the E3 ubiquitin ligases Mdm2 and CHIP by the HSP90/HDAC6 chaperone machinery. Recent mouse models provide convincing evidence that tumors with highly stabilized GOF mutp53 proteins depend on them for growth, maintenance, and metastasis, thus creating exploitable tumor-specific vulnerabilities that markedly increase lifespan if intercepted. This identifies mutp53 as a promising cancer-specific drug target. This review discusses direct mutp53 protein-targeting drug strategies that are currently being developed at various preclinical levels.
Over half of colorectal cancers (CRCs) harbor TP53 missense mutations (mutp53). We show that the most common mutp53 allele R248Q (p53Q) exerts gain of function (GOF) and creates tumor dependence in ...mouse CRC models. mutp53 protein binds Stat3 and enhances activating Stat3 phosphorylation by displacing the phosphatase SHP2. Ablation of the p53Q allele suppressed Jak2/Stat3 signaling, growth, and invasiveness of established, mutp53-driven tumors. Treating tumor-bearing mice with an HSP90 inhibitor suppressed mutp53 levels and tumor growth. Importantly, human CRCs with stabilized mutp53 exhibit enhanced Jak2/Stat3 signaling and are associated with poorer patient survival. Cancers with TP53R248Q/W are associated with a higher patient death risk than are those having nonR248 mutp53. These findings identify GOF mutp53 as a therapeutic target in CRC.
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•mutp53 R248Q, the most common p53 mutant in human CRC, promotes CRC in mice•mutp53 R248Q binds to and deregulates Stat3, correlating with poor patient survival•Genetic ablation of mutp53 R248Q reduces growth and invasion of established CRCs•Hsp90 inhibition reduces the mutp53 R248Q level and inhibits CRC progression
Schulz-Heddergott et al. show that the most common p53 mutant R248Q (mutp53) enhances Stat3 activation by binding to Stat3 and displacing SHP2 in colorectal cancer cells. Reduction of mutp53 genetically or by using the HSP90 inhibitor 17AAG reduces Stat3 signaling and the growth of mutp53-driven tumors.
The mitochondrial p53 pathway Vaseva, Angelina V; Moll, Ute M
Biochimica et biophysica acta,
05/2009, Letnik:
1787, Številka:
5
Journal Article
Recenzirano
Odprti dostop
p53 is one of the most mutated tumor suppressors in human cancers and as such has been intensively studied for a long time. p53 is a major orchestrator of the cellular response to a broad array of ...stress types by regulating apoptosis, cell cycle arrest, senescence, DNA repair and genetic stability. For a long time it was thought that these functions of p53 solely rely on its function as a transcription factor, and numerous p53 target genes have been identified 1. In the last 8 years however, a novel transcription-independent proapoptotic function mediated by the cytoplasmic pool of p53 has been revealed. p53 participates directly in the intrinsic apoptosis pathway by interacting with the multidomain members of the Bcl-2 family to induce mitochondrial outer membrane permeabilization. Our review will discuss these studies, focusing on recent advances in the field.
The MDM2-p53 interaction Moll, Ute M; Petrenko, Oleksi
Molecular cancer research
1, Številka:
14
Journal Article
Recenzirano
Activation of the p53 protein protects the organism against the propagation of cells that carry damaged DNA with potentially oncogenic mutations. MDM2, a p53-specific E3 ubiquitin ligase, is the ...principal cellular antagonist of p53, acting to limit the p53 growth-suppressive function in unstressed cells. In unstressed cells, MDM2 constantly monoubiquitinates p53 and thus is the critical step in mediating its degradation by nuclear and cytoplasmic proteasomes. The interaction between p53 and MDM2 is conformation-based and is tightly regulated on multiple levels. Disruption of the p53-MDM2 complex by multiple routes is the pivotal event for p53 activation, leading to p53 induction and its biological response. Because the p53-MDM2 interaction is structurally and biologically well understood, the design of small lipophilic molecules that disrupt or prevent it has become an important target for cancer therapy.
Proteasome inhibition represents a promising strategy of cancer pharmacotherapy, but resistant tumor cells often emerge. Here we show that the microRNA-101 (miR-101) targets the proteasome maturation ...protein POMP, leading to impaired proteasome assembly and activity, and resulting in accumulation of p53 and cyclin-dependent kinase inhibitors, cell cycle arrest, and apoptosis. miR-101-resistant POMP restores proper turnover of proteasome substrates and re-enables tumor cell growth. In ERα-positive breast cancers, miR-101 and POMP levels are inversely correlated, and high miR-101 expression or low POMP expression associates with prolonged survival. Mechanistically, miR-101 expression or POMP knockdown attenuated estrogen-driven transcription. Finally, suppressing POMP is sufficient to overcome tumor cell resistance to the proteasome inhibitor bortezomib. Taken together, proteasome activity can not only be manipulated through drugs, but is also subject to endogenous regulation through miR-101, which targets proteasome biogenesis to control overall protein turnover and tumor cell proliferation.
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•miR-101 functions as an endogenous proteasome inhibitor by targeting POMP•Targeting POMP is essential for cell growth suppression by miR-101•High miR-101 levels have good outcomes for ERα-positive breast cancer patients•Targeting POMP inhibits tumor progression and overcomes resistance to bortezomib
The proteasome represents a cancer drug target, and its inhibition results in the accumulation of tumor-suppressive proteins. Zhang et al. identify a microRNA that targets the proteasome maturation factor POMP and interferes with proteasome assembly. It thus serves as an endogenous proteasome antagonist and a suppressor of cancer cell survival.
The tight control of wild-type p53 by mainly MDM2 in normal cells is permanently lost in tumors harboring mutant p53, which exhibit dramatic constitutive p53 hyperstabilization that far exceeds that ...of wild-type p53 tumors. Importantly, mutant p53 hyperstabilization is critical for oncogenic gain of function of mutant p53 in vivo. Current insight into the mechanism of this dysregulation is fragmentary and largely derived from ectopically constructed cell systems. Importantly, mutant p53 knock-in mice established that normal mutant p53 tissues have sufficient enzymatic reserves in MDM2 and other E3 ligases to maintain full control of mutant p53. We find that in human cancer cells, endogenous mutant p53, despite its ability to interact with MDM2, suffers from a profound lack of ubiquitination as the root of its degradation defect. In contrast to wild-type p53, the many mutant p53 proteins which are conformationally aberrant are engaged in complexes with the HSP90 chaperone machinery to prevent its aggregation. In contrast to wild-type p53 cancer cells, we show that in mutant p53 cancer cells, this HSP90 interaction blocks the endogenous MDM2 and CHIP (carboxy-terminus of Hsp70-interacting protein) E3 ligase activity. Interference with HSP90 either by RNA interference against HSF1, the transcriptional regulator of the HSP90 pathway, or by direct knockdown of Hsp90 protein or by pharmacologic inhibition of Hsp90 activity with 17AAG (17-allylamino-17-demethoxygeldanamycin) destroys the complex, liberates mutant p53, and reactivates endogenous MDM2 and CHIP to degrade mutant p53. Of note, 17AAG induces a stronger viability loss in mutant p53 than in wild-type p53 cancer cells. Our data support the rationale that suppression of mutant p53 levels in vivo in established cancers might achieve clinically significant effects.
The tumor suppressor p53 is critically important in the cellular damage response and is the founding member of a family of proteins. All three genes regulate cell cycle and apoptosis after DNA ...damage. However, despite a remarkable structural and partly functional similarity among p53, p63, and p73, mouse knockout studies revealed an unexpected functional diversity among them. p63 and p73 knockouts exhibit severe developmental abnormalities but no increased cancer susceptibility, whereas this picture is reversed for p53 knockouts. Neither p63 nor p73 is the target of inactivating mutations in human cancers. Genomic organization is more complex in p63 and p73, largely the result of an alternative internal promoter generating NH2-terminally deleted dominant-negative proteins that engage in inhibitory circuits within the family. Deregulated dominant-negative p73 isoforms might play an active oncogenic role in some human cancers. Moreover, COOH-terminal extensions specific for p63 and p73 enable further unique protein-protein interactions with regulatory pathways involved in development, differentiation, proliferation, and damage response. Thus, p53 family proteins take on functions within a wide biological spectrum stretching from development (p63 and p73), DNA damage response via apoptosis and cell cycle arrest (p53, TAp63, and TAp73), chemosensitivity of tumors (p53 and TAp73), and immortalization and oncogenesis (DeltaNp73).
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