Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Genotoxic stress triggers a rapid translocation of p53 to the mitochondria, contributing to apoptosis in a transcription-independent manner. Using immunopurification protocols and mass spectrometry, we previously identified the proapoptotic protein BAK as a mitochondrial p53-binding protein and showed that recombinant p53 directly binds to BAK and can induce its oligomerization, leading to cytochrome c release. In this work we describe a combination of molecular modeling, electrostatic analysis, and site-directed mutagenesis to define contact residues between BAK and p53. Our data indicate that three regions within the core DNA binding domain of p53 make contact with BAK; these are the conserved H2 alpha-helix and the L1 and L3 loop. Notably, point mutations in these regions markedly impair the ability of p53 to oligomerize BAK and to induce transcription-independent cell death. We present a model whereby positively charged residues within the H2 helix and L1 loop of p53 interact with an electronegative domain on the N-terminal alpha-helix of BAK; the latter is known to undergo conformational changes upon BAK activation. We show that mutation of acidic residues in the N-terminal helix impair the ability of BAK to bind to p53. Interestingly, many of the p53 contact residues predicted by our model are also direct DNA contact residues, suggesting that p53 interacts with BAK in a manner analogous to DNA. The combined data point to the H2 helix and L1 and L3 loops of p53 as novel functional domains contributing to transcription-independent apoptosis by this tumor suppressor protein.
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PMID:Oligomerization of BAK by p53 utilizes conserved residues of the p53 DNA binding domain. 1852 70

Addition of a 5' cap to RNA polymerase II transcripts, the first step of pre-mRNA processing in eukaryotes from yeasts to mammals, is catalyzed by the sequential action of RNA triphosphatase, guanylyltransferase, and (guanine-N-7)methyltransferase. The effects of knockdown of these capping enzymes in mammalian cells were investigated using T7 RNA polymerase-synthesized small interfering RNA and also a lentivirus-based inducible, short hairpin RNA system. Decreasing either guanylyltransferase or methyltransferase resulted in caspase-3 activation and elevated terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) staining characteristic of apoptosis. Induction of apoptosis was independent of p53 tumor suppressor but dependent on BAK or BAX. In addition, levels of the BH3 family member Bim increased, while Mcl-1 and Bik levels remained unchanged during apoptosis. In contrast to capping enzyme knockdown, apoptosis induced by cycloheximide inhibition of protein synthesis required BAK but not BAX. Both Bim and Mcl-1 levels decreased in cycloheximide-induced apoptosis while Bik levels were unchanged, suggesting that apoptosis in siRNA-treated cells is not a direct consequence of loss of mRNA translation. siRNA-treated BAK(-/-) BAX(-/-) double-knockout mouse embryonic fibroblasts failed to activate capase-3 or increase TUNEL staining but instead exhibited autophagy, as demonstrated by proteolytic processing of microtubule-associated protein 1 light chain 3 (LC3) and translocation of transfected green fluorescent protein-LC3 from the nucleus to punctate cytoplasmic structures.
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PMID:Apoptosis and autophagy induction in mammalian cells by small interfering RNA knockdown of mRNA capping enzymes. 1867 51

Normal cellular lifespan is contingent upon preserving outer mitochondrial membrane (OMM) integrity, as permeabilization promotes apoptosis. BCL-2 family proteins control mitochondrial outer membrane permeabilization (MOMP) by regulating the activation of the pro-apoptotic BCL-2 effector molecules, BAX and BAK. Sustainable cellular stress induces proteins (e.g., BID, BIM, and cytosolic p53) capable of directly activating BAX and/or BAK, but these direct activators are sequestered by the anti-apoptotic BCL-2 proteins (e.g., BCL-2, BCL-xL, and MCL-1). In the event of accumulated or marked cellular stress, a coordinated effort between previously sequestered and nascent BH3-only proteins inhibits the anti-apoptotic BCL-2 repertoire to promote direct activator protein-mediated MOMP. We examined the effect of ABT-737, a BCL-2 antagonist, and PUMA, a BH3-only protein that inhibits the entire anti-apoptotic BCL-2 repertoire, with cells and mitochondria that sequestered direct activator proteins. ABT-737 and PUMA cooperated with sequestered direct activator proteins to promote MOMP and apoptosis, which in the absence of ABT-737 or PUMA did not influence OMM integrity or cellular survival. Our data show that the induction of apoptosis by inhibition of the anti-apoptotic BCL-2 repertoire requires "covert" levels of direct activators of BAX and BAK at the OMM.
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PMID:Mechanism of apoptosis induction by inhibition of the anti-apoptotic BCL-2 proteins. 1907 66

Three forms of cell death have been described: apoptosis, autophagic cell death, and necrosis. Although genetic and biochemical studies have formulated a detailed blueprint concerning the apoptotic network, necrosis is generally perceived as a passive cellular demise resulted from unmanageable physical damages. Here, we conclude an active de novo genetic program underlying DNA damage-induced necrosis, thus assigning necrotic cell death as a form of "programmed cell death." Cells deficient of the essential mitochondrial apoptotic effectors, BAX and BAK, ultimately succumbed to DNA damage, exhibiting signature necrotic characteristics. Importantly, this genotoxic stress-triggered necrosis was abrogated when either transcription or translation was inhibited. We pinpointed the p53-cathepsin axis as the quintessential framework underlying necrotic cell death. p53 induces cathepsin Q that cooperates with reactive oxygen species (ROS) to execute necrosis. Moreover, we presented the in vivo evidence of p53-activated necrosis in tumor allografts. Current study lays the foundation for future experimental and therapeutic discoveries aimed at "programmed necrotic death."
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PMID:The p53-cathepsin axis cooperates with ROS to activate programmed necrotic death upon DNA damage. 1914 18

The tumor suppressor p53 induces apoptosis by altering the transcription of pro-apoptotic targets in the nucleus and by a direct, nontranscriptional role at the mitochondria. Although the post-translational modifications regulating nuclear apoptotic functions of p53 have been thoroughly characterized, little is known of how transcription-independent functions are controlled. We and others identified acetylation of the p53 DNA binding domain at lysine 120 as a critical event in apoptosis induction. Although initial studies showed that Lys-120 acetylation plays a role in p53 function in the nucleus, we report here a role for Lys-120 acetylation in transcription-independent apoptosis. We demonstrate that the Lys-120-acetylated isoform of p53 is enriched at mitochondria. The acetylation of Lys-120 does not appear to regulate the ability of p53 to interact with the pro-apoptotic proteins BCL-XL and BAK. However, displacement of the inhibitory MCL-1 protein from BAK is compromised when Lys-120 acetylation is blocked. Functional studies show that mutation of Lys-120 to a nonacetylated residue, as occurs in human cancer, inhibits transcription-independent apoptosis, and enforced acetylation of Lys-120 enhances transcription-independent apoptosis. These data support a model whereby Lys-120 acetylation contributes to both the transcription-dependent and -independent apoptotic pathways induced by p53.
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PMID:Acetylation of the DNA binding domain regulates transcription-independent apoptosis by p53. 1949 19

Proteasome inhibitors induce rapid death of cancer cells. We show that in epithelial cancer cells, such death is associated with dramatic and simultaneous up-regulation of several BH3-only proteins, including BIK, BIM, MCL-1S, NOXA, and PUMA, as well as p53. Elevated levels of these proteins seem to be the result of direct inhibition of their proteasomal degradation, induction of transcription, and active translation. Subsequent cell death is independent of BAX, and probably BAK, and proceeds through the intrinsic mitochondrial apoptosis pathway. We identify the cascade of molecular events responsible for cell death induced by a prototypical proteasome inhibitor, MG132, starting with rapid accumulation of BH3-only proteins in the mitochondria, proceeding through mitochondrial membrane permeabilization and subsequent loss of DeltaPsi(m), and leading to irreversible changes of mitochondrial ultrastructure, degradation of mitochondrial network, and detrimental impairment of crucial mitochondrial functions. Our results also establish a rationale for the broader use of proteasome inhibitors to kill apoptosis-resistant tumor cells that lack functional BAX/BAK proteins.
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PMID:BAX/BAK-independent mitoptosis during cell death induced by proteasome inhibition? 1967 75

Antibodies against the COOH-terminal domain of cell surface GRP78 induce apoptosis in cancer cell lines via activation of p53 signaling. We now have studied the effects of PFT-alpha, an inhibitor of p53-mediated apoptotic pathways, on anti-GRP78 antibody-induced activation of p53 and pro-apoptotic signaling in 1-LN prostate cancer cells. Pretreatment of 1-LN cancer cells with this agent significantly inhibited antibody or doxorubicin-induced upregulation of p53. Concomitantly, PFT-alpha treatment prevented down regulation of ERK1/2 activation by either antibody or doxorubicin. Likewise, PFT-alpha prevented increases in the pro-apoptotic proteins BAD, BAK, BAX, PUMA, and NOXA as well as activation of caspases-3, -7, and -9. We conclude that antibody-induced apoptosis in prostate cancer cells is mediated predominantly by p53 using the mitochondrial pathway of apoptosis.
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PMID:PFT-alpha inhibits antibody-induced activation of p53 and pro-apoptotic signaling in 1-LN prostate cancer cells. 1991 99

The aim of this study was to evaluate the factors predisposing to implants of endometriotic lesions in normal ovarian cortexes of women with and without endometriosis by assessing the expression of pro-apoptotic and anti-apoptotic factors and follicular density. Ovarian biopsies were performed during laparoscopy in 18 patients with endometrioma and in 10 healthy women. Detection of apoptosis was performed with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling assay. p53 and BCL2 proteins were assessed by immunohistochemistry. Quantitative real-time polymerase chain reaction was performed to evaluate BAX , BAK , BCL2 , BCL-XL , survivin and beta-actin ( ACTB ) expression. The p53 protein was positive in a significantly higher number of secondary follicles, whereas the B-cell chronic lymphocytic leukaemia/lymphoma 2 (BCL2) protein was positive in all follicles in unaffected tissue of endometriotic women, compared with the controls. Overexpression of the BCL2 and survivin genes and a decreased BAX and BAK gene expression were observed in the endometriotic group although only the difference in survivin expression was significant (P = 0.016). The BCL2 / BAX ratio showed an increased value in the ovarian cortex in controls compared with endometriosis patients. In conclusion, the reduction of apoptosis in unaffected tissue in women with endometriosis suggests that they may be predisposed to develop endometriosis.
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PMID:Apoptosis in normal ovaries of women with and without endometriosis. 2003 Oct 21

We have previously shown that treatment of prostate cancer and melanoma cells expressing GRP78 on their cell surface with antibody directed against the COOH-terminal domain of GRP78 upregulates and activates p53 causing decreased cell proliferation and upregulated apoptosis. In this report, we demonstrate that treatment of 1-LN prostate cancer cells with this antibody decreases cell surface expression of GRP78, Akt(Thr308) and Akt(Ser473) kinase activities and reduces phosphorylation of FOXO, and GSK3beta. This treatment also suppresses activation of ERK1/2, p38 MAPK and MKK3/6; however, it upregulates MKK4 activity. JNK, as determined by its phosphorylation state, is subsequently activated, triggering apoptosis. Incubation of cells with antibody reduced levels of anti-apoptotic Bcl-2, while elevating pro-apoptotic BAD, BAX and BAK expression as well as cleaved caspases-3, -7, -8 and -9. Silencing GRP78 or p53 gene expression by RNAi prior to antibody treatment abrogated these effects. We conclude that antibody directed against the COOH-terminal domain of GRP78 may prove useful as a pan suppressor of proliferative/survival signaling in cancer cells expressing GRP78 on their cell surface.
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PMID:Ligation of cell surface GRP78 with antibody directed against the COOH-terminal domain of GRP78 suppresses Ras/MAPK and PI 3-kinase/AKT signaling while promoting caspase activation in human prostate cancer cells. 2002 5

Mutliple myeloma (MM) has one of the poorest prognosis of the hematological malignancies and novel therapeutic approaches are needed. Therapeutic induction of p53 might be important to evaluate the drugs either individually or in combination. Direct inhibition of MDM2 function by an MDM2 antagonist nutlin or blocking proteasomal degradation of p53 by a selective proteasome inhibitor velcade can stabilize p53 and activate the p53 apoptotic signaling pathway. We examined if inhibition of p53-MDM2 interaction by nutlin might potentiate the cytotoxic effects of velcade in MM cell lines and primary MM samples. Nutlin or velcade resulted in a reduction in cell proliferation or viability in MM cells harboring wild type p53. Nutlin plus velcade showed a synergistic anti-myeloma activity as evidenced by a significant increase of cytotoxicity with respect to each agonist alone. These effects were accompanied by accumulation of p53 and its two immediate downstream targets, p21 and MDM2, as well as caspase activation and induction of proapoptotic targets, PUMA, BAX and BAK. The induction of p53 target genes induced by nutlin and/or velcade was further validated by gene expression profiling and expression of some selective targets was quantified by qRT-PCR. These preclinical studies provide the framework for clinical trial of nutlin, alone and in combination with conventional and novel therapies such as velcade to increase efficacy and improve patient outcome in MM.
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PMID:MDM2 antagonist nutlin plus proteasome inhibitor velcade combination displays a synergistic anti-myeloma activity. 2041 64


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