Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P43146 (tumour suppressor)
 5,935 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mammalian cell mitochondria are believed to have prokaryotic ancestry. Mitochondria are not only the powerhouse of energy generation within the eukaryotic cell but they also play a major role in inducing apoptotic cell death through release of redox proteins such as cytochrome c and the apoptosis-inducing factor (AIF), a flavoprotein with NADH oxidase activity. Recent evidence indicates that some present day prokaryotes release redox proteins that induce apoptosis in mammalian cells through stabilization of the tumour suppressor protein p53. p53 interacts with mitochondria either directly or through activation of the genes for pro-apoptotic proteins such as Bax or NOXA or genes that encode redox enzymes responsible for the production of reactive oxygen species (ROS). The analogy between the ancient ancestors of present day bacteria, the mitochondria, and the present day bacteria with regard to their ability to release redox proteins for triggering mammalian cell death is an interesting example of functional conservation during the hundreds of millions of years of evolution. It is possible that the ancestors of the present day prokaryotes released redox proteins to kill the ancestors of the eukaryotes. During evolution of the mitochondria from prokaryotes as obligate endosymbionts, the mitochondria maintained the same functions to programme their own host cell death.
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PMID:Redox proteins in mammalian cell death: an evolutionarily conserved function in mitochondria and prokaryotes. 1267 80

HIC1 (hypermethylated in cancer) is a tumour suppressor gene located in 17p13.3, a region frequently hypermethylated or deleted in many types of prevalent human tumour. HIC1 is also a candidate for a contiguous-gene syndrome, the Miller-Dieker syndrome, a severe form of lissencephaly accompanied by developmental anomalies. HIC1 encodes a BTB/POZ-zinc finger transcriptional repressor. HIC1 represses transcription via two autonomous repression domains, an N-terminal BTB/POZ and a central region, by trichostatin A-insensitive and trichostatin A-sensitive mechanisms, respectively. The HIC1 central region recruits the corepressor CtBP (C-terminal binding protein) through a conserved GLDLSKK motif, a variant of the consensus C-terminal binding protein interaction domain PxDLSxK/R. Here, we show that HIC1 interacts with both CtBP1 and CtBP2 and that this interaction is stimulated by agents increasing NADH levels. Furthermore, point mutation of two CtBP2 residues forming part of the structure of the recognition cleft for a PxDLS motif also ablates the interaction with a GxDLS motif. Conversely, in perfect agreement with the structural data and the universal conservation of this residue in all C-terminal binding protein-interacting motifs, mutation of the central leucine residue (leucine 225 in HIC1) abolishes the interaction between HIC1 and CtBP1 or CtBP2. As expected from the corepressor activity of CtBP, this mutation also impairs the HIC1-mediated transcriptional repression. These results thus demonstrate a strong conservation in the binding of C-terminal binding protein-interacting domains despite great variability in their amino acid sequences. Finally, this L225A point mutation could also provide useful knock-in animal models to study the role of the HIC1-CtBP interaction in tumorigenesis and in development.
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PMID:A L225A substitution in the human tumour suppressor HIC1 abolishes its interaction with the corepressor CtBP. 1676 39

The intersection between regulatory pathways responsive to metabolic fluctuation on one hand, and to cellular stress on the other, is a fascinating area within which NAD/NADH responsive proteins play a major role [1, 2]. A key player amongst these is SIRT1, a member of the mammalian sirtuin family (SIRT1-7). SIRT1 is an NAD-dependent deacetylase with critical functions in the maintenance of homeostasis and cell survival. In this review I shall focus upon (i) the cellular regulation of SIRT1 expression and (ii) the cellular regulation of SIRT1 activity. In addition the distinction between basal and stress-induced functions will be addressed: do they simply reflect a sliding scale of response, or are they mechanistically distinct? Elevated levels of SIRT1 are evident in cancer and SIRT1 can function as a cancer-specific survival factor in human cell lines. However, in a mouse model SIRT1 is reported to function as a tumour suppressor. Possible explanations for this apparent discrepancy will be considered. Given the high profile of SIRT1 as a potential therapeutic target it is clearly important to clarify its basal functioning in relation to differentiation, cell type, intercellular communication, and to age-related disease states including neurodegeneration and cancer.
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PMID:Cellular regulation of SIRT1. 1914 1

WWOX is a tumour suppressor gene that spans the common fragile site FRA16D. Analysis of the WWOX expression pattern in normal human tissues showed the highest expression in testis, prostate, and ovary. Its altered expression has been demonstrated in different tissues and tumour types. The WWOX gene encodes a 414-amino acids protein, which is the first discovered protein with a short-chain dehydrogenase/reductase (SDR) central domain and two WW domains at the NH2 terminus. Due to its potential role in sex-steroid metabolism, using two bacterial expression systems, we have cloned WWOX fusion proteins showing oxidoreductase activity in a crude extract, defined a course of enzymatic reactions for selected steroid substrates, and determined related Km values. Our results show that the SDR domain of the WWOX protein has dehydrogenase activity and is reactive both in the presence of NAD+ and NADP+ for all examined steroid substrates. On the other hand, with the same substrates and reduced cofactors (NADH and NADPH) reduction activity was not observed.
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PMID:WWOX oxidoreductase--substrate and enzymatic characterization. 2147 39

Most cancer cells use aerobic glycolysis to fuel their growth. The enzyme lactate dehydrogenase-A (LDH-A) is key to cancer's glycolytic phenotype, catalysing the regeneration of nicotinamide adenine dinucleotide (NAD(+)) from reduced nicotinamide adenine dinucleotide (NADH) necessary to sustain glycolysis. As such, LDH-A is a promising target for anticancer therapy. Here we ask if the tumour suppressor p53, a major regulator of cellular metabolism, influences the response of cancer cells to LDH-A suppression. LDH-A knockdown by RNA interference (RNAi) induced cancer cell death in p53 wild-type, mutant and p53-null human cancer cell lines, indicating that endogenous LDH-A promotes cancer cell survival irrespective of cancer cell p53 status. Unexpectedly, however, we uncovered a novel role for p53 in the regulation of cancer cell NAD(+) and its reduced form NADH. Thus, LDH-A silencing by RNAi, or its inhibition using a small-molecule inhibitor, resulted in a p53-dependent increase in the cancer cell ratio of NADH:NAD(+). This effect was specific for p53(+/+) cancer cells and correlated with (i) reduced activity of NAD(+)-dependent deacetylase sirtuin 1 (SIRT1) and (ii) an increase in acetylated p53, a known target of SIRT1 deacetylation activity. In addition, activation of the redox-sensitive anticancer drug EO9 was enhanced selectively in p53(+/+) cancer cells, attributable to increased activity of NAD(P)H-dependent oxidoreductase NQO1 (NAD(P)H quinone oxidoreductase 1). Suppressing LDH-A increased EO9-induced DNA damage in p53(+/+) cancer cells, but importantly had no additive effect in non-cancer cells. Our results identify a unique strategy by which the NADH/NAD(+) cellular redox status can be modulated in a cancer-specific, p53-dependent manner and we show that this can impact upon the activity of important NAD(H)-dependent enzymes. To summarise, this work indicates two distinct mechanisms by which suppressing LDH-A could potentially be used to kill cancer cells selectively, (i) through induction of apoptosis, irrespective of cancer cell p53 status and (ii) as a part of a combinatorial approach with redox-sensitive anticancer drugs via a novel p53/NAD(H)-dependent mechanism.
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PMID:Identification of LDH-A as a therapeutic target for cancer cell killing via (i) p53/NAD(H)-dependent and (ii) p53-independent pathways. 2481 61

Carcinogens play a key role in cancer initiation. Conventional theories support the concept of genetic changes inducing tumorigenesis through proteomics and metabolomics which lead to cancer development. Current research provides evidence that metabolic genes may be altered long before mutation of tumour suppressor genes, strongly suggesting that metabolic changes may be preceding the changes seen at a genetic level. Since cancer has long been known to occur through gene regulation, an impaired cellular respiration without utilizing mitochondrial function has been an area of active interest. We hypothesize the activity of carcinogens as electron acceptors to disrupt the normal glycolysis cycle happening in a cell by acting as positive ligands. The continuous restoration of NAD+ to cytosol by oxidation of NADH with carcinogen as electron acceptor creates a metabolic pathway to assist in the carcinogenic process. This metabolic pathway continues through an adaptive process, supplemented by pyruvate converting to lactate providing a constant pool of NAD+ to continue the glycolytic pathway. We also hypothesize that carcinogenesis occurs as a precursor to metabolic stress which may promote altered genetic and protein expression causing aberrant epigenetic and cell signaling pathways.
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PMID:Are carcinogens electron acceptors? A novel hypothesis. 3320 2