Chemical and metabolic properties of adenosine diphosphate ribose derivatives of nuclear proteins.
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ABSTRACT:
SUBMITTER: Smith JA
PROVIDER: S-EPMC1165480 | biostudies-other | 1975 Jun
REPOSITORIES: biostudies-other
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Project description:Recently, the development of poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors as a synthetic lethality approach has brought a major breakthrough in the treatment of breast cancer susceptibility gene (BRCA)-mutant cancers. Because sporadic cancers have also been found to commonly have other defects in DNA repair, PARP inhibitors are under active clinical investigation in combination with DNA-damaging therapeutics in a wide range of sporadic cancers. In this review, the authors discuss DNA repair mechanisms and PARP as a therapeutic target and summarize an update on clinical trials of available PARP inhibitors and predictive biomarkers for their efficacy.
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Project description:1. The isolated nuclei of the slime mould Physarum polycephalum contain an enzyme that will incorporated [adenine-3H] NAD+ into an acid-insoluble product, which is shown to be poly(ADP-ribose). 2. This incorporation has an optimum pH of 8.2 and a temperature optimum below 10degreesC. 3. Optimum stimulation is given by 15 mM-Mg2+. 4. 2-Mercaptoethanol or dithiothreitol also stimulates the incorporation, the latter at an optimum concentration of about 1 mM. 5. Under optimum conditions the Km value for the reaction is 0.28 mM at 15degreesC. Nicotinamide inhibits the incorporation with a Ki of 5.7 muM. 6. Exogenous DNA stimulates the incorporation by about 100%. 7. Preincubation of the nuclei with deoxyribonuclease, but not with ribonuclease, almost completely inactivates the incorporation of NAD+. 8. The enzyme is unstable at both 0degrees and 15degreesC in the absence of dithiothreitol. The presence of dithiothreitol at a concentration of 1 mM stabilizes the enzyme at both these temperatures. 9. The activity of this enzyme per nucleus was shown in three separate experiments to fall by about one-half in early S phase and then to rise to its pre-mitotic value after about 3 h, that is in late S phase. 10. The possible physiological function of this enzyme system is discussed.
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Project description:Poly(ADP-ribose) polymerases are a family of DNA-dependent nuclear enzymes catalyzing the transfer of ADP-ribose moieties from cellular nicotinamide-adenine-dinucleotide to a variety of target proteins. Although they have been considered as resident nuclear elements of the DNA repair machinery, recent works revealed a more intricate physiologic role of poly(ADP-ribose) polymerases with numerous extranuclear activities. Indeed, poly(ADP-ribose) polymerases participate in fundamental cellular processes like chromatin remodelling, transcription or regulation of the cell-cycle. These new insight into the physiologic roles of poly(ADP-ribose) polymerases widens the range of human pathologies in which pharmacologic inhibition of these enzymes might have a therapeutic potential. Here, we overview our current knowledge on extranuclear functions of poly(ADP-ribose) polymerases with a particular focus on the mitochondrial ones and discuss potential fields of future clinical applications.
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Project description:Ovarian cancer is one of the leading causes of death from gynecologic cancers. In this present era of cancer treatment, therapeutic options for patients with advanced or recurrent ovarian cancer are limited. The present standard of care treatment for advanced ovarian cancer is a platinum-based doublet chemotherapy (paclitaxel and carboplatin with or without bevacizumab) after a maximum attempt of surgical cytoreduction. However, there are no promising options for the management of patients with ovarian cancer refractory to the platinum-based chemotherapy. Therefore, newer, safe, and more effective treatment modalities are required for patients with advanced or recurrent ovarian cancer. Poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) inhibitors have shown an impressive safety profile and anti-tumor efficacy in patients with breast cancer 1 and 2 (BRCA1 and BRCA2) gene-mutated ovarian cancer who were previously treated with the standard of care chemotherapy. We have done a detailed review of the literature to emphasize the role of PARP inhibitors in the treatment of advanced or relapsed ovarian cancer.
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Project description:Mycobacterium tuberculosis represents one of the world's most devastating infectious agents - with one third of the world's population infected and 1.5 million people dying each year from this deadly pathogen. As part of an effort to identify targets for therapeutic intervention, we carried out the kinetic characterization of the product of gene rv1700 of M. tuberculosis. Based on its sequence and its structure, the protein had been tentatively identified as a pyrophosphohydrolase specific for adenosine diphosphate ribose (ADPR), a compound involved in various pathways including oxidative stress response and tellurite resistance. In this work we carry out a kinetic, mutational and structural investigation of the enzyme, which provides a full characterization of this Mt-ADPRase. Optimal catalytic rates were achieved at alkaline pH (7.5-8.5) with either 0.5-1 mM Mg2+ or 0.02-1 mM Mn2+. K m and k cat values for hydrolysis of ADPR with Mg2+ ions are 200 ± 19 ?M and 14.4 ± 0.4 s-1, and with Mn2+ ions are 554 ± 64 ?M and 28.9 ± 1.4 s-1. Four residues proposed to be important in the catalytic mechanism of the enzyme were individually mutated and the kinetics of the mutant enzymes were characterized. In the four cases, the K m increased only slightly (2- to 3-fold) but the k cat decreased significantly (300- to 1900-fold), confirming the participation of these residues in catalysis. An analysis of the sequence and structure conservation patterns in Nudix ADPRases permits an unambiguous identification of members of the family and provides insight into residues involved in catalysis and their participation in substrate recognition in the Mt-ADPRase.
| S-EPMC5489420 | biostudies-literature
Project description:Adenosine 5'-diphosphate ribose (ADPR) is an intracellular signalling molecule generated from nicotinamide adenine dinucleotide (NAD+). Synthetic ADPR analogues can shed light on the mechanism of activation of ADPR targets and their downstream effects. Such chemical biology studies, however, are often challenging due to the negatively charged pyrophosphate, also sensitive to cellular pyrophosphatases, and prior work on an initial ADPR target, the transient receptor potential cation channel TRPM2, showed complete pyrophosphate group replacement to be a step too far in maintaining biological activity. Thus, we designed ADPR analogues with just one of the negatively charged phosphate groups removed, by employing a phosphonoacetate linker. Synthesis of two novel phosphonoacetate ADPR analogues is described via tandem N,N'-dicyclohexylcarbodiimide coupling to phosphonoacetic acid. Neither analogue, however, showed significant agonist or antagonist activity towards TRPM2, underlining the importance of a complete pyrophosphate motif in activation of this particular receptor.
| S-EPMC6957348 | biostudies-literature
Project description:BackgroundMore patients with ovarian cancer are being treated with poly(adenosine diphosphate-ribose) polymerase inhibitors because regulatory agencies have granted these drugs new approvals for a variety of treatment indications. However, poly(adenosine diphosphate-ribose) polymerase inhibitors are expensive. When administered as a maintenance therapy, these drugs may be administered for months or years. How much of this cost patients experience as out-of-pocket spending is unknown.ObjectiveThis study aimed to estimate the out-of-pocket spending that patients experience during poly(adenosine diphosphate-ribose) polymerase inhibitor treatment and to characterize which healthcare services account for that spending.Study designA retrospective cohort study was performed with a sample of patients with ovarian cancer treated between 2014 and 2017 with olaparib, niraparib, or rucaparib. Patients were identified using MarketScan, a health insurance claims database. All insurance claims during poly(adenosine diphosphate-ribose) polymerase inhibitor treatment were collected. The primary outcome variable was the patients' out-of-pocket spending (copayment, coinsurance, and deductibles) during poly(adenosine diphosphate-ribose) polymerase inhibitor treatment for the medication itself. Other outcomes of interest included out-of-pocket spending for other healthcare services, the types and frequency of other healthcare services used, health plan spending, the estimated proportion of patients' household income used each month for healthcare, and patients' out-of-pocket spending immediately before poly(adenosine diphosphate-ribose) polymerase inhibitor treatment.ResultsWe identified 503 patients with ovarian cancer with a median age of 55 years (interquartile range, 50-62 years); 83% of those had out-of-pocket spendings during poly(adenosine diphosphate-ribose) polymerase inhibitor treatment. The median treatment duration was 124 days (interquartile range, 66-240 days). The mean out-of-pocket spending for poly(adenosine diphosphate-ribose) polymerase inhibitors was $305 (standard deviation, $2275) per month. On average, this accounted for 44.8% (standard deviation, 34.8%) of the patients' overall monthly out-of-pocket spending. The mean out-of-pocket spending for other healthcare services was $165 (standard deviation, $769) per month. Health plans spent, on average, $12,661 (standard deviation, $15,668) per month for poly(adenosine diphosphate-ribose) polymerase inhibitors and $7108 (standard deviation, $15,254) per month for all other healthcare services. The cost sharing for office visits, laboratory tests, and imaging studies represented the majority of non-poly(adenosine diphosphate-ribose) polymerase inhibitor treatment out-of-pocket spending. The average amount patients paid for all healthcare services per month during poly(adenosine diphosphate-ribose) polymerase inhibitor treatment was $470 (standard deviation, $2407), which was estimated to be 8.7% of the patients' monthly household income. The mean out-of-pocket spending in the 12 months before poly(adenosine diphosphate-ribose) polymerase inhibitor treatment was $3110 (standard deviation, $6987).ConclusionPatients can face high out-of-pocket costs for poly(adenosine diphosphate-ribose) polymerase inhibitors, although the sum of cost sharing for other healthcare services used during poly(adenosine diphosphate-ribose) polymerase inhibitor treatment is often higher. The spending on healthcare costs consumes a large proportion of these patients' household income. Patients with ovarian cancer experience high out-of-pocket costs for healthcare, both before and during poly(adenosine diphosphate-ribose) polymerase inhibitor treatment.
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Project description:TRPM2 (transient receptor potential cation channel, subfamily M, member 2) is a nonselective cation channel involved in the response to oxidative stress and in inflammation. Its role in autoimmune and neurodegenerative diseases makes it an attractive pharmacological target. Binding of the nucleotide adenosine 5'-diphosphate ribose (ADPR) to the cytosolic NUDT9 homology (NUDT9 H) domain activates the channel. A detailed understanding of how ADPR interacts with the TRPM2 ligand binding domain is lacking, hampering the rational design of modulators, but the terminal ribose of ADPR is known to be essential for activation. To study its role in more detail, we designed synthetic routes to novel analogues of ADPR and 2'-deoxy-ADPR that were modified only by removal of a single hydroxyl group from the terminal ribose. The ADPR analogues were obtained by coupling nucleoside phosphorimidazolides to deoxysugar phosphates. The corresponding C2″-based analogues proved to be unstable. The C1″- and C3″-ADPR analogues were evaluated electrophysiologically by patch-clamp in TRPM2-expressing HEK293 cells. In addition, a compound with all hydroxyl groups of the terminal ribose blocked as its 1″-β- O-methyl-2″,3″- O-isopropylidene derivative was evaluated. Removal of either C1″ or C3″ hydroxyl groups from ADPR resulted in loss of agonist activity. Both these modifications and blocking all three hydroxyl groups resulted in TRPM2 antagonists. Our results demonstrate the critical role of these hydroxyl groups in channel activation.
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