ATIC as a link between antirheumatic drugs and regulation of energy metabolism in skeletal muscle

Chronic inflammatory rheumatic diseases, such as rheumatoid arthritis, psoriatic arthritis, and systemic lupus erythematosus, increase the risk of developing insulin resistance, metabolic syndrome, and/or type 2 diabetes. While inflammation is thought to be a major mechanism underlying metabolic dysregulation in rheumatic diseases, antirheumatic drugs that exert direct metabolic effects in addition to suppressing inflammation, might be particularly useful to prevent metabolic complications. Here we review antirheumatic drugs, such as methotrexate, that inhibit ATIC, the final enzyme in the de novo purine biosynthesis, responsible for conversion of ZMP to IMP. Inhibition of ATIC results in accumulation of ZMP, thus promoting activation of AMP-activated kinase (AMPK), a major regulator of cellular energy metabolism and one of the most promising targets for the treatment of insulin resistance and type 2 diabetes. We focus especially on ATIC inhibition and AMPK activation in skeletal muscle as this is the largest and one of the most metabolically active tissues with a major role in glucose homeostasis. As an important site of insulin resistance, skeletal muscle is also one of the main target tissues for pharmacological therapy of type 2 diabetes. Finally, we review the metabolic effects of ATIC-inhibiting antirheumatic drugs and discuss whether these drugs might improve systemic glucose homeostasis by inhibiting ATIC and activating AMPK in skeletal muscle.</p

Purine biosynthesis in archaea: variations on a theme

<p>Abstract</p> <p>Background</p> <p>The ability to perform <it>de novo </it>biosynthesis of purines is present in organisms in all three domains of life, reflecting the essentiality of these molecules to life. Although the pathway is quite similar in eukaryotes and bacteria, the archaeal pathway is more variable. A careful manual curation of genes in this pathway demonstrates the value of manual curation in archaea, even in pathways that have been well-studied in other domains.</p> <p>Results</p> <p>We searched the Integrated Microbial Genome system (IMG) for the 17 distinct genes involved in the 11 steps of <it>de novo </it>purine biosynthesis in 65 sequenced archaea, finding 738 predicted proteins with sequence similarity to known purine biosynthesis enzymes. Each sequence was manually inspected for the presence of active site residues and other residues known or suspected to be required for function.</p> <p>Many apparently purine-biosynthesizing archaea lack evidence for a single enzyme, either glycinamide ribonucleotide formyltransferase or inosine monophosphate cyclohydrolase, suggesting that there are at least two more gene variants in the purine biosynthetic pathway to discover. Variations in domain arrangement of formylglycinamidine ribonucleotide synthetase and substantial problems in aminoimidazole carboxamide ribonucleotide formyltransferase and inosine monophosphate cyclohydrolase assignments were also identified.</p> <p>Manual curation revealed some overly specific annotations in the IMG gene product name, with predicted proteins without essential active site residues assigned product names implying enzymatic activity (21 proteins, 2.8% of proteins inspected) or Enzyme Commission (E. C.) numbers (57 proteins, 7.7%). There were also 57 proteins (7.7%) assigned overly generic names and 78 proteins (10.6%) without E.C. numbers as part of the assigned name when a specific enzyme name and E. C. number were well-justified.</p> <p>Conclusions</p> <p>The patchy distribution of purine biosynthetic genes in archaea is consistent with a pathway that has been shaped by horizontal gene transfer, duplication, and gene loss. Our results indicate that manual curation can improve upon automated annotation for a small number of automatically-annotated proteins and can reveal a need to identify further pathway components even in well-studied pathways.</p> <p>Reviewers</p> <p>This article was reviewed by Dr. Céline Brochier-Armanet, Dr Kira S Makarova (nominated by Dr. Eugene Koonin), and Dr. Michael Galperin.</p

Nucleoside analogs and tuberculosis: new weapons against an old enemy

Purine and pyrimidine nucleoside and nucleotide analogs have been extensively studied as anticancer and antiviral agents. In addition to this, they have recently shown great potential against Mycobacterium Tuberculosis, the causative agent of TB. TB ranks as the tenth most common cause of death in the world. The current treatment for TB infection is limited by side effects and cost of the drugs and most importantly by the development of resistance to the therapy. Therefore the development of novel drugs, capable of overcoming the drawbacks of the existing treatments, has become the focus of many research programs. In parallel to that, a tremendous effort has been made to elucidate the unique metabolism of this pathogen with the aim to identify new possible targets. This review presents the state of the art in nucleoside and nucleotide analogs in the treatment of TB. In particular, we report on the inhibitory activity of this class of compounds, both in enzymatic and whole-cell assays, providing a brief insight to which reported target these novel compounds are hitting

Disruption of Nucleotide Homeostasis by the Antiproliferative Drug 5-Aminoimidazole-4-carboxamide-1-β-d-ribofuranoside Monophosphate (AICAR)

International audienceBackground: AICAR is a potent anti-proliferative compound, but the basis of its cytotoxicity is poorly understood. Results: AICAR affects NTP homeostasis in a carbon source-dependent way, in both yeast and human cells. Conclusion: AICAR balance with nucleotides triphosphate is critical for its in vivo effects. Significance: AICAR is significantly more cytotoxic on glucose and thus potentially targets cells prone to Warburg effect

Application of Squaric acid to The Preparation of Bioactive Compounds

Nucleosides and nucleoside analogues exhibit a broad spectrum of biological activities including antiviral, anticancer, antibacterial and antiparasitic activities, which generally result from their ability to inhibit specific enzymes. Nucleoside analogues can interact with cellular enzymes involved in the biosynthesis or degradation of RNA (ribonucleic acid) and/or DNA (deoxyribonucleic acid) or with specific viral enzymes to result in their biological activities and therapeutic effects. In addition, another possible target is their incorporation into DNA/RNA which could affect replication and transcription. They have been beneficial to the development of new pharmaceuticals. Squaric acid and its derivatives have been successfully used as a bioisosteric group in various biomedicinal areas. The aim of this research proposal was to apply squaric acid analogues to the design and synthesis of novel nucleoside analogues. Three squaric acid-based new nucleoside analogues were made starting from dimethyl squarate. The compounds were 4-amino-3-[((1R,3S)-3-hydroxymethyl-4-cyclopentene)-1-amino]-3-cyclobutene-1,2-dione, 4-methoxy-3-[((1R,3S)-3-hydroxymethyl-4-cyclopen tene)-1-amine]-3-cyclobutene-1,2-dione, and 4-hydroxy-3-[((1R,3S)-3-hydroxymethyl-4-cyclopentene)-1-amine]-3-cyclobutene-1,2-dionate, sodium salt. A key step in their synthesis was the reaction of (1R, 4S)-(-)-4-(hydroxymethyl)cyclopent-2-en-1-ylamine with 4-amino-3-methoxy-3-cyclobutene-1,2-dione, or 3,4-dimethoxy-3-cyclobutene-1,2-dione, followed by hydrolysis to give the above compounds. They were sent to the Developmental Therapeutics Program (DTP) of the National Cancer Institute (NCI, USA) to screen and test in vitro for their potential anticancer activity in cellular assays. Little to modest antitumour activity was detected for these compounds. Meanwhile, their cytotocity to HeLa cells was investigated as well. However, no significant effect was observed by these three compounds. Also, these compounds were sent out to the National Institute of Allergy and Infectious Diseases (NIAID, USA) to test their antiviral activity against various viruses. These tests are in progress

A novel method for the analysis of 5-aminoimidazole-4-carboxamide-1-ß-D-ribofuranoside (AICAR) in urine by isotope ratio mass spectrometry for anti-doping purposes

In the last 20 years, isotopic ratio mass spectrometry coupled with gas chromatography (GC/C/IRMS) applied to carbon stable isotope (13C/12C) ratios (CSIR) has been a fundamental tool in the field of anti-doping analysis. Some compounds, such as testosterone, can be found in human urine as the result of natural metabolism or exogenous intake, sometimes leaving its carbon isotopic signature as the only proof of an antidoping violation. More recently, the appearance of a new non-steroidal compound named 5-aminoimidazole-4-carboxamide-1-ß-D-ribofuranoside (AICAR) has been of major concern. Experiments made on mice, combined with rumors in the world of sport, has made the compound a suspect for anti-doping authorities. As an intermediate in the purine synthesis, AICAR is also present in urine. The development of a GC/C/IRMS method to distinguish between natural and synthetic AICAR therefore appears necessary, but is not done without issues as AICAR is a non-volatile and unstable molecule at high temperatures. Existing methods use trimethylsilyl (TMS) derivatization, which damages combustion furnaces and adds 9 carbon atoms to the AICAR molecule. This work therefore proposes a new GC/C/IRMS method that uses acetylation as an alternative route to analyze the CSIR of AICAR for anti-doping purposes. The different issues encountered when developing such method are described as well as the data obtained from its validation and from the analysis of 46 urines samples. A comparison of the results from this work with the existing literature is also made. The results suggest that the use of CSIR to determine the origin of AICAR in urine is more complex than previously reported

New biomarkers for early diagnosis of Lesch-Nyhan disease revealed by metabolic analysis on a large cohort of patients

International audienceBackground: Lesch-Nyhan disease is a rare X-linked neurodevelopemental metabolic disorder caused by a wide variety of mutations in the HPRT1 gene leading to a deficiency of the purine recycling enzyme hypoxanthine-guanine phosphoribosyltransferase (HGprt). The residual HGprt activity correlates with the various phenotypes of Lesch-Nyhan (LN) patients and in particular with the different degree of neurobehavioral disturbances. The prevalence of this disease is considered to be underestimated due to large heterogeneity of its clinical symptoms and the difficulty of diagnosing of the less severe forms of the disease. We therefore searched for metabolic changes that would facilitate an early diagnosis and give potential clues on the disease pathogenesis and potential therapeutic approaches

Multiple chemo-genetic interactions between a toxic metabolite and the ubiquitin pathway in yeast

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Dual control of NAD + synthesis by purine metabolites in yeast

International audienceMetabolism is a highly integrated process resulting in energy and biomass production. While individual metabolic routes are well characterized, the mechanisms ensuring crosstalk between pathways are poorly described, although they are crucial for homeostasis. Here, we establish a co-regulation of purine and pyridine metabolism in response to external adenine through two separable mechanisms. First, adenine depletion promotes transcriptional upregulation of the de novo NAD + biosynthesis genes by a mechanism requiring the key-purine intermediates ZMP/SZMP and the Bas1/Pho2 transcription factors. Second, adenine supplementation favors the pyridine salvage route resulting in an ATP-dependent increase of intracellular NAD +. This control operates at the level of the nicotinic acid mononucleotide adenylyl-transferase Nma1 and can be bypassed by overexpressing this enzyme. Therefore, in yeast, pyridine metabolism is under the dual control of ZMP/SZMP and ATP, revealing a much wider regulatory role for these intermediate metabolites in an integrated biosynthesis network

Unusual carbohydrate biosynthesis : mechanistic studies of DesII and the biosynthesis of formycin A

Carbohydrates are essential biomolecules in all living organisms. Besides serving as energy storage and structural building blocks in primary metabolism, carbohydrates represent the building blocks for numerous bioactive natural products. The presence of sugar moieties in secondary metabolites are important for the biological properties of these natural products. Thus, the study of biosynthetic pathways involving carbohydrate secondary metabolism can reveal some intriguing enzymatic transformations that lead to remarkable structural diversity. Understanding these pathways and the enzymes they contain can provide new insights for pathway engineering and the production of novel sugar structures. The radical S-adenosyl-L-methionine (SAM) enzymes are distinguished by their unique chemistry that results in the reductive homolysis of SAM to generate a reactive 5′- deoxyadenosyl radical. Subsequent formation of a substrate radical intermediate by this radical initiator permits a diverse set of biotransformations. DesII belongs to the radical SAM enzyme superfamily, and is involved in the biosynthesis of TDP-desosamine in Streptomyces venezuelae. DesII catalyzes the deamination of its biosynthetic substrate (i.e., TDP-4,6-dideoxy-3-keto-D-glucose), whereas it promotes an oxidative dehydrogenation reaction when the C4 amino group of the substrate is replaced by a hydroxyl group (i.e., TDP-D-quinovose). Control of the radical intermediate resulting in two distinct reaction outcomes has been a primary focus of this research. It has been proposed that the orbital geometry of the radical intermediates is an important factor in determining whether the enzyme functions as a lyase or a dehydrogenase. To investigate this hypothesis, several substrate analogs with altered stereochemistry of ring substituents were tested as potential substrates for DesII and the reaction products were characterized. While DesII deaminates the C4 axial amino substituent as it does with the C4 equatorial amino group, inversion of stereochemistry of a hydroxyl group at C4 allows dehydration to take place. These results support the working hypothesis that the stereochemical configuration of substrate radical in the active site plays an important role in controlling the partitioning into different reaction pathways. Formycin A and coformycin are nucleoside antibiotics produced by Nocardia interforma and Streptomyces kaniharaensis. Their biosynthetic pathways are of particular interest because of their unusual structural features such as the pyrazolopyrimidine nucleobase with a C-glycosidic linkage in formycin A and the 1,3-diazepine ring in coformycin. Genomic analysis of producing strain suggested that the pyrimidine ring of formycin A is formed in a pathway analogous to that for purines, which led to the identification of a potential biosynthetic gene cluster and pathway for formycin A. Conversion of the putative intermediate, carboxyaminopyrazole ribonucleotide, in this pathway to the final product was demonstrated to be catalyzed by enzymes encoded in the for cluster as proposed. It was also shown that one gene adjacent to the formycin A gene cluster encodes a reductase that catalyzes the last step in the biosynthesis of coformycin. This study aims to elucidate the biosynthetic pathways of formycin A and coformycin with an emphasis on the formation of pyrazolopyrimidine moiety and C-glycosidic bond.Chemistr