Poly(ADP-Ribose) Biosynthesis

Human single-chain antibodies that neutralize Pseudomonas aeruginosa-exotoxin A-mediated cellular apoptosis

Targeting bacterial virulence factors directly provides a new paradigm for the intervention and treatment of bacterial diseases. Pseudomonas aeruginosa produces a myriad of virulence factors to cause fatal diseases in humans. In this study, human single-chain antibodies (HuscFvs) that bound to P. aeruginosa exotoxin A (ETA) were generated by phage display technology using recombinant ETA, ETA-subdomains and the synthetic peptide of the ETA-catalytic site as baits for selecting ETA-bound-phages from the human-scFv phage display library. ETA-bound HuscFvs derived from three phage-transfected E. coli clones neutralized the ETA-induced mammalian cell apoptosis. Computerized simulation demonstrated that these HuscFvs used several residues in their complementarity-determining regions (CDRs) to form contact interfaces with the critical residues in ETA-catalytic domain essential for ADP-ribosylation of eukaryotic elongation factor 2, which should consequently rescue ETA-exposed-cells from apoptosis. The HuscFv-treated ETA-exposed cells also showed decremented apoptosis-related genes, i.e., cas3 and p53. The effective HuscFvs have high potential for future evaluation in animal models and clinical trials as a safe, novel remedy for the amelioration of exotoxin A-mediated pathogenesis. HuscFvs may be used either singly or in combination with the HuscFv cognates that target other P. aeruginosa virulence factors as an alternative therapeutic regime for difficult-to-treat infections.

Detection and quantification of poly-ADP-ribosylated cellular proteins of spleen and liver tissues of mice in vivo by slot and Western blot immunoprobing using polyclonal antibody against mouse ADP-ribose polymer

Poly-ADP-ribosylation (PAR) of cellular proteins has been shown to have decisive roles in diverse cellular functions including carcinogenesis. There are indications that metabolic level of poly-ADP-ribosylated cellular proteins might indicate carcinogenesis and, therefore, could be potentially used in cancer screening program. Keeping in mind the limitations of currently available assays of cellular PAR, a new assay is being reported that measures the metabolic level of poly-ADP-ribosylated cellular proteins. The ELISA based slot and Western blot immunoassay used polyclonal antibody against natural, heterogeneous ADP-ribose polymers. It could be successfully employed to qualitatively and quantitatively assay metabolic levels of poly-ADP-ribosylated proteins of spleen and liver tissues of normal mice or mice exposed to dimethylnitrosamine for up to 8 weeks; potentially PAR of cellular proteins could be assayed in any tissue or biopsy. Implications of the results in cancer screening program have been discussed.

Inhibitors and activators of ADP-ribosylation reactions

ADP-ribosylation reaction, that is the transfer of the ADP-ribose moiety of NAD+ to acceptor protein, is catalyzed by two classes of ADP-ribosyltransferases, i.e., poly(ADP-ribose) synthetase and mono(ADP-ribosyl)transferases. These two types differ not only in the number of transferring ADP-ribose units but also in the acceptor amino acid(s) and protein. Their inhibitors, particularly those of poly(ADP-ribose) synthetase, have been successfully employed in studies on biological functions of the enzymes and other related fields of research. Recently, we found many potent and specific inhibitors of poly(ADP-ribose) synthetase, and broadened their chemical as well as biochemical variety. More recently, we found several potent inhibitors of arginine-specific mono(ADP-ribosyl)transferases and activators of poly(ADP-ribose) synthetase.

Niacin deficiency and cancer in women

A new interest in the relationship between niacin and cancer has evolved from the discovery that the principal form of this vitamin, NAD, is consumed as a substrate in ADP-ribose transfer reactions. Poly(ADP-ribose) polymerase, an enzyme activated by DNA strand breaks, is the ADP-ribosyltransferase of greatest interest with regard to effects on the niacin status of cells since its Km for NAD is high, and its activity can deplete NAD. Studies of the consequences of DNA damage in cultured mouse and human cells as a function of niacin status have supported the hypothesis that niacin may be a protective factor that limits carcinogenic events. To test this hypothesis in humans, we used a biochemical method based on the observation that as niacin nutriture decreases, NAD readily declines and NADP remains relatively constant. This has been demonstrated in both fibroblasts and in whole blood from humans. Thus, we use "niacin number," (NAD/NAD+NADP) x 100% from whole blood, as a measure of niacin status. Healthy control subjects showed a mean niacin number of 62.8 +/- 3.0 compared to 64.0 for individuals on a niacin-controlled diet. Analyses of women in the Malmö Diet and Cancer Study showed a mean niacin number of 60.4 with a range of 44 to 75. The distribution of niacin status in this population was nongaussian, with an unpredictably large number of individuals having low values.

A biomarker for the assessment of niacin nutriture as a potential preventive factor in carcinogenesis

The study of protective cellular responses to DNA damage has led to the working hypothesis that optimal niacin nutriture is a preventive factor in cancer. Described here is the development of a biomarker for determining niacin status termed Niacin Number. The combination of this biomarker with diet and cancer epidemiology will allow evaluation of the possible role of this nutrient in cancer risk.