Poly(ADP-ribose) metabolism is involved in procyclic Trypanosoma brucei sensitivity to genotoxic damage

MARIANA SCHLESINGER; SALOMÉ VILCHEZ LARREA; GUILLERMO D. ALONSO; MIRTHA M. FLAWIÁ; SILVIA H. FERNÁNDEZ VILLAMIL

Mar del lPlata

Congreso; X Congreso de Protozoología y Enfermedades parasitarias; 2014

Sociedad Argentina de Protozoolgía

Poly(ADP-ribosyl)ation is a covalent modification of proteins catalyzed by poly(ADP-ribose) polymerases (PARPs). Poly(ADP-ribose) (pADPr) metabolism plays a role in a wide range of biological processes among which DNA damage signaling and repair are the most extensively studied functions. Poly(ADP-ribose) glycohydrolase (PARG) represents the main pADPr hydrolyzing activity in the cell. In contrast to human and other higher eukaryotes, T. brucei contains only one PARP (TbPARP) and PARG (TbPARG). We have identified potent TbPARP inhibitors using an in vitro activity assay and verified that these compounds effectively reduced the formation of pADPr in T. brucei parasites exposed to genotoxic stress. Our previous results suggest that TbPARP is not necessary for T. brucei growth under normal conditions. Surprisingly procyclic parasites become more resistant to stress induced by hydrogen peroxide when TbPARP activity is abolished by chemical inhibition or RNAi. On the other hand, large amounts of basal pADPr in the nucleus of the parasites over-expressing TbPARP and down-regulating TbPARG lead to an increased sensitivity towards genotoxic stimulus. Indeed, transgenic parasites undergo, after extensive DNA damage, a cell death pathway different from wild type trypanosomes, suggesting a role of pADP r polymer metabolism in cell death. The duality of pADPr as a central player in both life and cell death has been proposed by many authors. pADPr is required for proper mitosis and is involved in DNA damage response. However, an augmented pADPr synthesis may deplete NAD+ and consequently remove ATP from the cell, inducing cell death. We showed that not only the quantity of the synthesized pADPr might have an effect on parasite survival, but also the polymer subcellular localization seems to affect this outcome. Disrupted pADPr metabolism with nuclear accumulated polymer has deleterious consequences to the cell, an outcome that is accelerated by genotoxic stimulus.