title: Activation of cell death mediated by apoptosis-inducing factor due to the absence of poly(ADP-ribose) glycohydrolase.
abstract: We previously demonstrated that the absence of poly(ADP-ribose) glycohydrolase (PARG) led to increased cell death following DNA-damaging treatments. Here, we investigated cell death pathways following UV treatment. Decreased amounts of PARG-null embryonic trophoblast stem (TS) cells were observed following doses of 10-100 J/m2 as compared to wild-type cells. In wild-type cells, caspase-cleaved poly(ADP-ribose) polymerase-1 (PARP-1) and activated caspase-3 were detected 12-24 h after UV treatment. Surprisingly, both were detected at decreased levels only after 24 h in PARG-null TS cells, indicating a decreased level and delayed presence of caspase-mediated events. Further, a time- and dose-dependent accumulation of poly(ADP-ribose) (PAR) levels after UV was observed in PARG-null TS cells and not in wild-type cells. Determination of the levels of nicotinamide adenine dinucleotide (NAD+), the substrate for PAR synthesis and a coenzyme in cellular redox reactions, demonstrated a UV dose-dependent decrease in the level of NAD+ in wild-type cells, while NAD+ levels in PARG-null TS cells remained at higher levels. This indicates no depletion of NAD+ in PARG-null TS cells following increased levels of PAR. Lastly, cell death mediated by apoptosis-inducing factor (AIF) was analyzed because of its dependence on increased PAR levels. The results demonstrate nuclear AIF translocation only in PARG-null TS cells, which demonstrates the presence of AIF-mediated cell death. Herein, we provide compelling evidence that the absence of PARG leads to decreased caspase-3 activity and the specific activation of AIF-mediated cell death. Therefore, the absence of PARG may provide a strategy for specifically inducing an alternative apoptotic pathway.
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, Pullman, Washington 99164, United States.
authors.forename: Yiran
authors.initials: Y
authors.lastname: Zhou
authors.forename: Xiaoxing
authors.initials: X
authors.lastname: Feng
authors.forename: David W
authors.initials: DW
authors.lastname: Koh
mesh_terms: D000818:Animals; D017209:Apoptosis; D051033:Apoptosis Inducing Factor / Q000235:genetics / Q000378:metabolism*; D001549:Benzamides / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D053595:Embryonic Stem Cells / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D051379:Mice; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D011064:Poly Adenosine Diphosphate Ribose / Q000037:antagonists & inhibitors / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects / Q000528:radiation effects; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects; D014327:Trophoblasts / Q000166:cytology; D014466:Ultraviolet Rays
chemical_list: D051033:Apoptosis Inducing Factor; D001549:Benzamides; D009243:NAD; D011064:Poly Adenosine Diphosphate Ribose; C037689:benzamide; D011065:Poly(ADP-ribose) Polymerases; D006026:Glycoside Hydrolases; C022407:poly ADP-ribose glycohydrolase; D053148:Caspase 3