title: Impaired mitochondrial function results in increased tissue transglutaminase activity in situ.
abstract: Tissue transglutaminase (tTG) is a transamidating enzyme that is elevated in Huntington's disease (HD) brain and may be involved in the etiology of the disease. Further, there is evidence of impaired mitochondrial function in HD. Therefore, in this study, we examined the effects of mitochondrial dysfunction on the transamidating activity of tTG. Neuroblastoma SH-SY5Y cells stably overexpressing human tTG or mutated inactive tTG were treated with 3-nitropropionic acid (3-NP), an irreversible inhibitor of succinate dehydrogenase. 3-NP treatment of tTG-expressing cells resulted in a significant increase of TG activity in situ. In vitro measurements demonstrated that 3-NP had no direct effect on tTG activity. However, 3-NP treatment resulted in a significant decrease of the levels of GTP and ATP, two potent inhibitors of the transamidating activity of tTG. No significant changes in the intracellular levels of calcium were observed in 3-NP-treated cells. Treatment with 3-NP in combination with antioxidants significantly reduced the 3-NP-induced increase in in situ TG activity, demonstrating that oxidative stress is a contributing factor to the increase of TG activity. This study demonstrates for the first time that impairment of mitochondrial function significantly increases TG activity in situ, a finding that may have important relevance to the etiology of HD.
authors.affiliation: Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama 35294-0017, USA.
authors.forename: M
authors.initials: M
authors.lastname: Lesort
authors.forename: J
authors.initials: J
authors.lastname: Tucholski
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: G V
authors.initials: GV
authors.lastname: Johnson
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000975:Antioxidants / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D006816:Huntington Disease / Q000201:enzymology*; D008387:Marine Toxins / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009447:Neuroblastoma / Q000378:metabolism / Q000473:pathology; D009574:Nitro Compounds; D018384:Oxidative Stress / Q000187:drug effects; D035964:Oxocins; D011422:Propionates / Q000494:pharmacology; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D013385:Succinate Dehydrogenase / Q000037:antagonists & inhibitors; D014162:Transfection; D011503:Transglutaminases / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D000095702:Polyether Toxins
chemical_list: D000255:Adenosine Triphosphate; D000975:Antioxidants; D002118:Calcium; D019204:GTP-Binding Proteins; D006160:Guanosine Triphosphate; D008387:Marine Toxins; D009574:Nitro Compounds; D035964:Oxocins; D011422:Propionates; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D013385:Succinate Dehydrogenase; D011503:Transglutaminases; C020394:maitotoxin; D000095702:Polyether Toxins; C015392:3-nitropropionic acid