title: Autophagic degradation of caspase-8 protects U87MG cells against H2O2-induced oxidative stress.
abstract: Oxidative stress induces apoptosis in many cellular systems including glioblastoma cells, with caspase-8 activation was regarded as a major contribution to H2O2-induced cell death. This study focused on the role of the autophagic protein p62 in H2O2-induced apoptosis in U87MG cells. Oxidative stress was applied with H2O2, and cell apoptosis and viability were measured with use of caspase inhibitors or autophagic mediators or siRNA p62, GFP-p62 and GFP-p62-UBA (del) transfection. We found that H2O2 -induced U87MG cell death was correlated with caspase-8. To understand the role of p62 in MG132-induced cell death, the levels of p62/SQSTM1 or autophagy in U87MG cells were modulated with biochemical or genetic methods. The results showed that the over-expression of wild type p62/SQSTM1 significantly reduced H2O2 induced cell death, but knockdown of p62 aggravated the process. In addition, inhibition of autophagy promoted p62 and active caspase-8 increasing H2O2 -induced apoptosis while induction of autophagy manifested the opposite effect. We further demonstrated that the function of p62/SQSTM1 required its C-terminus UBA domain to attenuate H2O2 cytotoxity by inhibition of caspase-8 activity. Our results indicated that p62/SQSTM1 was a potential contributor to mediate caspase-8 activation by autophagy in oxidative stress process.
authors.affiliation: Department of Pathogen Biology, School of Basic Medical Sciences, Liaoning Medical University, Jinzhou, China. jyzyb2009@163.com
authors.forename: Yi-Bo
authors.initials: YB
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Zhao
authors.forename: Rui-Xia
authors.initials: RX
authors.lastname: Zeng
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D001343:Autophagy; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology; D053181:Caspase 8 / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D005910:Glioma / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007976:Leupeptins / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects*; D059748:Proteolysis / Q000187:drug effects*; D034741:RNA, Small Interfering / Q000235:genetics; D000071456:Sequestosome-1 Protein; D014407:Tumor Cells, Cultured
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D016877:Oxidants; D034741:RNA, Small Interfering; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D006861:Hydrogen Peroxide; D053181:Caspase 8; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde