title: Beta-actin is required for mitochondria clustering and ROS generation in TNF-induced, caspase-independent cell death.
abstract: Tumor necrosis factor (TNF)-alpha induces caspase-independent cell death in the fibrosarcoma cell line L929. This cell death has a necrotic phenotype and is dependent on production of reactive oxygen species (ROS) in the mitochondria. To identify genes involved in this TNF-induced, ROS-dependent cell death pathway, we utilized retrovirus insertion-mediated random mutagenesis to generate TNF-resistant L929 cell lines and we subsequently identified genes whose mutations are responsible for the TNF-resistant phenotype. In one such resistant line, beta-actin was disrupted by viral insertion, and subsequent reconstitution of beta-actin expression levels in the mutant line Actin(mut) restored its sensitivity to TNF. Resistance to TNF in Actin(mut) cells is signal specific since the sensitivity to other death stimuli is either unchanged or even increased. Comparable NF-kappaB activation and p38 phosphorylation in TNF-treated wild-type and Actin(mut) cells also indicates that reduced expression of actin only selectively blocked some of the TNF-induced cellular changes. Actin cleavage involved in apoptosis does not occur in TNF-treated L929 cell death, as in HeLa cells. Consistent over-expression of a caspase-cleaved product, a 15 kDa actin fragment, had no effect on TNF-induced necrosis of L929 cell. By contrast, TNF-induced mitochondria clustering and ROS production were dramatically reduced in Actin(mut) cells, indicating that actin-deficiency-mediated TNF resistance is most likely due to impaired mitochondrial responses to TNF stimulation. Our findings suggest that a full complement of actin is required for transduction of a cell death signal to mitochondria in TNF-treated L929 cells.
authors.affiliation: The Key Laboratory of the Ministry of Education for Cell Biology and Tumor Cell Engineering, School of Life Sciences, Xiamen University, Xiamen 361005, Fujian, China.
authors.forename: Jinquan
authors.initials: J
authors.lastname: Li
authors.forename: Qinxi
authors.initials: Q
authors.lastname: Li
authors.forename: Changchuan
authors.initials: C
authors.lastname: Xie
authors.forename: Huamin
authors.initials: H
authors.lastname: Zhou
authors.forename: Yuqian
authors.initials: Y
authors.lastname: Wang
authors.forename: Na
authors.initials: N
authors.lastname: Zhang
authors.forename: Hanjuan
authors.initials: H
authors.lastname: Shao
authors.forename: Siu Chiu
authors.initials: SC
authors.lastname: Chan
authors.forename: Xuanxian
authors.initials: X
authors.lastname: Peng
authors.forename: Sheng-Cai
authors.initials: SC
authors.lastname: Lin
authors.forename: Jiahuai
authors.initials: J
authors.lastname: Han
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death / Q000235:genetics* / Q000502:physiology; D002460:Cell Line; D004789:Enzyme Activation; D006801:Humans; D051379:Mice; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000199:Actins; D016328:NF-kappa B; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases