title: The involvement of β-actin in the signaling of transmembrane TNF-α-mediated cytotoxicity.
abstract: Actin cytoskeleton has been shown to play a regulating role in several signaling pathways, and disruption of actin filament has been reported to increase sTNF-α-induced cell death. However, whether actin is involved in tmTNF-α-mediated cytotoxicity remains unclear. Here, we demonstrated that pretreatment of HL-60 with CytD or LatA to depolymerize actin significantly suppressed tmTNF-α-mediated apoptosis. Interestingly, tmTNF-α increased the actin immunoprecipitated by anti-TNFR2 but not anti-TNFR1 antibody, and disruption of the actin filament totally blocked this effect. In addition, TNFR1 knockdown by siRNA did not affect tmTNF-α-mediated cytotoxicity and the inhibitory effect of CytD, suggesting that the involvement of actin in the tmTNF-α-induced apoptosis is linked to the TNFR2 pathway. Our results revealed further that tmTNF-α signaled the inhibition of IκB degradation and NF-κB activity by recruiting RIP1 to and uncoupling TRAF2 from the TNFR2 complex. Nevertheless, CytD totally reversed the tmTNF-α signaling and activated NF-κB by recruiting TRAF2 to and dissociating RIP1 from the TNFR2 complex. Furthermore, tmTNF-α led to activation of caspase-8 by dissociation of cFLIP from TNFR2 and inhibition of the cFLIP expression. Activated caspase-8 cleft RIP1 to suppress NF-κB activity and also mediated tmTNF-α-induced apoptosis. However, CytD blocked the tmTNF-α-induced uncoupling of cFLIP from TNFR2 and prevented caspase-8 activation and the resulting cleavage of RIP1, converting the signaling for tmTNF-α-mediated apoptosis into one for activating NF-κB to survive. These results suggest that the actin cytoskeleton functions in transmitting signals via TNFR2 to mediate tmTNF-α-induced apoptosis.
authors.affiliation: Department of Immunology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Chen
authors.forename: Li
authors.initials: L
authors.lastname: Xiao
authors.forename: Hailong
authors.initials: H
authors.lastname: Zhang
authors.forename: Na
authors.initials: N
authors.lastname: Liu
authors.forename: Tao
authors.initials: T
authors.lastname: Liu
authors.forename: Lili
authors.initials: L
authors.lastname: Liu
authors.forename: Xin
authors.initials: X
authors.lastname: Hu
authors.forename: Dan
authors.initials: D
authors.lastname: Yan
authors.forename: Kun
authors.initials: K
authors.lastname: Yang
authors.forename: Bingjiao
authors.initials: B
authors.lastname: Yin
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Qingfen
authors.initials: Q
authors.lastname: Li
authors.forename: Zhuoya
authors.initials: Z
authors.lastname: Li
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics / Q000378:metabolism; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D015638:Cytochalasin D / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D018922:HL-60 Cells; D006801:Humans; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism; D047468:Immunoprecipitation; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D041681:NIH 3T3 Cells; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D053778:Thiazolidines / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: C119724:AGFG1 protein, human; D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D020672:I-kappa B Proteins; D016209:Interleukin-8; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D028861:Nuclear Pore Complex Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D053778:Thiazolidines; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D015638:Cytochalasin D; D053181:Caspase 8; C037067:latrunculin A