title: Caspase-8 and c-FLIPL associate in lipid rafts with NF-kappaB adaptors during T cell activation.
abstract: Humans and mice lacking functional caspase-8 in T cells manifest a profound immunodeficiency syndrome due to defective T cell antigen receptor (TCR)-induced NF-kappaB signaling and proliferation. It is unknown how caspase-8 is activated following T cell stimulation, and what is the caspase-8 substrate(s) that is necessary to initiate T cell cycling. We observe that following TCR ligation, a small portion of total cellular caspase-8 and c-FLIP(L) rapidly migrate to lipid rafts where they associate in an active caspase complex. Activation of caspase-8 in lipid rafts is followed by rapid cleavage of c-FLIP(L) at a known caspase-8 cleavage site. The active caspase.c-FLIP complex forms in the absence of Fas (CD95/APO1) and associates with the NF-kappaB signaling molecules RIP1, TRAF2, and TRAF6, as well as upstream NF-kappaB regulators PKC theta, CARMA1, Bcl-10, and MALT1, which connect to the TCR. The lack of caspase-8 results in the absence of MALT1 and Bcl-10 in the active caspase complex. Consistent with this observation, inhibition of caspase activity attenuates NF-kappaB activation. The current findings define a link among TCR, caspases, and the NF-kappaB pathway that occurs in a sequestered lipid raft environment in T cells.
authors.affiliation: Immunobiology Program, Department of Medicine, University of Vermont College of Medicine, Burlington, Vermont 05405-0068, USA.
authors.forename: Ravi S
authors.initials: RS
authors.lastname: Misra
authors.forename: Jennifer Q
authors.initials: JQ
authors.lastname: Russell
authors.forename: Andreas
authors.initials: A
authors.lastname: Koenig
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Hinshaw-Makepeace
authors.forename: Renren
authors.initials: R
authors.lastname: Wen
authors.forename: Demin
authors.initials: D
authors.lastname: Wang
authors.forename: Hairong
authors.initials: H
authors.lastname: Huo
authors.forename: Dan R
authors.initials: DR
authors.lastname: Littman
authors.forename: Uta
authors.initials: U
authors.lastname: Ferch
authors.forename: Jurgen
authors.initials: J
authors.lastname: Ruland
authors.forename: Margot
authors.initials: M
authors.lastname: Thome
authors.forename: Ralph C
authors.initials: RC
authors.lastname: Budd
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D056769:Alstrom Syndrome; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D000074018:B-Cell CLL-Lymphoma 10 Protein; D053468:CARD Signaling Adaptor Proteins / Q000378:metabolism; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism*; D053181:Caspase 8 / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D020690:GTPase-Activating Proteins / Q000378:metabolism; D021962:Membrane Microdomains / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D000074884:Mucosa-Associated Lymphoid Tissue Lymphoma Translocation 1 Protein; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D047992:TNF Receptor-Associated Factor 2 / Q000378:metabolism; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D000074018:B-Cell CLL-Lymphoma 10 Protein; C488088:Bcl10 protein, mouse; D053468:CARD Signaling Adaptor Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C496467:Card11 protein, mouse; C506387:Cflar protein, mouse; D020690:GTPase-Activating Proteins; D046912:Multiprotein Complexes; D009363:Neoplasm Proteins; C490620:Ralbp1 protein, mouse; D011948:Receptors, Antigen, T-Cell; D047992:TNF Receptor-Associated Factor 2; D048029:TNF Receptor-Associated Factor 6; D019014:fas Receptor; D011493:Protein Kinase C; D053181:Caspase 8; D020169:Caspases; C498509:Malt1 protein, mouse; D000074884:Mucosa-Associated Lymphoid Tissue Lymphoma Translocation 1 Protein