title: Homotypic FADD interactions through a conserved RXDLL motif are required for death receptor-induced apoptosis.
abstract: Death receptors in the TNF receptor superfamily signal for apoptosis via the ordered recruitment of FADD and caspase-8 to a death-inducing signaling complex (DISC). However, the nature of the protein-protein interactions in the signaling complex is not well defined. Here we show that FADD self-associates through a conserved RXDLL motif in the death effector domain (DED). Despite exhibiting similar binding to both Fas and caspase-8 and preserved overall secondary structure, FADD RDXLL motif mutants cannot reconstitute FasL- or TRAIL-induced apoptosis and fail to recruit caspase-8 into the DISC of reconstituted FADD-deficient cells. Abolishing self-association can transform FADD into a dominant-negative mutant that interferes with Fas-induced apoptosis and formation of microscopically visible receptor oligomers. These findings suggest that lateral interactions among adapter molecules are required for death receptor apoptosis signaling and implicate self-association into oligomeric assemblies as a key function of death receptor adapter proteins in initiating apoptosis.
authors.affiliation: Immunoregulation Unit, Autoimmunity Branch, NIAMS, NIH, Bethesda, MD 20892, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Muppidi
authors.forename: A A
authors.initials: AA
authors.lastname: Lobito
authors.forename: M
authors.initials: M
authors.lastname: Ramaswamy
authors.forename: J K
authors.initials: JK
authors.lastname: Yang
authors.forename: L
authors.initials: L
authors.lastname: Wang
authors.forename: H
authors.initials: H
authors.lastname: Wu
authors.forename: R M
authors.initials: RM
authors.lastname: Siegel
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D017124:Conserved Sequence; D053200:Fas-Associated Death Domain Protein; D006801:Humans; D019169:Jurkat Cells; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D018124:Receptors, Tumor Necrosis Factor