title: Crystal structure of MC159 reveals molecular mechanism of DISC assembly and FLIP inhibition.
abstract: The death-inducing signaling complex (DISC) comprising Fas, Fas-associated death domain (FADD), and caspase-8/10 is assembled via homotypic associations between death domains (DDs) of Fas and FADD and between death effector domains (DEDs) of FADD and caspase-8/10. Caspase-8/10 and FLICE/caspase-8 inhibitory proteins (FLIPs) that inhibit caspase activation at the DISC level contain tandem DEDs. Here, we report the crystal structure of a viral FLIP, MC159, at 1.2 Angstroms resolution. It reveals a noncanonical fold of DED1, a dumbbell-shaped structure with rigidly associated DEDs and a different mode of interaction in the DD superfamily. Whereas the conserved hydrophobic patch of DED1 interacts with DED2, the corresponding region of DED2 mediates caspase-8 recruitment and contributes to DISC assembly. In contrast, MC159 cooperatively assembles with Fas and FADD via an extensive surface that encompasses the conserved charge triad. This interaction apparently competes with FADD self-association and disrupts higher-order oligomerization required for caspase activation in the DISC.
authors.affiliation: Department of Biochemistry, Weill Medical College of Cornell University, New York, New York 10021, USA.
authors.forename: Jin Kuk
authors.initials: JK
authors.lastname: Yang
authors.forename: Liwei
authors.initials: L
authors.lastname: Wang
authors.forename: Lixin
authors.initials: L
authors.lastname: Zheng
authors.forename: Fengyi
authors.initials: F
authors.lastname: Wan
authors.forename: Misonara
authors.initials: M
authors.lastname: Ahmed
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lenardo
authors.forename: Hao
authors.initials: H
authors.lastname: Wu
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D053455:Caspase 10; D053181:Caspase 8; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D053418:Death Domain Receptor Signaling Adaptor Proteins; D053200:Fas-Associated Death Domain Protein; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008977:Molluscum contagiosum virus / Q000737:chemistry* / Q000235:genetics; D046912:Multiprotein Complexes; D009154:Mutation; D011487:Protein Conformation; D016415:Sequence Alignment; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins / Q000737:chemistry / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D053418:Death Domain Receptor Signaling Adaptor Proteins; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D047908:Intracellular Signaling Peptides and Proteins; D046912:Multiprotein Complexes; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins; D014764:Viral Proteins; D019014:fas Receptor; C505530:CASP8 protein, human; D053455:Caspase 10; D053181:Caspase 8; D020169:Caspases; C506438:CASP10 protein, human