title: IG20 (MADD splice variant-5), a proapoptotic protein, interacts with DR4/DR5 and enhances TRAIL-induced apoptosis by increasing recruitment of FADD and caspase-8 to the DISC.
abstract: Recently, we identified Insulinoma-Glucagonoma clone 20 (IG20) that can render cells more susceptible to tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis. In addition, it can slow cell proliferation, and enhance drug- and radiation-induced cell death. TNF-related apoptosis-inducing ligand (TRAIL) can selectively induce apoptosis in some cancer cells and render others susceptible to cotreatment with drugs and irradiation, with little or no effect on most normal cells. In this study, we investigated the potential of IG20 to enhance TRAIL-induced apoptosis and found that it can render cells more susceptible to TRAIL treatment through enhanced activation of caspases. Further, we showed that this effect can be suppressed by caspase inhibitors, p35 and CrmA, and a dominant-negative Fas-associated death domain-containing protein (DN-FADD). Results from colocalization and immunoprecipitation studies showed that IG20 can interact with TRAIL death receptors (DR), DR4 and DR5 and increase recruitment of FADD and caspase-8 into the TRAIL death-inducing signaling complex (DISC). These results indicate that IG20 is a novel protein that can enhance TRAIL-induced apoptosis by facilitating DISC formation.
authors.affiliation: Department of Microbiology and Immunology, University of Illinois at Chicago, 835 South Wolcott Avenue, Chicago, IL 60612, USA.
authors.forename: Madhu
authors.initials: M
authors.lastname: Ramaswamy
authors.forename: Elena V
authors.initials: EV
authors.lastname: Efimova
authors.forename: Osvaldo
authors.initials: O
authors.lastname: Martinez
authors.forename: Nirupama U
authors.initials: NU
authors.lastname: Mulherkar
authors.forename: Surya P
authors.initials: SP
authors.lastname: Singh
authors.forename: Bellur S
authors.initials: BS
authors.lastname: Prabhakar
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins; D053181:Caspase 8; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D053418:Death Domain Receptor Signaling Adaptor Proteins; D053200:Fas-Associated Death Domain Protein; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology*; D046912:Multiprotein Complexes; D009154:Mutation; D021381:Protein Transport; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000032:analysis / Q000378:metabolism*; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000096:biosynthesis / Q000235:genetics; D053221:TNF-Related Apoptosis-Inducing Ligand; D014158:Transcription, Genetic; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D053418:Death Domain Receptor Signaling Adaptor Proteins; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D020662:Guanine Nucleotide Exchange Factors; C105852:MADD protein, human; D008562:Membrane Glycoproteins; D046912:Multiprotein Complexes; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D053221:TNF-Related Apoptosis-Inducing Ligand; C105190:TNFRSF10A protein, human; C505639:TNFRSF10B protein, human; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; C505530:CASP8 protein, human; D053181:Caspase 8; D020169:Caspases