title: Identification of Ipaf, a human caspase-1-activating protein related to Apaf-1.
abstract: Procaspase-9 contains an NH2-terminal caspase-associated recruitment domain (CARD), which is essential for direct association with Apaf-1 and activation. Procaspase-1 also contains an NH2-terminal CARD domain, suggesting that its mechanism of activation, like that of procaspase-9, involves association with an Apaf-1-related molecule. Here we describe the identification of a human Apaf-1-related protein, named Ipaf that contains an NH2-terminal CARD domain, a central nucleotide-binding domain, and a COOH-terminal regulatory leucine-rich repeat domain (LRR). Ipaf associates directly and specifically with the CARD domain of procaspase-1 through CARD-CARD interaction. A constitutively active Ipaf lacking its COOH-terminal LRR domain can induce autocatalytic processing and activation of procaspase-1 and caspase-1-dependent apoptosis in transfected cells. Our results suggest that Ipaf is a specific and direct activator of procaspase-1 and could be involved in activation of caspase-1 in response to pro-inflammatory and apoptotic stimuli.
authors.affiliation: Center for Apoptosis Research and the Department of Microbiology and Immunology, Kimmel Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Poyet
authors.forename: S M
authors.initials: SM
authors.lastname: Srinivasula
authors.forename: M
authors.initials: M
authors.lastname: Tnani
authors.forename: M
authors.initials: M
authors.lastname: Razmara
authors.forename: T
authors.initials: T
authors.lastname: Fernandes-Alnemri
authors.forename: E S
authors.initials: ES
authors.lastname: Alnemri
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis; D053477:Apoptotic Protease-Activating Factor 1; D020170:Caspase 1 / Q000378:metabolism*; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000378:metabolism; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry* / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014018:Tissue Distribution; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: C506592:APAF1 protein, human; D053477:Apoptotic Protease-Activating Factor 1; D018076:DNA, Complementary; D004792:Enzyme Precursors; D011506:Proteins; D005982:Glutathione Transferase; C506433:CASP9 protein, human; D053453:Caspase 9; D020169:Caspases; D020170:Caspase 1