ASC-mediated NF-kappaB activation leading to interleukin-8 production requires caspase-8 and is inhibited by CLARP.
ASC is an adaptor molecule that mediates apoptotic and inflammatory signals from several Apaf-1-like molecules, including CARD12/Ipaf, cryopyrin/PYPAF1, PYPAF5, PYPAF7, and NALP1. To characterize the signaling pathway mediated by ASC, we established cell lines in which muramyl dipeptide, the bacterial component recognized by another Apaf-1-like molecule, Nod2, induced an interaction between a CARD12-Nod2 chimeric protein and ASC, and elicited cell autonomous NF-kappaB activation. This response required caspase-8, and was suppressed by CLARP/FLIP, an inhibitor of caspase-8. The catalytic activity of caspase-8 was required for the ASC-mediated NF-kappaB activation when caspase-8 was expressed at an endogenous level, although it was not essential when caspase-8 was overexpressed. In contrast, FADD, the adaptor protein linking Fas and caspase-8, was not required for this response. Consistently, ASC recruited caspase-8 and CLARP but not FADD and Nod2 to its speck-like aggregates in cells. Finally, muramyl dipeptide induced interleukin-8 production in MAIL8 cells. These results are the first to indicate that caspase-8 plays an important role in the ASC-mediated NF-kappaB activation, and that the ASC-mediated NF-kappaB activation actually induces physiologically relevant gene expression.
Hasegawa
Mizuho
M
Center for the Development of Molecular Target Drugs, Cancer Research Institute, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa 920-0934, Japan.
Imamura
Ryu
R
Kinoshita
Takeshi
T
Matsumoto
Norihiko
N
Masumoto
Junya
J
Inohara
Naohiro
N
Suda
Takashi
T
D000119:Acetylmuramyl-Alanyl-Isoglutamine / Q000737:chemistry; D000818:Animals; D029681:Arabidopsis Proteins / Q000378:metabolism; D053468:CARD Signaling Adaptor Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D019556:COS Cells; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism*; D002384:Catalysis; D002460:Cell Line; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D044943:Fatty Acid Desaturases / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D007249:Inflammation; D007375:Interleukin-1 / Q000378:metabolism; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D016328:NF-kappa B / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D019014:fas Receptor / Q000378:metabolism
D029681:Arabidopsis Proteins; D053468:CARD Signaling Adaptor Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D003598:Cytoskeletal Proteins; D007375:Interleukin-1; D016209:Interleukin-8; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; C402202:PYCARD protein, human; D034741:RNA, Small Interfering; D019014:fas Receptor; D000119:Acetylmuramyl-Alanyl-Isoglutamine; D044943:Fatty Acid Desaturases; C084083:Fad7 protein, Arabidopsis; C505530:CASP8 protein, human; D053181:Caspase 8; D020169:Caspases