title: Casper/c-FLIP is physically and functionally associated with NF-kappaB1 p105.
abstract: Casper/c-FLIP is a caspase-8-related molecule critically involved in regulation of death receptor-induced apoptosis. It has been shown that Casper can either promote or antagonize apoptosis and can activate the transcription factor NF-kappaB. The exact functions of Casper are controversial. To further understand how Casper signals, we searched Casper-interacting proteins by yeast two-hybrid screening. This effort identified NF-kappaB1 (p105), an atypical IkappaB molecule and the precursor of NF-kappaB subunit p50. Co-immunoprecipitation experiments indicated that Casper interacted with p105 in 293 cells and this interaction was mediated through the C-terminal IkappaB-like domain (IkappaBgamma). Overexpression of p105 and IkappaBgamma inhibited Casper-induced NF-kappaB activation and potentiated Casper-induced apoptosis. Furthermore, Casper and its C-terminal caspase-like domain inhibited p105 processing into p50. Our findings suggest that p105 is involved in Casper-mediated regulation of apoptosis and NF-kappaB activation.
mesh_terms: D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit; D011485:Protein Binding; D011498:Protein Precursors / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D011498:Protein Precursors