title: A Disease-associated Mutant of NLRC4 Shows Enhanced Interaction with SUG1 Leading to Constitutive FADD-dependent Caspase-8 Activation and Cell Death.
abstract: Nod-like receptor family card containing 4 (NLRC4)/Ipaf is involved in recognition of pathogen-associated molecular patterns leading to caspase-1 activation and cytokine release, which mediate protective innate immune response. Point mutations in NLRC4 cause autoinflammatory syndromes. Although all the mutations result in constitutive caspase-1 activation, their phenotypic presentations are different, implying that these mutations cause different alterations in properties of NLRC4. NLRC4 interacts with SUG1 and induces caspase-8-mediated cell death. Here, we show that one of the autoinflammatory syndrome-causing mutants of NLRC4, H443P, but not T337A and V341A, constitutively activates caspase-8 and induces apoptotic cell death in human lung epithelial cells. Compared with wild type NLRC4, the H443P mutant shows stronger interaction with SUG1 and with ubiquitinated cellular proteins. Phosphorylation of NLRC4 at Ser533plays a crucial role in caspase-8 activation and cell death. However, H443P mutant does not require Ser533phosphorylation for caspase-8 activation and cell death. Caspase-8 activation by NLRC4 and its H443P mutant are dependent on the adaptor protein FADD. A phosphomimicking mutant of NLRC4, S533D does not require SUG1 activity for inducing cell death. Ubiquitin-tagged NLRC4 could induce cell death and activate caspase-8 independent of Ser533phosphorylation. Our work suggests that SUG1-mediated signaling results in enhanced ubiquitination and regulates FADD-dependent caspase-8 activation by NLRC4. We show that the autoinflammation-associated H443P mutant is altered in interaction with SUG1 and ubiquitinated proteins, triggering constitutive caspase-8-mediated cell death dependent on FADD but independent of Ser533phosphorylation.
authors.affiliation: From the CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India.
authors.forename: Akhouri Kishore
authors.initials: AK
authors.lastname: Raghawan
authors.affiliation: From the CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India.
authors.forename: Anand
authors.initials: A
authors.lastname: Sripada
authors.affiliation: From the CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India.
authors.forename: Gayathri
authors.initials: G
authors.lastname: Gopinath
authors.affiliation: From the CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India.
authors.forename: Pendyala
authors.initials: P
authors.lastname: Pushpanjali
authors.affiliation: From the CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India.
authors.forename: Yatender
authors.initials: Y
authors.lastname: Kumar
authors.affiliation: From the CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India vradha@ccmb.res.in.
authors.forename: Vegesna
authors.initials: V
authors.lastname: Radha
authors.affiliation: From the CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India gshyam@ccmb.res.in.
authors.forename: Ghanshyam
authors.initials: G
authors.lastname: Swarup
mesh_terms: D000072283:A549 Cells; D000074183:ATPases Associated with Diverse Cellular Activities; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D019943:Amino Acid Substitution; D053468:CARD Signaling Adaptor Proteins / Q000235:genetics / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death; D004789:Enzyme Activation / Q000235:genetics; D053200:Fas-Associated Death Domain Protein / Q000235:genetics / Q000378:metabolism*; D056660:Hereditary Autoinflammatory Diseases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D060588:LIM Domain Proteins / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D046988:Proteasome Endopeptidase Complex; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D053468:CARD Signaling Adaptor Proteins; D002135:Calcium-Binding Proteins; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D060588:LIM Domain Proteins; C435692:NLRC4 protein, human; C092282:PSMC5 protein, human; D014157:Transcription Factors; C505530:CASP8 protein, human; D053181:Caspase 8; D046988:Proteasome Endopeptidase Complex; D000074183:ATPases Associated with Diverse Cellular Activities
keywords: apoptosis; caspase; cell death; inflammasome; phosphorylation; ubiquitylation (ubiquitination)