title: Heterotypic interactions among NACHT domains: implications for regulation of innate immune responses.
abstract: Proteins of the NACHT [NAIP (neuronal apoptosis inhibitory protein), CIITA (MHC class II transcription activator), HET-E (incompatibility locus protein from Podospora anserina) and TP1 (telomerase-associated protein)] family may serve as critical pathogen-sensing and signal-transducing molecules within the innate immune system. In the present paper, we show that CLAN [CARD (caspase-recruitment domain), LRR (leucine-rich repeat) and NACHT domain-containing protein], a NACHT-containing protein originally demonstrated to bind and activate pro-caspase 1, is also capable of influencing the functions of other members of the NACHT family. Through heterotypic NACHT-domain interactions, CLAN was found to associate with Nod1, Nod2 and NAC [nucleotide-binding domain and CARD-containing protein; NALP1 (NACHT, LRR and PYRIN protein 1)] when co-expressed in HEK-293T (human embryonic kidney) cells. NF-kappaB (nuclear factor kappaB) reporter assays demonstrated that co-expression of either full-length CLAN or the NACHT domain of CLAN significantly inhibited NF-kappaB activation induced by Nod1 or Nod2 overexpression. In addition, co-expression of CLAN or the NACHT domain of CLAN with Nod1 or Nod2 inhibited the ability of these proteins to generate active IL-1beta (interleukin 1beta) through their association with pro-caspase 1. The NACHT domain of CLAN was demonstrated by co-immunoprecipitation experiments to bind all NACHT domains that were tested, including the NACHT domains from CLAN itself, Nod1, Nod2, cryopyrin, NAC, PAN2 [PAAD [pyrin, AIM (absent-in-melanoma), ASC (apoptosis-associated speck-like protein containing a CARD) and death-domain-like]- and NACHT-containing protein] and NAIP (neuronal apoptosis inhibitory protein). Finally, monocyte-expressed CLAN was found to associate with Nod2 following exposure to bacterial peptidoglycan, implying a regulatory role for interaction of these NACHT proteins in the innate immune response. These studies suggest that by mediating hetero-oligomerization, NACHT domains provide a means by which various NACHT-containing proteins may interact, creating protein-interaction networks that potentially modulate immune responses to invading pathogens.
authors.affiliation: The Burnham Institute, 10901 N. Torrey Pines Road, La Jolla, CA 92037, U.S.A.
authors.forename: Jason S
authors.initials: JS
authors.lastname: Damiano
authors.forename: Vasco
authors.initials: V
authors.lastname: Oliveira
authors.forename: Kate
authors.initials: K
authors.lastname: Welsh
authors.forename: John C
authors.initials: JC
authors.lastname: Reed
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D053468:CARD Signaling Adaptor Proteins; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D007113:Immunity, Innate; D007375:Interleukin-1 / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D007668:Kidney / Q000196:embryology; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009000:Monocytes / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000378:metabolism*; D051616:Neuronal Apoptosis-Inhibitory Protein; D053474:Nod1 Signaling Adaptor Protein; D053473:Nod2 Signaling Adaptor Protein; D009703:Nucleoside-Phosphate Kinase / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D010457:Peptidoglycan / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D053468:CARD Signaling Adaptor Proteins; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D018076:DNA, Complementary; D007375:Interleukin-1; D047908:Intracellular Signaling Peptides and Proteins; D046911:Macromolecular Substances; C496800:NAIP protein, human; D016328:NF-kappa B; C435692:NLRC4 protein, human; C119067:NOD1 protein, human; C429018:NOD2 protein, human; D009419:Nerve Tissue Proteins; D051616:Neuronal Apoptosis-Inhibitory Protein; D053474:Nod1 Signaling Adaptor Protein; D053473:Nod2 Signaling Adaptor Protein; D010455:Peptides; D010457:Peptidoglycan; D020033:Protein Isoforms; D011494:Protein Kinases; C506253:RIPK2 protein, human; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2; D009703:Nucleoside-Phosphate Kinase