ABSTRACT
Leucine-rich repeat (LRR) domains are evolutionarily conserved in proteins that function in development and immunity. Here we report strict exonic modularity of LRR domains of several human gene families, which is a precondition for alternative splicing (AS). We provide evidence for AS of LRR domain within several Nod-like receptors, most prominently the inflammasome sensor NLRP3. Human NLRP3, but not mouse NLRP3, is expressed as two major isoforms, the full-length variant and a variant lacking exon 5. Moreover, NLRP3 AS is stochastically regulated, with NLRP3 ∆ exon 5 lacking the interaction surface for NEK7 and hence loss of activity. Our data thus reveals unexpected regulatory roles of AS through differential utilization of LRRs modules in vertebrate innate immunity.
Subject(s)
Alternative Splicing , Exons/genetics , Inflammasomes/genetics , NLR Family, Pyrin Domain-Containing 3 Protein/genetics , Amino Acid Sequence , Animals , Cells, Cultured , HEK293 Cells , Humans , Immunity, Innate/genetics , Inflammasomes/chemistry , Inflammasomes/metabolism , Macrophages/metabolism , NIMA-Related Kinases/genetics , NIMA-Related Kinases/metabolism , NLR Family, Pyrin Domain-Containing 3 Protein/chemistry , NLR Family, Pyrin Domain-Containing 3 Protein/metabolism , Neoplasm Proteins/chemistry , Neoplasm Proteins/genetics , Neoplasm Proteins/metabolism , Protein Domains , Protein Isoforms/chemistry , Protein Isoforms/genetics , Protein Isoforms/metabolism , Stochastic Processes , SwineABSTRACT
NLRP3 nucleates the inflammasome, a protein complex responsible for cleavage of prointerleukin-1beta (IL-1beta) to its active form. Mutations in the NLRP3 gene cause the autoinflammatory disease spectrum cryopyrin-associated periodic syndromes (CAPS). The central role of IL-1beta in CAPS is supported by the response to IL-1-targeted therapy. We developed two Nlrp3 mutant knockin mouse strains to model CAPS to examine the role of other inflammatory mediators and adaptive immune responses in an innate immune-driven disease. These mice had systemic inflammation and poor growth, similar to some human CAPS patients, and demonstrated early mortality, primarily mediated by myeloid cells. Mating these mutant mice to various gene mutant backgrounds showed that the mouse disease phenotype required an intact inflammasome, was only partially dependent on IL-1beta, and was independent of T cells. These data suggest that CAPS are true inflammasome-mediated diseases and provide insight for more common inflammatory disorders.
