Abstract
In humans, ten Toll-like receptor (TLR) paralogues sense molecular components of microbes, initiating the production of cytokine mediators that create the inflammatory response. Using N-ethyl-N-nitrosourea, we induced a germline mutation called Lps2, which abolishes cytokine responses to double-stranded RNA and severely impairs responses to the endotoxin lipopolysaccharide (LPS), indicating that TLR3 and TLR4 might share a specific, proximal transducer. Here we identify the Lps2 mutation: a distal frameshift error in a Toll/interleukin-1 receptor/resistance (TIR) adaptor protein known as Trif or Ticam-1. Trif(Lps2) homozygotes are markedly resistant to the toxic effects of LPS, and are hypersusceptible to mouse cytomegalovirus, failing to produce type I interferons when infected. Compound homozygosity for mutations at Trif and MyD88 (a cytoplasmic TIR-domain-containing adaptor protein) loci ablates all responses to LPS, indicating that only two signalling pathways emanate from the LPS receptor. However, a Trif-independent cell population is detectable when Trif(Lps2) mutant macrophages are stimulated with LPS. This reveals that an alternative MyD88-dependent 'adaptor X' pathway is present in some, but not all, macrophages, and implies afferent immune specialization.
Publication types
- Research Support, U.S. Gov't, Non-P.H.S.
- Research Support, U.S. Gov't, P.H.S.
MeSH terms
- Adaptor Proteins, Signal Transducing
- Adaptor Proteins, Vesicular Transport / genetics
- Adaptor Proteins, Vesicular Transport / metabolism*
- Animals
- Antigens, Differentiation / genetics
- Antigens, Differentiation / physiology*
- Escherichia coli / physiology
- Homozygote
- Interferon Type I / metabolism
- Lipopolysaccharides / pharmacology*
- Macrophages, Peritoneal / drug effects
- Macrophages, Peritoneal / immunology
- Macrophages, Peritoneal / microbiology
- Macrophages, Peritoneal / virology
- Membrane Glycoproteins / metabolism
- Mice
- Mice, Inbred C57BL
- Mutation
- Myeloid Differentiation Factor 88
- Phenotype
- Physical Chromosome Mapping
- Receptors, Cell Surface / metabolism
- Receptors, Immunologic / genetics
- Receptors, Immunologic / physiology*
- Sequence Analysis, DNA
- Signal Transduction / drug effects*
- Substrate Specificity
- Toll-Like Receptor 3
- Toll-Like Receptor 4
- Toll-Like Receptors
- Tumor Necrosis Factor-alpha / metabolism
- Vaccinia virus / physiology
Substances
- Adaptor Proteins, Signal Transducing
- Adaptor Proteins, Vesicular Transport
- Antigens, Differentiation
- Interferon Type I
- Lipopolysaccharides
- Membrane Glycoproteins
- Myd88 protein, mouse
- Myeloid Differentiation Factor 88
- Receptors, Cell Surface
- Receptors, Immunologic
- TICAM-1 protein, mouse
- Toll-Like Receptor 3
- Toll-Like Receptor 4
- Toll-Like Receptors
- Tumor Necrosis Factor-alpha