What does TLR3 recognize?
Endosomal Toll-like receptor 3 (TLR3) serves as a sensor of viral infection and sterile tissue necrosis. Although TLR3 recognizes double-stranded RNA, little is known about structural features of virus- or host-derived RNAs that activate TLR3 in infection/inflammatory states.
What type of protein are TLR?
TLRs are type I transmembrane proteins composed of leucine-rich repeats (LRRs) in the ectodomain, a single transmembrane domain and a cytoplasmic Toll/IL-1 receptor (TIR) domain involved in recruitment of signaling adaptor molecules. TLRs form heterodimers or homodimers as a means of triggering a signal.
What is the role of TLR3?
Toll-like receptor 3 (TLR3) is an important member of the TLR family, which is an important group of pathogen-associated molecular patterns. TLR3 can recognize double-stranded RNA and induce activation of NF-κB and the production of type I interferons.
Is TLR 4 a protein?
TLR4 is a transmembrane protein, member of the toll-like receptor family, which belongs to the pattern recognition receptor (PRR) family. Its activation leads to an intracellular signaling pathway NF-κB and inflammatory cytokine production which is responsible for activating the innate immune system.
What cells express TLR3?
TLR3 is expressed in human dendritic cells, particularly in the immature myeloid subset (164,165), but expression is low or absent in monocytes, neutrophils, T and B lymphocytes, and natural killer cells (166).
What does TLR3 bind to?
Analysis of the crystal structure of a complex comprising TLR3 and dsRNA revealed that TLR3 binds to dsRNA molecules at two sites located at opposite ends of the TLR3 horseshoe [20,21]. Furthermore, data also suggest that TLR3 primarily senses unmethylated RNA molecules [22].
Where is TLR3 located?
TLR3 is localized to cell surfaces and endosomes in fibroblasts, macrophages, and some epithelial cell lines. In contrast, myeloid DCs only express TLR3 intracellularly. Immunofluoresence analysis has shown that endogenous TLR3 is localized to the early endosome, but not to late endosomes/lysosomes.
How does TLR work?
Toll-like receptors (TLRs) are a class of pattern recognition receptors (PRRs) that initiate the innate immune response by sensing conserved molecular patterns for early immune recognition of a pathogen (1).
Where is TLR3 found?
Is LPS a ligand?
This large internal pocket is ideally shaped for binding flat hydrophobic ligands like LPS.
How is TLR3 activated?
The NF-κB branch of TLR3 is activated by TRIF-dependent recruitment of RIP1, TAK1, and IKK. Activation of these transcription factors leads to their nuclear translocation, where they bind to their respective promoter elements of the target genes.
Why is it called toll-like receptors?
TLRs received their name from their similarity to the protein coded by the toll gene.
What cells are TLR3 expressed in?
TLR3 is expressed in various tissues and cells. In the human central nervous system, TLR3 is expressed constitutively in neurons, astrocytes, and microglia, suggesting a role in the response to viruses causing encephalopathy. 28,29 In immune cells, only myeloid DCs and macrophages express TLR3.
Which kinases are activated by TLR3 signaling?
Phosphoinositide 3-kinase (PI3K), p38-mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) are also activated by TLR3 signaling ( Schröder and Bowie, 2005 ).
What are the negative regulators of TLR3?
Negative regulation of TLR3 signaling. The trunk of the TLR3-TRIF signaling pathway is shown in purple; ubiquitination modifying enzymes that negatively regulate the pathway are in blue; other negative regulators, such as membrane proteins, adaptor proteins, and phosphatases, are in pink.
What RNA molecules activate TLR3 in viral infection?
TLR3 recognizes viral dsRNA and poly (I:C), but it is still unknown what RNA molecules activate TLR3 in viral infection and sterile inflammatory states.