The molecular structure of the Toll-like receptor 3 ligand-binding domain

Bell, Jessica K.; Botos, Istvan; Hall, Pamela R.; Askins, Janine; Shiloach, Joseph; Segal, David M.; Davies, David R.

doi:10.1073/pnas.0505077102

Cited by 347 publications

(287 citation statements)

References 44 publications

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“…The human TLRECDs contain 19 -25 predicted LRRs capped on either end by characteristic N-and C-terminal structures (20). The recently solved crystal structure of the TLR3 ECD reveals a solenoid structure, strongly suggesting that the ECDs of all TLR family members exhibit a classic solenoid structure (21,22).…”

Section: Discussionmentioning

confidence: 99%

The Polymorphism P315L of Human Toll-Like Receptor 1 Impairs Innate Immune Sensing of Microbial Cell Wall Components

Omueti

Mazur²,

Thompson³

et al. 2007

The Journal of Immunology

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As a pattern recognition receptor, TLR1 mediates innate immune responses to a variety of microbial cell wall components including bacterial lipoproteins. We have previously shown that the central region of the extracellular domain of human TLR1, comprising leucine-rich repeat (LRR) motifs 9–12, is required for the sensing of bacterial lipopeptides. In this study, we have investigated three nonsynonymous single nucleotide polymorphisms (SNPs) located in this region of TLR1 by generating these variants and examining receptor function. We have found that a variant of TLR1 based upon the SNP P315L, located in the loop of LRR motif 11 (LRR11), is greatly impaired in mediating responses to lipopeptides and a variety of other bacterial agonists for this receptor. Despite normal cell surface expression, the P315L variant also fails to bind to GD2.F4, a commonly used anti-TLR1 mAb. Although a number of amino acid substitutions at position 315 impair receptor function, the leucine substitution has the strongest deleterious effect. GD2.F4 inhibits agonist-induced activation of TLR1, supporting a crucial role for the loop of LRR11 in receptor function. These results also suggest that the P315L SNP may predispose certain individuals to infectious diseases for which the sensing of microbial cell components by TLR1 is critical to innate immune defense.

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Section: Discussionmentioning

confidence: 99%

The Polymorphism P315L of Human Toll-Like Receptor 1 Impairs Innate Immune Sensing of Microbial Cell Wall Components

Omueti

Mazur²,

Thompson³

et al. 2007

The Journal of Immunology

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“…More than 30 years ago, it was postulated that 20 nt of an RNA duplex comprises the minimum binding region to an unknown dsRNA receptor that drives IFN production (34). Gel filtration studies (35) and cell culture experiments (36) have shown that 21-nt dsRNAs can bind and initiate TLR3 signaling, respectively. We showed previously by using flow cytometry that binding of 21-nt siRNAs to mouse retinal and choroidal cells is eliminated by deletion of Tlr3 or competition with soluble TLR3 or poly(I:C) (12).…”

Section: Discussionmentioning

confidence: 99%

Small interfering RNA-induced TLR3 activation inhibits blood and lymphatic vessel growth

Cho

Albuquerque

Kleinman

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

133

120

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Neovascularization in response to tissue injury consists of the dual invasion of blood (hemangiogenesis) and lymphatic (lymphangiogenesis) vessels. We reported recently that 21-nt or longer small interfering RNAs (siRNAs) can suppress hemangiogenesis in mouse models of choroidal neovascularization and dermal wound healing independently of RNA interference by directly activating Toll-like receptor 3 (TLR3), a double-stranded RNA immune receptor, on the cell surface of blood endothelial cells. Here, we show that a 21-nt nontargeted siRNA suppresses both hemangiogenesis and lymphangiogenesis in mouse models of neovascularization induced by corneal sutures or hindlimb ischemia as efficiently as a 21-nt siRNA targeting vascular endothelial growth factor-A. In contrast, a 7-nt nontargeted siRNA, which is too short to activate TLR3, does not block hemangiogenesis or lymphangiogenesis in these models. Exposure to 21-nt siRNA, which we demonstrate is not internalized unless cell-permeating moieties are used, triggers phosphorylation of cell surface TLR3 on lymphatic endothelial cells and induces apoptosis. These findings introduce TLR3 activation as a method of jointly suppressing blood and lymphatic neovascularization and simultaneously raise new concerns about the undesirable effects of siRNAs on both circulatory systems.angiogenesis ͉ innate immunity ͉ lymphangiogenesis ͉ ischemia ͉ wound healing

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“…The effect of such mutations could be indirect by introducing a structural change in the TLR4 ectodomain such as changing the curvature, the overall twist (as opposed to the planarity described for the TLR3 ectodomain; Ref. 38), or the surface charge distribution.…”

Section: Discussionmentioning

confidence: 99%

Elucidation of the MD-2/TLR4 Interface Required for Signaling by Lipid IVa

Walsh

Gangloff

Monie

et al. 2008

The Journal of Immunology

115

137

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LPS signals through a membrane bound-complex of the lipid binding protein MD-2 and the receptor TLR4. In this study we identify discrete regions in both MD-2 and TLR4 that are required for signaling by lipid IVa, an LPS derivative that is an agonist in horse but an antagonist in humans. We show that changes in the electrostatic surface potential of both MD-2 and TLR4 are required in order that lipid IVa can induce signaling. In MD-2, replacing horse residues 57-66 and 82-89 with the equivalent human residues confers a level of constitutive activity on horse MD-2, suggesting that conformational switching in this protein is likely to be important in ligand-induced activation of MD-2/TLR4. We identify leucine-rich repeat 14 in the C terminus of TLR4 as essential for lipid IVa activation of MD-2/TLR4. Remarkably, we identify a single residue in the glycan-free flank of the horse TLR4 solenoid that confers the ability to signal in response to lipid IVa. These results suggest a mechanism of signaling that involves crosslinking mediated by both MD-2-receptor and receptor-receptor contacts in a model that shows striking similarities to the recently published structure ( L ipopolysaccharide molecules are complex glycolipids that form the outer layer of the outer membrane of Gramnegative bacteria (1). The lipid A domain of LPS is responsible for cellular activation and consists of a disaccharide to which various substituents, including acyl chains of variable length and number, are attached (2). Escherichia coli lipid A is usually hexa-acylated whereas a tetra-acylated lipid A, lipid IVa, is also produced by E. coli as an intermediate in the lipid A biosynthetic pathway (2). Lipid IVa was originally identified as an inhibitor at the human LPS receptor and was considered a candidate to be developed for clinical use as an endotoxin antagonist. Lipid A signals to host cells through a transmembrane complex consisting of the lipid-binding protein MD-2 and the type 1 receptor TLR4 (1, 3-5). MD-2 is probably the key player in lipid A recognition whereas TLR4, unlike other TLRs, is thought not to participate directly in lipid A binding (5).LPS and lipid A are believed to be recognized by MD-2 following transfer from CD14, which does not participate in the signaling complex (6). Contrary to expectations, ligand binding does not significantly alter the overall structure of MD-2 (7, 8), but the ligands used in the crystallographic studies (lipid IVa and eritoran) are antagonists to human MD-2/TLR4, so it remains unclear what happens to MD-2 and TLR4 upon agonist binding and activation. Active ligands such a lipid A (9) presumably induce structural rearrangements that trigger dimerization of TLR4 and initiate signal transduction (7, 10 -13). Mutagenesis studies identified amino acids 79 -83, 121-124, 125-129 (12), K128, and K132 of human MD-2 as being important in lipid A binding (13), but in the crystal structure of the inactive MD-2-lipid IVa complex, only residues I46, L78, I80, and F121-I124 contact the ligand. The other residues...

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The molecular structure of the Toll-like receptor 3 ligand-binding domain

Cited by 347 publications

References 44 publications

The Polymorphism P315L of Human Toll-Like Receptor 1 Impairs Innate Immune Sensing of Microbial Cell Wall Components

The Polymorphism P315L of Human Toll-Like Receptor 1 Impairs Innate Immune Sensing of Microbial Cell Wall Components

Small interfering RNA-induced TLR3 activation inhibits blood and lymphatic vessel growth

Elucidation of the MD-2/TLR4 Interface Required for Signaling by Lipid IVa

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