Physical contact between lipopolysaccharide and Toll-like receptor 4 revealed by genetic complementation

Poltorak, Alexander; Ricciardi‐Castagnoli, Paola; Citterio, Stefania; Beutler, Bruce

doi:10.1073/pnas.040565397

Cited by 396 publications

(266 citation statements)

References 33 publications

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“…This has been shown by genetic means (7,45), by Ab blockade of TLR4 (9), and by demonstration that species-specific variation in LPS structures recognition can be reproduced by transfection of cell lines with TLR4 clones from that species (12). By contrast, LPS responses of TLR2 knockout animals appear normal (6).…”

Section: Discussionmentioning

confidence: 99%

Evidence for an Accessory Protein Function for Toll-Like Receptor 1 in Anti-Bacterial Responses

Wyllie

Kiss-Tóth

Visintin

et al. 2000

The Journal of Immunology

245

149

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Members of the Toll-like receptor (TLR) family are components of the mammalian anti-microbial response, signaling with a domain closely related to that of IL-1 receptors. In this report the expression and function of TLR1, a TLR of unknown function, are examined. TLR1 is expressed by monocytes, as demonstrated using a novel mAb. Monocytes also express TLR2. TLR1 transfection of HeLa cells, which express neither TLR1 nor TLR2, was not sufficient to confer responsiveness to several microbial extracts. However, cotransfection of TLR1 and TLR2 resulted in enhanced signaling by HeLa cells to soluble factors released from Neisseria meningitidis relative to the response with either TLR alone. This phenomenon was also seen with high concentrations of some preparations of LPS. The N. meningitidis factors recognized by TLR1/TLR2 were not released by N. meningitidis mutant in the LpxA gene. Although LpxA is required for LPS biosynthesis, because cooperation between TLR1 and TLR2 was not seen with all LPS preparations, the microbial component(s) TLR1/2 recognizes is likely to be a complex of LPS and other molecules or a compound metabolically and chemically related to LPS. The functional IL-1R consists of a heterodimer; this report suggests a similar mechanism for TLR1 and TLR2, for certain agonists. These data further suggest that mammalian responsiveness to some bacterial products may be mediated by combinations of TLRs, suggesting a mechanism for diversifying the repertoire of Toll-mediated responses.

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Section: Discussionmentioning

confidence: 99%

Evidence for an Accessory Protein Function for Toll-Like Receptor 1 in Anti-Bacterial Responses

Wyllie

Kiss-Tóth

Visintin

et al. 2000

The Journal of Immunology

245

149

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“…These concentrations of flagellin are within the physiological range as during systemic infection serum flagellin levels can reach concentrations of up to 1.5 g/ml within 8 h of infection (Eaves-Pyles et al, 2001). Transfection of a dominant-negative (Poltorak et al, 1998), but this defect is restored by stable transfection with a functional mouse TLR4 cDNA (Poltorak et al, 2000). c TLR5 in BMDCs and C3H/HeJ cells is non-functional.…”

Section: Functional Analysis Of Tlr2 Tlr4 and Tlr5 In Mic Cl2 Cellsmentioning

confidence: 99%

“…The following cell lines were routinely grown in 25 cm 2 tissue culture flasks in 5 ml of DMEM with 10% fetal calf serum (FCS): human embryonic kidney (HEK293) cells, the murine macrophage cell lines J774.1, C3H/HeJ (TLR4-deficient) and C3H/HeJ stably transfected with mTLR4 (Poltorak et al, 2000), and HeLa cells (clone 57A) stably transfected with an NF-B luciferase reporter construct (Rodriguez et al, 1999).…”

Section: Cell Culturesmentioning

confidence: 99%

Ligand-induced differential cross-regulation of Toll-like receptors 2, 4 and 5 in intestinal epithelial cells

Aubel

Keestra

Krooshoop

et al. 2007

Molecular Immunology

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Toll-like receptors (TLR) 2, TLR4 and TLR5 are primary mucosal sensors of microbial patterns. Dissection of the cross-talk between TLRs in intestinal cells has thus far been hampered by the lack of functional TLR2 and TLR4 in in vitro model systems. Here we report that the mouse intestinal epithelial cell line mIC cl2 expresses these TLRs and that receptor expression and function are regulated by environmental TLR stimuli. Our results show that stimulation of TLR5 by bacterial flagellin resulted in upregulated TLR2 and TLR4 mRNA and concomitant sensitization of the cells for subsequent TLR2 (Pam 3 CSK 4 ) and TLR4 (LPS) stimulation. Exposure to low amounts of either Pam 3 CSK 4 or LPS in turn downregulated TLR5 mRNA and attenuated subsequent flagellin-mediated NF-B activation, pointing to a negative feedback mechanism. Pam 3 CSK 4 and LPS also downregulated TLR4 mRNA but upregulated TLR2 mRNA and sensitized cells for subsequent TLR2 stimulation. Inhibition of the phosphatidylinositol-3-kinase/Akt pathway only affected LPS-mediated TLR cross-talk indicating that differential TLR cross-regulation was conferred via different mechanisms. Together, our results demonstrate that the expression and function of TLR in intestinal cells are highly dynamic and tightly regulated in response to encountered bacterial stimuli.

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“…Among the most vexing issues is the mechanism by which TLRs specifically recognize their ligands. In the absence of definitive experimental data, several alternative models have been proposed, including direct physical contact between the microbial ligand and TLR, 77 formation of a macromolecular complex including ligand, adaptor molecule(s) and TLR(s), or generation of endogenous ligands in response to infection (analogous to the system in Drosophila) that bind and activate TLRs. Recognition of endogenous ligands by TLRs is also an area of active investigation due to its potential relevance to autoimmune diseases, noninfectious inflammatory disorders, and elimination of neoplastic or damaged cells.…”

Section: Future Directionsmentioning

confidence: 99%

Toll-like receptors and their role in experimental models of microbial infection

2003

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Effective host defense against microbial infection depends upon prompt recognition of pathogens, activation of immediate containment measures, and ultimately the generation of a specific and definitive adaptive immune response. The innate immune system of the host is responsible for providing constant surveillance against infection; when confronted by pathogens it deploys a series of rapidly acting antimicrobial effectors while simultaneously instructing the adaptive immune system as to the nature and context of the infectious threat. Pathogen recognition and activation of innate immunity is mediated by members of the Toll-like receptor (TLR) family through detection of conserved microbial structures that are absent from the host. Experimental models of infection using TLR-deficient mice, as well as limited human studies, have clearly demonstrated the critical role of TLRs in host defense against most major groups of mammalian pathogens.

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Physical contact between lipopolysaccharide and Toll-like receptor 4 revealed by genetic complementation

Cited by 396 publications

References 33 publications

Evidence for an Accessory Protein Function for Toll-Like Receptor 1 in Anti-Bacterial Responses

Evidence for an Accessory Protein Function for Toll-Like Receptor 1 in Anti-Bacterial Responses

Ligand-induced differential cross-regulation of Toll-like receptors 2, 4 and 5 in intestinal epithelial cells

Toll-like receptors and their role in experimental models of microbial infection

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