Toll-like Receptor-2 Mediates Treponema Glycolipid and Lipoteichoic Acid-induced NF-κB Translocation

Abstract

Recently Toll-like receptors (TLRs) have been found to be involved in cellular activation by microbial products, including lipopolysaccharide, lipoproteins, and peptidoglycan. Although for these ligands the specific transmembrane signal transducers TLR-4, TLR-2, or TLR-2 and -6 have now been identified, the molecular basis of recognition of lipoteichoic acids (LTAs) and related glycolipids has not been completely understood. In order to determine the role of TLRs in immune cell activation by these stimuli, experiments involving TLR-2-negative cell lines, TLR-expression plasmids, macrophages from TLR-4-deficient C3H/HeJ-mice, and inhibitory TLR-4/MD-2 antibodies were performed. Glycolipids from Treponema maltophilum and Treponema brennaborense, as well as highly purified LTAs from Staphylococcus aureus and Bacillus subtilis exhibited TLR-2 dependence in nuclear factor B activation and cytokine induction; however, T. brennaborense additionally appeared to signal via TLR-4. Fractionation of the T. brennaborense glycolipids by hydrophobic interaction chromatography and subsequent cell stimulation experiments revealed two peaks of activity, one exhibiting TLR-2-, and a second TLR-4-dependence. Furthermore, we show involvement of the signaling molecules MyD88 and NIK in cell stimulation by LTAs and glycolipids by dominant negative overexpression experiments. In summary, the results presented here indicate that TLR-2 is the main receptor for Treponema glycolipid and LTA-mediated inflammatory response.

Treponemal glycoconjugate inhibits Toll‐like receptor ligand‐induced cell activation by blocking LPS‐binding protein and CD14 functions

“…Taken together, we found that Tm-Gp, in contrast to the extracts of small-sized Treponema species [18,19], does not activate host cells but is capable of inhibiting intracellular signaling induced by LPS and PGN by blocking the function of LBP and/or CD14. In such immunomodulating active components, marginal variations of the detailed structures, such as the variations of acylation and phosphorylation patterns in the lipid A of LPS, are well-known to be closely related to their effects [43].…”

“…Glycolipids from small-sized Treponema species have been shown to exhibit activating ability upon host cells [18,19]. In contrast, Tm-Gp exhibited no activation of Mono Mac 6 cells at the highest concentration tested (100 ?…”

“…Since glycolipids from other Treponema species demonstrate TLR2-and/or TLR4-dependent cell activation [18,19], we used a luciferase assay to examine the TLR2-and TLR4-dependent activation of Tm-Gp in Ba/F3 cells stably expressing p55Ig ‹ Luc, an NF-‹ B-dependent luciferase reporter construct, alone (Ba/ ‹ B) or in combination with murine TLR2 (Ba/mTLR2) or murine TLR4/ MD-2 (Ba/mTLR4/mMD-2). All cell lines responded normally to stimulators such as PGN, LPS, and TNF- § , while Tm-Gp failed to induce NF-‹ B activation ( Fig.…”

“…New types of glycolipids were recently extracted from small-sized Treponema species including T. denticola, T. maltophilum, and T. brennaborense [17,18]. Glycolipids from T. maltophilum exhibit TLR2-dependence during NF-‹ B activation and cytokine production, while T. brennaborense glycolipids have been shown to contain TLR2-and TLR4-stimulating fractions [18,19]. However, a carbohydrate-containing component from intermediate-sized Treponema species has not been described.…”

Gene expression profiling in human gastric mucosa infected with Helicobacter pylori

“…These genes include TLR2 and LY96. TLR2 is known to be upregulated in response to peptidoglycan, lipoteichoic acid, 29 and bacterial lipoproteins 30 or LPS. TLR4 is activated by the LPS of Gram-negative bacteria 31 and LY96 is a protein associated with this receptor.…”