o-Vanillin binds covalently to MAL/TIRAP Lys-210 but independently inhibits TLR2.

Toll-like receptor (TLR) innate immunity signalling protects against pathogens, but excessive or prolonged signalling contributes to a range of inflammatory conditions. Structural information on the TLR cytoplasmic TIR (Toll/interleukin-1 receptor) domains and the downstream adaptor proteins can help us develop inhibitors targeting this pathway. The small molecule o-vanillin has previously been reported as an inhibitor of TLR2 signalling. To study its mechanism of action, we tested its binding to the TIR domain of the TLR adaptor MAL/TIRAP (MALTIR). We show that o-vanillin binds to MALTIR and inhibits its higher-order assembly in vitro. Using NMR approaches, we show that o-vanillin forms a covalent bond with lysine 210 of MAL. We confirm in mouse and human cells that o-vanillin inhibits TLR2 but not TLR4 signalling, independently of MAL, suggesting it may covalently modify TLR2 signalling complexes directly. Reactive aldehyde-containing small molecules such as o-vanillin may target multiple proteins in the cell.

Toll-like receptor signaling and serum levels of interferon ß and lipopolysaccharide binding protein are related to abdominal obesity: a case-control study between metabolically healthy and metabolically unhealthy obese individuals.

It is still unclear whether toll-like receptor (TLR) signaling and serum levels of inflammatory markers in metabolically unhealthy abdominally obese (MUAO) are due to their obesity and/or their metabolic state. We hypothesized that abdominal obesity is an important mediator of the association of metabolic state with TLR signaling and serum inflammatory markers. Therefore, in this case-control study, we compared the expression levels of TLR4 and Toll/interleukin-1 receptor domain containing adaptor protein-inducing interferon ß (TRIF) and serum concentrations of interferon ß and lipoprotein-binding protein (LBP) in metabolically healthy abdominally obese (MHAO) and MUAO individuals. Basal blood samples from 65 abdominally obese subjects with waist circumference (WC) of at least 95 cm were collected to determine serum metabolic parameters, IFNß, and LBP. Those with 3 or more metabolic alterations were defined as MUAO (n = 34), and those having 2 or less were classified as MHAO (n = 31). Furthermore, messenger RNA (mRNA) was isolated from peripheral blood mononuclear cells. TLR4 and TRIF gene expression assay was performed using quantitative real-time polymerase chain reaction. There were significant differences in serum fasting blood sugar (P = .017), triglyceride (P < .001), cholesterol (P = .002), and low-density lipoprotein cholesterol (P = .034) between the MUAO and MHAO groups, whereas no significant difference was observed in the expression ratio of TLR4 and TRIF mRNA and serum levels of IFNß and LBP. However, a significant correlation was noticed between mRNA expression levels of TLR4 and TRIF (r = 0.50, P < .001) and serum IFNß and LBP (r = 0.70, P < .001). It is concluded that the expression levels of TLR4 and TRIF as well as serum IFNß and LBP are more related to abdominal obesity than to metabolic health.

Insight into Phosphatidylinositol-Dependent Membrane Localization of the Innate Immune Adaptor Protein Toll/Interleukin 1 Receptor Domain-Containing Adaptor Protein.

The toll/interleukin 1 receptor (TIR) domain-containing adaptor protein (TIRAP) plays an important role in the toll-like receptor (TLR) 2, TLR4, TLR7, and TLR9 signaling pathways. TIRAP anchors to phosphatidylinositol (PI) 4,5-bisphosphate (PIP2) on the plasma membrane and PI (3,4,5)-trisphosphate (PIP3) on the endosomal membrane and assists in recruitment of the myeloid differentiation primary response 88 protein to activated TLRs. To date, the structure and mechanism of TIRAP's membrane association are only partially understood. Here, we modeled an all-residue TIRAP dimer using homology modeling, threading, and protein-protein docking strategies. Molecular dynamics simulations revealed that PIP2 creates a stable microdomain in a dipalmitoylphosphatidylcholine bilayer, providing TIRAP with its physiologically relevant orientation. Computed binding free energy values suggest that the affinity of PI-binding domain (PBD) for PIP2 is stronger than that of TIRAP as a whole for PIP2 and that the short PI-binding motif (PBM) contributes to the affinity between PBD and PIP2. Four PIP2 molecules can be accommodated by distinct lysine-rich surfaces on the dimeric PBM. Along with the known PI-binding residues (K15, K16, K31, and K32), additional positively charged residues (K34, K35, and R36) showed strong affinity toward PIP2. Lysine-to-alanine mutations at the PI-binding residues abolished TIRAP's affinity for PIP2; however, K34, K35, and R36 consistently interacted with PIP2 headgroups through hydrogen bond (H-bond) and electrostatic interactions. TIRAP exhibited a PIP2-analogous intermolecular contact and binding affinity toward PIP3, aided by an H-bond network involving K34, K35, and R36. The present study extends our understanding of TIRAP's membrane association, which could be helpful in designing peptide decoys to block TLR2-, TLR4-, TLR7-, and TLR9-mediated autoimmune diseases.

S100A proteins as molecular targets in the ocular surface inflammatory diseases.

The S100 proteins are calcium-binding proteins that are exclusively expressed in vertebrates, where they interact with enzymes, cytoskeletal proteins, receptors, transcription factors, and nucleic acids to regulate proliferation, differentiation, apoptosis, inflammation, cell migration, energy metabolism, and Ca(2+) homeostasis. In this review, we focus on the S100A8 and S100A9 members of the family that are involved in the regulation of neutrophil chemotaxis and inflammation related to ocular surface diseases such as dry eye, meibomian gland dysfunction, pterygium, and corneal neovascularization. In our previous studies, we have found that the levels of S100A8 and S100A9 were elevated in these inflammatory ocular diseases. For instance, S100A8 and A9 were found to be upregulated in pterygium tissues at both transcript and protein levels. These findings are consistent with the role of S100A8 and S100A9 proteins in activating the innate immune system in the eye via Toll-like receptors (TLRs) and altering the immune tolerance of the eye-associated lymphoid system. Recently, use of S100A8-targeting antibody has shown promising results in targeting corneal neovascularization. Injection of S100A8 has been shown to inhibit eosinophilic infiltration and thus may have potential therapeutic implications in allergic diseases.

Research on the association of TIRAP coding region polymorphism with susceptibility to tuberculosis in Chinese Han population / 中华微生物学和免疫学杂志

Objective To detect specific polymorphisms in Toll-interleukin 1 receptor domain containing adaptor protein(TIRAP) coding region for Chinese Han population, and verify whether they are associated with susceptibility to tuberculosis. Methods Search TIRAP polymorphisms by sequencing in small sample; detect single nucleotide polymorphism(SNP) by ligase detection reaction technique in large sample; analyze whether polymorphisms are related to tuberculosis by statistic methods. Results Four polymorphisms were present in the TIRAP coding region. 394A had higher frequencies in the tuberculosis(TB)group than the control. But allelic and genotypic analysis showed that there were no significant difference in statistic between TB patients and controls(P>0.05). The SNP G164A mutation related with TB patient's condition. Comparing to controls, retreatment patients' allelic frequencies had significant difference in statistic(P<0.05), sputum positive patients and lung cavitation patients had lower 164A frequencies. Conclusion TIRAP coding region polymorphisms may be risk factors for TB occurrence and development in Chinese Han population.