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The Toll-like receptor 4 polymorphism Asp299Gly but not Thr399Ile influences TLR4 signaling and function.

ABSTRACT: The common, co-segregating Toll-like receptor 4 (TLR4) non-synonymous single nucleotide polymorphisms (SNPs), Asp299Gly and Thr399Ile, are associated with hyporesponsiveness to inhaled lipopolysaccharide (LPS) and increased susceptibility to Gram negative pathogens in humans. The purpose of this study was to identify the relative contributions of the Asp299Gly and the Thr399Ile variants in inhibiting the function of TLR4. 293/hMD2-CD14 cell line was transfected with lentiviral constructs containing human wild type (WT) TLR4-EGFP or TLR4-EGFP with Asp299Gly, Thr399Ile or Asp299Gly/Thr399Ile complementary DNA (cDNA). Multiple stable cell lines were established for each construct: three for WT TLR4, Asp299Gly, and Thr399Ile, and only two for Asp299Gly/Thr399Ile mutants and EGFP control. We did not observe a significant effect of polymorphisms on cell surface and intracellular TLR4 expression nor were there any significant differences in TLR4 and EGFP protein levels assessed by Western blotting and confocal microscopy among the multiple cell lines of each of the constructs. All cell lines had a dose-dependent responsiveness to LPS stimulation. However, compared to the WT TLR4, cells expressing TLR4 with Asp299Gly but not Thr399Ile polymorphism produced significantly less (P<0.05) IL-8 following LPS stimulation. Similarly, cells expressing TLR4 Asp299Gly but not Thr399Ile allele had significantly lower percentage of phosphorylated and total NF-?B P65 following LPS stimulation. While we could not do statistics on the Asp299Gly/Thr399Ile group, we observed a reduced responsiveness to LPS compared to WT TLR4. Taken together, we observed that the TLR4 Asp299Gly variant, but not the Thr399Ile variant, is responsible for impaired responsiveness of TLR4 to LPS and corresponding activation of NF-?B.

SUBMITTER: Long H

PROVIDER: S-EPMC3973565 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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The Toll-like receptor 4 polymorphism Asp299Gly but not Thr399Ile influences TLR4 signaling and function.

Long Huaicong H O'Connor Brian P BP Zemans Rachel L RL Zhou Xiaofang X Yang Ivana V IV Schwartz David A DA

PloS one 20140402 4

The common, co-segregating Toll-like receptor 4 (TLR4) non-synonymous single nucleotide polymorphisms (SNPs), Asp299Gly and Thr399Ile, are associated with hyporesponsiveness to inhaled lipopolysaccharide (LPS) and increased susceptibility to Gram negative pathogens in humans. The purpose of this study was to identify the relative contributions of the Asp299Gly and the Thr399Ile variants in inhibiting the function of TLR4. 293/hMD2-CD14 cell line was transfected with lentiviral constructs contain ...[more]

PMID: 24695807

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Project description:ObjectiveDifferent studies have shown an association of TLR4 polymorphisms with susceptibility/resistance to malaria disease. In the current immunogenetic study, we assessed the TLR4 genotypes formed by the two common single nucleotide polymorphisms (SNPs) (Asp299Gly and Thr399Ile) in the co-segregate state in Baluchi Plasmodium falciparum infected and healthy populations from malaria hypoendemic areas of Iran. The study was performed to evaluate the distribution and correlation of TLR4 co-segregating genotypes in patients with mild malaria. Moreover, the frequency of these genotypes was compared with reported results from other populations in similar or contrasting malaria settings around the world.Materials and methodsIn this case control study, the presence of 2 SNPs in the TLR4 gene (Asp299Gly and Thr399Ile) were analyzed in 350 Baluchi patients with mild malaria and 350 unrelated healthy controls by using polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) techniques followed by sequencing analysis. Differences in the TLR4 co-segregate genotype frequencies among the studied group were determined by Fisher's exact test.ResultsAlthough the distribution of the two commonly co-segregating TLR4 genotypes presented a diverse and distinct pattern in the Baluchi population, no significant difference was detected between the cases and controls (p>0.05). A lower frequency of TLR4 Asp299Gly/Thr399Thr was observed in Baluchis with mild malaria compared to African populations (p< 0.05).ConclusionDifferences in the co-segregation patterns of TLR4 Asp299Gly/Thr399Ile genotypes in the Baluchi population compared to other malaria endemic populations may suggest different local evolutionary pressure on TLR4 polymorphisms by malaria in this region. The higher frequency of Asp299Gly/Thr399Ile genotypes among the Baluchi population compared with the African population (p< 0.05) which suffers from a larger number of severe cases might suggest that this genotype has a role in protecting against severe malaria. These findings are useful for further understanding the pathogenesis of severe malaria.

Dataset Information

The Toll-like receptor 4 polymorphism Asp299Gly but not Thr399Ile influences TLR4 signaling and function.

Publications

The Toll-like receptor 4 polymorphism Asp299Gly but not Thr399Ile influences TLR4 signaling and function.

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