MyD88 adaptor-like D96N is a naturally occurring loss-of-function variant of TIRAP

Toll-Like Receptors and Cancer Division, German Cancer Research Center, Heidelberg, Germany.
The Journal of Immunology (Impact Factor: 4.92). 02/2010; 184(6):3025-32. DOI: 10.4049/jimmunol.0901156
Source: PubMed


Signals elicited by TLRs following the detection of microbes are integrated and diversified by a group of four cytoplasmic adaptor molecules featuring an evolutionarily conserved Toll/IL-1R signaling domain. Single nucleotide polymorphisms (SNPs) in TLRs and their adaptor molecules have been shown to influence susceptibility to a range of infectious and other diseases. The adaptor MyD88 adaptor-like (Mal)/Toll/IL-1R-containing adaptor protein is involved in TLR2 and 4 signal transduction by recruiting another adaptor molecule, MyD88, to the plasma membrane. In this study, we used naturally occurring variants of Mal as tools to study the molecular biology of Mal in more detail in cellular model systems and to thereby identify functionally interesting variants whose corresponding nonsynonymous SNPs might be of further epidemiological interest. Of seven reported variants for Mal, we found Mal D96N associated with reduced NF-kappaB signaling and cytokine production after overexpression in HEK293 and Huh-7 cells. The D96N mutation prevented Mal from recruiting its signaling partner MyD88 to the plasma membrane and altered posttranslational modification of Mal. These findings led us to investigate the frequency of heterozygosity for the corresponding SNP rs8177400 in a Caucasian case-control study on the etiology of lymphoma, a disease in which TLRs have been implicated. Although rs8177400 did not modify lymphoma risk in general, its frequency of heterozygosity was accurately determined to 0.97%. Our data add rs8177400 (D96N) to the list of functionally important variants of Mal and warrant further research into its immunological, epidemiological, and diagnostic relevance.

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Available from: Andriy V Kubarenko
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    • "co-immunoprecipitation studies and computer modeling data (Nagpal et al., 2009; George et al., 2010) revealed that this variation results in conformation changes in the MyD88 binding site and thus the TIRAP G286A variant is unable to interact with MyD88, a prerequisite for downstream signaling to activate the responses to Mtb. These facts lead us to suggest that the 286A allele is a risk factor for increased susceptibility to TB. "
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    ABSTRACT: Toll-interleukin 1 receptor (TIR) domain containing adaptor protein (TIRAP; also known as MAL) is an essential adaptor molecule in Toll-like receptor signaling, involved in activating the innate immune response during infection. Genetic variations in the TIRAP gene may influence human susceptibility to infectious disease. To date, in the Chinese population, a possible predisposition of TIRAP gene variants to tuberculosis has not been reported. We investigated whether TIRAP gene polymorphisms are associated with the development of tuberculosis in a Chinese population. We investigated all the single-nucleotide polymorphisms (SNPs) within the TIRAP exon 5 in a case-control study of 212 patients with tuberculosis and 215 controls in a Chinese population. Genotyping was performed to identify the polymorphisms of TIRAP gene by PCR-DNA sequencing method. Haplotypes for the TIRAP gene variants were constructed using Haplo view version 4.2. Six polymorphisms of the SNPs listed in the National Center for Biotechnology Information database were detected in these Chinese tuberculosis patients. It was found that both the frequency of the 286A allele (odds ratio (OR) = 13.37; 95% confidence interval (CI) = 0.75-238.3; P < 0.01) and the frequency of 286AG genotype (OR = 13.57; 95%CI = 0.76-242.5; P < 0.01) were significantly higher in patients than in healthy controls. However, two other SNPs, C539T and C558T, reported to be associated with tuberculosis in other populations, were found not to be associated with tuberculosis in this Chinese population. We conclude that TIRAP G286A (D96N) polymorphism is associated with susceptibility to tuberculosis and may be a new risk factor for the development of tuberculosis in China.
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