rs3796508 — TLR6 Val327Met

Missense variant substituting valine with methionine at position 327 of TLR6, predicted damaging by SIFT and PolyPhen; the Met327 allele is rare globally but reaches 6% in East Asian populations

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TLR6 Val327Met — A Rare Damaging Variant in the Mycoplasma Alarm System

Every time your immune cells encounter diacylated lipopeptides — the molecular calling-card of mycoplasma, staphylococcal lipoproteins, and certain gram-positive bacteria — they rely on a precise molecular handshake between Toll-like Receptor 2 (TLR2)11 Toll-like Receptor 2 (TLR2)
TLR2 is the central scaffold for bacterial lipopeptide sensing; it forms heterodimers with either TLR1 (for triacylated lipopeptides) or TLR6 (for diacylated lipopeptides), activating NF-κB and driving TNF-α, IL-6, and IL-12 production and TLR622 TLR6
Toll-like Receptor 6, encoded at chromosome 4p14; forms obligate heterodimers with TLR2 and is distinguished from TLR1 by a blocked lipid channel that restricts ligand recognition to diacylated — not triacylated — lipopeptides. The rs3796508 Val327Met variant substitutes a structurally conservative valine with a bulkier, polar methionine at position 327 in TLR6's extracellular leucine-rich repeat (LRR) domain — a change that SIFT and PolyPhen independently predict to be damaging to protein function.

This variant is extremely rare in European populations (T allele ~0.2%) but reaches a frequency of approximately 6% in East Asian populations (gnomAD), making it clinically relevant primarily for individuals of East Asian ancestry. It has no ClinVar entry.

The Mechanism

The 2009 crystal structure of the TLR2/TLR6 heterodimer (Kang et al., Immunity 200933 Kang et al., Immunity 2009
PMID 19931471; first crystal structure of TLR2/TLR6 bound to diacylated lipopeptide; determined at 2.1 Å resolution) revealed the molecular basis for TLR6's unique specificity. Unlike TLR1, which accommodates a third fatty acid chain in an open lipid channel, TLR6 has its corresponding channel blocked by two conserved phenylalanines — physically preventing triacylated lipopeptide binding and enforcing diacylated specificity. When these phenylalanines are mutated, TLR2/TLR6 loses its diacyl-exclusivity. The compensating structural feature is a dimerization interface that is 80% larger than TLR2/TLR1, stabilising the heterodimer through extensive hydrophobic contacts in the absence of a full three-chain lipid anchor.

The Evidence

Compared to TLR6 Ser249Pro (rs5743810) — the more extensively studied variant in the same gene — rs3796508 Val327Met has a much smaller published literature, and no study has directly measured the impact of Met327 on TLR2/TLR6 heterodimer formation or NF-κB activation in primary cells. The evidence base is emerging and largely association-derived.

The most direct disease association comes from a Saudi Arabian colorectal cancer case-control study44 colorectal cancer case-control study
115 CRC cases, 102 healthy controls; genotyped by TaqMan assay by Semlali et al. (2019). In the global analysis, rs3796508 showed no significant association with CRC risk overall, but in subgroup analyses the Val/Met heterozygous genotype demonstrated a protective effect in males (OR=0.095, p=0.034) and in individuals over 57 years55 protective effect in males (OR=0.095, p=0.034) and in individuals over 57 years
these are suggestive findings from a small study (n=217) and require independent replication. The same paper noted that TLR6 expression was significantly reduced in colon cancer tissue versus normal colon (p<0.001), positioning TLR6 as a potential tumour-suppressive innate immune sensor in the gut.

In an inflammatory context, a 2026 Chinese Han study (Wang et al., Sci Rep 202666 Wang et al., Sci Rep 2026
PMID 41663697; 992 AR patients versus 992 healthy controls; primary focus on NFKB1 variants with TLR6 rs3796508 as a secondary finding) found that rs3796508 contributed to increased allergic rhinitis (AR) risk specifically in women.

Practical Implications

The evidence for rs3796508 is emerging and requires cautious interpretation. The variant is predicted damaging by two independent computational tools, which provides a biological prior for functional effects on TLR2/TLR6 signalling. However, no functional cellular studies have directly measured NF-κB output, cytokine production, or heterodimer formation efficiency in cells carrying the Met327 allele — these experiments are needed to validate computational predictions.

For carriers — predominantly individuals of East Asian descent (~6%) where the variant reaches population significance — the actionable implications centre on monitoring contexts where TLR2/TLR6 competence matters: respiratory allergy (sex-specific AR risk increase in women).

The TLR2/TLR6 pathway also serves as a critical interface between commensal gut bacteria and mucosal immune regulation. The beneficial gut bacterium Faecalibacterium prausnitzii77 Faecalibacterium prausnitzii
a major short-chain fatty acid producer and key modulator of gut immune homeostasis; low in IBD patients signals through TLR2/TLR6 to prime regulatory T cells.

Interactions

TLR6 operates exclusively through TLR2 (rs5743708). The TLR2 R753Q variant independently impairs TLR2 signalling from the intracellular TIR domain. TLR1 (rs5743618) handles the triacylated lipopeptide arm of pattern recognition and operates independently of TLR6.

Genotype Interpretations

What each possible genotype means for this variant.

CC Standard TLR6 Function Normal

Common TLR6 Val327 homozygote with standard diacylated lipopeptide sensing

You carry two copies of the valine-327 allele at TLR6 — the common form shared by approximately 98.7% of people globally. Your TLR2/TLR6 heterodimer is predicted to assemble normally and to respond to diacylated lipopeptides from mycoplasma and gram-positive bacteria at baseline efficiency. No disease associations have been identified for this genotype at rs3796508.

CT Val/Met TLR6 Heterozygote Intermediate

One Met327 allele — predicted damaging to TLR2/TLR6 heterodimer signaling; emerging associations with reduced innate sensing efficiency

The two published disease associations for this variant operate in apparently opposite directions — protective against colorectal cancer (in males) but potentially risk-increasing for allergic rhinitis (in females). These apparently contradictory findings may reflect genuine sex-specific effects. Both findings come from small studies and neither has been independently replicated — they define the hypothesis-generating stage of evidence for this variant.

No functional cell-based data yet exists measuring NF-κB activation, cytokine output, or TLR2/TLR6 heterodimer stability in Met327 carrier cells directly.

TT Met/Met TLR6 Homozygote Reduced

Two Met327 alleles — both copies of TLR6 carry the damaging variant, with predicted significant reduction in TLR2/TLR6 heterodimer signaling

This genotype is sufficiently rare (estimated <1 in 1,000) that no published study has reported a TT homozygote sub-analysis. All current associations derive from CT heterozygote data.