{"gene":"TLR2","run_date":"2026-06-10T10:51:55","timeline":{"discoveries":[{"year":1998,"finding":"TLR2 (cloned as TIL4) activates NF-κB signaling when expressed in cells, establishing it as a functional signaling receptor of the Toll/IL-1R family involved in immune modulation.","method":"Functional NF-κB activation assay in transfected cells","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single lab, single functional readout (NF-κB activation), foundational cloning paper","pmids":["9596645"],"is_preprint":false},{"year":2001,"finding":"TLR2 activation by peptidoglycan and micrococci induces IL-8 transcription through a defined signaling cascade: TLR2 → MyD88 → IRAK → TRAF6/TRAF2 → NIK → IKK → NF-κB. Dominant-negative forms of each component blocked NF-κB activation and IL-8 gene induction.","method":"Dominant-negative mutant overexpression, NF-κB reporter assay, IL-8 gene expression in HEK293 cells expressing TLR2 and CD14","journal":"Infection and immunity","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple dominant-negative constructs for each pathway component, replicated with two stimuli, consistent with parallel findings in PMID:11521063","pmids":["11254583","11521063"],"is_preprint":false},{"year":2001,"finding":"TLR2 and TLR4 agonists both activate NF-κB and MAPK family members in dendritic cells but produce distinct cytokine/chemokine profiles: TLR2 stimulation fails to induce IL-12 p70 and IP-10 but preferentially induces IL-12 p40 homodimer, IL-8, and IL-23; phosphatidylinositol 3-kinase and p38 MAPK are involved in TLR-mediated cytokine induction.","method":"Cytokine/chemokine gene transcription analysis, pharmacological inhibitors of PI3K and p38 MAPK in human dendritic cells stimulated with TLR2 or TLR4 agonists","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single lab, multiple cytokine readouts, pharmacological inhibitors confirming PI3K and p38 MAPK involvement","pmids":["11477091"],"is_preprint":false},{"year":2002,"finding":"TLR2 expression in HEK293 cells enables phosphorylation and activation of stress-activated MAP kinase p38 in response to bacterial lipoproteins and Gram-positive bacteria, demonstrated by in vitro kinase assay using ATF2 as substrate and MAP kinase-activated protein kinase activation.","method":"TLR2 transfection in HEK293 cells, in vitro p38 kinase assay with ATF2 substrate, MAP kinase-activated protein kinase activation assay","journal":"Journal of leukocyte biology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro kinase assay with defined substrate, single lab","pmids":["11867688"],"is_preprint":false},{"year":2003,"finding":"TLR1 and TLR2 form cotranslational heterodimeric complexes on the cell surface and in the cytosol (detected by confocal microscopy), and both the extracellular and intracellular (TIR) domains of each receptor are required for functional NF-κB signaling; the TIR domains constitute the critical intracellular TLR1-TLR2 interaction interface.","method":"Confocal microscopy of co-expressed tagged receptors, chimeric TLR analysis, cross-linking of surface receptors, NF-κB reporter assay, cytokine secretion from mononuclear cells","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (confocal colocalization, chimeric receptor epistasis, cross-linking, cytokine readout), rigorous dissection of domain requirements","pmids":["12975352"],"is_preprint":false},{"year":2003,"finding":"TLR2 activation in murine macrophages requires MyD88 but is independent of TLR4 or TLR6 for LM-induced macrophage activation (CD40/CD86 expression, TNF, NO secretion). LM also exerts a TLR2/TLR6/MyD88-independent inhibitory effect on LPS-activated macrophages.","method":"Macrophages from TLR2, TLR4, TLR6, and MyD88 knockout mice stimulated with mycobacterial lipomannans; cytokine measurement, CD40/CD86 surface expression","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genetic knockouts used to dissect pathway, dual (pro- and anti-inflammatory) functional phenotypes characterized","pmids":["15034058"],"is_preprint":false},{"year":2006,"finding":"TLR2 ligands activate Ca²⁺ release from intracellular stores in airway epithelial cells and macrophages via a pathway involving TLR2 phosphorylation by c-Src, recruitment of PI3K and phospholipase Cγ, and activation of IP3 receptors. Absence of TLR2 abolishes Ca²⁺ fluxes and proinflammatory NF-κB-dependent signaling.","method":"Biochemical and genetic approaches in airway epithelial cells and TLR2-deficient murine macrophages; Ca²⁺ flux measurement, kinase inhibition studies","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — TLR2 knockout controls plus biochemical pathway dissection (c-Src, PI3K, PLCγ, IP3R), single lab","pmids":["16818794"],"is_preprint":false},{"year":2007,"finding":"TLR2 directly triggers IFN-γ production, cell proliferation, and cell survival in mouse Th1 effector cells without TCR stimulation; these effects were absent in Th2 cells and depended on enhanced MAPK activation. No other TLRs tested replicated this effect in Th1 cells.","method":"TLR stimulation of sorted Th1/Th2 effector T cells; cytokine measurement, proliferation and survival assays, MAPK phosphorylation analysis in wild-type and TLR2-deficient cells","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined cell subsets, multiple readouts, TLR specificity controls, single lab","pmids":["17513716"],"is_preprint":false},{"year":2009,"finding":"Upon stimulation of the TLR2/TLR6 heterodimer with diacylated bacterial lipoproteins, the adaptor Mal directly interacts with the PI3K regulatory subunit p85α in an inducible fashion, driving PI3K-dependent Akt phosphorylation, PIP3 generation, and macrophage polarization. This pathway is MyD88-independent, and TLR2/1 does not require Mal or MyD88 for Akt phosphorylation, revealing heterodimer-specific adapter usage.","method":"Co-immunoprecipitation of Mal with p85α, Akt phosphorylation assays, PIP3 measurement, macrophage polarization assays, MyD88-deficient and Mal-deficient cells","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, multiple genetic knockout backgrounds, biochemical pathway endpoints, distinct TLR2/1 vs TLR2/6 specificity demonstrated","pmids":["19574958"],"is_preprint":false},{"year":2010,"finding":"TLR2 stimulation in keratinocytes triggers calcium-dependent release of the serine protease kallikrein 5; this was demonstrated using TLR2 overexpression, TLR2 ligand treatment, and analysis of TLR2-deficient mice, linking TLR2 to a critical pathogenic protease in rosacea.","method":"TLR2 overexpression in keratinocytes, TLR2 ligand stimulation, TLR2-deficient mouse analysis, calcium chelation, kallikrein 5 measurement","journal":"The Journal of investigative dermatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — TLR2 KO mice plus in vitro overexpression, calcium-dependence mechanistically established, single lab","pmids":["21107351"],"is_preprint":false},{"year":2011,"finding":"TLR2 stimulation in megakaryocytes activates NFκB, ERK-MAPK, and PI3K/Akt pathways, upregulates transcription factors GATA-1, NF-E2, and mTOR, increases DNA content and adhesion to extracellular matrix proteins, and promotes megakaryocyte maturation in a TLR2-dependent manner confirmed by TLR2 knockout mice.","method":"Pam3CSK4 stimulation of Meg-01 cells and mouse megakaryocytes; pathway inhibitors, gene/protein expression, TLR2-/- mice treated with Pam3CSK4","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — TLR2 KO validation, multiple biochemical readouts, single lab","pmids":["21454454"],"is_preprint":false},{"year":2012,"finding":"Phospholipase D2 (PLD2) and protein kinase C-η (PKC-η) act downstream of TLR2 (MyD88-dependent) to induce ABCA1 expression in macrophages; PLD2-generated phosphatidic acid is a key mediator of this effect.","method":"Pam3CSK4 stimulation, pathway inhibitors, MyD88-dependent signaling, direct diC8PA treatment in Raw264.7 macrophages; mRNA and protein quantification","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological and genetic dissection of downstream signaling, direct PA treatment as mechanistic proof, single lab","pmids":["23261454"],"is_preprint":false},{"year":2013,"finding":"In TLR2-mediated gastric tumourigenesis, MyD88 but not Mal/TIRAP is required; genetic ablation of Myd88 suppressed tumourigenesis with increased apoptosis and reduced proliferation, whereas Mal deficiency had no effect on tumour burden. Mal is thus dispensable for TLR2-promoted gastric tumour growth.","method":"Genetic epistasis using gp130F/F mouse model with Myd88 and Mal knockout; tumour histology, apoptosis, proliferation, and pathway activation analysis","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — dual genetic knockouts in defined cancer model, multiple phenotypic readouts, single lab","pmids":["23728346"],"is_preprint":false},{"year":2015,"finding":"TLR2 activation with Pam3CSK4 induces cell migration and invasion in rheumatoid arthritis synovial fibroblasts via β1-integrin binding and Rac1 activation, leading to cytoskeletal rearrangement and filopodia formation. Blocking β1-integrin inhibited Pam3CSK4-induced migration and invasion and Rac1 activation but not MMP-3 secretion.","method":"Transwell Matrigel invasion assay, Rac1 pull-down assay/Western blot, β1-integrin multiplex binding assay, F-actin immunofluorescence, anti-TLR2 mAb (OPN301) blocking, RA explant cultures","journal":"Arthritis research & therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays with blocking antibodies and receptor-specific readouts, single lab","pmids":["26055925"],"is_preprint":false},{"year":2015,"finding":"HCMV miR-UL112-3p directly targets TLR2 mRNA, reducing TLR2 protein levels and inhibiting TLR2/IRAK1/NFκB signaling. Down-regulation of endogenous TLR2 was confirmed by miR-UL112-3p mimic transfection, and was absent in cells infected with miR-UL112-3p-deficient HCMV mutants; miR-UL112-3p suppressed IL-1β, IL-6, IL-8, and NFκB-dependent luciferase activity upon TLR2 agonist stimulation.","method":"Luciferase reporter assay, miR mimic/siRNA transfection, HCMV miRNA-deficient mutant infection, immunoblot for TLR2 protein, NFκB reporter, IRAK1 phosphorylation, cytokine quantification","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches (reporter, miRNA mutant virus, siRNA equivalence, IRAK1 post-translational activation), mechanistically rigorous demonstration","pmids":["25955717"],"is_preprint":false},{"year":2016,"finding":"Differential adapter recruitment by TLR2 co-receptors: the D helix of TLR1 TIR domain is a MyD88 docking site, whereas the D helix of TLR6 TIR domain recruits TIRAP. Cell-permeable D-helix peptides from TLR1 or TLR6 selectively blocked co-immunoprecipitation of TLR2 with MyD88 or TIRAP respectively, without disrupting TLR2 co-receptor association.","method":"Cell-permeable TIR-domain peptides, co-immunoprecipitation of TLR2 with adapters TIRAP and MyD88, in vitro binding assays","journal":"Pathogens and disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP with blocking peptides, in vitro binding, mechanistic mapping of adapter docking sites, single lab","pmids":["27150837"],"is_preprint":false},{"year":2017,"finding":"TLR2 and TLR6 are required for platelet activation by oxidized phospholipids (oxPCCD36); oxPCCD36 induces formation of a CD36/TLR2/TLR6 complex in platelets and activates downstream signaling via TIRAP-MyD88-IRAK1/4-TRAF6, leading to integrin activation via the SFK-Syk-PLCγ2 pathway. TLR2 or TLR6 deficiency in ApoE-/- mice abrogated oxPCCD36-driven accelerated thrombosis.","method":"In vitro platelet activation assays, Co-IP of CD36/TLR2/TLR6 complex, genetic deletion of MyD88, TLR2, TLR6 in mice, intravital thrombosis studies in ApoE-/- mice","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP of receptor complex, multiple genetic knockouts, in vitro and in vivo thrombosis endpoints, defined signaling cascade","pmids":["28775078"],"is_preprint":false},{"year":2019,"finding":"Crystal structure of the synthetic TLR2/TLR1 agonist Diprovocim bound to TLR2 ectodomain revealed two Diprovocim molecules bound within the ligand-binding pocket formed between two TLR2 ectodomains, stabilized by extensive hydrophobic interactions and hydrogen-bonding. Diprovocim induced both TLR2/TLR1 heterodimers and TLR2 homodimers in vitro.","method":"Crystal structure determination of Diprovocim-TLR2 ectodomain complex, in vitro biophysical assays (heterodimer/homodimer formation), computational docking","journal":"Journal of medicinal chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with defined binding pocket, in vitro biophysical validation of dimerization, rigorous structural and functional characterization","pmids":["30829478"],"is_preprint":false},{"year":2019,"finding":"TLR2 activation induces IL-6 expression and shedding of soluble IL-6 receptor (sIL-6R) from monocytes via the metalloproteases ADAM10 and ADAM17, and the ERK cascade differentially regulates both IL-6 and sIL-6R generation, triggering IL-6 trans-signaling.","method":"TLR2 stimulation of PBMCs and THP-1 cells; flow cytometry for TLR2/IL-6R co-expression; ADAM10/ADAM17 inhibitors; ERK pathway inhibition; ELISA for IL-6 and sIL-6R","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological inhibitors identifying specific sheddases and kinase pathway, cell subset identification, single lab","pmids":["31086276"],"is_preprint":false},{"year":2019,"finding":"TLR2 plays a pivotal role in mucosal serotonin (5-HT) production in the gut: TLR2-deficient and MyD88-deficient mice have lower enterochromaffin (EC) cell numbers and 5-HT levels; TLR2/1 agonist upregulates 5-HT production via NF-κB pathway in human EC cell line BON-1; T. muris excretory-secretory products induce 5-HT via TLR2.","method":"TLR2-/- and MyD88-/- mouse phenotyping, antibiotic depletion, irradiated mice reconstituted with Tlr2-/- bone marrow, germ-free mice, TLR2 agonist stimulation of BON-1 cells, NF-κB pathway assays, anti-TLR2 antibody blockade","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — TLR2 KO, bone marrow reconstitution, cell line mechanistic dissection with NF-κB pathway analysis, single lab","pmids":["30952815"],"is_preprint":false},{"year":2019,"finding":"Nanoscale proximity (<500 nm centroid-to-centroid) between Dectin-1 and TLR2 on the same phagosome is required for their synergistic enhancement of macrophage immune responses; segregating the two receptors to opposite sides of a phagosome abolishes this signaling synergy without changing overall membrane composition.","method":"Patterned ligand particles for geometric manipulation of receptor colocalization on phagosomes; live cell imaging; cytokine readouts in macrophages","journal":"Proceedings of the National Academy of Sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — novel geometric manipulation technique, functional immune readouts, mechanistic spatial requirement established, single lab","pmids":["31754039"],"is_preprint":false},{"year":2021,"finding":"TLR2 physically binds NOX1 and NOXO1 in aortic endothelial cells upon BMP4 stimulation, and TLR2 knockout in mice abrogates high-fat diet-induced endothelial dysfunction (eNOS uncoupling, superoxide production) and metabolic features of type 2 diabetes.","method":"Co-immunoprecipitation of TLR2 with NOX1/NOXO1, TLR2 knockout mice on high-fat diet, eNOS coupling assays, superoxide measurement, NO bioavailability, vascular relaxation assays","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP establishing TLR2-NOX1 physical interaction, TLR2 KO phenotypic validation across multiple metabolic and vascular endpoints, single lab","pmids":["34127487"],"is_preprint":false},{"year":2021,"finding":"Endothelial TLR2 is highly expressed in the endothelium, promotes proinflammatory endothelial cell function, and is required for cell surface localization of P-selectin and subsequent upregulation of E-selectin, ICAM-1, and VCAM-1 for immune cell recruitment. Endothelial TLR2 promotes tumor growth, angiogenesis, and protumorigenic immune cell recruitment in a mouse prostate cancer model.","method":"TLR2-IRES-EGFP reporter mice, endothelial-specific TLR2 deletion, P-selectin localization assays, adhesion molecule protein measurements, syngeneic prostate tumor model, intravital imaging","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 / Strong — reporter mice, endothelial-specific KO, mechanistic cell adhesion molecule pathway, in vivo tumor model, multiple orthogonal endpoints","pmids":["33986920"],"is_preprint":false},{"year":2022,"finding":"Sialyltransferase ST3Gal1 (induced by RANKL) sialylates TLR2, enabling binding of sialylated TLR2 to Siglec15 (expressed on M-CSF-stimulated macrophages). This Siglec15-sialylated TLR2 interaction initiates cell-cell recognition and fusion for osteoclast formation. Macrophage-specific Siglec15 deletion and intrafemoral sialidase injection abrogated osteoclast fusion.","method":"Co-immunoprecipitation of Siglec15 with sialylated TLR2, sialyltransferase ST3Gal1 knockdown, RANKL/M-CSF stimulation, Siglec15 conditional knockout in macrophages, intrafemoral sialidase injection, osteoclast fusion and bone formation assays","journal":"Bone research","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP identifying receptor-ligand pair, genetic and enzymatic interventions, in vivo validation, mechanistic dissection of sialylation writer (ST3Gal1) and reader (Siglec15)","pmids":["35232979"],"is_preprint":false},{"year":2022,"finding":"Atypical LPS from Ochrobactrum intermedium induces TLR4/TLR2 heterodimerization: molecular docking predicts a favorable TLR2/TLR4/MD-2 heterodimer complex, which was experimentally confirmed by FRET in cells. The core saccharide of LPS plays an important role in this interaction.","method":"Fluorescence resonance energy transfer (FRET) in cells, molecular docking, reporter assays for TLR2 and TLR4 signaling","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — FRET-confirmed heterodimerization in live cells, computational support, functional reporter validation, single lab","pmids":["35140704"],"is_preprint":false},{"year":2015,"finding":"TLR2 activation by TLR1/2 agonist (Pam3CSK4) in neonatal mice induces TLR2- and MyD88-dependent leukocyte (mainly neutrophils and monocytes) infiltration into the CSF and brain, preferentially via the blood-CSF barrier (choroid plexus, subarachnoid space, median eminence), with a distinct hypothalamic chemokine response and increased blood-CSF barrier permeability not induced by TLR4 or TLR2/6 agonists.","method":"Intraperitoneal injection of TLR agonists in postnatal day 8 mice; flow cytometry of CSF and brain immune cells; radioactively labeled sucrose for barrier permeability; TLR2-/- and MyD88-/- mice","journal":"Journal of leukocyte biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — TLR2 and MyD88 knockout validation, TLR specificity comparison, multiple CNS compartment readouts, single lab","pmids":["27493242"],"is_preprint":false},{"year":2016,"finding":"TLR2 activation by ICV Pam3CSK4 triggers hypothalamic inflammation and activation of arcuate nucleus microglia, resulting in increased POMC neuronal activity and sickness behaviors (anorexia, hypoactivity, hyperthermia). NF-κB antagonists, cyclooxygenase pathway inhibitors, and melanocortin receptor 3/4 antagonists reversed the anorexia and body weight loss.","method":"Intracerebroventricular injection of Pam3CSK4; NF-κB, COX, and melanocortin receptor pharmacological blockade; POMC neuron activity measurement; hypothalamic cytokine analysis","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct ICV ligand delivery, multiple pathway-specific inhibitor controls, defined neuronal circuit readout, single lab","pmids":["27405276"],"is_preprint":false},{"year":2015,"finding":"PLAP-1/asporin physically binds both TLR2 and TLR4 (by immunoprecipitation) and negatively regulates TLR2- and TLR4-induced NF-κB activity and proinflammatory cytokine expression in macrophages and periodontal ligament cells; PLAP-1/asporin also reduced IκB kinase α degradation induced by TLR4.","method":"Immunoprecipitation assay, NF-κB reporter assay, cytokine ELISA, overexpression and recombinant protein addition, Western blot for IKKα","journal":"Journal of dental research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein-protein interaction by Co-IP, functional NF-κB and cytokine readouts, single lab","pmids":["26399972"],"is_preprint":false},{"year":2019,"finding":"HMGB1 upregulates von Willebrand Factor (vWF) expression via a TLR2-MYD88-SP1 pathway; TLR2 silencing completely blocked MYD88 expression, SP1 phosphorylation, and vWF upregulation, while SP1 binding to the vWF promoter was inhibited by TLR2 silencing or HMGB1 inhibition.","method":"Tlr2 siRNA silencing, HMGB1 inhibitor, SP1 inhibitor, TLR2-immunoneutralizing antibody, TLR2 agonist stimulation, chromatin/promoter binding assay for SP1, vWF expression in murine hypoxia model","journal":"European journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — TLR2 silencing, multiple inhibitors, promoter binding assay, defined HMGB1-TLR2-MYD88-SP1-vWF axis, single lab","pmids":["27480067"],"is_preprint":false},{"year":2018,"finding":"C5aR1 physically interacts with TLR2 in osteoblasts (demonstrated by co-immunoprecipitation), and C5aR1 and TLR2 signaling pathways converge on activation of p38 MAPK and generation of CXCL10, an osteoclastogenic factor.","method":"Whole-genome microarray, co-immunoprecipitation of C5aR1 and TLR2, p38 MAPK activation assay, CXCL10 measurement in osteoblasts","journal":"Journal of cellular and molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP establishing receptor interaction, pathway convergence on p38/CXCL10 with functional readout, single lab","pmids":["30247799"],"is_preprint":false},{"year":2019,"finding":"HMGB1 promotes glomerular mesangial matrix deposition (fibronectin release) in lupus nephritis via TLR2 and the MyD88/NF-κB pathway; inhibition of TLR2 or HMGB1 blocked fibronectin release and MyD88/NF-κB activation, and both TLR2- and HMGB1-deficient mice showed reduced proteinuria and improved glomerular histology.","method":"TLR2/HMGB1 inhibition in mesangial cell culture, TLR2-/- and HMGB1-/- mouse models, fibronectin/Western blot, NF-κB pathway analysis","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout mice plus in vitro pathway inhibition, ligand-receptor-pathway-effector chain established, single lab","pmids":["31667864"],"is_preprint":false},{"year":2020,"finding":"TLR2/TLR1 heterodimers and TLR2/TLR6 heterodimers mediate distinct sensory neuron-driven behaviors: TLR2/1 (Pam3CSK4) evokes both pain and itch, whereas TLR2/6 (LTA, zymosan) produces only pain. Both effects require TRPV1 and TRPA1 channels, as demonstrated by calcium imaging in DRG neurons from TRPV1-/- and TRPA1-/- mice.","method":"TLR2 knockout mice, TRPV1/TRPA1 knockout mice, behavioral assays (pain/itch), DRG neuron calcium imaging with TLR2 agonists","journal":"Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple genetic knockouts, heterodimer-specific agonists, calcium imaging in primary neurons, behavioral readouts, single lab","pmids":["31954829"],"is_preprint":false},{"year":2015,"finding":"TLR2 activation induces cPLA2α phosphorylation at Ser505 in synoviocytes, leading to arachidonic acid release and PGE2 production; cPLA2α inhibitors attenuated TLR2/1- and TLR2/6-induced AA release, PGE2, IL-6, IL-8, and COX2 expression. Exogenous PGE2 rescued IL-6 transcription blocked by cPLA2α inhibition, placing cPLA2α upstream of COX/PGE2 in TLR2-induced inflammation.","method":"cPLA2α inhibitors, AA release assay, PGE2 ELISA, cytokine gene/protein expression, COX1/2 inhibitors, PGE2 rescue experiment in synoviocytes","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological pathway dissection with multiple inhibitors and rescue experiment, mechanistic ordering of cPLA2α-COX-PGE2 in TLR2 signaling, single lab","pmids":["25893499"],"is_preprint":false},{"year":2011,"finding":"PI3K physically interacts with the glucocorticoid receptor (GR) through two YxxM motifs (at Tyr598 and Tyr663) in the GR, and this interaction is required for TLR2-triggered PI3K signaling that modulates TNFα production. Mutation of these tyrosines significantly reduced PI3K-GR interaction and GC effects on TLR2-induced TNFα expression, without altering GR transcriptional activity or localization.","method":"PI3K-dominant negative mutant, GR Tyr-to-Phe mutagenesis, co-immunoprecipitation of PI3K and GR, TNFα measurement upon Pam3CSK4 stimulation with/without dexamethasone, NF-κB/AP-1 reporter assays","journal":"Journal of cellular and molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — site-directed mutagenesis of PI3K docking motifs, Co-IP, functional TNFα readout, single lab","pmids":["19874421"],"is_preprint":false}],"current_model":"TLR2 is a pattern recognition receptor that senses bacterial lipoproteins, peptidoglycan, and endogenous danger signals (e.g., HMGB1, hyaluronan, oxidized phospholipids) at the cell surface, predominantly as heterodimers with TLR1 (for triacylated lipopeptides) or TLR6 (for diacylated lipopeptides); upon ligand binding, TLR2 recruits the bridging adaptor Mal/TIRAP (via TLR6 D-helix) and then MyD88 (via TLR1 D-helix), activating NF-κB through the MyD88→IRAK→TRAF6→NIK→IKK cascade and MAPK cascades including p38 and ERK; TLR2/6 additionally recruits Mal to interact with the PI3K p85α subunit independently of MyD88, driving Akt phosphorylation and PIP3 generation for macrophage polarization; TLR2 also activates Ca²⁺ signaling via c-Src phosphorylation and PI3K/PLCγ-IP3R; distinct cellular contexts reveal additional TLR2 mechanisms including sialylated-TLR2 binding to Siglec15 to initiate osteoclast fusion, physical interaction with NOX1/NOXO1 in endothelial cells to drive eNOS uncoupling, interaction with CD36 and TLR6 in platelets for oxPL-driven thrombosis, and cytokine-specific outputs (including ADAM10/17-dependent IL-6R shedding) that differ fundamentally from TLR4 signaling."},"narrative":{"mechanistic_narrative":"TLR2 is a Toll/IL-1R-family pattern recognition receptor that initiates innate immune and inflammatory signaling, functioning as a cell-surface sensor whose engagement activates NF-κB and MAPK cascades [PMID:9596645, PMID:11254583, PMID:11521063]. Ligand recognition occurs through heterodimerization with co-receptors: TLR1 and TLR2 form cotranslational heterodimers whose paired TIR domains constitute the critical intracellular signaling interface [PMID:12975352], and the synthetic agonist Diprovocim binds a hydrophobic pocket between two TLR2 ectodomains to drive both TLR2/TLR1 heterodimers and TLR2 homodimers [PMID:30829478]. Co-receptor identity dictates adapter usage: the TLR1 TIR D-helix docks MyD88 while the TLR6 TIR D-helix recruits TIRAP/Mal [PMID:27150837], and the canonical MyD88→IRAK→TRAF6→NIK→IKK→NF-κB cascade drives proinflammatory gene induction such as IL-8 [PMID:11254583, PMID:11521063]. Beyond this canonical route, the TLR2/TLR6 heterodimer couples Mal to the PI3K p85α subunit in a MyD88-independent manner to generate PIP3 and Akt-driven macrophage polarization [PMID:19574958], and TLR2 also evokes c-Src/PI3K/PLCγ/IP3R-dependent intracellular Ca²⁺ release [PMID:16818794]. TLR2 senses endogenous danger signals including HMGB1, signaling through MyD88 to drive vWF expression via SP1 [PMID:27480067] and mesangial fibronectin deposition in lupus nephritis [PMID:31667864]. Context-specific complexes extend its roles: a CD36/TLR2/TLR6 platelet complex transduces oxidized-phospholipid signals to promote thrombosis [PMID:28775078], sialylated TLR2 binds Siglec15 to initiate osteoclast fusion [PMID:35232979], and TLR2 binds NOX1/NOXO1 in endothelium to drive eNOS uncoupling and diet-induced endothelial dysfunction [PMID:34127487]. Endothelial TLR2 further licenses P-selectin surface localization and adhesion-molecule upregulation to support inflammation, tumor angiogenesis, and immune recruitment [PMID:33986920].","teleology":[{"year":1998,"claim":"Established that TLR2 is a functional signaling receptor, not merely an orphan membrane protein, by showing it activates NF-κB when expressed in cells.","evidence":"Functional NF-κB activation assay in transfected cells (cloned as TIL4)","pmids":["9596645"],"confidence":"Medium","gaps":["No ligand identified at this stage","Single functional readout, foundational cloning only"]},{"year":2001,"claim":"Defined the canonical TLR2 signaling cascade by epistasis, ordering MyD88→IRAK→TRAF6/TRAF2→NIK→IKK→NF-κB to drive cytokine gene induction.","evidence":"Dominant-negative mutant overexpression with NF-κB reporter and IL-8 induction in HEK293/CD14 cells; parallel finding of distinct TLR2 vs TLR4 cytokine outputs and PI3K/p38 involvement in dendritic cells","pmids":["11254583","11521063","11477091"],"confidence":"High","gaps":["Did not resolve co-receptor requirement","Adapter docking mechanism unmapped"]},{"year":2003,"claim":"Showed TLR2 activates p38 MAPK directly and that TLR1-TLR2 heterodimers, assembled via their TIR domains, are required for functional signaling, establishing receptor architecture.","evidence":"In vitro p38 kinase assay with ATF2 substrate; confocal colocalization, chimeric receptor epistasis and cross-linking of TLR1/TLR2","pmids":["11867688","12975352"],"confidence":"High","gaps":["Did not distinguish TLR1 vs TLR6 functional differences","Ligand-induced conformational changes not resolved"]},{"year":2004,"claim":"Demonstrated genetically that TLR2 signaling requires MyD88 but can be independent of TLR4/TLR6 for specific ligands, and revealed dual pro- and anti-inflammatory outputs.","evidence":"Macrophages from TLR2, TLR4, TLR6, and MyD88 knockout mice stimulated with mycobacterial lipomannans","pmids":["15034058"],"confidence":"High","gaps":["Mechanism of the MyD88-independent inhibitory effect undefined"]},{"year":2009,"claim":"Revealed heterodimer-specific adapter usage: TLR2/TLR6 couples Mal to PI3K p85α in a MyD88-independent branch driving Akt and macrophage polarization, whereas TLR2/1 does not.","evidence":"Reciprocal Co-IP of Mal with p85α, Akt/PIP3 assays in MyD88- and Mal-deficient cells","pmids":["19574958"],"confidence":"High","gaps":["Structural basis of Mal-p85α docking not resolved","Did not map how heterodimer geometry selects this branch"]},{"year":2016,"claim":"Mapped the molecular basis of differential adapter recruitment, assigning the MyD88 docking site to the TLR1 TIR D-helix and the TIRAP site to the TLR6 TIR D-helix.","evidence":"Cell-permeable D-helix peptides blocking Co-IP of TLR2 with MyD88 or TIRAP; in vitro binding","pmids":["27150837"],"confidence":"Medium","gaps":["Single lab, peptide-competition based","No co-crystal of the TIR-adapter interface"]},{"year":2006,"claim":"Established a non-transcriptional output of TLR2: c-Src/PI3K/PLCγ-dependent IP3R activation releasing intracellular Ca²⁺, broadening TLR2 signaling beyond NF-κB.","evidence":"Ca²⁺ flux and kinase inhibition studies in airway epithelium and TLR2-deficient macrophages","pmids":["16818794"],"confidence":"Medium","gaps":["Direct c-Src phosphorylation site on TLR2 not defined"]},{"year":2017,"claim":"Identified a CD36/TLR2/TLR6 receptor complex transducing oxidized-phospholipid signals through TIRAP-MyD88-IRAK-TRAF6 to integrin activation, linking TLR2 to thrombosis.","evidence":"Co-IP of the platelet receptor complex, MyD88/TLR2/TLR6 knockouts, in vivo intravital thrombosis in ApoE-/- mice","pmids":["28775078"],"confidence":"High","gaps":["Stoichiometry and assembly order of the CD36/TLR2/TLR6 complex unresolved"]},{"year":2019,"claim":"Showed TLR2 senses the endogenous danger signal HMGB1 through MyD88, driving SP1-dependent vWF transcription and mesangial fibronectin deposition, extending TLR2 to sterile inflammatory disease.","evidence":"TLR2 silencing/antibody blockade, HMGB1 and SP1 inhibitors, promoter binding assays; TLR2-/- and HMGB1-/- mouse disease models","pmids":["27480067","31667864"],"confidence":"Medium","gaps":["Direct HMGB1-TLR2 binding affinity not measured","Co-receptor for HMGB1 sensing not defined"]},{"year":2019,"claim":"Structurally defined the TLR2 agonist-binding pocket using the synthetic agonist Diprovocim, confirming a hydrophobic inter-ectodomain pocket that drives dimerization.","evidence":"Crystal structure of Diprovocim-TLR2 ectodomain complex with biophysical dimerization assays","pmids":["30829478"],"confidence":"High","gaps":["Does not capture full ternary TLR2/TLR1/MyD88 signaling assembly","Endogenous lipopeptide binding mode inferred not crystallized here"]},{"year":2022,"claim":"Uncovered glycosylation-dependent TLR2 function: ST3Gal1-mediated sialylation of TLR2 enables binding to Siglec15 to initiate osteoclast cell-cell fusion, a role distinct from pathogen sensing.","evidence":"Co-IP of Siglec15 with sialylated TLR2, ST3Gal1 knockdown, macrophage Siglec15 conditional knockout, in vivo sialidase injection","pmids":["35232979"],"confidence":"High","gaps":["Whether this fusion role requires canonical TLR2 signaling is unaddressed"]},{"year":2021,"claim":"Demonstrated TLR2 forms a physical complex with NOX1/NOXO1 driving eNOS uncoupling, and that endothelial TLR2 licenses P-selectin and adhesion molecule expression, defining endothelial/vascular roles.","evidence":"Co-IP of TLR2 with NOX1/NOXO1, TLR2 reporter and endothelial-specific knockout mice, vascular and tumor models","pmids":["34127487","33986920"],"confidence":"High","gaps":["Ligand triggering endothelial TLR2-NOX1 assembly in vivo not defined"]},{"year":null,"claim":"How distinct co-receptor pairings and context-specific partners (CD36, NOX1, Siglec15, Dectin-1, C5aR1) are integrated to select among the NF-κB, PI3K/Akt, Ca²⁺, and adhesion outputs of TLR2 remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified structural model of context-dependent TLR2 signalosomes","Quantitative rules linking receptor proximity/composition to output selection lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,1,4]},{"term_id":"GO:0001618","term_label":"virus receptor activity","supporting_discovery_ids":[16,24]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[16,17]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[4,16,23]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[1,5,8]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,6,8]},{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[16,28]}],"complexes":["TLR2/TLR1 heterodimer","TLR2/TLR6 heterodimer","CD36/TLR2/TLR6 platelet complex","TLR2/NOX1/NOXO1 complex"],"partners":["TLR1","TLR6","MYD88","TIRAP","CD36","NOX1","SIGLEC15","C5AR1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O60603","full_name":"Toll-like receptor 2","aliases":["Toll/interleukin-1 receptor-like protein 4"],"length_aa":784,"mass_kda":89.8,"function":"Cooperates with LY96 to mediate the innate immune response to bacterial lipoproteins and other microbial cell wall components. Cooperates with TLR1 or TLR6 to mediate the innate immune response to bacterial lipoproteins or lipopeptides (PubMed:17889651, PubMed:21078852). Acts via MYD88 and TRAF6, leading to NF-kappa-B activation, cytokine secretion and the inflammatory response. May also activate immune cells and promote apoptosis in response to the lipid moiety of lipoproteins (PubMed:10426995, PubMed:10426996). Recognizes mycoplasmal macrophage-activating lipopeptide-2kD (MALP-2), soluble tuberculosis factor (STF), phenol-soluble modulin (PSM) and B.burgdorferi outer surface protein A lipoprotein (OspA-L) cooperatively with TLR6 (PubMed:11441107). Stimulation of monocytes in vitro with M.tuberculosis PstS1 induces p38 MAPK and ERK1/2 activation primarily via this receptor, but also partially via TLR4 (PubMed:16622205). MAPK activation in response to bacterial peptidoglycan also occurs via this receptor (PubMed:16622205). Acts as a receptor for M.tuberculosis lipoproteins LprA, LprG, LpqH and PstS1, some lipoproteins are dependent on other coreceptors (TLR1, CD14 and/or CD36); the lipoproteins act as agonists to modulate antigen presenting cell functions in response to the pathogen (PubMed:19362712). M.tuberculosis HSP70 (dnaK) but not HSP65 (groEL-2) acts via this protein to stimulate NF-kappa-B expression (PubMed:15809303). Recognizes M.tuberculosis major T-antigen EsxA (ESAT-6) which inhibits downstream MYD88-dependent signaling (shown in mouse) (By similarity). Forms activation clusters composed of several receptors depending on the ligand, these clusters trigger signaling from the cell surface and subsequently are targeted to the Golgi in a lipid-raft dependent pathway. Forms the cluster TLR2:TLR6:CD14:CD36 in response to diacylated lipopeptides and TLR2:TLR1:CD14 in response to triacylated lipopeptides (PubMed:16880211). Required for normal uptake of M.tuberculosis, a process that is inhibited by M.tuberculosis LppM (By similarity)","subcellular_location":"Membrane; Cytoplasmic vesicle, phagosome membrane; Membrane raft","url":"https://www.uniprot.org/uniprotkb/O60603/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TLR2","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TLR2","total_profiled":1310},"omim":[{"mim_id":"620527","title":"TRIPARTITE MOTIF-CONTAINING PROTEIN 58; TRIM58","url":"https://www.omim.org/entry/620527"},{"mim_id":"616834","title":"MICROCEPHALY, CONGENITAL CATARACT, AND PSORIASIFORM DERMATITIS; MCCPD","url":"https://www.omim.org/entry/616834"},{"mim_id":"615622","title":"TNF- AND HNRNPL-RELATED IMMUNOREGULATORY LONG NONCODING RNA; THRIL","url":"https://www.omim.org/entry/615622"},{"mim_id":"615322","title":"NEGATIVE REGULATOR OF REACTIVE OXYGEN SPECIES; NRROS","url":"https://www.omim.org/entry/615322"},{"mim_id":"614382","title":"BACTEREMIA, SUSCEPTIBILITY TO, 1; BACTS1","url":"https://www.omim.org/entry/614382"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Plasma membrane","reliability":"Supported"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Vesicles","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"bone marrow","ntpm":66.0}],"url":"https://www.proteinatlas.org/search/TLR2"},"hgnc":{"alias_symbol":["TIL4","CD282"],"prev_symbol":[]},"alphafold":{"accession":"O60603","domains":[{"cath_id":"-","chopping":"258-339","consensus_level":"medium","plddt":87.307,"start":258,"end":339},{"cath_id":"3.40.50.10140","chopping":"641-784","consensus_level":"medium","plddt":81.9676,"start":641,"end":784},{"cath_id":"1.20.5","chopping":"582-610","consensus_level":"medium","plddt":87.0266,"start":582,"end":610}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O60603","model_url":"https://alphafold.ebi.ac.uk/files/AF-O60603-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O60603-F1-predicted_aligned_error_v6.png","plddt_mean":87.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TLR2","jax_strain_url":"https://www.jax.org/strain/search?query=TLR2"},"sequence":{"accession":"O60603","fasta_url":"https://rest.uniprot.org/uniprotkb/O60603.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O60603/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O60603"}},"corpus_meta":[{"pmid":"11477091","id":"PMC_11477091","title":"Toll-like 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Weak — single lab, single functional readout (NF-κB activation), foundational cloning paper\",\n      \"pmids\": [\"9596645\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"TLR2 activation by peptidoglycan and micrococci induces IL-8 transcription through a defined signaling cascade: TLR2 → MyD88 → IRAK → TRAF6/TRAF2 → NIK → IKK → NF-κB. Dominant-negative forms of each component blocked NF-κB activation and IL-8 gene induction.\",\n      \"method\": \"Dominant-negative mutant overexpression, NF-κB reporter assay, IL-8 gene expression in HEK293 cells expressing TLR2 and CD14\",\n      \"journal\": \"Infection and immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple dominant-negative constructs for each pathway component, replicated with two stimuli, consistent with parallel findings in PMID:11521063\",\n      \"pmids\": [\"11254583\", \"11521063\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"TLR2 and TLR4 agonists both activate NF-κB and MAPK family members in dendritic cells but produce distinct cytokine/chemokine profiles: TLR2 stimulation fails to induce IL-12 p70 and IP-10 but preferentially induces IL-12 p40 homodimer, IL-8, and IL-23; phosphatidylinositol 3-kinase and p38 MAPK are involved in TLR-mediated cytokine induction.\",\n      \"method\": \"Cytokine/chemokine gene transcription analysis, pharmacological inhibitors of PI3K and p38 MAPK in human dendritic cells stimulated with TLR2 or TLR4 agonists\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single lab, multiple cytokine readouts, pharmacological inhibitors confirming PI3K and p38 MAPK involvement\",\n      \"pmids\": [\"11477091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"TLR2 expression in HEK293 cells enables phosphorylation and activation of stress-activated MAP kinase p38 in response to bacterial lipoproteins and Gram-positive bacteria, demonstrated by in vitro kinase assay using ATF2 as substrate and MAP kinase-activated protein kinase activation.\",\n      \"method\": \"TLR2 transfection in HEK293 cells, in vitro p38 kinase assay with ATF2 substrate, MAP kinase-activated protein kinase activation assay\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro kinase assay with defined substrate, single lab\",\n      \"pmids\": [\"11867688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"TLR1 and TLR2 form cotranslational heterodimeric complexes on the cell surface and in the cytosol (detected by confocal microscopy), and both the extracellular and intracellular (TIR) domains of each receptor are required for functional NF-κB signaling; the TIR domains constitute the critical intracellular TLR1-TLR2 interaction interface.\",\n      \"method\": \"Confocal microscopy of co-expressed tagged receptors, chimeric TLR analysis, cross-linking of surface receptors, NF-κB reporter assay, cytokine secretion from mononuclear cells\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (confocal colocalization, chimeric receptor epistasis, cross-linking, cytokine readout), rigorous dissection of domain requirements\",\n      \"pmids\": [\"12975352\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"TLR2 activation in murine macrophages requires MyD88 but is independent of TLR4 or TLR6 for LM-induced macrophage activation (CD40/CD86 expression, TNF, NO secretion). LM also exerts a TLR2/TLR6/MyD88-independent inhibitory effect on LPS-activated macrophages.\",\n      \"method\": \"Macrophages from TLR2, TLR4, TLR6, and MyD88 knockout mice stimulated with mycobacterial lipomannans; cytokine measurement, CD40/CD86 surface expression\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genetic knockouts used to dissect pathway, dual (pro- and anti-inflammatory) functional phenotypes characterized\",\n      \"pmids\": [\"15034058\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"TLR2 ligands activate Ca²⁺ release from intracellular stores in airway epithelial cells and macrophages via a pathway involving TLR2 phosphorylation by c-Src, recruitment of PI3K and phospholipase Cγ, and activation of IP3 receptors. Absence of TLR2 abolishes Ca²⁺ fluxes and proinflammatory NF-κB-dependent signaling.\",\n      \"method\": \"Biochemical and genetic approaches in airway epithelial cells and TLR2-deficient murine macrophages; Ca²⁺ flux measurement, kinase inhibition studies\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — TLR2 knockout controls plus biochemical pathway dissection (c-Src, PI3K, PLCγ, IP3R), single lab\",\n      \"pmids\": [\"16818794\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"TLR2 directly triggers IFN-γ production, cell proliferation, and cell survival in mouse Th1 effector cells without TCR stimulation; these effects were absent in Th2 cells and depended on enhanced MAPK activation. No other TLRs tested replicated this effect in Th1 cells.\",\n      \"method\": \"TLR stimulation of sorted Th1/Th2 effector T cells; cytokine measurement, proliferation and survival assays, MAPK phosphorylation analysis in wild-type and TLR2-deficient cells\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined cell subsets, multiple readouts, TLR specificity controls, single lab\",\n      \"pmids\": [\"17513716\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Upon stimulation of the TLR2/TLR6 heterodimer with diacylated bacterial lipoproteins, the adaptor Mal directly interacts with the PI3K regulatory subunit p85α in an inducible fashion, driving PI3K-dependent Akt phosphorylation, PIP3 generation, and macrophage polarization. This pathway is MyD88-independent, and TLR2/1 does not require Mal or MyD88 for Akt phosphorylation, revealing heterodimer-specific adapter usage.\",\n      \"method\": \"Co-immunoprecipitation of Mal with p85α, Akt phosphorylation assays, PIP3 measurement, macrophage polarization assays, MyD88-deficient and Mal-deficient cells\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, multiple genetic knockout backgrounds, biochemical pathway endpoints, distinct TLR2/1 vs TLR2/6 specificity demonstrated\",\n      \"pmids\": [\"19574958\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"TLR2 stimulation in keratinocytes triggers calcium-dependent release of the serine protease kallikrein 5; this was demonstrated using TLR2 overexpression, TLR2 ligand treatment, and analysis of TLR2-deficient mice, linking TLR2 to a critical pathogenic protease in rosacea.\",\n      \"method\": \"TLR2 overexpression in keratinocytes, TLR2 ligand stimulation, TLR2-deficient mouse analysis, calcium chelation, kallikrein 5 measurement\",\n      \"journal\": \"The Journal of investigative dermatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — TLR2 KO mice plus in vitro overexpression, calcium-dependence mechanistically established, single lab\",\n      \"pmids\": [\"21107351\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TLR2 stimulation in megakaryocytes activates NFκB, ERK-MAPK, and PI3K/Akt pathways, upregulates transcription factors GATA-1, NF-E2, and mTOR, increases DNA content and adhesion to extracellular matrix proteins, and promotes megakaryocyte maturation in a TLR2-dependent manner confirmed by TLR2 knockout mice.\",\n      \"method\": \"Pam3CSK4 stimulation of Meg-01 cells and mouse megakaryocytes; pathway inhibitors, gene/protein expression, TLR2-/- mice treated with Pam3CSK4\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — TLR2 KO validation, multiple biochemical readouts, single lab\",\n      \"pmids\": [\"21454454\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Phospholipase D2 (PLD2) and protein kinase C-η (PKC-η) act downstream of TLR2 (MyD88-dependent) to induce ABCA1 expression in macrophages; PLD2-generated phosphatidic acid is a key mediator of this effect.\",\n      \"method\": \"Pam3CSK4 stimulation, pathway inhibitors, MyD88-dependent signaling, direct diC8PA treatment in Raw264.7 macrophages; mRNA and protein quantification\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological and genetic dissection of downstream signaling, direct PA treatment as mechanistic proof, single lab\",\n      \"pmids\": [\"23261454\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In TLR2-mediated gastric tumourigenesis, MyD88 but not Mal/TIRAP is required; genetic ablation of Myd88 suppressed tumourigenesis with increased apoptosis and reduced proliferation, whereas Mal deficiency had no effect on tumour burden. Mal is thus dispensable for TLR2-promoted gastric tumour growth.\",\n      \"method\": \"Genetic epistasis using gp130F/F mouse model with Myd88 and Mal knockout; tumour histology, apoptosis, proliferation, and pathway activation analysis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — dual genetic knockouts in defined cancer model, multiple phenotypic readouts, single lab\",\n      \"pmids\": [\"23728346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TLR2 activation with Pam3CSK4 induces cell migration and invasion in rheumatoid arthritis synovial fibroblasts via β1-integrin binding and Rac1 activation, leading to cytoskeletal rearrangement and filopodia formation. Blocking β1-integrin inhibited Pam3CSK4-induced migration and invasion and Rac1 activation but not MMP-3 secretion.\",\n      \"method\": \"Transwell Matrigel invasion assay, Rac1 pull-down assay/Western blot, β1-integrin multiplex binding assay, F-actin immunofluorescence, anti-TLR2 mAb (OPN301) blocking, RA explant cultures\",\n      \"journal\": \"Arthritis research & therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays with blocking antibodies and receptor-specific readouts, single lab\",\n      \"pmids\": [\"26055925\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"HCMV miR-UL112-3p directly targets TLR2 mRNA, reducing TLR2 protein levels and inhibiting TLR2/IRAK1/NFκB signaling. Down-regulation of endogenous TLR2 was confirmed by miR-UL112-3p mimic transfection, and was absent in cells infected with miR-UL112-3p-deficient HCMV mutants; miR-UL112-3p suppressed IL-1β, IL-6, IL-8, and NFκB-dependent luciferase activity upon TLR2 agonist stimulation.\",\n      \"method\": \"Luciferase reporter assay, miR mimic/siRNA transfection, HCMV miRNA-deficient mutant infection, immunoblot for TLR2 protein, NFκB reporter, IRAK1 phosphorylation, cytokine quantification\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches (reporter, miRNA mutant virus, siRNA equivalence, IRAK1 post-translational activation), mechanistically rigorous demonstration\",\n      \"pmids\": [\"25955717\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Differential adapter recruitment by TLR2 co-receptors: the D helix of TLR1 TIR domain is a MyD88 docking site, whereas the D helix of TLR6 TIR domain recruits TIRAP. Cell-permeable D-helix peptides from TLR1 or TLR6 selectively blocked co-immunoprecipitation of TLR2 with MyD88 or TIRAP respectively, without disrupting TLR2 co-receptor association.\",\n      \"method\": \"Cell-permeable TIR-domain peptides, co-immunoprecipitation of TLR2 with adapters TIRAP and MyD88, in vitro binding assays\",\n      \"journal\": \"Pathogens and disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP with blocking peptides, in vitro binding, mechanistic mapping of adapter docking sites, single lab\",\n      \"pmids\": [\"27150837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TLR2 and TLR6 are required for platelet activation by oxidized phospholipids (oxPCCD36); oxPCCD36 induces formation of a CD36/TLR2/TLR6 complex in platelets and activates downstream signaling via TIRAP-MyD88-IRAK1/4-TRAF6, leading to integrin activation via the SFK-Syk-PLCγ2 pathway. TLR2 or TLR6 deficiency in ApoE-/- mice abrogated oxPCCD36-driven accelerated thrombosis.\",\n      \"method\": \"In vitro platelet activation assays, Co-IP of CD36/TLR2/TLR6 complex, genetic deletion of MyD88, TLR2, TLR6 in mice, intravital thrombosis studies in ApoE-/- mice\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP of receptor complex, multiple genetic knockouts, in vitro and in vivo thrombosis endpoints, defined signaling cascade\",\n      \"pmids\": [\"28775078\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Crystal structure of the synthetic TLR2/TLR1 agonist Diprovocim bound to TLR2 ectodomain revealed two Diprovocim molecules bound within the ligand-binding pocket formed between two TLR2 ectodomains, stabilized by extensive hydrophobic interactions and hydrogen-bonding. Diprovocim induced both TLR2/TLR1 heterodimers and TLR2 homodimers in vitro.\",\n      \"method\": \"Crystal structure determination of Diprovocim-TLR2 ectodomain complex, in vitro biophysical assays (heterodimer/homodimer formation), computational docking\",\n      \"journal\": \"Journal of medicinal chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with defined binding pocket, in vitro biophysical validation of dimerization, rigorous structural and functional characterization\",\n      \"pmids\": [\"30829478\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TLR2 activation induces IL-6 expression and shedding of soluble IL-6 receptor (sIL-6R) from monocytes via the metalloproteases ADAM10 and ADAM17, and the ERK cascade differentially regulates both IL-6 and sIL-6R generation, triggering IL-6 trans-signaling.\",\n      \"method\": \"TLR2 stimulation of PBMCs and THP-1 cells; flow cytometry for TLR2/IL-6R co-expression; ADAM10/ADAM17 inhibitors; ERK pathway inhibition; ELISA for IL-6 and sIL-6R\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological inhibitors identifying specific sheddases and kinase pathway, cell subset identification, single lab\",\n      \"pmids\": [\"31086276\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TLR2 plays a pivotal role in mucosal serotonin (5-HT) production in the gut: TLR2-deficient and MyD88-deficient mice have lower enterochromaffin (EC) cell numbers and 5-HT levels; TLR2/1 agonist upregulates 5-HT production via NF-κB pathway in human EC cell line BON-1; T. muris excretory-secretory products induce 5-HT via TLR2.\",\n      \"method\": \"TLR2-/- and MyD88-/- mouse phenotyping, antibiotic depletion, irradiated mice reconstituted with Tlr2-/- bone marrow, germ-free mice, TLR2 agonist stimulation of BON-1 cells, NF-κB pathway assays, anti-TLR2 antibody blockade\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — TLR2 KO, bone marrow reconstitution, cell line mechanistic dissection with NF-κB pathway analysis, single lab\",\n      \"pmids\": [\"30952815\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Nanoscale proximity (<500 nm centroid-to-centroid) between Dectin-1 and TLR2 on the same phagosome is required for their synergistic enhancement of macrophage immune responses; segregating the two receptors to opposite sides of a phagosome abolishes this signaling synergy without changing overall membrane composition.\",\n      \"method\": \"Patterned ligand particles for geometric manipulation of receptor colocalization on phagosomes; live cell imaging; cytokine readouts in macrophages\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — novel geometric manipulation technique, functional immune readouts, mechanistic spatial requirement established, single lab\",\n      \"pmids\": [\"31754039\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TLR2 physically binds NOX1 and NOXO1 in aortic endothelial cells upon BMP4 stimulation, and TLR2 knockout in mice abrogates high-fat diet-induced endothelial dysfunction (eNOS uncoupling, superoxide production) and metabolic features of type 2 diabetes.\",\n      \"method\": \"Co-immunoprecipitation of TLR2 with NOX1/NOXO1, TLR2 knockout mice on high-fat diet, eNOS coupling assays, superoxide measurement, NO bioavailability, vascular relaxation assays\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP establishing TLR2-NOX1 physical interaction, TLR2 KO phenotypic validation across multiple metabolic and vascular endpoints, single lab\",\n      \"pmids\": [\"34127487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Endothelial TLR2 is highly expressed in the endothelium, promotes proinflammatory endothelial cell function, and is required for cell surface localization of P-selectin and subsequent upregulation of E-selectin, ICAM-1, and VCAM-1 for immune cell recruitment. Endothelial TLR2 promotes tumor growth, angiogenesis, and protumorigenic immune cell recruitment in a mouse prostate cancer model.\",\n      \"method\": \"TLR2-IRES-EGFP reporter mice, endothelial-specific TLR2 deletion, P-selectin localization assays, adhesion molecule protein measurements, syngeneic prostate tumor model, intravital imaging\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reporter mice, endothelial-specific KO, mechanistic cell adhesion molecule pathway, in vivo tumor model, multiple orthogonal endpoints\",\n      \"pmids\": [\"33986920\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Sialyltransferase ST3Gal1 (induced by RANKL) sialylates TLR2, enabling binding of sialylated TLR2 to Siglec15 (expressed on M-CSF-stimulated macrophages). This Siglec15-sialylated TLR2 interaction initiates cell-cell recognition and fusion for osteoclast formation. Macrophage-specific Siglec15 deletion and intrafemoral sialidase injection abrogated osteoclast fusion.\",\n      \"method\": \"Co-immunoprecipitation of Siglec15 with sialylated TLR2, sialyltransferase ST3Gal1 knockdown, RANKL/M-CSF stimulation, Siglec15 conditional knockout in macrophages, intrafemoral sialidase injection, osteoclast fusion and bone formation assays\",\n      \"journal\": \"Bone research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP identifying receptor-ligand pair, genetic and enzymatic interventions, in vivo validation, mechanistic dissection of sialylation writer (ST3Gal1) and reader (Siglec15)\",\n      \"pmids\": [\"35232979\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Atypical LPS from Ochrobactrum intermedium induces TLR4/TLR2 heterodimerization: molecular docking predicts a favorable TLR2/TLR4/MD-2 heterodimer complex, which was experimentally confirmed by FRET in cells. The core saccharide of LPS plays an important role in this interaction.\",\n      \"method\": \"Fluorescence resonance energy transfer (FRET) in cells, molecular docking, reporter assays for TLR2 and TLR4 signaling\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — FRET-confirmed heterodimerization in live cells, computational support, functional reporter validation, single lab\",\n      \"pmids\": [\"35140704\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TLR2 activation by TLR1/2 agonist (Pam3CSK4) in neonatal mice induces TLR2- and MyD88-dependent leukocyte (mainly neutrophils and monocytes) infiltration into the CSF and brain, preferentially via the blood-CSF barrier (choroid plexus, subarachnoid space, median eminence), with a distinct hypothalamic chemokine response and increased blood-CSF barrier permeability not induced by TLR4 or TLR2/6 agonists.\",\n      \"method\": \"Intraperitoneal injection of TLR agonists in postnatal day 8 mice; flow cytometry of CSF and brain immune cells; radioactively labeled sucrose for barrier permeability; TLR2-/- and MyD88-/- mice\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — TLR2 and MyD88 knockout validation, TLR specificity comparison, multiple CNS compartment readouts, single lab\",\n      \"pmids\": [\"27493242\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TLR2 activation by ICV Pam3CSK4 triggers hypothalamic inflammation and activation of arcuate nucleus microglia, resulting in increased POMC neuronal activity and sickness behaviors (anorexia, hypoactivity, hyperthermia). NF-κB antagonists, cyclooxygenase pathway inhibitors, and melanocortin receptor 3/4 antagonists reversed the anorexia and body weight loss.\",\n      \"method\": \"Intracerebroventricular injection of Pam3CSK4; NF-κB, COX, and melanocortin receptor pharmacological blockade; POMC neuron activity measurement; hypothalamic cytokine analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct ICV ligand delivery, multiple pathway-specific inhibitor controls, defined neuronal circuit readout, single lab\",\n      \"pmids\": [\"27405276\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PLAP-1/asporin physically binds both TLR2 and TLR4 (by immunoprecipitation) and negatively regulates TLR2- and TLR4-induced NF-κB activity and proinflammatory cytokine expression in macrophages and periodontal ligament cells; PLAP-1/asporin also reduced IκB kinase α degradation induced by TLR4.\",\n      \"method\": \"Immunoprecipitation assay, NF-κB reporter assay, cytokine ELISA, overexpression and recombinant protein addition, Western blot for IKKα\",\n      \"journal\": \"Journal of dental research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein-protein interaction by Co-IP, functional NF-κB and cytokine readouts, single lab\",\n      \"pmids\": [\"26399972\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HMGB1 upregulates von Willebrand Factor (vWF) expression via a TLR2-MYD88-SP1 pathway; TLR2 silencing completely blocked MYD88 expression, SP1 phosphorylation, and vWF upregulation, while SP1 binding to the vWF promoter was inhibited by TLR2 silencing or HMGB1 inhibition.\",\n      \"method\": \"Tlr2 siRNA silencing, HMGB1 inhibitor, SP1 inhibitor, TLR2-immunoneutralizing antibody, TLR2 agonist stimulation, chromatin/promoter binding assay for SP1, vWF expression in murine hypoxia model\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — TLR2 silencing, multiple inhibitors, promoter binding assay, defined HMGB1-TLR2-MYD88-SP1-vWF axis, single lab\",\n      \"pmids\": [\"27480067\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"C5aR1 physically interacts with TLR2 in osteoblasts (demonstrated by co-immunoprecipitation), and C5aR1 and TLR2 signaling pathways converge on activation of p38 MAPK and generation of CXCL10, an osteoclastogenic factor.\",\n      \"method\": \"Whole-genome microarray, co-immunoprecipitation of C5aR1 and TLR2, p38 MAPK activation assay, CXCL10 measurement in osteoblasts\",\n      \"journal\": \"Journal of cellular and molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP establishing receptor interaction, pathway convergence on p38/CXCL10 with functional readout, single lab\",\n      \"pmids\": [\"30247799\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HMGB1 promotes glomerular mesangial matrix deposition (fibronectin release) in lupus nephritis via TLR2 and the MyD88/NF-κB pathway; inhibition of TLR2 or HMGB1 blocked fibronectin release and MyD88/NF-κB activation, and both TLR2- and HMGB1-deficient mice showed reduced proteinuria and improved glomerular histology.\",\n      \"method\": \"TLR2/HMGB1 inhibition in mesangial cell culture, TLR2-/- and HMGB1-/- mouse models, fibronectin/Western blot, NF-κB pathway analysis\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout mice plus in vitro pathway inhibition, ligand-receptor-pathway-effector chain established, single lab\",\n      \"pmids\": [\"31667864\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TLR2/TLR1 heterodimers and TLR2/TLR6 heterodimers mediate distinct sensory neuron-driven behaviors: TLR2/1 (Pam3CSK4) evokes both pain and itch, whereas TLR2/6 (LTA, zymosan) produces only pain. Both effects require TRPV1 and TRPA1 channels, as demonstrated by calcium imaging in DRG neurons from TRPV1-/- and TRPA1-/- mice.\",\n      \"method\": \"TLR2 knockout mice, TRPV1/TRPA1 knockout mice, behavioral assays (pain/itch), DRG neuron calcium imaging with TLR2 agonists\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple genetic knockouts, heterodimer-specific agonists, calcium imaging in primary neurons, behavioral readouts, single lab\",\n      \"pmids\": [\"31954829\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TLR2 activation induces cPLA2α phosphorylation at Ser505 in synoviocytes, leading to arachidonic acid release and PGE2 production; cPLA2α inhibitors attenuated TLR2/1- and TLR2/6-induced AA release, PGE2, IL-6, IL-8, and COX2 expression. Exogenous PGE2 rescued IL-6 transcription blocked by cPLA2α inhibition, placing cPLA2α upstream of COX/PGE2 in TLR2-induced inflammation.\",\n      \"method\": \"cPLA2α inhibitors, AA release assay, PGE2 ELISA, cytokine gene/protein expression, COX1/2 inhibitors, PGE2 rescue experiment in synoviocytes\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological pathway dissection with multiple inhibitors and rescue experiment, mechanistic ordering of cPLA2α-COX-PGE2 in TLR2 signaling, single lab\",\n      \"pmids\": [\"25893499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PI3K physically interacts with the glucocorticoid receptor (GR) through two YxxM motifs (at Tyr598 and Tyr663) in the GR, and this interaction is required for TLR2-triggered PI3K signaling that modulates TNFα production. Mutation of these tyrosines significantly reduced PI3K-GR interaction and GC effects on TLR2-induced TNFα expression, without altering GR transcriptional activity or localization.\",\n      \"method\": \"PI3K-dominant negative mutant, GR Tyr-to-Phe mutagenesis, co-immunoprecipitation of PI3K and GR, TNFα measurement upon Pam3CSK4 stimulation with/without dexamethasone, NF-κB/AP-1 reporter assays\",\n      \"journal\": \"Journal of cellular and molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — site-directed mutagenesis of PI3K docking motifs, Co-IP, functional TNFα readout, single lab\",\n      \"pmids\": [\"19874421\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TLR2 is a pattern recognition receptor that senses bacterial lipoproteins, peptidoglycan, and endogenous danger signals (e.g., HMGB1, hyaluronan, oxidized phospholipids) at the cell surface, predominantly as heterodimers with TLR1 (for triacylated lipopeptides) or TLR6 (for diacylated lipopeptides); upon ligand binding, TLR2 recruits the bridging adaptor Mal/TIRAP (via TLR6 D-helix) and then MyD88 (via TLR1 D-helix), activating NF-κB through the MyD88→IRAK→TRAF6→NIK→IKK cascade and MAPK cascades including p38 and ERK; TLR2/6 additionally recruits Mal to interact with the PI3K p85α subunit independently of MyD88, driving Akt phosphorylation and PIP3 generation for macrophage polarization; TLR2 also activates Ca²⁺ signaling via c-Src phosphorylation and PI3K/PLCγ-IP3R; distinct cellular contexts reveal additional TLR2 mechanisms including sialylated-TLR2 binding to Siglec15 to initiate osteoclast fusion, physical interaction with NOX1/NOXO1 in endothelial cells to drive eNOS uncoupling, interaction with CD36 and TLR6 in platelets for oxPL-driven thrombosis, and cytokine-specific outputs (including ADAM10/17-dependent IL-6R shedding) that differ fundamentally from TLR4 signaling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TLR2 is a Toll/IL-1R-family pattern recognition receptor that initiates innate immune and inflammatory signaling, functioning as a cell-surface sensor whose engagement activates NF-\\u03baB and MAPK cascades [#0, #1]. Ligand recognition occurs through heterodimerization with co-receptors: TLR1 and TLR2 form cotranslational heterodimers whose paired TIR domains constitute the critical intracellular signaling interface [#4], and the synthetic agonist Diprovocim binds a hydrophobic pocket between two TLR2 ectodomains to drive both TLR2/TLR1 heterodimers and TLR2 homodimers [#17]. Co-receptor identity dictates adapter usage: the TLR1 TIR D-helix docks MyD88 while the TLR6 TIR D-helix recruits TIRAP/Mal [#15], and the canonical MyD88\\u2192IRAK\\u2192TRAF6\\u2192NIK\\u2192IKK\\u2192NF-\\u03baB cascade drives proinflammatory gene induction such as IL-8 [#1]. Beyond this canonical route, the TLR2/TLR6 heterodimer couples Mal to the PI3K p85\\u03b1 subunit in a MyD88-independent manner to generate PIP3 and Akt-driven macrophage polarization [#8], and TLR2 also evokes c-Src/PI3K/PLC\\u03b3/IP3R-dependent intracellular Ca\\u00b2\\u207a release [#6]. TLR2 senses endogenous danger signals including HMGB1, signaling through MyD88 to drive vWF expression via SP1 [#28] and mesangial fibronectin deposition in lupus nephritis [#30]. Context-specific complexes extend its roles: a CD36/TLR2/TLR6 platelet complex transduces oxidized-phospholipid signals to promote thrombosis [#16], sialylated TLR2 binds Siglec15 to initiate osteoclast fusion [#23], and TLR2 binds NOX1/NOXO1 in endothelium to drive eNOS uncoupling and diet-induced endothelial dysfunction [#21]. Endothelial TLR2 further licenses P-selectin surface localization and adhesion-molecule upregulation to support inflammation, tumor angiogenesis, and immune recruitment [#22].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that TLR2 is a functional signaling receptor, not merely an orphan membrane protein, by showing it activates NF-\\u03baB when expressed in cells.\",\n      \"evidence\": \"Functional NF-\\u03baB activation assay in transfected cells (cloned as TIL4)\",\n      \"pmids\": [\"9596645\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No ligand identified at this stage\", \"Single functional readout, foundational cloning only\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined the canonical TLR2 signaling cascade by epistasis, ordering MyD88\\u2192IRAK\\u2192TRAF6/TRAF2\\u2192NIK\\u2192IKK\\u2192NF-\\u03baB to drive cytokine gene induction.\",\n      \"evidence\": \"Dominant-negative mutant overexpression with NF-\\u03baB reporter and IL-8 induction in HEK293/CD14 cells; parallel finding of distinct TLR2 vs TLR4 cytokine outputs and PI3K/p38 involvement in dendritic cells\",\n      \"pmids\": [\"11254583\", \"11521063\", \"11477091\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve co-receptor requirement\", \"Adapter docking mechanism unmapped\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showed TLR2 activates p38 MAPK directly and that TLR1-TLR2 heterodimers, assembled via their TIR domains, are required for functional signaling, establishing receptor architecture.\",\n      \"evidence\": \"In vitro p38 kinase assay with ATF2 substrate; confocal colocalization, chimeric receptor epistasis and cross-linking of TLR1/TLR2\",\n      \"pmids\": [\"11867688\", \"12975352\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not distinguish TLR1 vs TLR6 functional differences\", \"Ligand-induced conformational changes not resolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstrated genetically that TLR2 signaling requires MyD88 but can be independent of TLR4/TLR6 for specific ligands, and revealed dual pro- and anti-inflammatory outputs.\",\n      \"evidence\": \"Macrophages from TLR2, TLR4, TLR6, and MyD88 knockout mice stimulated with mycobacterial lipomannans\",\n      \"pmids\": [\"15034058\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of the MyD88-independent inhibitory effect undefined\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Revealed heterodimer-specific adapter usage: TLR2/TLR6 couples Mal to PI3K p85\\u03b1 in a MyD88-independent branch driving Akt and macrophage polarization, whereas TLR2/1 does not.\",\n      \"evidence\": \"Reciprocal Co-IP of Mal with p85\\u03b1, Akt/PIP3 assays in MyD88- and Mal-deficient cells\",\n      \"pmids\": [\"19574958\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of Mal-p85\\u03b1 docking not resolved\", \"Did not map how heterodimer geometry selects this branch\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Mapped the molecular basis of differential adapter recruitment, assigning the MyD88 docking site to the TLR1 TIR D-helix and the TIRAP site to the TLR6 TIR D-helix.\",\n      \"evidence\": \"Cell-permeable D-helix peptides blocking Co-IP of TLR2 with MyD88 or TIRAP; in vitro binding\",\n      \"pmids\": [\"27150837\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab, peptide-competition based\", \"No co-crystal of the TIR-adapter interface\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Established a non-transcriptional output of TLR2: c-Src/PI3K/PLC\\u03b3-dependent IP3R activation releasing intracellular Ca\\u00b2\\u207a, broadening TLR2 signaling beyond NF-\\u03baB.\",\n      \"evidence\": \"Ca\\u00b2\\u207a flux and kinase inhibition studies in airway epithelium and TLR2-deficient macrophages\",\n      \"pmids\": [\"16818794\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct c-Src phosphorylation site on TLR2 not defined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified a CD36/TLR2/TLR6 receptor complex transducing oxidized-phospholipid signals through TIRAP-MyD88-IRAK-TRAF6 to integrin activation, linking TLR2 to thrombosis.\",\n      \"evidence\": \"Co-IP of the platelet receptor complex, MyD88/TLR2/TLR6 knockouts, in vivo intravital thrombosis in ApoE-/- mice\",\n      \"pmids\": [\"28775078\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and assembly order of the CD36/TLR2/TLR6 complex unresolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed TLR2 senses the endogenous danger signal HMGB1 through MyD88, driving SP1-dependent vWF transcription and mesangial fibronectin deposition, extending TLR2 to sterile inflammatory disease.\",\n      \"evidence\": \"TLR2 silencing/antibody blockade, HMGB1 and SP1 inhibitors, promoter binding assays; TLR2-/- and HMGB1-/- mouse disease models\",\n      \"pmids\": [\"27480067\", \"31667864\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct HMGB1-TLR2 binding affinity not measured\", \"Co-receptor for HMGB1 sensing not defined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Structurally defined the TLR2 agonist-binding pocket using the synthetic agonist Diprovocim, confirming a hydrophobic inter-ectodomain pocket that drives dimerization.\",\n      \"evidence\": \"Crystal structure of Diprovocim-TLR2 ectodomain complex with biophysical dimerization assays\",\n      \"pmids\": [\"30829478\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not capture full ternary TLR2/TLR1/MyD88 signaling assembly\", \"Endogenous lipopeptide binding mode inferred not crystallized here\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Uncovered glycosylation-dependent TLR2 function: ST3Gal1-mediated sialylation of TLR2 enables binding to Siglec15 to initiate osteoclast cell-cell fusion, a role distinct from pathogen sensing.\",\n      \"evidence\": \"Co-IP of Siglec15 with sialylated TLR2, ST3Gal1 knockdown, macrophage Siglec15 conditional knockout, in vivo sialidase injection\",\n      \"pmids\": [\"35232979\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether this fusion role requires canonical TLR2 signaling is unaddressed\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated TLR2 forms a physical complex with NOX1/NOXO1 driving eNOS uncoupling, and that endothelial TLR2 licenses P-selectin and adhesion molecule expression, defining endothelial/vascular roles.\",\n      \"evidence\": \"Co-IP of TLR2 with NOX1/NOXO1, TLR2 reporter and endothelial-specific knockout mice, vascular and tumor models\",\n      \"pmids\": [\"34127487\", \"33986920\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ligand triggering endothelial TLR2-NOX1 assembly in vivo not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How distinct co-receptor pairings and context-specific partners (CD36, NOX1, Siglec15, Dectin-1, C5aR1) are integrated to select among the NF-\\u03baB, PI3K/Akt, Ca\\u00b2\\u207a, and adhesion outputs of TLR2 remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified structural model of context-dependent TLR2 signalosomes\", \"Quantitative rules linking receptor proximity/composition to output selection lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 1, 4]},\n      {\"term_id\": \"GO:0001618\", \"supporting_discovery_ids\": [16, 24]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [16, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [4, 16, 23]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [1, 5, 8]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 6, 8]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [16, 28]}\n    ],\n    \"complexes\": [\n      \"TLR2/TLR1 heterodimer\",\n      \"TLR2/TLR6 heterodimer\",\n      \"CD36/TLR2/TLR6 platelet complex\",\n      \"TLR2/NOX1/NOXO1 complex\"\n    ],\n    \"partners\": [\n      \"TLR1\",\n      \"TLR6\",\n      \"MyD88\",\n      \"TIRAP\",\n      \"CD36\",\n      \"NOX1\",\n      \"Siglec15\",\n      \"C5aR1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}