TLR2 — Toll-Like Receptor 2
Pathway Diagram
Mermaid diagram (expand to render)
Introduction
Tlr2 — Toll Like Receptor 2 is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
<div class="infobox infobox-gene"> [@zhang2019]
<span class="infobox-title">TLR2 Gene</span> [@fellner2013]
| Property | Value | [@liu2020]
|----------|-------| [@bsibsi2014]
| Gene Symbol | TLR2 |
| Full Name | Toll-Like Receptor 2 |
| Chromosomal Location | 4q31.3 |
| NCBI Gene ID | 7103 |
| OMIM ID | 603028 |
| Ensembl ID | ENSG00000137462 |
| UniProt ID | Q9Y257 |
| Associated Diseases | Alzheimer's Disease, Parkinson's Disease, Multiple Sclerosis, Neuroinflammation |
</div>
Overview
TLR2 (Toll-Like Receptor 2) encodes a pattern recognition receptor that recognizes pathogen-associated molecular patterns (PAMPs) from Gram-positive bacteria, fungi, and viruses. TLR2 plays a critical role in the innate immune response and has been increasingly recognized as a key contributor to neuroinflammation in neurodegenerative diseases. The gene is located on chromosome 4q31.3 and encodes a 784-amino acid type I transmembrane protein.
Normal Function
TLR2 is expressed in [microglia](/cell-types/microglia-neuroinflammation), astrocytes, and neurons throughout the brain. It functions as part of the innate immune system by:
- Recognizing microbial components: Lipoproteins, peptidoglycan, lipoteichoic acid from bacteria; zymosan from fungi
- Forming heterodimers: TLR2 pairs with TLR1 or TLR6 to recognize different lipopeptide patterns
- Activating [NF-κB](/entities/nf-kb) signaling: Through MyD88 and TRAF6, leading to pro-inflammatory cytokine production
- Modulating phagocytosis: Enhancing microglial clearance of pathogens and debris
- Coordinating adaptive immunity: TLR2 signaling influences T cell responses and B cell activation
Signaling Pathways
TLR2 activation triggers multiple downstream signaling cascades:
MyD88-dependent pathway: MyD88 → IRAK4 → IRAK1/2 → TRAF6 → NF-κB/AP-1
TRIF-dependent pathway: For some ligands, TLR2 can activate IRF3 via TRIF
PI3K/Akt pathway: Provides anti-inflammatory signals to balance TLR2 responsesGene Structure
The TLR2 gene spans approximately 13 kb and consists of 3 exons. The coding sequence is contained in exon 3, which encodes the leucine-rich repeat (LRR) extracellular domain, transmembrane region, and Toll/IL-1 receptor (TIR) intracellular domain.
Disease Associations
Alzheimer's Disease
- TLR2 is upregulated in microglia surrounding amyloid plaques
- Activation contributes to chronic neuroinflammation and [Aβ](/proteins/amyloid-beta) clearance
- Genetic variants may influence AD risk
- Therapeutic targeting: TLR2 antagonists being investigated to reduce neuroinflammation
- Studies show TLR2 can both promote and inhibit [Aβ](/proteins/amyloid-beta) clearance depending on context
Parkinson's Disease
- TLR2 recognizes [α-synuclein](/proteins/alpha-synuclein) aggregates as damage-associated molecular patterns (DAMPs)
- Mediates microglial activation in response to Lewy bodies
- Contributes to dopaminergic neuron loss
- Elevated TLR2 expression in PD substantia nigra
- TLR2 deletion protects against α-synuclein-induced neurodegeneration in mouse models
Multiple Sclerosis
- TLR2 mediates demyelination and axonal injury
- Involved in autoimmune responses against myelin
- Therapeutic potential of TLR2 modulation
- TLR2 polymorphisms associated with MS susceptibility
Other Neurodegenerative Conditions
- Amyotrophic Lateral Sclerosis (ALS): TLR2 activation in motor neuron disease, contributes to neuroinflammation
- Frontotemporal Dementia (FTD): Neuroinflammation contribution through microglial activation
- Huntington's Disease: Mutant [huntingtin](/proteins/huntingtin-protein) effects on TLR2 signaling and immune dysregulation
Expression Pattern
TLR2 is expressed at moderate to high levels in:
- [Microglia](/entities/microglia) (highest expression)
- [Astrocytes](/entities/astrocytes)
- [Oligodendrocytes](/cell-types/oligodendrocytes) [Neurons](/entities/neurons) (lower expression)
Expression increases with age and in neurodegenerative conditions. Single-cell RNA-seq studies show distinct TLR2 expression patterns across microglial subpopulations.
Therapeutic Targeting
| Strategy | Approach | Status |
|----------|----------|--------|
| TLR2 Antagonists | Small molecule inhibitors (e.g., C29) | Preclinical |
| Anti-TLR2 Antibodies | Blocking antibody therapy | Research |
| Natural Compounds | Curcumin, resveratrol | In vitro studies |
| Gene Therapy | siRNA approaches | Experimental |
Animal Models
- TLR2 knockout mice: Used to study neuroinflammation and amyloid pathology
- TLR2 transgenic mice: Overexpression models to investigate immune responses
- α-synuclein/TLR2 double transgenic mice: PD model demonstrating TLR2-mediated toxicity
Research Directions
- Developing selective TLR2 antagonists for neurodegenerative diseases
- Understanding TLR2 ligand specificity and signaling bias
- Biomarker development: soluble TLR2 as a marker of neuroinflammation
- Combination therapies targeting multiple pattern recognition receptors
Background
The study of Tlr2 — Toll Like Receptor 2 has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
Brain Atlas Resources
- Allen Human Brain Atlas: [TLR2 expression](https://human.brain-map.org/microarray/search/show?search_term=TLR2)
- Allen Cell Type Atlas: [TLR2 cell type expression](https://celltypes.brain-map.org/)
- BrainSpan: [TLR2 developmental expression](https://brainspan.org/)
See Also
- [TLR4 Gene — Related toll-like receptor](/genes/tlr4)
- [Neuroinflammation — Inflammatory mechanisms](/content/mechanisms)
- [Microglia — Brain immune cells](/cell-types/microglia)
- [TREM2 — Microglial receptor](/cell-types/microglia)
- [Alzheimer's Disease — AD overview](/diseases/alzheimers-disease)
- [Parkinson's Disease — PD overview](/proteins/parkin)
External Links
- [NCBI Gene: TLR2](https://www.ncbi.nlm.nih.gov/gene/7103)
- [UniProt: TLR2](https://www.uniprot.org/uniprot/Q9Y257)
- [Ensembl: TLR2](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000137462)
- [GeneCards: TLR2](https://www.genecards.org/cgi-bin/carddisp.pl?gene=TLR2)
References
[Song M, et al, TLR2 mediates β-amyloid-induced microglial activation and neuroinflammation (2011)](https://pubmed.ncbi.nlm.nih.gov/21368038/))
[Zhang Y, et al, TLR2 gene polymorphisms and Alzheimer's disease risk: A meta-analysis (2019)](https://pubmed.ncbi.nlm.nih.gov/30340073/))
[Fellner L, et al, Toll-like receptor 2 is activated by α-synuclein and drives neuroinflammation in Parkinson's disease (2013)](https://pubmed.ncbi.nlm.nih.gov/23922071/))
[Liu S, et al, TLR2 deficiency attenuates Parkinson's disease through inhibition of microglial activation (2020)](https://pubmed.ncbi.nlm.nih.gov/32201234/))
[Bsibsi M, et al, Toll-like receptors in multiple sclerosis: Expression and potential role in disease and therapy (2014)](https://pubmed.ncbi.nlm.nih.gov/24514909/))Pathway Diagram
The following diagram shows the key molecular relationships involving TLR2 — Toll-Like Receptor 2 discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)