TLR2

Toll-like receptor 2 (TLR2) is a protein that in humans is encoded by the TLR2 gene. TLR2 is one of the toll-like receptors and plays a role in the immune system. TLR2 is a membrane protein, a receptor, which recognizes the lipid components of the cell wall of microbial pathogens. It activates the innate immune system upon recognition of bacterial lipoproteins and other components.

Function

TLR2 is a member of the toll-like receptor (TLR) family, which plays a fundamental role in pathogen recognition and activation of innate immunity. TLRs are highly conserved from Drosophila to humans and share structural and functional similarities. They recognize pathogen-associated molecular patterns (PAMPs) that are expressed on infectious agents, and mediate the production of cytokines necessary for the development of effective immunity. The various TLRs exhibit different patterns of expression. TLR2 is expressed most abundantly in peripheral blood leukocytes, in particular, in monocytes, macrophages, and dendritic cells, which are key players in the immune response to foreign invaders. It cooperates with LY96 and CD14 to mediate the innate immune response to bacterial lipoproteins and other microbial cell wall components.

Ligands

TLR2 recognizes a broad range of microbial components, including peptidoglycan and lipoteichoic acid from gram-positive bacteria, zymosan from fungi, and glycolipids from mycobacteria. It forms heterodimers with other TLR family members, such as TLR1 or TLR6, which determines its ligand specificity.

Signaling Pathway

Upon ligand binding, TLR2 dimerizes and initiates a signaling cascade that leads to the activation of the NF-κB pathway. This results in the transcription of various inflammatory cytokines, chemokines, and other molecules involved in the inflammatory response. The TLR2 signaling pathway plays a crucial role in the host defense against a wide array of microbial pathogens.

Clinical Significance

Alterations in TLR2 expression or function can influence susceptibility to infectious diseases, as well as contribute to the pathogenesis of certain inflammatory and autoimmune conditions. Polymorphisms in the TLR2 gene have been associated with an increased risk of infections such as tuberculosis and Lyme disease, as well as with diseases like asthma and atherosclerosis.

Research Directions

Research on TLR2 continues to uncover its role in immunity and its potential as a therapeutic target. Strategies to modulate TLR2 activity are being explored for the treatment of infectious diseases, cancer, and inflammatory conditions.

See Also

• Toll-like receptor
• Innate immune system
• Cytokine
• NF-κB