Toll-like receptor 4 – Lymphocyte antigen 96 complex (TLR4-MD-2) (TLR4-MD-2)

The Toll-like receptor 4 – Lymphocyte antigen 96 (TLR4-MD-2) complex is a primary component of the innate immune system responsible for the detection of lipopolysaccharide (LPS) from Gram-negative bacteria (UniProt: O00206, Q9Y6Y9). TLR4 is a transmembrane protein that requires the extracellular co-receptor MD-2 to successfully bind LPS and initiate a signaling cascade (Park et al., Nature, 2009). Upon ligand recognition, the complex undergoes a conformational change leading to the dimerization of two TLR4-MD-2-LPS units, which recruits intracellular adapter proteins like MyD88 and TRIF to trigger the production of pro-inflammatory cytokines and type I interferons (Ciesielska et al., 2021). Dysregulation or overactivation of this complex is a central driver in the pathogenesis of septic shock, chronic inflammatory conditions, and certain types of neuropathic pain (Kuzmich et al., 2017). Consequently, the TLR4-MD-2 complex is a major therapeutic target, with drug development focusing on antagonists to treat sepsis and inflammation, as well as agonists used as potent vaccine adjuvants to enhance adaptive immunity (Lu et al., 2008).

Other names

TLR4-LY96 complexMD2-TLR4 complexLipopolysaccharide receptor complexLPS receptor

Antagonists bind to the MD-2 hydrophobic pocket or the TLR4-MD-2 interface to prevent lipopolysaccharide (LPS) binding or inhibit the dimerization of the TLR4-MD-2 complex, thereby blocking the activation of MyD88- and TRIF-dependent signaling pathways. Agonists mimic the lipid A portion of LPS to induce controlled receptor dimerization and immune activation.