Toll-like receptor 4 (TLR4) complex (TLR4 complex)

The Toll-like receptor 4 (TLR4) complex is a pivotal pattern recognition receptor of the innate immune system, primarily recognized for its role in detecting lipopolysaccharide (LPS) from Gram-negative bacteria (UniProt O00206). The functional complex is composed of the TLR4 transmembrane protein and the extracellular accessory protein myeloid differentiation factor 2 (MD-2), with additional support from CD14 and LPS-binding protein (LBP) (PubMed 35307617). Upon activation, the complex undergoes homodimerization, which recruits intracellular adaptor proteins such as MyD88 and TRIF to initiate pro-inflammatory and antiviral signaling cascades. These pathways culminate in the activation of transcription factors like NF-κB and IRF3, leading to the secretion of cytokines such as TNF-α and IL-6 (Wikipedia). While essential for host defense, excessive or chronic activation of the TLR4 complex is implicated in the pathogenesis of sepsis, autoimmune disorders, and various cancers (PubMed 35307617). Therapeutic strategies targeting this complex include antagonists like Eritoran and TAK-242 to mitigate hyper-inflammation, as well as agonists like monophosphoryl lipid A (MPLA) used as potent vaccine adjuvants (PubMed 35307617).

Other names

TLR4/MD-2 complexCD284 complexLPS receptor complexToll-like receptor 4/Myeloid differentiation factor 2 complex

The TLR4 complex recognizes lipopolysaccharide (LPS) through the coordinated action of LBP, CD14, and MD-2, leading to TLR4 dimerization. This dimerization recruits intracellular adaptors (MyD88, TIRAP, TRIF, TRAM) to the TIR domain, activating NF-κB and IRF pathways to induce pro-inflammatory cytokines and type I interferons (Wikipedia, PubMed 35307617).