Recombinant Rat Toll-like receptor 4 (Tlr4), partial Protein

Function

Transmembrane receptor that functions as a pattern recognition receptor recognizing pathogen- and damage-associated molecular patterns (PAMPs and DAMPs) to induce innate immune responses via downstream signaling pathways. At the plasma membrane, cooperates with LY96 to mediate the innate immune response to bacterial lipopolysaccharide (LPS). Also involved in LPS-independent inflammatory responses triggered by free fatty acids, such as palmitate, and Ni(2+). Mechanistically, acts via MYD88, TIRAP and TRAF6, leading to NF-kappa-B activation, cytokine secretion and the inflammatory response. Alternatively, CD14-mediated TLR4 internalization via endocytosis is associated with the initiation of a MYD88-independent signaling via the TICAM1-TBK1-IRF3 axis leading to type I interferon production. In addition to the secretion of proinflammatory cytokines, initiates the activation of NLRP3 inflammasome and formation of a positive feedback loop between autophagy and NF-kappa-B signaling cascade. In complex with TLR6, promotes inflammation in monocytes/macrophages by associating with TLR6 and the receptor CD86. Upon ligand binding, such as oxLDL or amyloid-beta 42, the TLR4:TLR6 complex is internalized and triggers inflammatory response, leading to NF-kappa-B-dependent production of CXCL1, CXCL2 and CCL9 cytokines, via MYD88 signaling pathway, and CCL5 cytokine, via TICAM1 signaling pathway. In myeloid dendritic cells, vesicular stomatitis virus glycoprotein G but not LPS promotes the activation of IRF7, leading to type I IFN production in a CD14-dependent manner

Subcellular Location

Cell membrane (Single-pass type I membrane protein); Early endosome; Cell projection, ruffle

Subunit

Belongs to the lipopolysaccharide (LPS) receptor, a multi-protein complex containing at least CD14, LY96 and TLR4. Binding to bacterial LPS leads to homodimerization. Interacts with LY96 via the extracellular domain. Interacts with MYD88 and TIRAP via their respective TIR domains. Interacts with TICAM2. Interacts with NOX4. Interacts with CNPY3 and HSP90B1; this interaction is required for proper folding in the endoplasmic reticulum. Interacts with MAP3K21; this interaction leads to negative regulation of TLR4 signaling. Interacts with CD36, following CD36 stimulation by oxLDL or amyloid-beta 42, and forms a heterodimer with TLR6. The trimeric complex is internalized and triggers inflammatory response. LYN kinase activity facilitates TLR4-TLR6 heterodimerization and signal initiation. Interacts with TICAM1 in response to LPS in a WDFY1-dependent manner. Interacts with WDFY1 in response to LPS. Interacts with SMPDL3B. Interacts with CEACAM1; upon lipopolysaccharide stimulation, forms a complex including TLR4 and the phosphorylated form of SYK and CEACAM1, which in turn, recruits PTPN6 that dephosphorylates SYK, reducing the production of reactive oxygen species (ROS) and lysosome disruption, which in turn, reduces the activity of the inflammasome. Interacts with RFTN1; the interaction occurs in response to lipopolysaccharide stimulation. Interacts with SCIMP; the interaction occurs in response to lipopolysaccharide stimulation and is enhanced by phosphorylation of SCIMP by LYN (By similarity). This interaction facilitates the phosphorylation of TLR4 by LYN which elicits a selective cytokine response in macrophages (By similarity). Interacts with TRAF3IP3 (By similarity). Interacts with TREM1; this interaction enhances TLR4-mediated inflammatory response (By similarity). Interacts with ZG16B/PAUF (By similarity). Interacts with CD82; this interaction inhibits TLR4-mediated signaling pathway (By similarity)

• Frantz S. et al. Toll4 (TLR4) expression in cardiac myocytes in normal and failing myocardium. — J. Clin. Invest. (1999)
• Chao C.N. et al. CHIP attenuates lipopolysaccharide-induced cardiac hypertrophy and apoptosis by promoting NFATc3 proteasomal degradation. — J. Cell. Physiol. (2019)