|Detection of TLR6 in RAW 264.7 Mouse Cell Line by Flow Cytometry. RAW 264.7 mouse monocyte/macrophage cell line was stained with Rat Anti-Mouse TLR6 APC‑conjugated Monoclonal Antibody (Catalog # FAB1533A, filled histogram) or isotype control antibody (Catalog # IC006A, open histogram). View our protocol for Staining Membrane-associated Proteins.|
The Toll-like family of molecules are a group of integral membrane proteins that serve as pattern recognition receptors for microbial pathogens. There are at least eleven mouse and ten human members that activate the innate immune system following exposure to a variety of microbial species (1‑4). All Toll-like receptors (TLRs) are type I transmembrane (TM) proteins that exist either in the plasma membrane or in the membranes of endosomal structures (where they bind intracellular microbial nucleic acids). All TLRs also contain a large number of extracellular leucine-rich repeats (LRRs) and a cytoplasmic tail with a Toll/IL-1 receptor (TIR) domain. The mouse TLR6 cDNA encodes a 795 amino acid (aa) precursor that includes a 27 aa signal sequence, a 557 aa extracellular domain (ECD), a 21 aa transmembrane segment, and a 190 aa cytoplasmic domain. The ECD contains 14 Leu-rich repeats, and the cytoplasmic region contains one TIR domain (5). Within the ECD, mouse TLR6 shares 59% aa sequence identity with mouse TLR1 and 20‑27% aa sequence identitity with mouse TLR2, -3, -4, -5, -7, -8, -9, -11, -12, and -13. It shares 71%, 72%, and 86% aa sequence identity with bovine, human, and rat TLR6, respectively. TLR6 is expressed on the cell surface of macrophages, monocytes, neutrophils, and dermal endothelial cells in ligand-independent association with TLR2 (6‑9). TLR2 also associates with TLR1, a functional complex with specificity for distinct but related microbial ligands (6‑8). TLR6 and TLR2 cooperate in the recognition of acylated bacterial and mycoplasma lipopeptides, peptidoglycan, and glycosylphosphatidylinositols (7‑14). The cytoplasmic TIR domain is necessary and sufficient to initiate signal transduction which leads to activation of NF kappa B (7, 15).