Researches on the Evolution, Function, and Related Diseases of TLR5
LIU Yu1,2,3#, YIN Haoran1#, GENG Ming1,2,3, LI Qingwei1,2,3*, ZHU Ting1,2,3*
Since the discovery of the first TLR (Toll-like receptor) protein, several TLR family members have been identified. TLR5, an important member of the TLR family, is the major extracellular receptor that recognizes flagellin. TLR5 in vertebrates has highly conserved structure and function, with a typical TLR domain that consists of a variable number of leucine-rich repeats, a transmembrane domain, and an intracellular Toll/IL-1 receptor domain. It is only in fish that TLR5 has two forms, namely TLR5M (the membrane-anchored form TLR5) and TLR5S (the soluble form TLR5). Both TLR5M and TLR5S function by forming a dimer complex, amplifying the signaling cascade, and rapidly initiating the immune response. Upon flagellin ligation, TLR5 dimerizes and activates signaling cascades, leading to the release of pro- or anti-inflammatory cytokines or antibacterial compounds. Hence, TLR5 plays an essential role in providing host defense against flagellated pathogens and maintaining or re-establishing homeostasis in the gastrointestinal tract. Although there have been relatively few studies on TLR5 functions, TLR5/MyD88/NF-κB is found to be an important signaling pathway in the diagnosis and treatment of diseases, and it has great research value. Researches on TLR5 can provide new insights for exploring host-microbe interactions and may provide an important basis for disease prevention and diagnosis.
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