Identification of a gene encoding a membrane-anchored toll-like receptor 5 (TLR5M) in Oplegnathus fasciatus that responds to flagellin challenge and activates NF-κB. Issue 62 (March 2017)

• Record Type: Journal Article
• Authors: Umasuthan, Navaneethaiyer; Bathige, S.D.N.K.; Thulasitha, William Shanthakumar; Jayasooriya, R.G.P.T.; Shin, Younhee; Lee, Jehee
• Is Part Of: Fish & shellfish immunology. Issue 62(2017)
• Page Start: 276
• Page End: 290
• Publication Date: 2017-03
• Subjects: Membrane-anchored toll-like receptor 5 (TLR5M) -- Myeloid differentiation primary response gene 88 (MyD88) -- Flagellin (FLA) sensing -- Genomic evolution -- NF-κB activation; Fishes -- Immunology -- Periodicals; Shellfish -- Immunology -- Periodicals; Poissons -- Immunologie -- Périodiques; Crustacés -- Immunologie -- Périodiques; 571.9617
• DOI: 10.1016/j.fsi.2017.01.020
• Languages: English
• ISSNs: 1050-4648

Abstract

Abstract: Toll-like receptor 5 (TLR5) recognizes bacterial flagellin and induces the downstream signaling through the myeloid differentiation primary response gene 88 (MyD88) protein to produce proinflammatory cytokines. In this study, we describe a TLR5 membrane form (OfTLR5M) and its adaptor protein MyD88 (OfMyD88) in rock bream, Oplegnathus fasciatus. Both Oftlr5m (6.7 kb) and Ofmyd88 (3.7 kb) genes displayed a quinquepartite structure with five exons and four introns. Protein structure of OfTLR5M revealed the conventional architecture of TLRs featured by an extracellular domain with 22 leucine rich repeats (LRR), a transmembrane domain and an endodomain with TIR motif. Primary OfTLR5M sequence shared a higher homology with teleost TLR5M. The evolutional analysis confirmed that TLR5 identified in the current study is a membrane receptor and the data further suggested the co-evolution of the membrane-anchored and soluble forms of TLR5 in teleosts. Inter-lineage comparison of gene structures in vertebrates indicated that the tlr5m gene has evolved with extensive rearrangement; whereas, the myd88 gene has maintained a stable structure throughout the evolution. Inspection of 5′ flanking region of these genes disclosed the presence of several transcription factor binding sites including NF-κB. Quantitative real-time PCR (qPCR) detected Oftlr5m mRNA in eleven tissues with the highest abundance in liver. In vivo flagellin administration strongly induced the transcripts of both Oftlr5m and Ofmyd88 in gills and head kidney tissues suggesting their ligand-mediated upregulation. In a luciferase assay, HEK293T cells transiently transfected with Oftlr5m and Ofmyd88 demonstrated a higher NF-κB activity than the mock control, and the luciferase activity was intensified when cells were stimulated with flagellin. Collectively, our study represents the genomic, evolutional, expressional and functional insights into a receptor and adaptor molecules of teleost origin that are involved in flagellin sensing. Highlights: Oftlr5m and Ofmyd88 genes in rock bream display quinquepartite structure. While gene structure of tlr5m is evolved with rearrangements, myd88 is preserved. Oftlr5m and Ofmyd88 showed similar tissue mRNA profile with highest level in liver. Oftlr5m and Ofmyd88 were induced by ultrapure flagellin in gill and head kidney. They individually and synergetically activated NF-κB upon flagellin-stimulation.