Molecular cloning and characterization of Toll-like receptor 14 in Japanese flounder, Paralichthys olivaceus.
ABSTRACT Toll-like receptors (TLRs) are essential for activation of the innate immune system in response to invading pathogens. TLR14, which is unique to fish, has been identified in several fish species, but its function is unclear. In this study, Japanese flounder (Paralichthys olivaceus) TLR14 gene (JfTLR14) was cloned and its expression profiles were analyzed after infection with viral hemorrhagic septicemia virus, gram-positive Streptococcus iniae and gram-negative Edwardsiella tarda. The coding region of JfTLR14 cDNA was 2,607 bp, encoding 878 amino acid residues. JfTLR14 was highly expressed in head kidney of healthy flounder. In response to infection with VHSV and S. iniae, the JfTLR14 gene was up-regulated at only 1 day post-infection (dpi). However, E. tarda infection increased JfTLR14 gene expression from 1 to 6 dpi. These results imply that JfTLR14 participates more in the immune response against E. tarda infection than in the immune responses to other pathogen infections.
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ABSTRACT: During the past decade, huge progress has been made in research into teleost PAMPs (pathogen-associated molecule patterns) recognition receptors (PRRs). Numerous fish PRR genes have been identified, and the primordial functions of PRRs involved in the innate immune response to viral infection (especially those responsible for sensing viral RNA) have been increasingly clarified in teleosts. Particular progress has been made in our understanding of Toll-like receptors (TLRs) and retinoic acid inducible gene I (RIG-I)-like receptors (RLRs). However, there are important evolutionary differences between teleosts and mammals; for instance, seven TLR repertoires (TLR5S, -14, -19, -20, -21, -22 and -23) are present in teleosts but not in mammals, indicating that some TLRs likely possess different functions. Thus, comparison of PRRs in teleosts and mammals may help us understand the immune responses triggered by host-pathogen interactions in teleosts. In this article, the evolutionary conservations and divergences in the PRR mechanisms of teleosts and mammals are examined, with a focus on their molecular features and the recognition of viral RNA by fish TLRs and RLRs. In addition, the mechanism of type I interferon gene expression in teleosts, which is enhanced after the recognition of viral RNA by fish TLRs and RLRs, is also introduced.Fish & Shellfish Immunology 02/2013; · 2.96 Impact Factor
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ABSTRACT: A comprehensive survey of channel catfish Toll-like receptors (TLRs) was undertaken following a genomic PCR approach based on degenerate primers. Twenty different TLRs were identified in channel catfish. Channel catfish TLR sequences were characterized by phylogenetic analysis based on their conserved Toll/interleukin-1 receptor domain and by in-depth analysis of leucine-rich repeat (LRR) motifs of the ligand binding extracellular domain (ECD). The catfish have representatives of all the TLR types defined in vertebrates with the exception of TLR6, TLR10, TLR11, TLR12, TLR13, TLR15, TLR23, and TLR24. Additionally, two new types were discovered: TLR25 and TLR26. TLR25 is also present in cyprinids, cichlids, plecoglossids, and adrianichthyids, suggesting its presence early in fish evolution. To date, TLR26 was found only in channel catfish. Like TLR18-23, TLR25 and TLR26 were not found in any other vertebrate classes and appear to be fish specific. Data mining using the catfish TLR sequences revealed that in addition to ictalurids and cyprinids, TLR4 is also present in salmonids. TLR19 and TLR20 were both found in ictalurids, cyprinids, and salmonids, demonstrating a wider range than previously known. The LRR structure within ECDs appeared generally well conserved. TLR7 demonstrated a very high identity to human TLR7 strongly suggesting that ligand specificity maybe conserved. Finally, expression profiling confirmed that most TLRs are widely expressed in a diversity of tissues and revealed marked differences of expression level.Immunogenetics 04/2013; · 2.89 Impact Factor
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ABSTRACT: Toll-like receptor (TLR) is believed to play crucial role in host defense of pathogenic microbes in innate immune system. In the present study, the full-length cDNA of Paralichthys olivaceus Toll-like receptor 21 (Po-TLR21) was cloned by homology cloning and rapid amplification of cDNA ends (RACE) technique. The Po-TLR21 cDNA sequence was 3687 bp, containing an open reading frame of 2922 bp encoding 973 amino acids. TMHMM and SMART program analysis indicated that protein contained one transmembrane domain, eighteen leucine-rich repeats (LRRs), and one Toll/IL-1 receptor homology domain (TIR). Multiple alignment analysis of the Po-TLR21 protein-coding sequence with other known TLR21 from grouper, pufferfish, zebrafish, cod, catfish, carp and chicken showed the homology of 67%, 63%, 54%, 52%, 51%, 49%, and 39%, respectively. The Po-TLR21 mRNA expression patterns were measured by real-time PCR. The results revealed that TLR21 is widely expressed in various tested healthy tissues, and highly expressed in spleen and gill. In vivo immunostimulation experiments revealed that expression of TLR21 is modulated by Vibrio anguillarum (V. anguillarum), CpG oligodeoxynucleotides (CpG ODN) and poly I:C. Moreover, the inhibitor of homodimerization of myeloid differentiation factor 88 (MyD88) could significantly reduce the up-regulation of TLR21, MyD88, and tumor necrosis factor (TNF) expression in CpG ODN or poly I:C-treated head kidney cells in vitro. These results indicate that TLR21 may be involved in the pathogen recognition in the early innate immune.Fish & Shellfish Immunology 07/2013; · 2.96 Impact Factor