Cloning and expression study of a Toll-like receptor 2 (tlr2) gene from turbot, Scophthalmus maximus

Aeromonas hydrophila infection induces Toll-like receptor 2 (tlr2) and associated downstream signaling in Indian catfish, Clarias magur (Hamilton, 1822)

“…Structurally, mtlr2 is closely related to channel catfish tlr2 gene, which also consists of an ORF of 2,373 bp encoding protein of 790 amino acids ( Baoprasertkul et al, 2007 ). Our finding on number of LRRs are similar to finding by Samanta et al (2012) ; Fink et al (2016) ; Zhang et al (2016) . Also, the genomic structure of a single exon and no intron reported in human, zebra fish, and channel catfish tlr2 ( Baoprasertkul et al, 2007 ), but fugu and Japanese flounder tlr2 gene encoded by 11 and 12 exons, respectively ( Oshiumi et al, 2003 ; Hirono et al, 2004 ).…”

“…Two mRNA instability motifs (ATTTA) were found in the 3′-UTR, which suggest that mtlr2 may be transiently expressed. Two mRNA instability motifs (ATTTA) were also reported in turbot ( Zhang et al, 2016 ). The full-length cDNA of mtlr2 is of 3,066 bp and comprised of an ORF of 2,373 bp nucleotide in length, encoding 790 amino acid residues.…”

“…, signal peptide, one LRR each at N-and C-terminal, twenty extracellular LRR domains in between N-and C-terminal, trans-membrane domain and highly conserved cytoplasmic TIR domain. Number of LRR domain in other fishes reported are nine LRRs in channel catfish ( Baoprasertkul et al, 2007 ), 21 in rohu ( Samanta et al, 2012 ), 20 LRRs in human, zebra fish, channel catfish, common carp ( Fink et al, 2016 ), 19 in turbot ( Zhang et al, 2016 ), 11 in silvery pomfret ( Gao et al, 2016 ), 8 in yellow catfish ( Pelteobagrus fulvidraco ) ( Zhang et al, 2017 ), 8 in Dabry’s sturgeon ( Tang et al, 2020 ). The number of LRR signifies the functional capability to respond various agonists.…”

“…Upon binding to its cognate ligands, TLR2 then recruit the MYD88 and TIRAP ( mal ) that activate the IRAK(1 and 4)/TRAF6/IKK(α or β)/MAPKS cascade, which subsequently leads to the ubiquitination of IκB α and the activation of transcription factor NF-kb or AP-1 to induce the expression of host defense genes and subsequent production of pro-, anti-inflammatory cytokines, chemokines, immunomodulatory molecules ( Zhang et al, 2014 ). In recent years, structure and expression pattern of tlr2 has been characterized in few important fish species including zebra fish ( Jault, Pichon & Chluba, 2004 ), Japanese flounder ( Hirono et al, 2004 ), channel catfish ( Baoprasertkul et al, 2007 ), grouper ( Wei et al, 2011 ), rohu ( Samanta et al, 2012 ), Antratic teleosts ( Varriale et al, 2012 ), shark ( Anandhakumar et al, 2012 ), miiuy croaker ( Xu et al, 2013 ), yellow croaker ( Fan, Jia & Yao, 2015 ), rainbow trout ( Brietzke et al, 2016 ), tongue sole ( Li & Sun, 2016 ), silvery pomfret ( Gao et al, 2016 ), turbot ( Zhang et al, 2016 ; Liu et al, 2016 ), grass carp ( He et al, 2016 ; Liao et al, 2017 ), common carp ( Fink et al, 2016 ), golden pompano ( Wu et al, 2018 ) and Dabry’s sturgeon ( Tang et al, 2020 ). These studies have provided background information on genomic structure of tlr2 and also reported expression profile of tlr2 upon stimulation with ligand or bacterial infection.…”

Molecular characterization of four innate immune genes in Tor putitora and their comparative transcriptional abundance during wild- and captive-bred ontogenetic developmental stages

“…The number of LRR domains in TLR2 protein varies in different species, suggesting a change in their TLR2 ligand binding; like, Danio rerio TLR2 contained 7 LRRs, Cyprinus carpio, Oncorhynchus mykiss, and Ictalurus punctatus TLR2 contained 8 LRRs, Takifugu rubripes and Homo sapiens TLR2 contained 9 LRRs [ 39 , 40 ]. The TIR domain in TpTLR2 contained three conserved motifs: motif 1- Y/FDA; motif 2- DFXPG and motif 3- a conserved tryptophan (W) residue surrounded by a basic amino acid residue; and it also shared high sequence similarity with other teleost species and higher vertebrates, suggesting a common mechanism in signal transduction [ 41 , 42 ]. Motif 1 and motif 2 played roles in mediating downstream inflammation signalling pathways, whereas motif 3 was reported to be involved in cellular localization of the receptor by interacting with cytoskeletal elements [43] .…”