Two Cathelicidin Genes Are Present in both Rainbow Trout ( Oncorhynchus mykiss ) and Atlantic Salmon ( Salmo salar )

Abstract

Further to the previous finding of the rainbow trout rtCATH_1 gene, this paper describes three more cathelicidin genes found in salmonids: two in Atlantic salmon, named asCATH_1 and asCATH_2, and one in rainbow trout, named rtCATH_2. All the three new salmonid cathelicidin genes share the common characteristics of mammalian cathelicidin genes, such as consisting of four exons and possessing a highly conserved preproregion and four invariant cysteines clustered in the C-terminal region of the cathelin-like domain. The asCATH_1 gene is homologous to the rainbow trout rtCATH_1 gene, in that it possesses three repeat motifs of TGGGGGTGGC in exon IV and two cysteine residues in the predicted mature peptide, while the asCATH_2 gene and rtCATH_2 gene are homologues of each other, with 96% nucleotide identity. Salmonid cathelicidins possess the same elastase-sensitive residue, threonine, as hagfish cathelicidins and the rabbit CAP18 molecule. The cleavage site of the four salmonid cathelicidins is within a conserved amino acid motif of QKIRTRR, which is at the beginning of the sequence encoded by exon IV. Two 36-residue peptides corresponding to the core part of rtCATH_1 and rtCATH_2 were chemically synthesized and shown to exhibit potent antimicrobial activity. rtCATH_2 was expressed constitutively in gill, head kidney, intestine, skin and spleen, while the expression of rtCATH_1 was inducible in gill, head kidney, and spleen after bacterial challenge. Four cathelicidin genes have now been characterized in salmonids and two were identified in hagfish, confirming that cathelicidin genes evolved early and are likely present in all vertebrates.

Cloning of two rainbow trout nucleotide-binding oligomerization domain containing 2 (NOD2) splice variants and functional characterization of the NOD2 effector domains

“…The cells were washed immediately with culture medium and incubated at 20 C for 6 h. The RNA preparation and real-time PCR analysis was as described above. The genes studied by real time PCR were trNOD2 (this paper), IRF3 and IRF7 [26], IFN1 and IFN2 [19], IFN-g1 [23], IFN-g2 [27], IL-1b1 [28], IL-6 [29], IL-8 [30], TNFa [31], CATH2 [32], caspase-1 (TC Number of rainbow trout EST, TC172333), -2 (TC Number of rainbow trout EST, TC170354), -3 (TC Number of rainbow trout EST, TC148559), -6 [24], -7 (TC Number of rainbow trout EST, TC154414), -8 (TC Number of rainbow trout EST, TC133215), and -9 (GeneBank accession no. NP_001118119).…”

“…In rainbow trout, Chang et al [32] have previously identified two cathelicidin genes, with the expression of cathelicidin-2 (cath2) high in RTG-2 cells. Thus, we next examined the expression of cath2 in cells tranfected with the trout NOD2 effector ptGFP1-trNOD2a CARD, ptGFP1-trNOD2b CARD, ptGFP1-NACHT or ptGFP1-LRR plasmid.…”

An Overview of the Immunological Defenses in Fish Skin

“…By screening cDNA libraries or by using molecular methodology, putative cathelicidins have been found from rainbow trout [159], Atlantic salmon [174], Arctic char (Salvelinus alpines), Atlantic cod, and brook trout (Salvelinus fontinalis) [175]. Moreover, cathelicidin genes have been reported for jawless fish, namely, the Atlantic hagfish (Myxine glutinosa) [176].…”

“…Moreover, cathelicidin genes have been reported for jawless fish, namely, the Atlantic hagfish (Myxine glutinosa) [176]. Little information is available with respect to the native peptides, but synthetic rainbow trout cathelicidins are active against Gram-positive and Gram-negative bacteria [174].…”

Structural and functional characterization of CATH_BRALE, the defense molecule in the ancient salmonoid, Brachymystax lenok

“…Although numerous previous studies predicted mature peptide only against valine, in current work we consult the sequences alignment result (Fig. 3), aided with enzymatic cleavage study carried out by Chang et al [12], where a full-length recombinant protein and Western blot analysis were explored followed by a precise mass spectroscopic confirmation. Thus, threonine (146) of prepropeptide is assumed to be the processing site for B. lenoks elastase-like protease to generate the mature peptide, CATH_BRALE.…”