title: Characterization and expression of sweetfish (Pleco glossus altivelis) cathepsin D.
abstract: Cathepsin D (CTSD) is a lysosomal acidic endoproteinase that plays an important role in immune response. In this study, we obtained sweetfish (Plecoglossus altivelis) CTSD (PaCTSD) via de-novo transcriptome sequencing of sweetfish macrophages. The full length cDNA sequence of PaCTSD was 1 955 bp encoding a propeptide of 397 amino acids. The deduced protein had a calculated molecular weight of 43.17 × 10³. Multiple alignment with other known CTSD amino acid sequences revealed amino acid conservation through the teleosts. Phylogenetic tree analysis showed that PaCTSD grouped tightly with other fish CTSD, and was close to that of Atlantic salmon and rainbow trout. Subsequently, PaCTSD was prokaryotically expressed and refolded by the urea gradient method on a nickel-nitrilotriacetic acid column. Enzyme activity analysis showed that PaCTSD exhibited pH-dependent proteolytic activity. Quantitative real-time PCR showed that PaCTSD mRNA was expressed in all detected tissues in healthy sweetfish. The highest expression was observed in the spleen and white blood cells, followed by liver, head-kidney, kidney, intestine, gill, and muscle. After Listonella anguillarum infection, PaCTSD transcripts were up-regulated significantly in liver, spleen, white blood cells, and head-kidney of sweetfish. In summary, PaCTSD has proteolytic activity and is closely involved in the immune response of sweetfish.
authors.affiliation: Key Laboratory of Applied Marine Biotechnology, Ministry of Education, Ningbo University, Ningbo 315211, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Jiao
authors.affiliation: Key Laboratory of Applied Marine Biotechnology, Ministry of Education, Ningbo University, Ningbo 315211, China.
authors.forename: Chang-Hong
authors.initials: CH
authors.lastname: Li
authors.affiliation: Key Laboratory of Applied Marine Biotechnology, Ministry of Education, Ningbo University, Ningbo 315211, China . lxj711043@163.com.
authors.forename: Xin-Jiang
authors.initials: XJ
authors.lastname: Lu
authors.affiliation: Key Laboratory of Applied Marine Biotechnology, Ministry of Education, Ningbo University, Ningbo 315211, China.
authors.forename: Jiong
authors.initials: J
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002402:Cathepsin D / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D008969:Molecular Sequence Data; D036441:Osmeriformes / Q000378:metabolism*; D058974:Phylogeography; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D002402:Cathepsin D
keywords: Bacterial infection; Cathepsin D; Plecolossus altivelis; Prokaryotic expression; qRT-PCR