Molecular characterization and expression analysis of cathepsin C in the marine crab Charybdis japonica (A. Milne-Edwards, 1861) (Decapoda, Brachyura, Portunidae)

Cathepsin C is a crucial lysosomal cysteine proteinase that takes part in protein degradation and proenzyme activation. In this study, cDNA of cathepsin C in Charybdis japonica (A. Milne-Edwards, 1861) (designated as Cj-cath C ) was cloned and characterized. The results showed that the open reading frame (ORF) of Cj-cath C was 1356 bp and encoded a protein of 451 amino acids. Cj-cath C contained two catalytic residues, a Cathepsin C exclusion domain and a Peptidase_C1 domain. The Cj-cath C was widely expressed in all tissues, with highest expression in hepatopancreas and heart. The transcript levels of Cj-cath C in the hepatopancreas and haemolymph were up-regulated after stimulation by Vibrio anguillarum Bergeman, 1909 and reached a peak value at 6 h post-infection, followed by a gradual decrease. These observations indicate that Cj-cath C might be a constitutive and inducible acute-phase protein that is involved in the immune defense of C. japonica .