Molecular characterization of CathepsinH identified in the sevenband grouper, Hyporthodus septemfasciatus and its functional analysis against NNV infection

Abstract

Nervous necrosis virus (NNV) has caused mass mortality in aqua-farms of seven band groupers during the summer season and has made huge economic losses in Korea. However, the infection mechanisms of NNV are not clear yet. Cathepsin H, a lysosomal cysteine proteinase involved in overall lysosomal protein breakdown was one of the most highly expressed proteins. The counting sequence of Cathepsin H was 1409 nucleotide lengths. The open reading frame (ORF) of the seven-band grouper Cathepsin H (SG.CatsH) was 987bp in length and the deduced protein consisted of 329 amino acids (approximately 20 kDa molecular weight). The highest identity (98%) from the BLAST search was observed with Cathepsin H from the giant grouper (Epinephelus lanceolatus). The spleen, heart, gill, brain, eye, liver, kidney, and blood of Hyporthodus septemfasciatus and CatsH was highly expressed in the kidney. In the experiment, we made CatsH transfection to striped snakehead cell (SSN-1) fish cell line and challenge with NNV. In NNV infection the gene expression increase in the brain. The expression of SG.CatsH in SSN-1 cells delayed the appened of cytopathic effect (CPE) by NNV infection. Further elucidation indicates that Cathepsin H can significantly delay CPE in the SSN-1 cell line. This study will provide new ideas and effects in the prevention of NNV and understanding of NNV infection mechanisms.