Identification and Expression of Cathepsin B from Yellow Catfish (Pelteobagrusfulvidraco) in Response to Bacteria and Poly (I:C)

Abstract

Cathepsin B, a major lysosomal cysteine protease of the papain-like superfamily, plays an important role in host immune response. To study the immune response of yellow catfish (Pelteobagrus fulvidraco) to pathogens, a 1297- bp cDNA of cathepsin B (PfCTSB) from yellow catfish was cloned. It contained a 993-bp ORF flanked by a 25-bp 5′-untranslated region (UTR) and a 279- bp 3′-UTR. The ORF encoded a 36.1 kDa cysteine protease with its deduced amino acid sharing a 90% sequence identity with that of Ictalurus punctatus. Besides, the predicted PfCTSB was a precursor, including a signal peptide, a propeptide, and a mature peptide. The mature peptide was predicted to be both an endopeptidase based on a catalytic triad (Cys107, His277 and Asn297) and an exopeptidase based on an occluding loop. Furthermore, PfCTSB mRNA was constitutively expressed in all examined tissues, with the highest level seen in liver. Yellow catfish were then injected with inactivated Aeromonas hydrophilaor poly (I:C), and PfCTSB mRNA remarkably increased in the liver, spleen and head kidney when compared with the PBS control. It can be speculated that the identified cathepsin B from yellow catfish was involved in host d-efense against infection.