Transferrin Mediated NCC Killing Activity through NCCRP-1 in Nile Tilapia (<i>Oreochromis niloticus</i>)

Abstract

Non-specific cytotoxic cell l (NCC) is a kind of important lymphocyte participating in the non-specific immune response in teleost. Non-specific cytotoxic cell receptor protein 1 (NCCRP-1) is a receptor molecule on the surface of NCC and plays an important role in mediating the activity of NCC. However, there are few reports on which signal molecule could transmit signals through NCCRP-1. In this study, yeast two-hybrid library of tilapia liver and head kidney was constructed, and a transferrin from Oreochromis niloticus (On-TF) with interaction protein sequence was obtained by screening the library with bait vector NCCRP-1 of Oreochromis niloticus (On-NCCRP-1). Then, the open reading frame (ORF) of On-TF was cloned, which had 2088 bp in length, encoding polypeptides of 695 amino acids. The deduced amino acid sequence was highly homologous to teleost and similar to mammalian TF, containing two TR_FER domains (25-343th aa and 344-686th aa) for binding iron ions. Furthermore, a point-to-point yeast two-hybrid method was used to further verify whether On-NCCRP-1 could bind to On-TF. The recombinant On-TF (rOn-TF) protein was purified by prokaryotic expression system. In vitro experiments showed that rOn-TF could up-regulate the expression of killing effector molecule of NCC by On-NCCRP-1, and rOn-TF-activated NCCs showed a significantly improved ability to kill FHM cells, indicating that rOn-TF could regulate the NCC signaling pathway through NCC receptor molecule On-NCCRP-1. The results provide a more theoretical basis for understanding the regulation mechanism of NCC activity.

Keywords

• aquaculture
• cytotoxicity
• immune response
• natural killer cell
• apoptosis