Identification Of Cathepsin S In Lutjanus Argentimaculatus And Its Role In Antigen Presentation

Cathepsin S belongs to the papain superfamily of cysteine proteases, has been purified from bovine lymph nodes originally and bovine spleen in 1970s. It was found that the cathepsin S plays a key role in antigen presentation in human and mouse. this protein can cleave the invariant chain (Ii chain) leaving the CLIP fragment occupying the peptide-binding groove, then the CLIP is removed and replaced by antigen peptide, at last MHC II-peptide complex molecular are present to CD4+ T helper cells.There were a few researches about the cathepsin S in fish, however, its function in antigen presentation was not known clearly. In this experiment we constructed the cDNA library of the Lutjanus argentimaculatus previously and then cloned and expressed a protein which similar to cathepsin S. The identity of the Lutjanus argentimaculatus cathepsin S and other species reached to 83%. The purified protein can catalyze the Z-Phe-Arg-NMec and be inhibited by E-64 and it was stable and active in vitro at slightly basic pH. These conformed the protein was cathepsin S.We noticed that the up-regulation of CTSS transcript in macrophages cells after 24 hours stimulation with the Bacillus subtilis and we also found that the active CTSS can cleave the Ii chain in vitro. All these results showed that the CTSS plays a key role in antigen presentation in Lutjanus argentimaculatus.