Kwang-Min Choia, Min-Soo Jooa, Dong-Hee Choa, Jin-Sol Baea, Ji-Min Jeonga, Won-Sik Wooa,Hyun-Ja Hanb, Deok Chan Leeb, Mi Young Chob, Sung Hee Jungb, Do-Hyung Kimc,**, Chan-Il Parka,*
aDepartment of Marine Biology & Aquaculture, College of Marine Science, Gyeongsang National University, 455, Tongyeong, 650-160, Republic of Korea
bPathology Research Division, National Institute of Fisheries Science, 408-1 Sirang-ri, Gijang-up, Gijang-gun, Busan, 46083, Republic of Korea
cDepartment of Aquatic Life Medicine, College of Fisheries Science, Pukyong National University, 45, Yongso-ro, Nam-Gu., Busan, Republic of Korea
*Corresponding author : Chan-Il Park
**Corresponding author : Do-Hyung Kim
Abstract
Peptidoglycan recognition proteins are members of the family of pattern recognition receptors (PRRs), that play important roles in the recognition of peptidoglycan and various biological processes. In this study, we have characterized peptidoglycan recognition protein-SC2 (PGRP-SC2) in rock bream (Oplegnathus fasciatus) (RbPGRP-SC2) and analysed its expression in various tissues after pathogen challenge. A sequence alignment revealed that the residues essential to zinc binding of the deduced protein were highly conserved among all the organisms. Phylogenetic analysis revealed that RbPGRP-SC2 is most closely related to the large yellow croaker PGRP-SC2. RbPGRP-SC2 was ubiquitously expressed in all tissues analysed, predominantly distributed in muscle and skin. After challenge with microbial pathogens (Edwardsiella piscicida), Streptococcus iniae or red seabream iridovirus [RSIV]), RbPGRP-SC2 was up-regulated in all the tissues examined, especially in liver. We produced recombinant RbPGRP-SC2 (rRbPGRP-SC2) using an Escherichia coli expression system. The rRbPGRP-SC2 had agglutination activity towards both Gram-negative (E. piscicida) and Gram-positive bacteria (S. iniae). In addition, rRbPGRP-SC2 induced leukocyte apoptosis and promoted leukocyte phagocytosis. These results suggest that the RbPGRP-SC2 plays an important role in the immune system and in maintaining cellular homeostasis of rock bream.
Keywords : Innate immunity, Peptidoglycan recognition protein-SC2, Oplegnathus fasciatus, Apoptosis, Phagocytosis