Peptidoglycan recognition protein of Solen grandis (SgPGRP-S1) mediates immune recognition and bacteria clearance

Abstract

Peptidoglycan recognition proteins (PGRPs) are indispensable molecules in innate immunity due to their prominent function in sensing and eliminating invading microorganisms. In the present study, a short type PGRP from razor clam Solen grandis (SgPGRP-S1) was recombinantly expressed and purified to investigate its potential function in innate immunity. As a pattern recognition receptor, recombinant SgPGRP-S1 (rSgPGRP-S1) specifically bind Lys-type and Dap-type peptidoglycan in vitro, but not lipopolysaccharide or β-glucan. The peptidoglycan binding ability of rSgPGRP-S1 resulted in significant agglutination activity against Gram-negative Escherichia coli and Listonella anguillarum, as well as Gram-positive Micrococcus luteus. Furthermore, rSgPGRP-S1 was bactericidal, significantly suppressing the growth of both E. coli and Gram-positive Staphylococcus aureus. The protein also exhibited strong amidase activity and degraded bacterial peptidoglycan in the presence of Zn, suggesting amidase activity might contribute to SgPGRP-S1 antibacterial activity. These results indicate SgPGRP-S1 is multifunctional in innate immunity, mediating both immune recognition and bacteria elimination.

A peptidoglycan recognition protein involved in immune recognition and immune defenses in Ruditapes philippinarum

“…In the present study, Zn 2+ binding sites and amidase catalytic sites were both well conserved in RpPGRP. Notably, significant degradation of PGN was detected after incubated with rRpPGRP in the presence of Zn 2+ , consistent with the amidase activities of scallop [13] and razor clam [35].…”

Molecular and Functional Characterization of a Short-Type Peptidoglycan Recognition Protein, Ct-PGRP-S1 in the Giant Triton Snail Charonia tritonis

“…As we know, invertebrates rely solely on innate immunity to protect themselves against various microorganisms because they lack an acquired immune system as vertebrates have. Innate immunity employs several kinds of pattern recognition receptors (PRRs) to discriminate self from non-self, and initiate subsequent immune cascades to eliminate harmful invaders [ 1 ]. Peptidoglycan recognition proteins (PGRPs), one of the PRRs, specifically recognize bacterial peptidoglycan (PGN) [ 2 ], which is a unique component from the cytoderm of prokaryotic organisms, which helps to maintain the integrity of the microbial cells [ 3 ].…”

“…To date, there have been over 100 PGRPs found in all species and expressed in various tissues, especially in immune tissues [ 10 , 11 ]. According to their structure and molecular weight, PGRPs are divided into three classes: short and extracellular (20–25 kDa, PGRP-S), intermediate (PGRP-I) with two transmembrane domains, and long and intercellular (>90 kDa, PGRP-L) types [ 1 , 12 , 13 ]. The diversity of PGRPs in structure and classification indicates that PGRPs perform multiple functions.…”

“…In recent years, studies focusing on marine PGRPs have made great progress. These marine PGRPs were proven to act as PRRs, opsonins, and bactericidal amidases similarly to their counterparts in terrestrial vertebrates [ 1 ]. For example, some marine PGRPs serve as PRRs by specifically binding PGN and/or bacteria [ 11 , 15 , 16 , 17 ], while others enhance agglutination or phagocytosis [ 1 , 18 , 19 , 20 ].…”

“…These marine PGRPs were proven to act as PRRs, opsonins, and bactericidal amidases similarly to their counterparts in terrestrial vertebrates [ 1 ]. For example, some marine PGRPs serve as PRRs by specifically binding PGN and/or bacteria [ 11 , 15 , 16 , 17 ], while others enhance agglutination or phagocytosis [ 1 , 18 , 19 , 20 ]. Moreover, many marine PGRPs exhibit amidase activity and degrade PGN, thereby suppressing bacterial growth [ 18 , 19 ].…”