Involvement of Pacific oyster CgPGRP-S1S in bacterial recognition, agglutination and granulocyte degranulation

• Published in: Developmental and comparative immunology 2014-03, Vol.43 (1), p.30-34
• Main Authors: Iizuka, Masao, Nagasaki, Toshihiro, Takahashi, Keisuke G., Osada, Makoto, Itoh, Naoki
• Format: Article
• Language: English
• Subjects: Agglutination; Animals; Bacillus subtilis; Bacillus subtilis - immunology; Bivalves; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Degranulation; Cells, Cultured; Escherichia coli; Escherichia coli - immunology; Gills - metabolism; Granulocyte; Granulocytes - immunology; Hemocyte; Hemocytes - immunology; Immune mediator; Immunity, Innate; Ostreidae - immunology; Pattern recognition; Peptidoglycan - metabolism; Peptidoglycan recognition protein; Protein Binding; Receptors, Pattern Recognition - genetics; Receptors, Pattern Recognition - metabolism; Transgenes - genetics; Vibrio - immunology; Vibrio anguillarum
• ISSN: 0145-305X; 1879-0089
• DOI: 10.1016/j.dci.2013.10.011

•CgPGRP-S1S in the Pacific oyster specifically recognizes DAP-type PGN and Escherichia coli cells.•CgPGRP-S1S does not have bactericidal activity, but agglutinates E. coli cells.•CgPGRP-S1S functions as an immune mediator by inducing granulocyte degranulation. Peptidoglycan recognition protein (PGRP) recognizes invading bacteria through their peptidoglycans (PGN), a component of the bacterial cell wall. Insect PGRPs contribute to effective immune systems as inducers of other host defense responses, while this function has not been reported from PGRP of bivalves. In this study, recombinant CgPGRP-S1S (rCgPGRP-S1S), produced in the mantle and the gill, was synthesized and used to elucidate the immunological function of CgPGRP-S1S. rCgPGRP-S1S bound specifically to DAP-type PGN and to Escherichia coli cells, but not to other DAP-type PGN-containing bacterial species, Vibrio anguillarum, or Bacillus subtilis. Antibacterial activity was not detected, but E. coli cells were agglutinated. Moreover, in addition to these direct interactions with bacterial cells, rCgPGRP-S1S induced secretion of granular contents by hemocyte degranulation. Taken together, these results suggest for the first time that a PGRP of bivalves is, just as in insects, involved in host defense, not only by direct interaction with bacteria, but also by triggering other defense pathways.