A hexokinase from the oyster Crassostrea gigas is involved in immune recognition as a pattern recognition receptor. (September 2021)

• Record Type: Journal Article
• Authors: Chen, Xiaowei; Liu, Zhaoqun; Gu, Yifan; Zhang, Yukun; Liu, Yu; Wang, Lingling; Song, Linsheng
• Is Part Of: Developmental and comparative immunology. Volume 122(2021)
• Publication Date: 2021-09
• Subjects: Crassostrea gigas -- Hexokinase -- Pattern recognition receptor -- IL17-5 -- Immune response; Immunology -- Periodicals; Developmental immunology -- Periodicals; 616.079
• DOI: 10.1016/j.dci.2021.104083
• Languages: English
• ISSNs: 0145-305X

Abstract

Abstract: Hexokinase (HK) is generally recognized as a crucial enzyme participating in glycolysis. In the present study, a HK (named Cg HK) was identified as a potential pattern recognition receptor (PRR) from the Pacific oyster Crassostrea gigas . The open reading frame (ORF) of Cg HK was of 1395 bp, encoding a peptide of 464 amino acids with one Hexokinase_1 domain and one Hexokinase_2 domain. The predicted amino acid sequence of Cg HK shared 17%–29% similarities with that of other known HKs. The mRNA transcripts of Cg HK were constitutively detected in all the examined tissues, with relative high expression level in labial palp and haemocytes. Cg HK protein was mainly observed in the cytoplasm of oyster haemocytes. The mRNA expression level of Cg HK in haemocytes was significantly up-regulated and peaked at 3 h after Vibrio splendidus (7.64-fold, p < 0.001) and lipopolysaccharide (LPS) (11.86-fold, p < 0.001) stimulations. The recombinant Cg HK protein (r Cg HK) exhibited Mg 2+ -dependent adenosine triphosphate (ATP) binding activity in vitro and activity to bind D-(+)-glucose (GLU) and various pathogen-associated molecular pattern (PAMPs) such as LPS and peptidoglycan (PGN) in the absence of Mg 2+ . It also displayed higher binding activity towards V. splendidus and relatively lower binding activity towards Staphylococcus aureus, Escherichia coli, and Micrococcus luteus . After the mRNA expression of Cg HK in haemocytes was knocked down by dsRNA interference, the expression of Cg IL17-5 mRNA in haemocytes was considerably down-regulated at 3 h after the stimulation with V. splendidus (0.33-fold, p < 0.001). These results collectively indicated that Cg HK was able to recognize various PAMPs and pathogenic bacteria as a PRR apart from being the enzyme to exert ATP binding activity in glycolysis, and activate the anti-bacterial immune response by promoting the expression of pro-inflammatory cytokines Cg IL17-5 in oyster haemocytes. Highlights: A HK homologue was identified from oyster with a conserved site to bind ATP coupling with Mg 2+ . The mRNA expression of Cg HK in haemocytes was induced significantly by LPS or V. splendidu. Cg HK exhibited high binding affinity to LPS and PGN as well as pathogenic bacteria. The expression of Cg IL17-5 was down-regulated after Cg HK was knocked down by RNAi.