The glutaminase (CgGLS-1) mediates anti-bacterial immunity by prompting cytokine synthesis and hemocyte apoptosis in Pacific oyster Crassostrea gigas

• Published in: Scientific Reports
• Main Authors: Liang, Yage, Li, Meijia, Liu, Zhaoqun, Li, Yuanmei, Wang, Lingling, Song, Linsheng
• Other Authors: the National Key Research and Development Program of China, Key R&D Program of Liaoning Province, National Science Foundation of China
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 2021
• Subjects: Multidisciplinary; Pacific; Crassostrea gigas; Pacific oyster
• Online Access: http://dx.doi.org/10.1038/s41598-020-80552-2; http://www.nature.com/articles/s41598-020-80552-2.pdf; http://www.nature.com/articles/s41598-020-80552-2

Abstract Glutaminase, an amidohydrolase enzyme that hydrolyzes glutamine to glutamate, plays crucial roles in various immunomodulatory processes such as cell apoptosis, proliferation, migration, and secretion of cytokines. In the present study, a glutaminase homologue (designated as Cg GLS-1) was identified from Pacific oyster Crassostrea gigas , whose open reading frame was of 1836 bp. Cg GLS-1 exhibited high sequence identity with vertebrate kidney-type GLS, and closely clustered with their homologues from mollusc C. virginica . The enzyme activity of recombinant Cg GLS-1 protein (rCgGLS-1) was estimated to be 1.705 U/mg. Cg GLS-1 mRNA was constitutively expressed in all the tested tissues of oysters, with the highest expression level in hemocytes. Cg GLS-1 mRNA expression in hemocytes was significantly up-regulated and peaked at 6 h (2.07-fold, p < 0.01) after lipopolysaccharide (LPS) stimulation. The Cg GLS-1 protein was mainly distributed in the cytoplasm with a significant co-location with mitochondria in oyster hemocytes. The content of Glu in the oyster serum was significantly decreased after the inhibition of Cg GLS-1 using specific inhibitor Bis-2- [5-(phenyl acetamido)-1,3,4-thiadiazol-2-yl] ethyl sulfide (BPTES), and the expression levels of Cg mGluR6, Cg AP-1, cytokines Cg IL17-5 and Cg TNF-1 were significantly decreased after BPTES and LPS stimulation. The transcripts of Cg Caspase3 as well as the apoptosis index of hemocytes were also decreased. These results collectively suggest that Cg GLS-1 is the enzyme to synthesize Glu in oyster, which can modulate anti-bacterial immunity by regulating the secretion of pro-inflammatory cytokines Cg IL17-5 and Cg TNF-1, as well as hemocyte apoptosis.