A membrane-bound dopamine β-hydroxylase highly expressed in granulocyte of Pacific oyster Crassostrea gigas. (March 2020)

• Record Type: Journal Article
• Authors: Li, Meijia; Dong, Miren; Wang, Weilin; Li, Huan; Liu, Zhaoqun; Wang, Lingling; Wang, Kejian; Song, Linsheng
• Is Part Of: Developmental and comparative immunology. Volume 104(2020)
• Publication Date: 2020-03
• Subjects: Crassostrea gigas -- Dopamine β-hydroxylase -- Granulocytes -- Immune regulation; Immunology -- Periodicals; Developmental immunology -- Periodicals; 616.079
• DOI: 10.1016/j.dci.2019.103563
• Languages: English
• ISSNs: 0145-305X

Abstract

Abstract: Dopamine β-hydroxylase (DBH) is one of key rate-limiting enzymes converting dopamine to norepinephrine. It locates not only in catecholaminergic neuron system, but also in immunocytes and plays roles in the immune response of vertebrates. However, the knowledge about the function of DBH in immune system is still very limited in invertebrates. In the present study, the DBH gene family with seven members was screened from Crassostrea gigas genome, and their mRNA expressions in various tissues were recorded. Among them, one DBH (designated Cg DBH-1) with high expression level in oyster hemocytes was further characterized. The deduced amino acid sequence of Cg DBH-1 was predicted to contain a transmembrane domain and shared 30.1% and 30.9% similarity with that in Mus musculus and Homo sapiens, respectively. Cg DBH-1 was closely clustered with DBH from Aplysia californica in the phylogenetic tree. The recombinant protein of Cg DBH-1 (r Cg DBH-1) exhibited significant enzymatic activity (0.54 ± 0.019 pmol L −1 min −1 ) to synthesize norepinephrine. Importantly, the mRNA transcript of Cg DBH-1 was highly expressed in oyster hemocytes, and the highest expression level was observed in granulocytes among the three types of hemocytes, which was 8.18-fold ( p < 0.01) of that in agranulocytes. Moreover, the expression of Cg DBH-1 in hemocytes was significantly increased at the late stage of immune response. The Cg DBH-1 protein was mainly co-localized with the granules and endoplasmic reticulum (ER) of granulocytes. These results collectively suggested that Cg DBH-1, as a novel molluscan norepinephrine synthesizing enzyme highly expressed in granulocytes, involved in the late-stage immune response of oysters, which provided vital insight to understand the crosstalk between neuroendocrine and immune systems in invertebrates. Highlights: Seven DBH genes with tissue-specific expression patterns were screened from oyster Crassostrea gigas. Cg DBH-1 mRNA was mainly expressed in oyster hemocytes, specifically in granulocytes. Cg DBH-1 in hemocytes could respond to LPS stimulation at the late-stage of immune response. r Cg DBH-1 displayed the enzymatic activity for synthesizing NE. The Cg DBH-1 protein was mainly located in the endoplasmic reticulum (ER) of granulocytes.