Identification of a dopamine receptor in Sinonovacula constricta and its antioxidant responses

The dopamine (DA) D2 receptor is a member of the G protein-coupled receptors of organisms and plays an important role in immune system regulation. The presence of DA receptors has been widely reported in vertebrates, but few studies have been conducted in shellfish. Here, we identified a novel DA-D2 receptor gene, ScDopR2-1, in the razor clam Sinonovacula constricta. ScDopR2-1 belongs to the family of G protein-coupled receptors, containing seven hydrophobic transmembrane domains, along with 16 predicted N-glycosylation sites and 69 phosphorylation sites. A longer third intracellular loop and a shorter C-terminus in ScDopR2-1 are characteristic features of D2 receptors. ScDopR2-1 is widely expressed in tissues from adult clams, showing high expression in siphon and foot tissues. Furthermore, in response to Vibrio anguillarum challenge, ScDopR2-1 expression levels are significantly increased in liver tissue. Moreover, changes in the activities of catalase (CAT) and superoxide dismutase (SOD) also indicate that the organism causes an immune response. In summary, the results indicate that ScDopR2-1 plays a pivotal role in antioxidant responses in S. constricta.