Characterization of an octopamine receptor, and its involvement in the immune response of cuttlefish Sepiella japonica.

Octopamine (OA) can regulate immune response because immune cells exist their receptors. In the study, the full-length cDNA of octopamine receptor (OAR) from Sepiella japonica (termed as Sj-OAR) was amplified. Sj-OAR was 1633 bp in length encoding 348 amino acid residues. Sj-OAR owned seven conserved transmembrane domains. Sj-OAR shared the highest identity with β2-adrenergic OARs of cephalopods, and clustered together with β2 OAR clade. Sj-OAR had the highest expression level in pancreas, followed in liver, optic lobe and brain; Sj-OAR kept increasing in pancreas during the whole growth period. Plenty of Sj-OAR signals were distributed in the epithelial cells and photoreceptor cells of retina, outer and inner granular cell layer, and central medulla of optic lobe. Sj-OAR mRNA appeared significant expression change in cuttlefish larvae challenged by Vibrio harveyi, and adult cuttlefish naturally diseased with skin canker. Subcellular localization observed that Sj-OAR mapped on the cytomembrane. Octopamine hydrochloride inhibited NO production in macrophage RAW 264.7 cells induced by lipopolysaccharide. However, after heterologous expression of Sj-OAR in RAW 264.7 cell, octopamine hydrochloride significantly improved the production of NO. Furtherly, the pretreatment by β-adrenergic receptor antagonist propranolol reduced NO production again. The study would provide key information of Sj-OAR involving in immune regulation.