Prostaglandin E₂ (PGE₂) plays an important role in immune activities in teleost fish, including seabream. However, receptors involved in PGE₂ signaling, as well as the pathways activated downstream, are largely unknown. In this study, one ortholog of mammalian PTGER1, PTGER3 and PTGER4, and two of PTGER2 (Ptger2a and Ptger2b) were identified and characterized in gilthead seabream. In silico analysis showed that all these receptors possessed the organization domain of G protein-coupled receptors, with the exception of Ptger2b. The corresponding in vivo studies revealed that they were expressed in all the tissues examined, the highest mRNA levels of ptger1 and ptger3 being observed in the spleen and of ptger2a and ptger4 in the blood. Bacterial infection induced higher mRNA levels of ptger2a, ptger3 and ptger4 in peritoneal exudate (the site of bacterial injection). In addition, head kidney acidophilic granulocytes and macrophages displayed different ptger1, ptger2a, ptger3 and ptger4 expression profiles. Furthermore, in macrophages the expression of the receptors was weakly affected by stimulation with bacterial DNA or with PGE₂, while in acidophilic granulocytes stimulation resulted in the upregulation of ptger2a and ptger4. Taken together, these results suggest different roles for seabream PGE₂ receptors in the regulation of the immune responses.

前列腺素 E ₂ (PGE ₂ ) 在包括鲷鱼在内的硬骨鱼的免疫活动中起重要作用。然而，参与 PGE ₂信号传导的受体以及下游激活的途径在很大程度上是未知的。在这项研究中，在金头鲷中鉴定和表征了哺乳动物 PTGER1、PTGER3 和 PTGER4 的一个直系同源物，以及 PTGER2 的两个（Ptger2a 和 Ptger2b）。计算机分析表明，除 Ptger2b 外，所有这些受体都具有 G 蛋白偶联受体的组织结构域。相应的体内研究表明，它们在所有检查的组织中都有表达，ptger1和ptger3的 mRNA 水平最高在脾脏和血液中观察到ptger2a和ptger4。细菌感染导致腹膜渗出液（细菌注射部位）中ptger2a、ptger3和ptger4的mRNA 水平升高。此外，头肾嗜酸粒细胞和巨噬细胞表现出不同的 ptger1、ptger2a、ptger3和ptger4表达谱。此外，在巨噬细胞中，受体的表达受到细菌 DNA 或 PGE ₂刺激的微弱影响，而在嗜酸粒细胞中，刺激导致ptger2a和ptger4的上调. 总之，这些结果表明鲷鱼 PGE ₂受体在调节免疫反应中的不同作用。