Fishery College, Guangdong Ocean University, Zhanjiang, Guangdong, 524088, China; Academician Joint Laboratory of Germplasm Resource Exploitation, Utilization and Health Assessment for Aquatic Animal, Guangdong Ocean University, Zhanjiang, Guangdong, 524088, China.
Fishery College, Guangdong Ocean University, Zhanjiang, Guangdong, 524088, China.
Fish Shellfish Immunol. 2023 Jul;138:108809. doi: 10.1016/j.fsi.2023.108809. Epub 2023 May 13.
cAMP response element binding protein 2 (CREB2) acts as an intracellular transcriptional factor and regulates many physiological processes, including melanogenesis and melanocyte differentiation. In our previous research, the Creb2 gene has been characterized from Pteria penguin (P. penguin), but its role and regulatory mechanism in P. penguin are still unclear. In this study, first, the function of PpCreb2 in melanogenesis and innate immunity were identified. PpCreb2 silencing significantly decreased the tyrosinase activity and melanin content, indicating PpCreb2 played an important role in melanogenesis. Meanwhile, PpCreb2 silencing visibly suppressed the antibacterial activity of hemolymph supernatant, indicating that PpCreb2 was involved in innate immunity of P. penguin. Second, the PpCreb2 was confirmed to perform immune function by regulating the melanogenesis. The decreased melanin oxidation product due to PpCreb2 silencing triggered the declining of antibacterial activity of hemolymph supernatant, which then could be rescued by adding exogenous melanin oxidation products. Third, the regulation pathway of PpCreb2 involved in innate immunity was analyzed. The promoter sequence analysis of PpMitf discovered 5 conserved cAMP response element (CRE), which were specifically recognized by basic Leucine zipper domain (bZIP) of upstream activation transcription factor. The luciferase activities analysis showed that PpCreb2 could activate the CRE in PpMitf promoter via highly conserved bZIP domain and regulate the expression of PpMitf, which further regulated the PpTyr expression. Therefore, the results collectively demonstrated that PpCreb2 participated in innate immunity by activating PpMitf-mediated melanogenesis in P. penguin.
环磷酸腺苷反应元件结合蛋白 2（CREB2）作为细胞内转录因子，调节许多生理过程，包括黑色素生成和黑素细胞分化。在我们之前的研究中，已经从大珠母贝（Pteria penguin）中鉴定出 Creb2 基因，但它在大珠母贝中的作用和调控机制尚不清楚。在这项研究中，首先确定了 PpCreb2 在黑色素生成和先天免疫中的功能。PpCreb2 沉默显著降低了酪氨酸酶活性和黑色素含量，表明 PpCreb2 在黑色素生成中发挥重要作用。同时，PpCreb2 沉默明显抑制了血淋巴上清液的抗菌活性，表明 PpCreb2 参与了大珠母贝的先天免疫。其次，通过调节黑色素生成来证实 PpCreb2 具有免疫功能。由于 PpCreb2 沉默导致黑色素氧化产物减少，触发血淋巴上清液抗菌活性下降，然后可以通过添加外源性黑色素氧化产物来恢复。第三，分析了 PpCreb2 参与先天免疫的调控途径。对 PpMitf 的启动子序列分析发现了 5 个保守的环磷酸腺苷反应元件（CRE），这些 CRE 被上游激活转录因子的碱性亮氨酸拉链域（bZIP）特异性识别。荧光素酶活性分析表明，PpCreb2 可以通过高度保守的 bZIP 结构域激活 PpMitf 启动子中的 CRE，调节 PpMitf 的表达，进而调节 PpTyr 的表达。因此，这些结果表明，PpCreb2 通过激活 PpMitf 介导的黑色素生成参与了大珠母贝的先天免疫。
