Wang Jingya, Wu Jing, Ma Yanping, Hao Le, Huang Wen, Liu Zhenxing, Li Yugu
College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China.
Institute of Animal Health, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China.
Fish Physiol Biochem. 2024 Jun;50(3):1123-1140. doi: 10.1007/s10695-024-01325-6. Epub 2024 Feb 26.
Fc receptors (FcRs), specific to the Fc portion of immunoglobulin (Ig), are required to regulate immune responses against pathogenic infections. However, FcγR is a member of FcRs family, whose structure and function remains to be elucidated in teleost fish. In this study, the FcγRII, from largemouth bass (Micropterus saloumoides), named membrane MsFcγRII (mMsFcγRII), was cloned and identified. The opening reading frame (ORF) of mMsFcγRII was 750 bp, encoding 249 amino acids with a predicted molecular mass of 27 kDa. The mMsFcγRII contained a signal peptide, two Ig domains, a transmembrane domain, and an intracellular region, which was highly homology with FcγR from other teleost fish. The mRNA expression analysis showed that mMsFcγRII was widely distributed in all tested tissues and with the highest expression level in spleen. After bacterial challenge, the expression of mMsFcγRII was significantly upregulated in vivo (spleen and head kidney), as well as in vitro (leukocytes from head kidney). The subcellular localization assay revealed that mMsFcγRII was mostly observed on the membrane of HEK293T cells which were transfected with mMsFcγRII overexpression plasmid. Flow cytometric analysis showed that natural mMsFcγRII protein was highly expressed in head kidney lymphocytes. Moreover, indirect immunofluorescence assay and pull-down assay indicated that mMsFcγRII could bind to IgM purified from largemouth bass serum. These results suggested that mMsFcγRII was likely to play an influential role in the immune response against pathogens and provided valuable insights for studying the function of FcRs in teleost.
免疫球蛋白（Ig）Fc段特异性的Fc受体（FcRs）是调节针对病原体感染的免疫反应所必需的。然而，FcγR是FcRs家族的成员，其结构和功能在硬骨鱼中仍有待阐明。在本研究中，克隆并鉴定了来自大口黑鲈（Micropterus saloumoides）的FcγRII，命名为膜MsFcγRII（mMsFcγRII）。mMsFcγRII的开放阅读框（ORF）为750 bp，编码249个氨基酸，预测分子量为27 kDa。mMsFcγRII包含一个信号肽、两个Ig结构域、一个跨膜结构域和一个细胞内区域，与其他硬骨鱼的FcγR具有高度同源性。mRNA表达分析表明，mMsFcγRII广泛分布于所有检测组织中，在脾脏中表达水平最高。细菌攻击后，mMsFcγRII在体内（脾脏和头肾）以及体外（头肾白细胞）的表达均显著上调。亚细胞定位分析显示，在转染了mMsFcγRII过表达质粒的HEK293T细胞膜上大多能观察到mMsFcγRII。流式细胞术分析表明，天然mMsFcγRII蛋白在头肾淋巴细胞中高表达。此外，间接免疫荧光分析和下拉分析表明，mMsFcγRII可以与从大口黑鲈血清中纯化的IgM结合。这些结果表明，mMsFcγRII可能在针对病原体的免疫反应中发挥重要作用，并为研究硬骨鱼中FcRs的功能提供了有价值的见解。
