Laboratory of Molecular Fish Immunology and Genetics, Department of Tropical Agriculture and International Cooperation, National Pingtung University of Science and Technology, Pingtung, 91201, Taiwan; Research Center for Animal Biologics, National Pingtung University of Science and Technology, Pingtung, 91201, Taiwan.
Laboratory of Molecular Fish Immunology and Genetics, Department of Tropical Agriculture and International Cooperation, National Pingtung University of Science and Technology, Pingtung, 91201, Taiwan; Polytechnic of Marine and Fisheries Sidoarjo, Department of Aquaculture, East Java, 61253, Indonesia.
Fish Shellfish Immunol. 2020 Apr;99:239-242. doi: 10.1016/j.fsi.2020.02.017. Epub 2020 Feb 11.
The co-receptor CD4 plays an important role in distinguishing between helper T-cell (Th) and cytotoxic T lymphocyte (CTL). In the present study, we investigated the molecular features of CD4-2 cDNA to facilitate understanding of their roles in cobia (Rachycentron canadum). Two CD4-2 molecules have been identified and exhibited 16.10% amino acids identity with each other. The cDNA of CD4-2A consists of a 993 bp ORF encoding 330 aa with long intracytoplasmic tail containing conserved protein tyrosine kinase p56 binding (C-X-C) motif, a transmembrane region, and two extracellular Ig-like (Ig-like) domains are predicted. Comparatively, the cDNA of cobia CD4-2B consists of a 990 bp ORF encoding 329 aa without a transmembrane domain as well as C-X-C motif, and three Ig-like domains are present. Homology comparison showed that the CD4-2A aa sequence of cobia showed high similarity and similar structural features to CD4-2 from other species, while the deduced CD4-2B protein shares higher structural similarity to CD4-1 group. Phylogenetic analysis indicated that cobia CD4-2A was closer with CD4-2 molecules in other fish species, distant from the clade formed by fish CD4-1 and mammalian CD4 sequences. However, cobia CD4-2B grouped with other known teleost CD4-1 sequences. The expression pattern of CD4-2A and CD4-2B mRNA during the embryonic development followed the trend of an initial increase after fertilized, providing evidence of maternal transfer of CD4-2 homologues to the developing cobia embryos and larvae. All of these results are useful for better understanding of cell-mediated immunity of cobia.
CD4 共受体在辅助性 T 细胞（Th）和细胞毒性 T 淋巴细胞（CTL）的区分中发挥重要作用。本研究旨在探讨 CD4-2 cDNA 的分子特征，以促进对其在军曹鱼（Rachycentron canadum）中的作用的理解。鉴定出两种 CD4-2 分子，它们彼此之间具有 16.10%的氨基酸同一性。CD4-2A 的 cDNA 由一个 993 bp 的 ORF 组成，编码 330 个氨基酸，胞内尾部含有保守的蛋白酪氨酸激酶 p56 结合（C-X-C）基序、跨膜区和两个细胞外 Ig 样（Ig-like）结构域。相比之下，军曹鱼 CD4-2B 的 cDNA 由一个 990 bp 的 ORF 组成，编码 329 个氨基酸，没有跨膜结构域和 C-X-C 基序，并且存在三个 Ig 样结构域。同源性比较表明，军曹鱼 CD4-2A 的 aa 序列与其他物种的 CD4-2 具有高度相似性和相似的结构特征，而推断的 CD4-2B 蛋白与 CD4-1 组具有更高的结构相似性。系统发育分析表明，军曹鱼 CD4-2A 与其他鱼类的 CD4-2 分子更为接近，与鱼类 CD4-1 和哺乳动物 CD4 序列形成的分支较远。然而，军曹鱼 CD4-2B 与其他已知的硬骨鱼 CD4-1 序列聚集在一起。CD4-2A 和 CD4-2B mRNA 在胚胎发育过程中的表达模式遵循受精后最初增加的趋势，这为 CD4-2 同源物向发育中的军曹鱼胚胎和幼虫的母体转移提供了证据。所有这些结果有助于更好地理解军曹鱼的细胞介导免疫。
