School of Marine Science and Engineering, Qingdao Agricultural University, Qingdao, 266109, China.
School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA.
Fish Shellfish Immunol. 2020 May;100:358-367. doi: 10.1016/j.fsi.2020.03.014. Epub 2020 Mar 10.
Class B scavenger receptor type 1 (SRB1) serves as a high-density lipoprotein (HDL) receptor essential for HDL metabolism, and plays vital roles in innate immunity. In this study, the turbot (Scophthalmus maximus) SRB1 was cloned and characterized. The gene structure consists of a coding region of 1,527 bp nucleotides dividing into 13 exons and 12 introns. Such genome structure is highly conserved among teleost fishes. The deduced SRB1 encodes 508 amino acids that mainly has a CD36 transmembrane domain. Tissue distribution of SRB1 showed the lowest expression in liver, while the highest expression was found in intestine. Significantly down-regulation pattern of SmSRB1 expression in intestine was shared after infection with Vibrio anguillarum and Streptococcus iniae. Brach and site models in CODEML program showed that SmSRB1 underwent a conservative evolutionary and three potential positive selected sites 470K, 496E, and 501Y were detected, which requires further investigation and confirmation using base-editing technologies. Subcellular localization demonstrated that turbot SRB1 was distributed in the membrane and cytoplasm. rSmSRB1 showed binding ability in vitro to bacteria, LPS, PGN, LTA and virus. Protein-protein interaction network agrees the function of SRB1 as lipoprotein receptor. Our results indicated SmSRB1 might act as co-receptors to TLRs and NLRs to modulate the immune response to pathogens. Further studies should pay attention to evaluate the specific co-receptor for SRB1 in recognition of different pathogens and selective mechanisms involved.
B 型清道夫受体 1（SRB1）是一种高密度脂蛋白（HDL）受体，对 HDL 的代谢至关重要，在先天免疫中发挥着重要作用。本研究克隆和鉴定了大菱鲆（Scophthalmus maximus）SRB1。该基因结构由 1527bp 的编码区组成，分为 13 个外显子和 12 个内含子。这种基因组结构在硬骨鱼类中高度保守。推导的 SRB1 编码 508 个氨基酸，主要具有 CD36 跨膜结构域。组织分布显示 SRB1 在肝脏中的表达最低，而在肠道中的表达最高。感染鳗弧菌和迟缓爱德华氏菌后，肠道中 SmSRB1 的表达呈显著下调模式。CODEML 程序中的 Brach 和 site 模型表明，SmSRB1 经历了保守进化，检测到三个潜在的阳性选择位点 470K、496E 和 501Y，这需要进一步使用碱基编辑技术进行调查和确认。亚细胞定位表明大菱鲆 SRB1 分布在膜和细胞质中。rSmSRB1 在体外显示出与细菌、LPS、PGN、LTA 和病毒结合的能力。蛋白质-蛋白质相互作用网络证实了 SRB1 作为脂蛋白受体的功能。我们的结果表明，SmSRB1 可能作为 TLR 和 NLR 的共受体，调节对病原体的免疫反应。进一步的研究应该注意评估 SRB1 在识别不同病原体和参与选择机制中的特定共受体。
