C-type lectin 12B/4E of black rockfish (Sebastes schlegelii) macrophages as pattern recognition receptors in the antibacterial mechanism of exploration

• Published in: Fish & shellfish immunology 2024-07, Vol.150, p.109636, Article 109636
• Main Authors: Duan, Zhixiang, Zhang, Fan, Wang, Xuangang, Li, Hengshun, Zhou, Dianyang, Chen, Qiannan, Tao, Ze, Chen, Zhentao, Yu, Gan, Yu, Haiyang
• Format: Article
• Language: English
• Subjects: C-type lectin; Innate immune; PRR; Sebastes schlegelii
• ISSN: 1050-4648; 1095-9947; 1095-9947
• DOI: 10.1016/j.fsi.2024.109636

As lower vertebrates, fish have both innate and adaptive immune systems, but the role of the adaptive immune system is limited, and the innate immune system plays an important role in the resistance to pathogen infection. C-type lectins (CLRs) are one of the major pattern recognition receptors (PRRs) of the innate immune system. CLRs can combine with pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) to trigger NF-κB signaling pathway and exert immune efficacy. In this study, Ssclec12b and Ssclec4e of the C-type lectins, were found to be significantly up-regulated in the transcripts of Sebastes schlegelii macrophages stimulated by bacteria. The identification, expression and function of these lectins were studied. In addition, the recombinant proteins of the above two CLRs were obtained by prokaryotic expression. We found that rSsCLEC12B and rSsCLEC4E could bind to a variety of bacteria in a Ca2+-dependent manner, and promoted the agglutination of bacteria and blood cells. rSsCLEC12B and rSsCLEC4E assisted macrophages to recognize PAMPs and activate the NF-κB signaling pathway, thereby promoting the expression of inflammatory factors (TNF-α, IL-1β, IL-6, IL-8) and regulating the early immune inflammation of macrophages. These results suggested that SsCLEC12B and SsCLEC4E could serve as PRRs in S. schlegelii macrophages to recognize pathogens and participate in the host antimicrobial immune process, and provided a valuable reference for the study of CLRs involved in fish innate immunity. •The expression changes of Ssclec12b and Ssclec4e before and after bacterial stimulation were investigated in immunologic tissues.•The bacterial binding activity and the Ca2+-dependent bacterial agglutination activity of rSsCLEC12B and rSsCLEC4E had been demonstrated, which proved the important role in the process of S. schlegelii resisting pathogen infection.•The expression of p65, TRAF3, TAK1 and NIK1of NF-κB signaling pathway was significantly up-regulated in macrophages infected with A. johnsonii. The addition of rSsCLEC12B and rSsCLEC4E further increased the expression of the above four genes.•rSsCLEC12B and rSsCLEC4E significantly increased the expression of pro-inflammatory factors in macrophages.