CgHMGB1 functions as a broad-spectrum recognition molecule to induce the expressions of CgIL17-5 and Cgdefh2 via MAPK or NF-KB signaling pathway in Crassostrea gigas

High-mobility group box 1 (HMGB1), a highly conserved nucleoprotein, functions in immune recognition, inflammation and antibacterial immunization in vertebrates. In the present study, the mediation mechanism of CgHMGB1 in activating MAPK and NF-KB/Rel signaling pathways to induce the expressions of immune effectors was investigated. CgHMGB1 mRNA was detected in all tested developmental stages from fertilized egg to Dlarvae, with the higher expressions in 4 cells and 8 cells stages. CgHMGB1 proteins were mainly distributed in haemocyte granulocytes. The expressions of CgHMGB1 mRNA in haemocytes increased significantly after Vibrio splendidus stimulation, and CgHMGB1 protein translocated into the haemocyte cytoplasm and release into cellfree haemolymph. The phosphorylation of CgERK and CgP38 were induced, the nuclear translocation of CgRel were promoted, and the mRNA expressions of CgIL17-5 and Cgdefh2 increased significantly after rCgHMGB1 treatment. Obvious branchial swelling and cilium shedding were observed after rCgHMGB1 treatment. rCgHMGB1 exhibited binding activity to different polysaccharides, bacteria, and fungi. rCgHMGB1 also displayed obvious antibacterial activity to V. splendidus and E. coli. These results indicated that CgHMGB1 functioned as an immune recognition molecule to recognize various PAMPs and bacteria to induce the mRNA expressions of CgIL17-5 and Cgdefh2 via the activation of MAPK and NF-KB signaling pathways in oysters.

Automated summary

The study investigates the role of CgHMGB1 in immune recognition and signaling pathways in oysters. CgHMGB1 functions as an immune recognition molecule, inducing the expression of immune effectors through MAPK and NF-KB pathways. This indicates its ability to recognize various PAMPs and bacteria.