CgIL17-5 regulates the mRNA expressions of immune effectors through inducing the phosphorylation of CgMAPKs and the nuclear translocation of CgRel and CgAP-1 in the Pacific oyster Crassostrea gigas

Interleukin-17 (IL-17) is a classic pro-inflammatory cytokine that plays an important role in the immune and inflammatory response. In the present study, the sequence feature of CgIL17-5 and its function as a pro inflammatory factor in inducing the mRNA expressions of downstream immune effectors were investigated in oyster Crassostrea gigas. There were two tightly folded alpha helixes and two pairs of antiparallel beta-pleated sheet in the amino acid sequence of CgIL17-5. The mRNA transcripts of CgIL17-5 were constitutively distributed in all the tested tissues, with the highest level in haemocytes. The mRNA expression level of CgIL17-5 in haemocytes increased significantly at 24 h after Vibrio splendidus stimulation. CgIL17-5 protein was mainly detected in granulocytes which were the main immunocompetent haemocytes in C. gigas. The phosphorylation of mitogen-activated protein kinases (CgJNK, CgERK and CgP38) and nuclear translocation of the transcription factors (CgRel and CgAP-1) in haemocytes were induced after the oysters received an injection of recombinant CgIL17-5 for 2 h. The mRNA expression levels of CgIL-17s, CgTNF-1, Cgdefh1 and Cgdefh2 increased significantly in haemocytes. At the same time, obvious branchial swelling and cilium shedding in gills were observed at 24 h after the oysters received an injection of rCgIL17-5. All the results collectively suggested that CgIL17-5 promoted the activation of CgMAPKs and the nuclear translocation of CgRel and CgAP-1 to promote the mRNA expressions of cytokines and antibacterial peptides.

Automated summary

The study found that CgIL17-5 is an important pro-inflammatory factor in oysters, promoting the activation of CgMAPKs and nuclear translocation of CgRel and CgAP-1, leading to increased mRNA expressions of cytokines and antibacterial peptides.