Molecular characterization of peroxiredoxin 5 from Mytilus coruscus and its roles in antioxidant defense and immune regulation

Peroxiredoxins (Prxs) are crucial antioxidant enzymes that protect against oxidative damage and participate in immune responses. However, the immunological function of Prx5 in bivalves remains unclear. In this study, the peroxiredoxin gene McPrx5 was cloned from Mytilus coruscus , and its molecular characteristics and biological functions were analyzed. A 1491 bp cDNA sequence was obtained, containing a 573 bp open reading frame (ORF) that encodes a 190-amino-acid protein (20.29 kDa) with features of an atypical 2-Cys Prx. Tissue distribution analysis revealed that McPrx5 was highly expressed in the foot, gill, and digestive gland. Immune challenges with LPS, poly I:C, and Perkinsus olseni induced dynamic changes in McPrx5 expression. Subcellular localization analysis of the McPrx5-GFP fusion protein showed that McPrx5 was exclusively localized in the cytoplasm. Recombinant McPrx5 enhanced the tolerance of Escherichia coli BL21 to H₂O₂, confirming its antioxidant activity. Importantly, in vivo experiments demonstrated that McPrx5 negatively regulates the expression of key molecules in the TLR4 / MyD88 / NF-κB signaling pathway, as well as FOXO transcription factors, suggesting its important role in linking redox homeostasis with immune regulation. These findings clarify the biological functions of McPrx5 in M. coruscus and provide a new basis for understanding the coordinated regulatory mechanisms linking antioxidant defense to innate immunity in bivalves.