Identification of Galectin-2 from Mugil cephalus: A multifunctional immune effector with antibacterial activity associated with disruption of membrane potential and metabolic perturbation.

Galectin-2 plays important roles in innate immunity, but its function in teleost fish remains poorly understood. In this study, we identified and characterized a galectin-2 from Mugil cephalus (McGal-2). The McGal-2 gene encodes a 135-amino acid protein containing a conserved carbohydrate-recognition domain with the HFNPR motif. McGal-2 was highly expressed in the gill and liver of healthy M. cephalus, and exhibited tissue-specific expression patterns upon LPS stimulation, with significant upregulation in the head kidney and liver but downregulation in the gill. Recombinant McGal-2 (rMcGal-2) demonstrated hemagglutination activity and significantly inhibited the growth of V. parahaemolyticus and Escherichia coli. Furthermore, rMcGal-2 suppressed biofilm formation by V. parahaemolyticus, E. coli, and Staphylococcus aureus. Mechanistic studies revealed that rMcGal-2 exerted antibacterial effects accompanied by alterations in bacterial membrane potential and succinate dehydrogenase activity, suggesting that its antibacterial action may involve disruption of bacterial energy homeostasis rather than direct membrane lysis. These findings demonstrate that McGal-2 is a multifunctional immune molecule that plays a positive role in M. cephalus.