The Role of NFAT5 in Immune Response and Antioxidant Defense in the Thick-Shelled Mussel (Mytilus coruscus)

Nuclear Factor of Activated T Cells 5 (<i>NFAT5</i>) is a transcription factor that plays a pivotal role in immune regulation. While its functions have been extensively studied in mammalian immune systems, its role in marine invertebrates, particularly in bivalves, remains largely unexplored. This study provides the first characterization of the <i>NFAT5</i> gene in the thick-shelled mussel (<i>Mytilus coruscus</i>), investigating its evolutionary characteristics and immunological functions. Using direct RNA sequencing, <i>McNFAT5</i> was comprehensively analyzed, revealing its critical involvement in the innate immune response of <i>M. coruscus</i> to <i>Vibrio alginolyticus</i> challenge. Differential expression patterns of <i>McNFAT5</i> were observed across various tissues with the highest expression detected in hemolymphs. The knockdown of <i>McNFAT5</i> using small interfering RNA (siRNA) led to a significant reduction in the activities of superoxide dismutase (SOD), Na⁺/K⁺-ATPase, and antioxidant enzymes compared to levels observed post-infection. These findings highlight the central role of <i>McNFAT5</i> in modulating antioxidant defense mechanisms. In conclusion, <i>McNFAT5</i> is a key regulatory factor in the innate immune system of <i>M. coruscus</i>, providing valuable insights into the immune adaptive mechanisms and evolutionary mechanisms of bivalve immunity. This study contributes to a deeper understanding of the immune regulatory networks in marine invertebrates.