Immunomodulatory Effects of SPHK1 and Its Interaction with TFAP2A in Yellow Drum (Nibea albiflora)

Sphingosine kinases (SPHKs) are essential enzymes that catalyze the phosphorylation of sphingosine to produce sphingosine-1-phosphate (S1P), which plays pivotal roles in inflammation and immune regulation. In this study, genome-wide association analysis (GWAS) identified the <i>Ydsphk1</i> gene as closely associated with the resistance of yellow drum (<i>Nibea albiflora</i>) to <i>Vibrio harveyi</i>. Structural prediction showed that YDSPHK1 contains a typical diacylglycerol kinase catalytic (DAGKc) domain (154-291 aa). By constructing and transfecting <i>Ydsphk1</i> expression plasmids into yellow drum kidney cells, we found that YDSPHK1 is localized in the cytoplasm. Subsequent RNA-Seq analysis of an overexpression plasmid identified 25 differentially expressed genes (DEGs), including 13 upregulated and 12 downregulated. Notably, <i>nsun5</i> and <i>hsp90aa1</i> were significantly upregulated, while <i>Nfkbia</i> and <i>hmox1</i> were downregulated. Promoter analysis indicated that the core regulatory regions of <i>Ydsphk1</i> are located between -1931~-1679 bp and -419~+92 bp, with two predicted TFAP2A binding sites in the -419~+92 bp region. Further studies demonstrated that varying concentrations of TFAP2A significantly reduced <i>Ydsphk1</i> promoter activity. These findings underscore the pivotal role of <i>Ydsphk1</i> in regulating immune responses in yellow drum, particularly through its impact on key immune-related genes and pathways such as NF-κB signaling and ferroptosis. The identification of <i>Ydsphk1</i> as a mediator of immune regulation provides valuable insights into the molecular mechanisms of immune defense and highlights its potential as a target for enhancing pathogen resistance in aquaculture practices. This study lays a strong foundation for future research aimed at developing innovative strategies for disease management in aquaculture species.