Molecular Characterization of DUSP5 in Large Yellow Croaker (Larimichthys crocea) and Its Potential Immunoregulatory Role in Macrophages

Dual-specificity phosphatase 5 (DUSP5) is a negative regulator of mitogen-activated protein kinase (MAPK) signaling and has been implicated in inflammation and immune regulation. However, its role in teleost fish remains incompletely understood. In this study, DUSP5 from large yellow croaker (Larimichthys crocea), designated as LcDUSP5, was characterized with respect to its molecular features, tissue distribution, subcellular localization, and transcriptomic associations following transient overexpression in macrophages. The full-length open reading frame (ORF) of LcDUSP5 is 1131 bp and encodes a 376-amino-acid protein containing a conserved rhodanese homology domain and a dual-specificity phosphatase catalytic domain. LcDUSP5, was broadly expressed in the examined tissues, with the highest expression in the liver. Subcellular localization analysis showed that LcDUSP5 was predominantly localized in the nucleus. A transient overexpression model was established in the large yellow croaker head kidney-derived macrophage cell line LM10, and samples collected at 24 h post-transfection were subjected to transcriptome sequencing. A total of 365 differentially expressed genes were identified, including 283 up-regulated and 82 down-regulated genes. GO and KEGG enrichment analyses suggested that these genes were associated with pathways related to endocytosis, chemokine signaling, phagosome function, calcium signaling, and lipid metabolism. These results provide the first characterization of DUSP5 in large yellow croaker combined with transcriptomic analysis of macrophage responses and suggest that LcDUSP5 may be associated with immune-related pathways in teleost macrophages.