Characteristics and preliminary immune function of SRA5 in Lateolabrax maculatus.

Scavenger receptors (SRs) are crucial for pattern recognition in the innate immune system. However, the role of Scavenger Receptors class A member 5 (SRA5) in the immunological response of bony fish to pathogen invasion remains unclear. This study identified and characterized the SRA5 of Lateolabrax maculatus (LmSRA5) from its transcriptome database. LmSRA5 has a 1494 bp open reading frame, encodes 497 amino acids, has a molecular weight of 55.01 kDa, and contains a collagen domain and a conserved Scavenger Receptor Cysteine-Rich domain. LmSRA5 exhibited high sequence similarity to previously reported SRA5 genes. LmSRA5 exhibited high sequence similarity to previously reported SRA5 genes. LmSRA5 is primarily localized in the cytoplasm, with its encoded proteins distributed in both the cytoplasm and the cell membrane. LmSRA5 was expressed in all tissues. The highest expression was observed in the pituitary gland, with significant levels in the stomach, intestines, liver, and kidney. LmSRA5 expression in the head kidney, spleen, blood, and intestines initially increased, then decreased following infection with Aeromonas veronii. The binding affinity of LmSRA5 for A. veronii was enhanced by increasing concentrations of the extracellular domain recombinant LmSRA5. Knockdown and overexpression experiments in liver cells demonstrated that LmSRA5 significantly regulates the expression of IL-8 and c-Jun. LmSRA5 participates in the immune response by recognizing pathogen-associated molecular patterns (PAMPs) and contributes to immune regulation through modulation IL-8 and c-Jun. This study offers valuable insights into the role of SRA5 in pathogen resistance and immune regulation in bony fish, thereby contributing to the advancement of aquaculture under escalating disease pressures.