Expression profiling and antibacterial analysis of cd36 in mandarin fish, Siniperca chuatsi

Cd36 is classified as a class B scavenger receptor and has also been identified as a pattern recognition receptor. In this study, we investigated the genomic structure and molecular characteristics of cd36 in mandarin fish (Siniperca chuatsi), examined its tissue distribution, and evaluated its antibacterial activity. Genomic structure analysis showed that Sccd36 consists of 12 exons and 11 introns. Sequencing analysis confirmed that the open reading frame of Sccd36 contains 1410 bp, encoding 469 amino acids. Sccd36 is deeply conserved with other vertebrates in terms of genomic structure, gene loci and molecular evolution, and the feature of two transmembrane was observed in ScCd36 through structural prediction. Sccd36 was constitutively expressed in all tissues tested, with the strongest expression in the intestine, followed by the heart and the kidney. Dramatic changes of Sccd36 mRNA were detected in mucosal tissues, including the intestine, gill and skin, when stimulated by the microbial ligands lipopolysaccharide and lipoteichoic acid. In addition, ScCd36 was identified as having strong binding ability to microbial ligands and antibacterial activity against the gram-negative bacteria Aeromonas hydrophila and the gram-positive bacteria Streptococcus lactis. Furthermore, we verified that the genetic ablation of cd36 impaired the resistance of fish to bacterial challenge by using zebrafish cd36 knockout line. In conclusion, our findings suggest that ScCd36 plays a crucial role in the innate immune response of mandarin fish against bacterial infections. This also sets the stage for further exploration into the antibacterial function of Cd36 in lower vertebrate species.