Molecular characterization and functional analysis of AAT and SAA in Lateolabrax maculatus and Micropterus salmoides

Both alpha-1 antitrypsin (AAT) and serum amyloid A (SAA) are involved in the regulation of infection, tissue damage and inflammation. In this study, AAT and SAA genes from spotted seabass (Lateolabrax maculatus) and largemouth bass (Micropterus salmoides) were cloned and characterized, named LmAAT, MsAAT, LmSAA and MsSAA, respectively. LmAAT, MsAAT, LmSAA and MsSAA were 1664 bp, 1688 bp, 505 bp and 476 bp long, encoded 404, 409, 121 and 122 amino acid residues. These genes shared similar protein domain, high identities and closely evolutionary relationships with their teleost counterparts, separately. These four genes were expressed in all tissues tested, with the highest levels in the liver. Lipopolysaccharide (LPS) and Edwardsiella tarda significantly induced the expression of these four genes in the liver, head kidney, spleen, gills and intestine. Further analysis showed that LmAAT and MsAAT were predominantly localized to the plasma membrane of HEK-293T cells, while LmSAA and MsSAA were mainly expressed in the nucleus. Moreover, TNFα expression was induced by overexpression of LmAAT or MsAAT in L. maculatus brain cells (LMB). Our results lay the foundation for further investigations into the immune function of AAT and SAA in fish.