Peroxisome proliferator-activated receptor alpha1 in yellow catfish Pelteobagrus fulvidraco: molecular characterization, mRNA tissue expression and transcriptional regulation by insulin in vivo and in vitro.

Peroxisome proliferator-activated receptor alpha1 (PPARα1) cDNA was isolated from liver of yellow catfish Pelteobagrus fulvidraco by RT-PCR and RACE. Its molecular characterization, tissue expression and transcriptional regulation by insulin in vitro and in vivo were determined. PPARα1 mRNA covered 1879 bp, with an open reading frame (ORF) of 1410 bp encoding 469 amino acid residues, a 5'-untranslated region (UTR) of 49 bp, and a 3'-UTR of 421 bp. PPARα1 consisted of 4 domains, the A/B domain, DNA-binding domain (DBD), D domain, and ligand-binding domain (LBD). The predicted tertiary structure of yellow catfish PPARα1 showed an increased size of the main cavity that was made up of side chains from helices 3, 5, 10, 11, and 12. Changes of PPARα1 structure might affect binding of mammalian PPARα1-specific ligand and cofactor in yellow catfish and may endow yellow catfish PPARα1 with new ligand-independent or -dependent transactivation activity. PPARα1 was differentially expressed in various tissues during development. Furthermore, intraperitoneal injection in vivo and incubation in vitro of insulin reduced the mRNA expression of PPARα1 in the liver and hepatocytes of yellow catfish. Based on the observation above, the present study provides evidence that PPARα1 is differentially expressed within and among tissues during three developmental stages and also regulated by insulin both in vivo and in vitro, which warrants further investigation of PPARα1 physiological function in fish.