Hepatic nuclear receptor PPARalpha in the koala (Phascolarctos cinereus): cloning and molecular characterisation

Peroxisome proliferator-activated receptor alpha (PPARalpha) is a member of the nuclear/steroid receptor gene superfamily that plays an essential role in fatty acid metabolism. PPARalpha modulates the expression of genes encoding peroxisomal fatty acid beta-oxidation enzymes and microsomal fatty acid hydroxylases CYP4As. We have previously reported that the obligate Eucalyptus feeder koala (Phascolarctos cinereus) exhibits a higher hepatic CYP4A activity and an absence of peroxisomal palmitoyl-CoA oxidation as compared to non-Eucalyptus feeders human, rat or wallaby. Here we describe the cloning, expression and molecular characterisation of koala hepatic PPARalpha. A full-length PPARalpha cDNA of size 1515 bp was cloned by reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The koala PPARalpha cDNA encodes a protein of 468 amino acids. Transfection of the koala PPARalpha cDNA into Cos-7 cells resulted in the expression of a protein recognised by a rabbit anti-human PPARalpha polyclonal antibody. PPARalpha immunoreactive bands of the same molecular mass were detected in nuclear extracts of koala livers. The results of this study demonstrate the presence of koala hepatic PPARalpha which shares several common features with other published PPARalphas; however, it exhibits important differences in both the DNA and ligand binding domains.