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Hepatic nuclear receptor PPARα in the koala (Phascolarctos cinereus): Cloning and molecular characterisation

Ngo, SNT, McKinnon, RA & Stupans, I 2007, Comparative Biochemistry and Physiology, part C, vol. 146, pp. 375-382.

Peroxisome proliferator-activated receptor α, or PPARα, is a protein that is involved in lipid homeostasis. It controls gene expression of certain enzymes, such as CYP4As, which play a role in digesting eucalyptus leaves. The molecular characteristics of PPARα in koala liver are reported in this study.

  Liver tissue was obtained from a koala and processed to extract a gene sequence of PPARα in the form of messenger RNA (mRNA). This mRNA sequence was used to derive the coding DNA sequence by reverse transcription polymerase chain reaction. The PPARα gene was found to have 1515 base pairs which in turn code for 468 amino acids. The amino acid sequence had high similarity to human, rat and mouse PPARα. The sequence was different from human, rat and mouse at the beginning (N-terminus) and the end (C-terminus) of the amino acid chain. There were also differences found in binding domains for DNA and ligands, or factors that bind to receptors and activate a response. Further research is required, however, to determine what effect these differences have on targets binding PPARα in the koala. When PPARα was transfected into cells in a petri dish and then harvested for analysis, an anti-PPARα antibody detected a protein 52 kDa in size. This size is similar to the mouse (53 kDa) and rat PPARα (54 kDa). Similarly, when liver tissues from koala, wallaby, possum and rat were probed for PPARα gene, bands of 53-54 kDa in size were detected. Koalas have a unique diet consisting almost exclusively of eucalyptus leaves. Essential oils in eucalypts, or terpenes, may play a role in activating enzymes that are controlled by PPARα receptor.

  The results of this study indicate that koala PPARα protein can be accurately detected by conventional anti-PPARα antibodies. Studying the structure and function of PPARα may further explain how other enzymes activated by PPARα interact with drugs that act on these enzymes.

 

Summarised by Alexandra Selivanova

 

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