[PPARs: structure, mechanisms of action and control. Note I].

PPARs (peroxisome proliferator activated receptors) are proteine receptors that act as transcription factors activated by ligands. There are three known isoforms of PPARs (alpha, beta/delta, gamma) with similar modulated structure, consisting of distinct regions with specific functions. PPARs activate transcription of their target genes by forming cytoplasmatic heterodimers (PPARs:RXR) with his partner RXR (retinoid X receptor), and once translocated into the nucleus bind to specific DNA sequence called PPRE (peroxisome proliferator response elements) and modulate the expression of genes. Each PPAR is differently expressed in various tissues. Modulatory function of PPARs is induced by natural or synthetic ligand binding. Additional activator proteins are recruited to form a complex that coordinates and regulates the expression of many genes. Moreover, nuclear receptors' activity is also regulated by posttranslational changes.