The nuclear receptors ERRα and PPARα co-ordinately control starvation-induced gene expression in hepatocytes.

Peroxisome-proliferator activated receptor α (PPARα) activation reprograms liver gene expression to support fatty acid oxidation during fasting. How PPARα engages in transcriptional programs coping with catabolic fasting responses is insufficiently understood. By applying a protein-protein interaction methodology that also captures transient interactions, we revealed the orphan nuclear receptor estrogen-related receptor α (ERRα) as a novel interaction partner of liganded PPARα and found that this interaction is enhanced following cellular nutrient starvation. Among target genes affected by PPARα-ERRα transcriptional crosstalk in fasted murine livers, multiple components of the electron transport chain were identified. Using pharmacological tools to study hepatic gene subsets under dual PPARα and ERRα control and moving from short-term to prolonged nutrient deprivation, we found that ERRα can switch from being a PPARα target gene suppressor to a marked PPARα target gene activator. Mechanistically, ERRα may control PPARα transcriptional activity via binding onto PPARα’s coactivator interaction site and via facilitating cofactor relays. In sum, a variety of crosstalk mechanisms between PPARα and ERRα seems to co-ordinately drive essential gene regulatory changes in the starving hepatocyte.