Biophysical Characterization of Binding Interactions of Ppar with THC

Peroxisome proliferator-activated receptors (PPAR) is a nuclear receptor with three isoforms α, γ, and d that are involved in the regulation of lipid metabolism, inflammatory processes, and cell differentiation. Each isoform contains a DNA binding domain, ligand binding domain (LBD), and two activation function domains. Upon ligand binding, PPARs heterodimerize with retinoid X receptor to bind DNA and modulate transcription of target genes. Ligands corresponding to each isoform are unique despite similar secondary protein structure. Recent evidence shows cannabinoids activate PPARα and PPARγ. However, few studies have been done on PPARd. This implies that synthetic cannabinoids, such as Δ9-tetrahydrocannabinol (THC), may act by mediating PPAR-related pathways unrelated to canonical CB1 and CB2 cannabinoid receptor interactions. Due to the specific ligand profiles and target genes of each PPAR isoform, understanding each PPAR isoforms’ binding with THC would shed light on the role PPAR plays in cannabinoid activated pathways. Here we use microscale thermophoresis, isothermal titration calorimetry, and fluorescence to quantify the binding affinities of PPAR LBD isoforms with THC.