Acyl-CoA esters antagonize the effects of ligands on peroxisome proliferator-activated receptor α conformation, DNA binding, and interaction with co-factors

The peroxisome proliferator-activated receptor alpha (PPAR alpha) is a ligand-activated transcription factor and a key regulator of lipid homeostasis. Numerous fatty acids and eicosanoids serve as ligands and activators for PPAR. Here we demonstrate that S-hexadecyl-CoA, a nonhydrolyzable palmitoyl-CoA analog, antagonizes the effects of agonists on PPAR alpha conformation and function in vitro, In electrophoretic mobility shift assays, S-hexadecyl-CoA prevented agonist-induced binding of the PPAR alpha -retinoid X receptor alpha heterodimer to the acyl-CoA oxidase peroxisome proliferator response element. PPAR alpha bound specifically to immobilized palmitoyl-CoA and Wy14643, but not BRL49653, abolished binding. S-Hexadecyl-CoA increased in a dose-dependent and reversible manner the sensitivity of PPAR alpha to chymotrypsin digestion, and the S-hexadecyl-CoA-induced sensitivity required a functional PPAR alpha ligand-binding pocket. S-Hexadecyl-CoA prevented ligand-induced interaction between the co-activator SRC-1 and PPAR alpha but increased recruitment of the nuclear receptor corepressor NCoR, In cells, the concentration of free acyl-CoA esters is kept in the low nanomolar range due to the buffering effect of high affinity acyl-CoA-binding proteins, especially the acyl-CoA-binding protein. By using PPAR alpha expressed in Sf21 cells for electrophoretic mobility shift assays, we demonstrate that S-hexadecyl-CoA was able to increase the mobility of the PPAR alpha -containing heterodimer even in the presence of a molar excess of acyl-CoA-binding protein, mimicking the conditions found in vivo.