Mutations in Liver X Receptor Alpha that Impair Dimerization and Ligand Dependent Transactivation

assay and a cell based assay demonstrated that LXRα L414R was specifically impaired for interactions with RXRα but not PPARα suggesting that charge reversal at the interface provides selectivity to LXRα dimerization. Furthermore, binding of LXRα L414R or R415A with PPARα exhibited minimal conformational changes in the dimer secondary structure. Interestingly, all LXRα mutants exhibited lower levels of ligand dependent luciferase activity driven by the SREBP-1c or ApoA1 promoter. Taken together, our data demonstrates that intact hydrophobic interactions and salt bridges at the interface mediate efficient ligand-dependent transactivation activities.