TY - JOUR T1 - The Biarylpyrazole Compound AM251 Alters Mitochondrial Physiology via Proteolytic Degradation of ERR<em>α</em> JF - Molecular Pharmacology JO - Mol Pharmacol SP - 157 LP - 166 DO - 10.1124/mol.112.082651 VL - 83 IS - 1 AU - Susan M. Krzysik-Walker AU - Isabel González-Mariscal AU - Morten Scheibye-Knudsen AU - Fred E. Indig AU - Michel Bernier Y1 - 2013/01/01 UR - http://molpharm.aspetjournals.org/content/83/1/157.abstract N2 - The orphan nuclear receptor estrogen-related receptor alpha (ERRα) directs the transcription of nuclear genes involved in energy homeostasis control and the regulation of mitochondrial mass and function. A crucial role for controlling ERRα-mediated target gene expression has been ascribed to the biarylpyrazole compound 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-1-piperidinyl-1H-pyrazole-3-carboxamide (AM251) through direct binding to and destabilization of ERRα protein. Here, we provide evidence that structurally related AM251 analogs also have negative impacts on ERRα protein levels in a cell-type-dependent manner while having no deleterious actions on ERRγ. We show that these off-target cellular effects of AM251 are mediated by proteasomal degradation of nuclear ERRα. Cell treatment with the nuclear export inhibitor leptomycin B did not prevent AM251-induced destabilization of ERRα protein, whereas proteasome inhibition with MG132 stabilized and maintained its DNA-binding function, indicative of ERRα being a target of nuclear proteasomal complexes. NativePAGE analysis revealed that ERRα formed a ∼220-kDa multiprotein nuclear complex that was devoid of ERRγ and the coregulator peroxisome proliferator-activated receptor γ coactivator-1. AM251 induced SUMO-2,3 incorporation in ERRα in conjunction with increased protein kinase C activity, whose activation by phorbol ester also promoted ERRα protein loss. Down-regulation of ERRα by AM251 or small interfering RNA led to increased mitochondria biogenesis while negatively impacting mitochondrial membrane potential. These results reveal a novel molecular mechanism by which AM251 and related compounds alter mitochondrial physiology through destabilization of ERRα. ER -