The biarylpyrazole compound AM251 alters mitochondrial physiology via proteolytic degradation of ERRα

Mol Pharmacol. 2013 Jan;83(1):157-66. doi: 10.1124/mol.112.082651. Epub 2012 Oct 12.


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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Cell Line
  • DNA-Binding Proteins / metabolism
  • Energy Metabolism
  • Humans
  • Membrane Potential, Mitochondrial
  • Mitochondria / diagnostic imaging
  • Mitochondria / drug effects*
  • Mitochondria / metabolism
  • Multiprotein Complexes / metabolism
  • Phosphorylation
  • Piperidines / pharmacology*
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Stability
  • Pyrazoles / pharmacology*
  • Receptors, Estrogen / metabolism*
  • Sumoylation
  • Ultrasonography


  • DNA-Binding Proteins
  • ERRalpha estrogen-related receptor
  • Multiprotein Complexes
  • Piperidines
  • Pyrazoles
  • Receptors, Estrogen
  • AM 251
  • Proteasome Endopeptidase Complex