A Dominant-negative Peroxisome Proliferator-activated Receptor γ (PPARγ) Mutant Is a Constitutive Repressor and Inhibits PPARγ-mediated Adipogenesis

• Published in: The Journal of biological chemistry 2000-02, Vol.275 (8), p.5754
• Main Authors: Mark Gurnell, John M. Wentworth, Maura Agostini, Maria Adams, Trevor N. Collingwood, Claudia Provenzano, Paul O. Browne, Odelia Rajanayagam, Thomas P. Burris, John W. Schwabe, Mitchell A. Lazar, V. Krishna K. Chatterjee
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.275.8.5754

The nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) promotes adipocyte differentiation, exerts atherogenic and anti-inflammatory effects in monocyte/macrophages, and is believed to mediate the insulin-sensitizing action of antidiabetic thiazolidinedione ligands. As no complete PPARγ antagonists have been described hitherto, we have constructed a dominant-negative mutant receptor to inhibit wild-type PPARγ action. Highly conserved hydrophobic and charged residues (Leu 468 and Glu 471 ) in helix 12 of the ligand-binding domain were mutated to alanine. This compound PPARγ mutant retains ligand and DNA binding, but exhibits markedly reduced transactivation due to impaired coactivator (cAMP-response element-binding protein-binding protein and steroid receptor coactivator-1) recruitment. Unexpectedly, the mutant receptor silences basal gene transcription, recruits corepressors (the silencing mediator of retinoid and thyroid receptors and the nuclear corepressor) more avidly than wild-type PPARγ, and exhibits delayed ligand-dependent corepressor release. It is a powerful dominant-negative inhibitor of cotransfected wild-type receptor action. Furthermore, when expressed in primary human preadipocytes using a recombinant adenovirus, this PPARγ mutant blocks thiazolidinedione-induced differentiation, providing direct evidence that PPARγ mediates adipogenesis. Our observations suggest that, as in other mutant nuclear receptor contexts (acute promyelocytic leukemia, resistance to thyroid hormone), dominant-negative inhibition by PPARγ is linked to aberrant corepressor interaction. Adenoviral expression of this mutant receptor is a valuable means to antagonize PPARγ signaling.