Journal of Biological Chemistry
Volume 275, Issue 8, 25 February 2000, Pages 5754-5759
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GENES: STRUCTURE AND REGULATION
A Dominant-negative Peroxisome Proliferator-activated Receptor γ (PPARγ) Mutant Is a Constitutive Repressor and Inhibits PPARγ-mediated Adipogenesis*

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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 (Leu468 and Glu471) 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.

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*

This work was supported in part by the Wellcome Trust (to V. K. K. C. and M. G.), The Raymond and Beverly Sackler Foundation (to M. G.), The Cambridge Commonwealth Trust (to J. W.), and the Francis and Augustus Newman Foundation (to J. W.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

§

These authors contributed equally to this work.