Altering PPARgamma ligand selectivity impairs adipogenesis by thiazolidinediones but not hormonal inducers.
Altering PPARgamma ligand selectivity impairs adipogenesis by thiazolidinediones but not hormonal inducers.
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DOI：
10.1038/oby.2008.629
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发表时间：
2009-05
期刊：
影响因子：
6.9
通讯作者：
Cohen, Ronald N.
中科院分区：
文献类型：
--
作者：
Samarasinghe, Shanika P.;Sutanto, Maria M.;Danos, Arpad M.;Johnson, Daniel N.;Brady, Matthew J.;Cohen, Ronald N.
过氧化物酶体增殖物激活受体γ（Peroxisome proliferator-activated receptor γ，PPARγ）是一种配体依赖性转录因子，在调节脂肪细胞分化和胰岛素敏感性中发挥重要作用。最近，我们和其他人已经表明，PPARγ募集核辅阻遏物NCoR和类维生素A和甲状腺激素受体（SMRT）的沉默介质来调节脂肪形成。虽然PPARγ的合成配体噻唑烷二酮（TZD）广泛用于治疗2型糖尿病，但参与脂肪形成的生物学相关内源性PPARγ配体仍未确定。为了进一步了解配体结合和辅阻遏物相互作用在PPARγ介导的脂肪形成中的作用，在小鼠PPARγ的配体结合结构域（LBD）中引入突变。PPARγmut是通过两个氨基酸取代产生的，已知这两个氨基酸取代是PPAR同种型H323 Y和R288 M中配体选择性的主要决定因素。这些突变将PPARγ改变为PPARα的相应残基。通过对该突变体的体外功能特性进行表征，我们发现，与TZD吡格列酮相比，PPARγmut优先对PPARα激动剂WY-14643产生反应。当使用重组腺病毒在3 T3-L1前脂肪细胞中表达时，野生型PPARγ在激素和TZD处理下均导致脂肪细胞形成。PPARγmut阻断TZD对脂肪细胞特异性蛋白的上调，但令人惊讶的是，不是通过标准的激素诱导剂。我们的数据表明，TZDs和所谓的内源性配体不以相同的方式与PPARγ LBD相互作用。我们提出，内源性配体具有独特的特性，允许在疏水性的PPAR配体结合口袋内的混杂，但促进适当的辅因子招募和释放，使脂肪生成进行。
Peroxisome proliferator–activated receptor γ (PPARγ) acts as a ligand-dependent transcription factor with a key role in mediating adipocyte differentiation and insulin sensitivity. Recently, we and others have shown that PPARγ recruits the nuclear corepressors NCoR and silencing mediator for retinoid and thyroid hormone receptors (SMRT) to modulate adipogenesis. While the synthetic ligands for PPARγ, the thiazolidinediones (TZD), are widely used in the treatment of type 2 diabetes mellitus, the biologically relevant endogenous PPARγ ligand involved in adipogenesis remains unidentified. To further understand the role of ligand binding and corepressor interaction in PPARγ-mediated adipogenesis, a mutation was introduced in the ligand-binding domain (LBD) of murine PPARγ. PPARγmut was created via two amino acid substitutions known to be major determinants of ligand selectivity among PPAR isotypes, H323Y and R288M. These mutations alter PPARγ to the corresponding residues of the PPARα. Characterizing the in vitro functional properties of this mutant, we show that PPARγmut preferentially responds to the PPARα agonist, WY-14643, over the TZD, pioglitazone. When expressed in 3T3-L1 preadipocytes using recombinant adenovirus, wild-type PPARγ leads to adipocyte formation with both hormonal and TZD treatment. PPARγmut blocks the upregulation of adipocyte-specific proteins by TZD, but surprisingly, not by standard hormonal inducers. Our data suggest that TZDs and the purported endogenous ligand do not interact in the same way with the PPARγ LBD. We propose that the endogenous ligand has distinct properties that allow for promiscuity within the hydrophobic PPAR ligand-binding pocket, yet fosters appropriate cofactor recruitment and release to allow adipogenesis to proceed.
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