Structural Analysis of Corepressor Binding to PPARγ

 描述（由申请方提供）：核受体转录因子PPARγ是FDA批准用于治疗II型糖尿病（T2 DM）患者的药物的既定靶点。这些药物和许多其他已知的结合PPARγ的配体增加T2 DM患者的胰岛素敏感性。大多数PPARγ结合药物也显示出不良副作用，包括骨折、体重增加和心脏病的风险增加。尽管存在这些阴性适应症，但PPARγ仍然是重要的T2 DM治疗靶点。详细了解配体如何影响PPARγ活性可能有助于开发副作用较少的新药。PPARγ靶基因的转录部分受到小分子配体的影响，小分子配体与其配体结合结构域（LBD）结合，改变了PPARγ与辅调节蛋白（辅阻遏物和辅激活物）之间的相互作用。在无活性的转录抑制形式中，PPARγ与辅阻遏蛋白结合。激动剂配体（包括FDA批准的靶向PPARγ的药物）的结合导致构象变化，释放辅阻遏物并允许辅激活物结合;这通常导致PPARγ靶基因表达增加。虽然已经报道了与辅激活肽和激动剂配体结合的PPARγ的许多晶体结构，但尚未报道与辅阻遏物结合的PPARγ的结构数据。激动剂配体稳定活化功能-2（AF-2）表面，降低对辅阻遏物的结合亲和力，同时增加对辅激活物的亲和力。具有共激活剂的稳定的AF-2表面可能解释了与共激活剂肽结合的许多PPARγ晶体结构。然而，我们的初步数据表明，一个动态的AF-2表面，样品多种构象，促进辅阻遏物结合。AF-2表面与辅阻遏物结合时的动力学可以解释为什么没有报道过与辅阻遏物结合的PPARγ的晶体结构，因为动态表面可以抑制晶体形成。利用NMR、生物化学、生物物理学和细胞功能学方法相结合的多学科方法，我们试图报道辅阻遏蛋白如何结合PPARγ的第一个结构理解。将PPARγ辅阻遏物与功能效应联系起来可以帮助设计具有较低不良副作用的靶向PPARγ的新型化合物。

 DESCRIPTION (provided by applicant): The nuclear receptor transcription factor PPARγ is an established target for FDA approved drugs for patients with type II diabetes mellitus (T2DM). These drugs and numerous other known ligands that bind PPARγ increase insulin sensitivity T2DM patients. Most of the PPARγ-binding drugs also display adverse side effects, including increased risk of bone fractures, weight gain, and heart disease. Despite these negative indications, PPARγ remains an important T2DM therapeutic target. Detailed understanding of how ligands affect PPARγ activity may facilitate the development of new drugs with fewer adverse effects. The transcription of PPARγ target genes is affected, in part, by small molecule ligands that bind to its ligand-binding domain (LBD) and change the interaction between PPARγ and coregulator proteins (corepressors and coactivators). In the inactive transcriptionally repressive form, PPARγ is bound to corepressor proteins. Binding of an agonist ligand, including FDA approved drugs that target PPARγ, causes a conformational change that releases corepressors and allows binding of coactivators; this generally results in an increase the expression of PPARγ target genes. While many crystal structures have been reported for PPARγ bound to coactivator peptides and agonist ligands, no structural data has been reported for PPARγ bound to a corepressor. Agonist ligands stabilize the activation function-2 (AF-2) surface, decreasing binding affinity for corepressors while increasing affinity for coactivators. The stabilized AF-2 surface with coactivators likely explains the numerous PPARγ crystal structures bound to coactivator peptides. However, our preliminary data show that a dynamic AF-2 surface, which samples multiple conformations, facilitates corepressor binding. The dynamics of the AF-2 surface when bound to a corepressor may explain why no crystal structure of PPARγ bound to a corepressor has been reported, since the dynamic surface could inhibit crystal formation. Using a multidisciplinary approach combining NMR, biochemical, biophysical and cell- based functional methods we seek to report the first structural understanding of how corepressor proteins bind PPARγ. The connection of PPARγ corepressor binding to functional effects could aid in the design of novel compounds targeting PPARγ with lower unwanted side effects profiles.