Structural Basis for the Enhanced Anti-Diabetic Efficacy of Lobeglitazone on PPAR\u03b3

Jun Young Jang,Seung Bum Park,Byung Woo Han,Young Il Choi,Se Won Suh,Sang Wan Kim,Hyun-Jung Kim,Hwan Bae,Yong Jae Lee

doi:10.1038/s41598-017-18274-1

Abstract

Peroxisome proliferator-activated receptor γ (PPARγ) is a member of the nuclear receptor superfamily. It functions as a ligand-activated transcription factor and plays important roles in the regulation of adipocyte differentiation, insulin resistance, and inflammation. Here, we report the crystal structures of PPARγ in complex with lobeglitazone, a novel PPARγ agonist, and with rosiglitazone for comparison. The thiazolidinedione (TZD) moiety of lobeglitazone occupies the canonical ligand-binding pocket near the activation function-2 (AF-2) helix (i.e., helix H12) in ligand-binding domain as the TZD moiety of rosiglitazone does. However, the elongated p-methoxyphenol moiety of lobeglitazone interacts with the hydrophobic pocket near the alternate binding site of PPARγ. The extended interaction of lobeglitazone with the hydrophobic pocket enhances its binding affinity and could affect the cyclin-dependent kinase 5 (Cdk5)-mediated phosphorylation of PPARγ at Ser245 (in PPARγ1 numbering; Ser273 in PPARγ2 numbering). Lobeglitazone inhibited the phosphorylation of PPARγ at Ser245 in a dose-dependent manner and exhibited a better inhibitory effect on Ser245 phosphorylation than rosiglitazone did. Our study provides new structural insights into the PPARγ regulation by TZD drugs and could be useful for the discovery of new PPARγ ligands as an anti-diabetic drug, minimizing known side effects.

Highlights

Peroxisome proliferator-activated receptor γ (PPARγ) has a remarkably larger ligand-binding pocket (LBP) than other nuclear receptors[5] and is known to be activated by a wide range of endogenous ligands and synthetic ligands
To gain further insight on the binding mode of lobeglitazone, we solved the crystal structure of PPARγ LBD in complex with lobeglitazone in the presence of a peptide derived from the human steroid receptor coactivator-1 (SRC-1) coactivator protein at 2.15 Å resolution, using X-ray crystallography
The canonical helical LXXLL motif of the SRC-1 coactivator is stabilized by hydrophobic cleft that is formed by helices H3, H4, H5, and H12 of PPARγ LBD (Fig. 2)[11]

Summary

Introduction

PPARγ has a remarkably larger ligand-binding pocket (LBP) than other nuclear receptors[5] and is known to be activated by a wide range of endogenous ligands and synthetic ligands. In 1990s, TZD drugs were found to bind to PPARγ16, and as mentioned above, various synthetic ligands for PPARγ have been developed so far. Full agonists such as TZD drugs are effective in treating type 2 diabetes mellitus, but adverse effects have been problematic, including fluid retention, edema, bone loss, and weight gain[17]. TZD drugs have been known to strongly regulate both the Cdk5-mediated phosphorylation of PPARγ and the expression of PPARγ target genes[18]. Studies of PPARγ-ligand complex structures are crucial to better understand the mechanism of PPARγ modulation and it is true with a more potent anti-diabetic drug, lobeglitazone. Our results enhance the current understanding of PPARγ regulation by TZD drugs more in detail

Methods

Results

Conclusion