Proline cis/trans-Isomerase Pin1 Regulates Peroxisome Proliferator-activated Receptor γ Activity through the Direct Binding to the Activation Function-1 Domain

Yoshito Fujimoto,Takuma Shiraki,Yuji Horiuchi,Tsuyoshi Waku,Akira Shigenaga,Akira Otaka,Tsuyoshi Ikura,Kazuhiko Igarashi,Saburo Aimoto,Shin-Ichi Tate,Kosuke Morikawa

doi:10.1074/jbc.m109.055095

Abstract

The important roles of a nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) are widely accepted in various biological processes as well as metabolic diseases. Despite the worldwide quest for pharmaceutical manipulation of PPARgamma activity through the ligand-binding domain, very little information about the activation mechanism of the N-terminal activation function-1 (AF-1) domain. Here, we demonstrate the molecular and structural basis of the phosphorylation-dependent regulation of PPARgamma activity by a peptidyl-prolyl isomerase, Pin1. Pin1 interacts with the phosphorylated AF-1 domain, thereby inhibiting the polyubiquitination of PPARgamma. The interaction and inhibition are dependent upon the WW domain of Pin1 but are independent of peptidyl-prolyl cis/trans-isomerase activity. Gene knockdown experiments revealed that Pin1 inhibits the PPARgamma-dependent gene expression in THP-1 macrophage-like cells. Thus, our results suggest that Pin1 regulates macrophage function through the direct binding to the phosphorylated AF-1 domain of PPARgamma.

Highlights

Peroxisome proliferator-activated receptor ␥ (PPAR␥; NR1C3)3 is a key regulator of adipocyte differentiation, glucose homeostasis, and macrophage function [1, 2]
We examined the mechanism of phosphorylation-dependent regulation of PPAR␥ and revealed that the phosphorylated activation function-1 (AF-1) domain targets only the WW domain of peptidyl-prolyl cis/trans-isomerase (PPIase), Pin1, and was not a substrate for the PPIase of Pin1
Coexpression of the constitutively active form of the Ras protein (RasV12G), to induce the phosphorylation of PPAR␥ through the Ras-mitogen-activated protein kinase (MAPK) pathway, inhibited AF-1 activity, but the S84A mutation in the AF-1 domain abolished the inhibitory effects of RasV12G (Fig. 1B, left panel)

Summary

Introduction

Peroxisome proliferator-activated receptor ␥ (PPAR␥; NR1C3)3 is a key regulator of adipocyte differentiation, glucose homeostasis, and macrophage function [1, 2]. The direct binding of Pin1 to the AF-1 domain resulted in inhibiting the polyubiquitination and the transcriptional activity of PPAR␥ revealed by overexpression and knockdown experiments using cell lines. Data presented here suggest that the phosphorylation-dependent regulation of PPAR␥ activity is mediated by the direct binding to Pin1 without proline isomerization.

Results

Conclusion