%0 Journal Article
%T Solution Structures of PPAR¦Ă2/RXR¦Á Complexes
%A Judit Osz
%A Maxim V. Pethoukhov
%A Serena Sirigu
%A Dmitri I. Svergun
%A Dino Moras
%A Natacha Rochel
%J PPAR Research
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/701412
%X PPAR¦Ă is a key regulator of glucose homeostasis and insulin sensitization. PPAR¦Ă must heterodimerize with its dimeric partner, the retinoid X receptor (RXR), to bind DNA and associated coactivators such as p160 family members or PGC-1¦Á to regulate gene networks. To understand how coactivators are recognized by the functional heterodimer PPAR¦Ă/RXR¦Á and to determine the topological organization of the complexes, we performed a structural study using small angle X-ray scattering of PPAR¦Ă/RXR¦Á in complex with DNA from regulated gene and the TIF2 receptor interacting domain (RID). The solution structures reveal an asymmetry of the overall structure due to the crucial role of the DNA in positioning the heterodimer and indicate asymmetrical binding of TIF2 to the heterodimer. 1. Introduction PPAR¦Ă, a member of the nuclear receptor family, is a key regulator of adipocyte differentiation and is involved in glucose homeostasis and insulin sensitization (reviewed in [1, 2]). PPAR¦Ă together with the CCAAT/enhancer-binding proteins had been identified as key transcription factors of driving fat cell differentiation (reviewed in [3]). PPAR¦Ă is absolutely required for both white and brown fat cell development. Several PPAR¦Ă coregulators have also been shown to affect positively or negatively this differentiation (reviewed in [4]). PPAR¦Ă is activated through the binding of diverse ligands including natural fatty acid derivatives and nonsteroidal drugs and is the target of therapeutically active antidiabetics such as rosiglitazone (reviewed in [5]). Furthermore, cdk-5 phosphorylation of PPAR¦Ă leads to deregulation of some genes involved in metabolism [6]. The actions of PPAR¦Ă are mediated by 2 isoforms that result from alternative splicing. PPAR¦Ă2 is 28 amino acids longer at the N-terminal end (Figure 1(a)) and is mainly expressed in adipocyte cells, while PPAR¦Ă1 is ubiquitously expressed. Interestingly, PPAR¦Ă2 is ten times more active in ligand-independent transcriptional activation than PPAR¦Ă1 [7, 8]. Figure 1: Biophysical characterization of the stoichiometry of the TIF2 RID/PPAR ¦Ă/RXR complexes. (a) Structural organization of hPPAR ¦Ă1, hPPAR ¦Ă2, and hTIF2. (b) ESI mass spectra of TIF2 RID/PPAR ¦Ă/RXR LBDs recorded under nondenaturing conditions in 200ŁżmM ammonium acetate at . The different charge states of the proteins are indicated above the peaks. The calculated molecular mass of the first peak corresponds to PPAR ¦Ă/RXR ¦Á LBDs and the second one to the complex containing one PPAR ¦Ă/RXR ¦Á LBDs dimer and one TIF2 RID. (c) Sedimentation equilibrium experiments. Best
%U http://www.hindawi.com/journals/ppar/2012/701412/