title: The role of the amino-terminal domain in the interaction of unliganded peroxisome proliferator-activated receptor gamma-2 with nuclear receptor co-repressor.
abstract: Peroxisome proliferator-activated receptor gamma-2 (PPARG2) is a ligand-dependent transcriptional factor involved in the pathogenesis of insulin resistance. In the presence of a ligand, PPARG2 associates with co-activators, while it recruits co-repressors (CoRs) in the absence of a ligand. It has been reported that the interaction of liganded PPARG2 with co-activators is regulated by the amino-terminal A/B domain (NTD) via inter-domain communication. However, the role of the NTD is unknown in the case of the interaction between unliganded PPARG2 and CoRs. To elucidate this, total elimination of the influence of ligands is required, but the endogenous ligands of PPARG2 have not been fully defined. PPARG1-P467L, a naturally occurring mutant of PPARG1, was identified in a patient with severe insulin resistance. Reflecting its very low affinity for various ligands, this mutant does not have transcriptional activity in the PPAR response element, but exhibits dominant negative effects (DNEs) on liganded wild-type PPARG2-mediated transactivation. Using the corresponding PPARG2 mutant, PPARG2-P495L, we evaluated the role of the NTD in the interaction between unliganded PPARG2 and CoRs. Interestingly, the DNE of PPARG2-P495L was increased by the truncation of its NTD. NTD deletion also enhanced the DNE of a chimeric receptor, PT, in which the ligand-binding domain of PPARG2 was replaced with that of thyroid hormone receptor beta-1. Moreover, NTD deletion facilitated the in vitro binding of nuclear receptor CoR with wild-type PPARG2, mutant P495L, and the PT chimera (PPARG2-THRB). Inter-domain communication in PPARG2 regulates not only ligand-dependent transactivation but also ligand-independent silencing.
authors.affiliation: Second Division, Department of Internal Medicine, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan.
authors.forename: Sadako
authors.initials: S
authors.lastname: Suzuki
authors.forename: Shigekazu
authors.initials: S
authors.lastname: Sasaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Morita
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Oki
authors.forename: Daisuke
authors.initials: D
authors.lastname: Turiya
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ito
authors.forename: Hiroko
authors.initials: H
authors.lastname: Misawa
authors.forename: Keiko
authors.initials: K
authors.lastname: Ishizuka
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000818:Animals; D002460:Cell Line; D056970:Co-Repressor Proteins / Q000378:metabolism*; D005799:Genes, Dominant; D006801:Humans; D008024:Ligands; D051379:Mice; D050505:Mutant Proteins / Q000378:metabolism; D047495:PPAR gamma / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D017384:Sequence Deletion / Q000235:genetics; D013329:Structure-Activity Relationship; D037042:Thyroid Hormone Receptors beta / Q000235:genetics / Q000378:metabolism
chemical_list: D056970:Co-Repressor Proteins; D008024:Ligands; D050505:Mutant Proteins; D047495:PPAR gamma; D011994:Recombinant Proteins; D037042:Thyroid Hormone Receptors beta