PDBsum entry 4prg

Receptor

PDB id: 4prg

Contents

Protein chain

270 a.a. *

Ligands

072 ×4

* Residue conservation analysis

References listed in PDB file

Key reference

Title

A peroxisome proliferator-Activated receptor gamma ligand inhibits adipocyte differentiation.

Authors

J.L.Oberfield, J.L.Collins, C.P.Holmes, D.M.Goreham, J.P.Cooper, J.E.Cobb, J.M.Lenhard, E.A.Hull-Ryde, C.P.Mohr, S.G.Blanchard, D.J.Parks, L.B.Moore, J.M.Lehmann, K.Plunket, A.B.Miller, M.V.Milburn, S.A.Kliewer, T.M.Willson.

Ref.

Proc Natl Acad Sci U S A, 1999, 96, 6102-6106. [DOI no: 10.1073/pnas.96.11.6102]

PubMed id

10339548

Abstract

The peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors that regulate glucose and lipid homeostasis. The PPARgamma subtype plays a central role in the regulation of adipogenesis and is the molecular target for the 2, 4-thiazolidinedione class of antidiabetic drugs. Structural studies have revealed that agonist ligands activate the PPARs through direct interactions with the C-terminal region of the ligand-binding domain, which includes the activation function 2 helix. GW0072 was identified as a high-affinity PPARgamma ligand that was a weak partial agonist of PPARgamma transactivation. X-ray crystallography revealed that GW0072 occupied the ligand-binding pocket by using different epitopes than the known PPAR agonists and did not interact with the activation function 2 helix. In cell culture, GW0072 was a potent antagonist of adipocyte differentiation. These results establish an approach to the design of PPAR ligands with modified biological activities.

Figure 2.
Fig. 2. GW0072 is a PPAR ligand with a unique functional profile. (A) Dose response on the PPAR -GAL4 chimera for GW0072 ( circle ) and GW0072 plus 100 nM rosiglitazone ( ). Reporter activity was expressed as the % of the maximal activation by 1 µM rosiglitazone. GW0072 demonstrates competitive antagonism of rosiglitazone but retains weak agonist activity at µM concentrations. (B) Activity on full-length PPAR 2 for 100 nM rosiglitazone (TZD), 10 µM GW0072 (GW), and 100 nM rosiglitazone plus 10 µM GW0072 (TZD + GW). Vehicle was 0.1% DMSO. Reporter activity was expressed as the % of the maximal activation by 1 µM rosiglitazone. (C-F) The functional activity of GW0072 is paralleled by its effects on coactivator recruitment to PPAR 2 in a mammalian two-hybrid assay. GW0072 (GW) (10 µM) antagonizes recruitment of the coactivators CBP and SRC1 promoted by 1 µM rosiglitazone (TZD). GW0072 (GW) (10 µM) does not recruit the corepressors NCoR or SMRT.

Figure 4.
Fig. 4. GW0072 defines an additional class of nuclear receptor ligands. Agonist ligands (gray) shift the AF-2 helix (yellow) into a position that stabilizes recruitment of coactivator (green) to the receptor ligand-binding domain (white). Antagonist ligands (gray) bind to the receptor by using the same epitopes, but their larger size shifts the AF-2 helix into a position that displaces the coactivator. Antagonist ligands also recruit corepressor (red) to the receptor ligand-binding domain. The partial agonist GW0072 (gray) binds to its receptor by using different epitopes, such that it does not directly interact with the AF-2 helix.

Secondary reference #1

Title

Ligand binding and co-Activator assembly of the peroxisome proliferator-Activated receptor-Gamma.

Authors

R.T.Nolte, G.B.Wisely, S.Westin, J.E.Cobb, M.H.Lambert, R.Kurokawa, M.G.Rosenfeld, T.M.Willson, C.K.Glass, M.V.Milburn.

Ref.

Nature, 1998, 395, 137-143. [DOI no: 10.1038/25931]

PubMed id

9744270

Figure 1.
Figure 1: Crystal structure of the apo-PPAR- bold gamma-. a, Ribbons drawing of the apo-PPAR- LBD, amino acids 207–476. The nomenclature of the helices is based on the RXR- crystal structure^16. -Helices are light blue; -strands are green; loops are brown. b, A worm backbone tracing of PPAR- , with a surface representation of the unoccupied van der Waals space in the ligand-binding site. We determined the 'unoccupied' volume by fitting in virtual atoms that did not occupy the van der Waals surface of the protein. The total unoccupied volume is 1,300 Å^3. c, Sequence alignment of the human PPAR LBDs. Amino acids that are conserved between PPARs , and are in yellow; the secondary structure that the sequence adopts in PPAR- is shown in red boxes for -helices and blue arrows for -strands. Residues involved in rosiglitazone binding are underlined. The sequence alignment predicts that several residues involved in direct interactions of PPAR- with ligand are not conserved in the other PPAR subtypes, and explains the specificity of TZDs for PPAR- : residue H323 is not found in PPAR- , and Q286 is not found in PPAR- or PPAR- .

Figure 3.
Figure 3: SRC-1 interactions with PPAR- bold gamma-. a, A sigma-weighted 2 F [o]– F [c] omit electron-density map is shown contoured at 1.0 for the area surrounding the rosiglitazone ligand. b, A ribbons drawing of the PPAR- LBD dimer and SRC-1, including the ligand rosiglitazone. The two PPAR- monomers are blue and green and the two SRC-1 interacting helices are yellow. The structure of SRC-1 was determined from amino acids 628–640 and 684–703 and was crystallographically refined. Very weak electron density from residues 670 to 684 was visible but was not crystallographically refined and is shown as a dashed line. SRC-1 amino acids 642–669 were disordered and not structurally determined. The diagram shows how one SRC-1 molecule, with two interacting domains, forms a complex with a PPAR- homodimer. The dashed line connecting the two structurally determined domains of SRC-1 is the proposed connection between these two domains. c, The binding of SRC-1 (amino acids 628–642) to the LXXLL-binding site of PPAR- . SRC-1 is coloured: yellow, carbon; blue, nitrogen; red, oxygen. The ribbon backbone of the PPAR- LBD is in green. PPAR- amino acids binding to the LXXLL helix are also shown in green. d, Residues H631–T640 of SRC-1 are coloured as in c, with an electrostatic surface of PPAR- showing the coactivator-binding site. E471 and K301 side chains result in the red (negative) and blue (positive) charges on the surface of the coactivator-binding site at the N and C termini of the SRC-1 helix, respectively. e, Residues H687–E696 of SRC-1 are coloured as in c, with an electrostatic surface of PPAR- showing the coactivator-binding site. f, Amino acids L465–K474 of the PPAR- AF-2 helix of one monomer in the apo structure are shown in: green, carbon; blue, nitrogen; red, oxygen, with an electrostatic surface of PPAR- showing the coactivator-binding site. E471 and K301 side chains result in the red (negative) and blue (positive) charges on the surface at the N and C terminus of the other PPAR- monomer. This figure shows how one monomer in the apo crystal structure orientates its AF-2 helix into the coactivator-binding site of another crystallographically related monomer.

The above figures are reproduced from the cited reference with permission from Macmillan Publishers Ltd