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Solution Structures of PPARγ2/RXRα Complexes.

Osz J, Pethoukhov MV, Sirigu S, Svergun DI, Moras D, Rochel N - PPAR Res (2012)

Bottom Line: PPARγ is a key regulator of glucose homeostasis and insulin sensitization.PPARγ must heterodimerize with its dimeric partner, the retinoid X receptor (RXR), to bind DNA and associated coactivators such as p160 family members or PGC-1α to regulate gene networks.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative Structural Biology, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Centre National de Recherche Scientifique (CNRS) UMR 7104, Institut National de Santé et de Recherche Médicale (INSERM) U964, Université de Strasbourg, 67404 Illkirch, France.

ABSTRACT
PPARγ is a key regulator of glucose homeostasis and insulin sensitization. PPARγ must heterodimerize with its dimeric partner, the retinoid X receptor (RXR), to bind DNA and associated coactivators such as p160 family members or PGC-1α to regulate gene networks. To understand how coactivators are recognized by the functional heterodimer PPARγ/RXRα and to determine the topological organization of the complexes, we performed a structural study using small angle X-ray scattering of PPARγ/RXRα 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.

No MeSH data available.


Related in: MedlinePlus

Molecular envelope of PPARγ/RXRα LBDs complexes and comparison with the crystal structure of PPARγ/RXRα LBDs. (a) Crystal structure of PPARγ/RXRα LBDs in complex with TIF2 coactivator peptide (PDB ID: 1H0A) shown in schematic cartoon representations with PPARγ in yellow, RXRα in cyan, and the coactivator peptides in pink. (b) Crystal structure of PPARγ LBD bound to PGC-1α NR2 motif (PDB ID: 3CS8). (c) Molecular envelopes of the complexes PPARγ/RXRα LBDs (grey surface) together with the crystal structure of the complex. (d) Molecular envelope of the complexes TIF2 RID/PPARγ/RXRα LBDs (grey surface).
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fig3: Molecular envelope of PPARγ/RXRα LBDs complexes and comparison with the crystal structure of PPARγ/RXRα LBDs. (a) Crystal structure of PPARγ/RXRα LBDs in complex with TIF2 coactivator peptide (PDB ID: 1H0A) shown in schematic cartoon representations with PPARγ in yellow, RXRα in cyan, and the coactivator peptides in pink. (b) Crystal structure of PPARγ LBD bound to PGC-1α NR2 motif (PDB ID: 3CS8). (c) Molecular envelopes of the complexes PPARγ/RXRα LBDs (grey surface) together with the crystal structure of the complex. (d) Molecular envelope of the complexes TIF2 RID/PPARγ/RXRα LBDs (grey surface).

Mentions: The molecular envelopes as bead models, derived from the SAXS data, were computed for PPARγ/RXRα LBDs and TIF2 RID/PPARγ/RXRα LBDs (Figure 3). It corresponds to a symmetrical globular shape for the LBD dimer (Figure 3(c)). In contrast, for the TIF2 RID complex, a marked asymmetry as compared to the LBD dimer is observed (Figure 3(d)). In analogy with the TIF2 RID and SRC-1 RID complexes with RAR/RXR and RAR homodimer [16, 29], we can speculate that the globular region of the molecular envelope corresponds to the LBD dimer and the asymmetric extended tail to TIF2 RID. The large difference in the structural parameters of the TIF2 RID complex compared to the LBD dimer and the molecular envelope of the complex suggests that TIF2 RID is flexibly attached asymmetrically to the PPARγ/RXRα through only one LXXLL motif. Importantly, the data preclude a model in which two LXXLL motifs bind to each subunit of the PPARγ/RXR heterodimer. A preliminary SAXS study of PPARγ/RXRα bound to PGC-1α RID provides similar results with similar Rg and Dmax⁡ values suggesting that in both cases the architecture of the two different complexes is similar with the CoA RID asymmetrically bound to PPAR subunit through only one LXXLL motif. Interestingly, it has been shown that NR2 motif of PGC-1α is sufficient to have a full transcriptional response by PPARγ/RXRα [14]. While for TIF2, it has been shown that the third LXXLL motif binds preferentially to PPARγ [14] and a combination of LXXLL motifs is required for a full transcriptional response [30]. However the SAXS data are in agreement with the crystal structure of PPARγ/RXRα LBDs (PDB ID: 3H0A) that reveals one coactivator peptide tightly bound to PPARγ and one coactivator peptide loosely bound to RXRα as indicated by the poor electron density and high B factor for the peptide bound to RXR (averaged B factor for the peptide bound to RXR is 116.2 compared to the averaged B factor for the CoA peptide bound to PPARγ, 31.6). These observations demonstrate that TIF2 RID binds asymmetrically to PPARγ subunit within the heterodimer through one LXXLL.


Solution Structures of PPARγ2/RXRα Complexes.

Osz J, Pethoukhov MV, Sirigu S, Svergun DI, Moras D, Rochel N - PPAR Res (2012)

Molecular envelope of PPARγ/RXRα LBDs complexes and comparison with the crystal structure of PPARγ/RXRα LBDs. (a) Crystal structure of PPARγ/RXRα LBDs in complex with TIF2 coactivator peptide (PDB ID: 1H0A) shown in schematic cartoon representations with PPARγ in yellow, RXRα in cyan, and the coactivator peptides in pink. (b) Crystal structure of PPARγ LBD bound to PGC-1α NR2 motif (PDB ID: 3CS8). (c) Molecular envelopes of the complexes PPARγ/RXRα LBDs (grey surface) together with the crystal structure of the complex. (d) Molecular envelope of the complexes TIF2 RID/PPARγ/RXRα LBDs (grey surface).
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fig3: Molecular envelope of PPARγ/RXRα LBDs complexes and comparison with the crystal structure of PPARγ/RXRα LBDs. (a) Crystal structure of PPARγ/RXRα LBDs in complex with TIF2 coactivator peptide (PDB ID: 1H0A) shown in schematic cartoon representations with PPARγ in yellow, RXRα in cyan, and the coactivator peptides in pink. (b) Crystal structure of PPARγ LBD bound to PGC-1α NR2 motif (PDB ID: 3CS8). (c) Molecular envelopes of the complexes PPARγ/RXRα LBDs (grey surface) together with the crystal structure of the complex. (d) Molecular envelope of the complexes TIF2 RID/PPARγ/RXRα LBDs (grey surface).
Mentions: The molecular envelopes as bead models, derived from the SAXS data, were computed for PPARγ/RXRα LBDs and TIF2 RID/PPARγ/RXRα LBDs (Figure 3). It corresponds to a symmetrical globular shape for the LBD dimer (Figure 3(c)). In contrast, for the TIF2 RID complex, a marked asymmetry as compared to the LBD dimer is observed (Figure 3(d)). In analogy with the TIF2 RID and SRC-1 RID complexes with RAR/RXR and RAR homodimer [16, 29], we can speculate that the globular region of the molecular envelope corresponds to the LBD dimer and the asymmetric extended tail to TIF2 RID. The large difference in the structural parameters of the TIF2 RID complex compared to the LBD dimer and the molecular envelope of the complex suggests that TIF2 RID is flexibly attached asymmetrically to the PPARγ/RXRα through only one LXXLL motif. Importantly, the data preclude a model in which two LXXLL motifs bind to each subunit of the PPARγ/RXR heterodimer. A preliminary SAXS study of PPARγ/RXRα bound to PGC-1α RID provides similar results with similar Rg and Dmax⁡ values suggesting that in both cases the architecture of the two different complexes is similar with the CoA RID asymmetrically bound to PPAR subunit through only one LXXLL motif. Interestingly, it has been shown that NR2 motif of PGC-1α is sufficient to have a full transcriptional response by PPARγ/RXRα [14]. While for TIF2, it has been shown that the third LXXLL motif binds preferentially to PPARγ [14] and a combination of LXXLL motifs is required for a full transcriptional response [30]. However the SAXS data are in agreement with the crystal structure of PPARγ/RXRα LBDs (PDB ID: 3H0A) that reveals one coactivator peptide tightly bound to PPARγ and one coactivator peptide loosely bound to RXRα as indicated by the poor electron density and high B factor for the peptide bound to RXR (averaged B factor for the peptide bound to RXR is 116.2 compared to the averaged B factor for the CoA peptide bound to PPARγ, 31.6). These observations demonstrate that TIF2 RID binds asymmetrically to PPARγ subunit within the heterodimer through one LXXLL.

Bottom Line: PPARγ is a key regulator of glucose homeostasis and insulin sensitization.PPARγ must heterodimerize with its dimeric partner, the retinoid X receptor (RXR), to bind DNA and associated coactivators such as p160 family members or PGC-1α to regulate gene networks.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative Structural Biology, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Centre National de Recherche Scientifique (CNRS) UMR 7104, Institut National de Santé et de Recherche Médicale (INSERM) U964, Université de Strasbourg, 67404 Illkirch, France.

ABSTRACT
PPARγ is a key regulator of glucose homeostasis and insulin sensitization. PPARγ must heterodimerize with its dimeric partner, the retinoid X receptor (RXR), to bind DNA and associated coactivators such as p160 family members or PGC-1α to regulate gene networks. To understand how coactivators are recognized by the functional heterodimer PPARγ/RXRα and to determine the topological organization of the complexes, we performed a structural study using small angle X-ray scattering of PPARγ/RXRα 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.

No MeSH data available.


Related in: MedlinePlus