Abstract
Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) has been shown to play an important role in energy metabolism by coordinating transcriptional programs involved in mitochondrial biogenesis, adaptive thermogenesis, gluconeogenesis, and fatty acid oxidation. PGC-1α also plays a crucial role in cholesterol metabolism by serving as a coactivator of the liver X receptor-α and inducing the expression of cholesterol 7-α-hydroxylase. Here, we demonstrate that PGC-1α also functions as an effective coactivator of farnesoid X receptor (FXR), the bile acid receptor. Transient cotransfection assays demonstrate that PGC-1α enhances ligand-mediated FXR transcription when either full-length FXR or Gal4 DNA binding domain-FXR-ligand binding domain chimeras were analyzed. Mammalian two-hybrid analyses, glutathione S-transferase affinity chromatography and biochemical coactivator recruitment assays demonstrate ligand-dependent interaction between the two proteins both in vivo and in vitro. PGC-1α-mediated coactivation of FXR was highly ligand-dependent and absolutely required an intact activation function-2 (AF-2) domain of FXR and the LXXLL motif in PGC-1α. The integrity of the charge clamp was required, further illustrating the role of the ligand binding domain of FXR in PGC-1α recognition. Together, these results indicate that PGC-1α functions as a potent coactivator for FXR and further implicates its role in the regulation of genes that are involved in bile acid and lipid metabolism.
Footnotes
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doi:10.1124/jpet.104.072124.
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ABBREVIATIONS: CYP7A1, cholesterol 7-α-hydroxylase; NR, nuclear receptor; LXR, liver X receptor; FXR, farnesoid X receptor; PGC-1α, peroxisome proliferator-activated receptor γ coactivator-1α; DBD, DNA-binding domain; LBD, ligand binding domain; RXR, retinoid X receptor; PPAR, peroxisome proliferator-activated receptor; BSEP, bile salt export pump; TR, thyroid hormone receptor; TK, thymidine kinase; HEK, human embryonic kidney; DMSO, dimethyl sulfoxide; CDCA, chenodeoxycholic acid; GFP, green fluorescent protein; GST, glutathione S-transferase; AF-2, activation function-2; PLTP, phospholipid transfer protein.
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↵1 R.S.S. and J.S.T. contributed equally to this manuscript.
- Received June 2, 2004.
- Accepted August 24, 2004.
- The American Society for Pharmacology and Experimental Therapeutics
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