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Selective targeting of nuclear receptor FXR by avermectin analogues with therapeutic effects on nonalcoholic fatty liver disease.

Jin L, Wang R, Zhu Y, Zheng W, Han Y, Guo F, Ye FB, Li Y - Sci Rep (2015)

Bottom Line: Mechanistically, the avermectin analogues that interact with FXR exhibited features as partial agonists, with distinctive properties in modulating coregulator recruitment.Structural features critical for avermectin analogues to selectively bind to FXR were also revealed.Additionally, the structural features that discriminate the selective binding of FXR by avermectin analogues may provide a unique safe approach to design drugs targeting FXR signaling.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian 361005, China.

ABSTRACT
Non-alcoholic fatty liver disease (NAFLD) has become a predictive factor of death from many diseases. Farnesoid X receptor (FXR) is an ideal target for NAFLD drug development due to its crucial roles in lipid metabolism. The aim of this work is to examine the molecular mechanisms and functional roles of FXR modulation by avermectin analogues in regulating metabolic syndromes like NAFLD. We found that among avermectin analogues studied, the analogues that can bind and activate FXR are effective in regulating metabolic parameters tested, including reducing hepatic lipid accumulation, lowering serum cholesterol and glucose levels, and improving insulin sensitivity, in a FXR dependent manner. Mechanistically, the avermectin analogues that interact with FXR exhibited features as partial agonists, with distinctive properties in modulating coregulator recruitment. Structural features critical for avermectin analogues to selectively bind to FXR were also revealed. This study indicated that in addition to antiparasitic activity, avermectin analogues are promising drug candidates to treat metabolism syndrome including NAFLD by directly targeting FXR. Additionally, the structural features that discriminate the selective binding of FXR by avermectin analogues may provide a unique safe approach to design drugs targeting FXR signaling.

No MeSH data available.


Related in: MedlinePlus

Functional correlation of the avermectins/FXR interactions.(a–d) Molecular determinants of the interaction between FXR with avermectins. Overlays of avermectin (green) and GW4064 (salmon red) in the FXR structure (grey). The selected residues important for ligand interaction are shown in stick representation with wild-type and mutant depicted in white and blue, respectively. The hydrogen bonds are shown with arrows. The potential hydrophobic interactions, if the corresponding mutations are made as indicated in (e), are shown in dashed lines. (e) Differential effects of mutations of key FXR residues on its transcriptional activity in response to 1 μM avermectin analogues in reporter assays. Values are the means ± SEM of three independent experiments.
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f8: Functional correlation of the avermectins/FXR interactions.(a–d) Molecular determinants of the interaction between FXR with avermectins. Overlays of avermectin (green) and GW4064 (salmon red) in the FXR structure (grey). The selected residues important for ligand interaction are shown in stick representation with wild-type and mutant depicted in white and blue, respectively. The hydrogen bonds are shown with arrows. The potential hydrophobic interactions, if the corresponding mutations are made as indicated in (e), are shown in dashed lines. (e) Differential effects of mutations of key FXR residues on its transcriptional activity in response to 1 μM avermectin analogues in reporter assays. Values are the means ± SEM of three independent experiments.

Mentions: To validate the roles of pocket residues in macrocyclic lactones binding and FXR activation, we mutated several key FXR residues that contact different groups of doramectin and abamectin and tested the transcriptional activity of these mutated FXR in response to the compounds in cell-based reporter assays. As shown in Fig. 8a, A291W mutation reduced the size of FXR pocket for the long heterocycle group of avermectins, thereby preventing the binding of these bulky avermectin ligands. As expected, this mutation abolished the transcriptional activity of FXR by doramectin, abamectin, ivermectin, and also GW4064 (Fig. 8e). R331M mutation was supposed to strengthen the hydrophobic interactions by displacing the corresponding residue of polar arginine to a hydrophobic methionine (Fig. 8b). Accordingly, this mutation increased the ability to be activated by avermectin ligands (Fig. 8e). For H447F mutation, the corresponding residue of histidine with a side chain of imidazole group was replaced by the nonpolar phenylalanine with a side chain of benzene ring (Fig. 8c). In the same way, this mutation increased the FXR activity response to doramectin and abamectin due to the consolidation of hydrophobic interactions (Fig. 8e). N283L mutation disrupts a key hydrogen bond between FXR and avermectin compounds (Fig. 8d). Accordingly, this mutant abolished avermectins-mediated FXR transcriptional activity but retained the ability to be activated by GW4064 (Fig. 8e). Taken together, our mutagenic analysis showed distinct results on the activation of FXR by different avermectins and GW4064, highlighting the differential roles of FXR pocket residues in recognizing various ligands.


Selective targeting of nuclear receptor FXR by avermectin analogues with therapeutic effects on nonalcoholic fatty liver disease.

Jin L, Wang R, Zhu Y, Zheng W, Han Y, Guo F, Ye FB, Li Y - Sci Rep (2015)

Functional correlation of the avermectins/FXR interactions.(a–d) Molecular determinants of the interaction between FXR with avermectins. Overlays of avermectin (green) and GW4064 (salmon red) in the FXR structure (grey). The selected residues important for ligand interaction are shown in stick representation with wild-type and mutant depicted in white and blue, respectively. The hydrogen bonds are shown with arrows. The potential hydrophobic interactions, if the corresponding mutations are made as indicated in (e), are shown in dashed lines. (e) Differential effects of mutations of key FXR residues on its transcriptional activity in response to 1 μM avermectin analogues in reporter assays. Values are the means ± SEM of three independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664883&req=5

f8: Functional correlation of the avermectins/FXR interactions.(a–d) Molecular determinants of the interaction between FXR with avermectins. Overlays of avermectin (green) and GW4064 (salmon red) in the FXR structure (grey). The selected residues important for ligand interaction are shown in stick representation with wild-type and mutant depicted in white and blue, respectively. The hydrogen bonds are shown with arrows. The potential hydrophobic interactions, if the corresponding mutations are made as indicated in (e), are shown in dashed lines. (e) Differential effects of mutations of key FXR residues on its transcriptional activity in response to 1 μM avermectin analogues in reporter assays. Values are the means ± SEM of three independent experiments.
Mentions: To validate the roles of pocket residues in macrocyclic lactones binding and FXR activation, we mutated several key FXR residues that contact different groups of doramectin and abamectin and tested the transcriptional activity of these mutated FXR in response to the compounds in cell-based reporter assays. As shown in Fig. 8a, A291W mutation reduced the size of FXR pocket for the long heterocycle group of avermectins, thereby preventing the binding of these bulky avermectin ligands. As expected, this mutation abolished the transcriptional activity of FXR by doramectin, abamectin, ivermectin, and also GW4064 (Fig. 8e). R331M mutation was supposed to strengthen the hydrophobic interactions by displacing the corresponding residue of polar arginine to a hydrophobic methionine (Fig. 8b). Accordingly, this mutation increased the ability to be activated by avermectin ligands (Fig. 8e). For H447F mutation, the corresponding residue of histidine with a side chain of imidazole group was replaced by the nonpolar phenylalanine with a side chain of benzene ring (Fig. 8c). In the same way, this mutation increased the FXR activity response to doramectin and abamectin due to the consolidation of hydrophobic interactions (Fig. 8e). N283L mutation disrupts a key hydrogen bond between FXR and avermectin compounds (Fig. 8d). Accordingly, this mutant abolished avermectins-mediated FXR transcriptional activity but retained the ability to be activated by GW4064 (Fig. 8e). Taken together, our mutagenic analysis showed distinct results on the activation of FXR by different avermectins and GW4064, highlighting the differential roles of FXR pocket residues in recognizing various ligands.

Bottom Line: Mechanistically, the avermectin analogues that interact with FXR exhibited features as partial agonists, with distinctive properties in modulating coregulator recruitment.Structural features critical for avermectin analogues to selectively bind to FXR were also revealed.Additionally, the structural features that discriminate the selective binding of FXR by avermectin analogues may provide a unique safe approach to design drugs targeting FXR signaling.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian 361005, China.

ABSTRACT
Non-alcoholic fatty liver disease (NAFLD) has become a predictive factor of death from many diseases. Farnesoid X receptor (FXR) is an ideal target for NAFLD drug development due to its crucial roles in lipid metabolism. The aim of this work is to examine the molecular mechanisms and functional roles of FXR modulation by avermectin analogues in regulating metabolic syndromes like NAFLD. We found that among avermectin analogues studied, the analogues that can bind and activate FXR are effective in regulating metabolic parameters tested, including reducing hepatic lipid accumulation, lowering serum cholesterol and glucose levels, and improving insulin sensitivity, in a FXR dependent manner. Mechanistically, the avermectin analogues that interact with FXR exhibited features as partial agonists, with distinctive properties in modulating coregulator recruitment. Structural features critical for avermectin analogues to selectively bind to FXR were also revealed. This study indicated that in addition to antiparasitic activity, avermectin analogues are promising drug candidates to treat metabolism syndrome including NAFLD by directly targeting FXR. Additionally, the structural features that discriminate the selective binding of FXR by avermectin analogues may provide a unique safe approach to design drugs targeting FXR signaling.

No MeSH data available.


Related in: MedlinePlus