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Discovery And Optimization Of Natural Product Ligands Targeting FXR With The Study Of Functional And Structural Mechanisms

Posted on:2019-09-09Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y LuFull Text:PDF
GTID:1364330545983690Subject:Biochemistry and Molecular Biology
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Natural products with struactal diversity is an important source for drug development.The potential molecular target mechanism of many medicinal active natural products remains unclear.The bile acid receptor FXR plays an important role in the development of various metabolic diseases and has become a promising drug target.FXR modulators play an important role in disease treatment through different biological functions by the regulation of FXR activity.Based on this,we discovered a novel FXR modulator Tschimganine,a natural monocyclic compound terpene ester.Through the analysis of the binding modes in FXR complex crystals,it was found that the ligand has a unique hydrogen bond interaction on Thr288 of FXR.Based on t the characteristics of the binding modet,a series of fragment replaced derivatives were designed and synthesized.The structure-activity relationship study was carried out.Also,the binding mode and site were confirmed by crystal structure and the mutation assay.Finally,two high activity and Synthesizable compounds XD5 and XD10 were obtained.Based on a mouse pharmacological model evaluation,both can reduce lipid accumulation and inflammation in obese mice with non-toxic.Theredore,they can be used as preclinical candidates for the treatment of nonalcoholic fatty liver disease(NAFLD).On the other hand,the G protein-coupled receptors GPBAR1(or TGR5)and FXR are both bile acid receptors.The underlying regulation mechanism for their intrinsic functions is not clear.Abd their ligands overlap in chemical space and many ligands have been found to active both.Thus,selective ligands are important to study the function of two bile acid receptors.The currently study reported that oleanane-type pentacyclic triterpenoids are physiologically active and considered to be selective ligands for TGR5.Here,we report the natural triterpene hedragonic acid that has been isolated from the stem and root of Celastrus orbiculatus Thunb.(COT)as an effective agonist for FXR.Both biochemical AlphaScreen and cell-based reporter assays showed thathedragonic acid regulated the transcriptional activity of FXR.CD spectroscopy further suggested the conformational changes of FXR upon the binding of hedragonic acid.Interestingly,the crystal structure of hedragonic acid-bound FXR revealed a unique binding mode with hedragonic acid occupying a novel binding pocket different from the classical binding position.The structural comparison between hedragonic acid-bound FXR and oleanolic acid-bound GPBAR1 explained the molecular basis for the selectivity of oleanane-type triterpenes for FXR.Moreover,hedragonic acid treatment protected mice from liver injury induced by overdose acetaminophen and decreased hepatic inflammatory responses in an FXR-dependent manner,suggesting that hedragonic acid might be one of the major components of COT for its multifunctional pharmaceutical uses.Through the above study,we discovered new targets and functional mechanisms for the active ingredients of herbal medicine and provide novel structure templates for drug design based on natural terpenes by targeting FXR,provide the foundation for the further development of therapeutic drugs for metabolic diseases with independent intellectual property rights.
Keywords/Search Tags:Bile acid receptor FXR, Natural compounds, Selective modulator
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