Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


Thesis_PhD_Bedi.pdf (3.1 MB)

ETD Abstract Container

Abstract Header

Identification of Novel Ligands and Structural Requirements for Heterodimerization of the Liver X Receptor Alpha

Bedi, Shimpi
http://rave.ohiolink.edu/etdc/view?acc_num=wright1495630797912988

Abstract Details

2017, Doctor of Philosophy (PhD), Wright State University, Biomedical Sciences PhD.
LXRs, LXRa (NR1H3) and LXRß (NR1H2), are ligand-activated transcription factors that are members of the nuclear receptor superfamily. Oxysterols and nonsteroidal synthetic compounds bind directly to LXRs and influence the expression of LXR dependent genes. The use of murine models and LXR-selective agonists have established the important role of LXRs as sterol sensors that govern the absorption, transport, and catabolism of cholesterol. Upon activation, these receptors have been shown to increase reverse cholesterol transport from the macrophage back to the liver to aid in the removal of excess cholesterol. Not surprisingly, LXR dysregulation is a feature of several human diseases, including metabolic syndrome. Due to their roles in the regulation of lipid and cholesterol metabolism, LXRs are potentially attractive pharmaceutical targets. As ligand binding and dimerization play pivotal roles in modulating LXR activity, the identification of novel ligands and requirements for LXR dimerization can potentially aid the drug development process. Herein, using a variety of biophysical assays, including fluorescence based assays coupled with in silico molecular modeling, I have identified medium chain fatty acids and/or their metabolites as the novel endogenous agonists of LXRa. There is mounting evidence that ligand induced dimerization regulates the transcriptional output of nuclear receptors. Thus, it is important to identify factors that modulate protein-protein interactions. This work demonstrated that (a) LXRa binds PPARa with a high affinity (low nanomolar concentration), (b) ligands for LXRa alter the binding dissociation constant values of LXRa-PPARa interaction, and (c) ligand binding induces conformational changes in the dimer secondary structure. Furthermore, site-directed mutagenesis investigated the strength of individual contributions of residues located in the ligand binding domain to dimerization and transactivation properties of LXRa. Data herein highlight the importance of hydrophobic interactions and salt bridges at the interface, and suggest that key interface residues are required for the ligand-dependent activation of LXRa in a promoter specific manner. Mutagenesis of LXRa L414 to an arginine revealed the importance of this site in dimerization, specifically with RXRa. This work showed that this particular mutation specifically abolished dimerization with RXRa. Taken together, this study provided insights into the functional roles of fatty acids as novel LXRa ligands and the effects mutations may have in modulating molecular interactions and activity profile of LXRa.
Stanley Dean Rider, Jr., Ph.D. (Advisor)
Heather Hostetler, Ph.D. (Advisor)
Gerald Alter, Ph.D. (Committee Member)
Lawrence Prochaska, Ph.D. (Committee Member)
Katherine Excoffon, Ph.D. (Committee Member)
Nicholas Reo, Ph.D. (Committee Member)
Ashot Kozak, Ph.D. (Committee Member)
206 p.
Biochemistry; Biomedical Research; Cellular Biology; Molecular Biology
Liver X Receptor; Peroxisome Proliferator-Activated Receptor; nuclear receptor; transcription factor; oxysterols; fatty acids; molecular docking; protein interface; ligand binding; binding affinities; protein-protein interactions; SREBP-1c; ApoA1

Recommended Citations

Citations

  • Bedi, S. (2017). Identification of Novel Ligands and Structural Requirements for Heterodimerization of the Liver X Receptor Alpha [Doctoral dissertation, Wright State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=wright1495630797912988

    APA Style (7th edition)

  • Bedi, Shimpi. Identification of Novel Ligands and Structural Requirements for Heterodimerization of the Liver X Receptor Alpha . 2017. Wright State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=wright1495630797912988.

    MLA Style (8th edition)

  • Bedi, Shimpi. "Identification of Novel Ligands and Structural Requirements for Heterodimerization of the Liver X Receptor Alpha ." Doctoral dissertation, Wright State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1495630797912988

    Chicago Manual of Style (17th edition)

wright1495630797912988
445
© 2017, some rights reserved.Creative Commons License Identification of Novel Ligands and Structural Requirements for Heterodimerization of the Liver X Receptor Alpha by Shimpi Bedi is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Wright State University and OhioLINK.