Graduation Date

Fall 12-20-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Pharmaceutical Sciences

First Advisor

Jonathan L. Vennerstrom, Ph.D.

Second Advisor

Haizhen A. Zhong, Ph.D.

Abstract

The peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-dependent transcription factor of the nuclear receptor superfamily that controls the expression of a variety of genes involved in fatty acid metabolism, adipogenesis, and insulin sensitivity. PPARγ is a target for insulin-sensitizing drugs, and it plays a significant function in prostate cancer. PPARγ antagonists have anti-proliferative effects in a broad range of hematopoietic and epithelial cell lines. The ligand binding domain (LBD) of PPARγ is large and has orthosteric and allosteric binding sites. Several PPARγ-ligand co-crystal structures show two bound molecules, one to the orthosteric pocket and a second to the allosteric site. We ran docking studies against the orthosteric and allosteric binding sites to determine the most favorable binding site for PPARγ antagonists. We found that Glide docking performed well in predicting PPARγ antagonist binding affinities, and that the allosteric site of PPARγ was the most favorable binding site for antagonists. We also investigated PPARγ ligand-protein interactions to better define a structural basis for the binding selectivity of PPARγ antagonists. We found that Phe282, Arg288, and Lys367 interact with antagonists more than with agonists and partial agonists. We then identified several potential PPARγ antagonists by virtual screening of the PPARγ allosteric pocket. The glucose transporter 1 (GLUT1) is a uniporter protein that facilitates the transport of glucose across the plasma membranes of mammalian cells. As GLUT1 is overexpressed in numerous tumors, this transporter is a potential target for cancer treatment. GLUT1 works through conformational switching from an outward-open (OOP) to an inward-open (IOP) conformation passing through an occluded conformation. We sought to determine which conformation is favored for ligand binding by molecular docking studies of known GLUT1 inhibitors with the different GLUT1 conformers. Our data revealed that the IOP is the preferred conformation and that residues Phe291, Phe379, Glu380, Trp388, and Trp412 may play important roles in ligand binding to GLUT1. To identify new chemotypes targeting GLUT1, we built a pharmacophore model and searched against an NCI compound database. Sixteen hit molecules with good docking scores were screened for GLUT1 inhibition and anti-proliferative activities. From these, we identified four compounds that inhibited cell viability in an HCT116 colon cancer cell line. We also determined that one of these, NSC295720, inhibited GLUT1 in a biochemical assay.

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