Date of Award
Doctor of Philosophy
Autotaxin (ATX) is a ubiquitous ectoenzyme that hydrolyzes lysophosphatidylcholine (LPC) to form the bioactive lipid mediator lysophosphatidic acid (LPA). LPA activates specific G-protein coupled receptors (GPCR) to elicit downstream effects leading to cellular motility, survival, and invasion. Through these downstream effects, autotaxin is involved in many diseases including cancer, heart disease, chronic pain, asthma, and other inflammatory diseases. Inhibition of autotaxin activity is therefore a therapeutically attractive goal. Initial ATX inhibitors included L-histidine and analogs which acted as metal chelators. Subsequently, LPA and sphingosine-1-phosphate were identified as ATX inhibitors, leading to extensive structure-activity relationship (SAR) studies on phospholipid analogs. Later, computational and experimental SAR studies led to the discovery of smaller, non-lipid molecules which could avoid off-target effects through G-protein coupled receptor interactions. In 2011, crystal structures confirmed earlier enzyme kinetic studies that suggested multiple inhibitor binding sites by revealing a unique allosteric hydrophobic pocket. Further exploration of this hydrophobic pocket, both computationally and experimentally, has been undertaken to develop new ATX inhibitor which can take advantage of hydrophobic interactions. In order to explore the hydrophobic tunnel of ATX, a structure-based pharmacophore model was developed. This model was used to screen a large database of diverse compounds, discovering a new inhibitor scaffold, GRI 392104 (IC50 4µM). This scaffold was used as a lead to develop sixty-six additional compounds. In total twelve newly synthesized inhibitors of ATX were more potent than GRI 392104 and were selective for ATX as they had no effect on other LPC-specific NPP family members or LPA1-5 GPCR. Concurrent to this work, another promising inhibitor with a similar scaffold was discovered in collaboration with Dr. Tigyi at University of Tennessee Health Science Center, GRI 182135 (IC50 154 nM). The potency of this compound was four-fold that of the best compound from initial optimization of the GRI 392104 scaffold, so an additional nine molecules were studied to explore the differences in activity, resulting in a twelve-fold improvement in potency from the initial structure-activity relationship of GRI 392104 and almost three-fold improvement over the initial screening of GRI 182135.
dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.
Ragle, Lauren Elizabeth, "Computational and Experimental Tools to Explore Autotaxin Inhibition by Novel Small Molecules" (2016). Electronic Theses and Dissertations. 1496.