Structural Studies of Integral Membrane Proteins Involved in GPCR Signaling and Sterol Homeostasis

Membrane proteins are crucial molecules for cellular survival, and can take on multiple and diverse roles within the native membrane. In this dissertation, I will detail my efforts to understand and study two different types of membrane proteins. First, I will discuss my research developing and applying a strategy to use NMR spectroscopy to study specific receptors within the large family of G protein-coupled receptors. This strategy enabled the first methyl-TROSY experiments on a wild-type human GPCR, and have significant value for future drug discovery efforts on this important class of membrane proteins. Second, I will discuss my endeavors to understand the important role of the protein Scap, which can both sense and respond to differences in cholesterol levels within the ER membrane. Scap is a central player in the SREBP pathway, which is targeted by multiple classes of pharmaceuticals, including statins. Through efforts described in the second half of this dissertation, I have been able to demonstrate the first biochemical characterization of the full-length mammalian Scap/Insig complex, which has led to the first structural characterization of this important machinery. The long-term goal of both of these projects is aimed at having a more complete understanding of how these important membrane proteins respond to ligands and other environmental changes within their native cell membrane. This information will further our ability to diagnose and treat diseases ranging from insomnia and chronic pain to atherosclerosis and hypercholesterolemia.