The Interactions of Two Disease-Linked Membrane Proteins with Their Bilayer Milieu

Abstract

This project is concerned with the study of human integral membrane proteins involved in neurodegenerative disorders. In this dissertation, I explore the synergistic interactions between membrane proteins and their resident lipid environment utilizing in vitro techniques. In the first part of the dissertation, I focus on the development of novel membrane mimetics for the study of the 99-residue C-terminal fragment (C99) of the amyloid precursor protein, a protein involved in the etiology of Alzheimer’s disease. In these studies, I developed novel bicelles suitable for solution NMR with varying bilayer hydrophobic width. By employing NMR, I learned that C99 structure is not altered by the hydrophobic width of its membrane environment but that C99 burial in the membrane adjusts asymmetrically to increased hydrophobic width. This adjustment may explain previous observations regarding differential C99 cleavage by the intramembrane protease γ-secretase in different membrane widths and shed light on disease outcomes. In the second half of this dissertation, I have focused on the structure and function of peripheral myelin protein 22 (PMP22), a protein involved in the etiology of inherited peripheral neuropathy. Through computational homology modeling studies, I have learned that severe disease causing mutations likely affect the core of the helical bundle, contributing to protein instability. By employing vesicle reconstitution of purified, recombinant PMP22 followed by various forms of electron microscopy, I have learned that PMP22 is involved in shaping membranes into complex architectures that resemble myelin assemblies. In sum, this dissertation provides new insight into ways that membranes and membrane proteins mutually influence one another and how that relationship may contribute to disease outcome.