Studying Lipid-Protein Interaction Using Proteinacous Supported Lipid Bilayers from Cell Membranes

Abstract

Membrane proteins play important roles in cell biology and thus it is crucial to develop methods to access their functional information for further applications such as drug discovery screening or disease prevention. In order to study membrane species in their natural structure and functions, we introduce platforms using supported lipid bilayers (SLB) to house these targeted species. SLBs not only mimic natural cell membrane environments but also allow heterogeneous bilayer patterning. It is known that the cell membrane is not merely composed of a well-mixed single lipid phase, but has distinct lipid micro-domains of co-existing phases, lipid raft and liquid-disorder phase, and this feature has been suggested to play a key role in regulating several cellular activities, as some proteins have been shown to exhibit different activity levels depending on specific lipid interactions. Therefore, we aim to determine the preference of membrane proteins with lipid raft phases, and understand the influence of lipid environment on regulating protein activity level, revealing important mechanisms of membrane proteins function in cells. Toward this goal, we first patterned two-phase coexistent SLBs inside a microfluidic to mimic membrane heterogeneities and quantify partition kinetics of membrane-bound species in this platform (Chapter 2). To further extend the platform to study membrane protein behavior, we then developed a novel strategy to incorporate membrane proteins in SLBs without exposing them to harsh detergent to retain their native structure and functionality. In this dissertation, I will present our advances on using mammalian cell blebs (Chapter 3) and bacterial outer membrane vesicles (Chapter 4) as an intermediate to delivery membrane proteins into a SLB. A detailed characterization of bilayer properties and membrane protein functionalities will also be covered in these chapters. Finally, in Chapter 5 I will provide a broader view of how our work could be useful to study and identify the regulatory lipid-protein interactions, which is a pressing issue for a better understanding of a wide range of biological processes.