Lipids solvate membrane proteins and in many cases regulate their activity through direct, specific contacts. Receptor tyrosine kinases (RTKs) are integral membrane proteins that sense a variety of chemical signals. Both the extracellular domain (ECD) and the intracellular domain (ICD) of RTKs associate directly with the plasma membrane. Our lab is currently investigating how specific lipids bind to and regulate the structure and function of RTKs.
This work is currently funded by an NSF CAREER Award.
This project takes advantage of model membrane systems to study lipid-protein complexes with PIE-FCCS and single-particle tracking. Our first contribution to this field was to investigate the mobility of fluorescent PIP2 lipids in the presence of adsorbed cationic macromolecules. We observed that mobility coupling depends on the ionic strength of the buffer and showed that classic Debye-Hückel screening is significant at physiological salt concentrations. Recently, we discovered a simple vesicle fusion-based protocol for preparing asymmetric supported lipid bilayers (asy-SLBs) in which fluorescent PIP2 lipid analogues are only in the top leaflet of the supported membrane facing the bulk solution. Asymmetric bilayers are an ideal platform for investigating the interaction of PIP2 with peripheral membrane proteins, using fluorescence-based imaging approaches.
Shi, X., Kohram, M., Zhuang, X., Smith, A. W. (2016) Interactions and translational dynamics of phosphatidylinositol bisphosphate (PIP2) lipids in asymmetric lipid bilayers. Langmuir 32, 1732-1741.
Shi, X., Li, X., Kaliszewski, M. J., Zhuang, X., and Smith, A. W. (2015) Tuning the Mobility Coupling of Quaternized Polyvinylpyridine and Anionic Phospholipids in Supported Lipid Bilayers. Langmuir 31, 1784-1791.