Molecular organization and dynamics in biological membranes
The live-cell plasma membrane presents a serious challenge to modern physical chemistry. Biological function at the plasma membrane depends directly on protein-protein and protein-lipid associations, but surprisingly limited information is available about the structure and dynamics of these interactions in situ. My research group develops and applies advanced methods in fluorescence microscopy–including time-correlated single photon counting and single molecule imaging–to measure protein-protein and protein-lipid associations within live cells and in model membranes.
Membrane receptor clustering and its role in signaling
Protein-protein interactions are critical for cell surface receptors, for which clustering and dynamic assembly is a fundamental step in signal transduction. For many receptors, however, there is no consensus regarding the size, composition, and exact role of the oligomeric complexes. My research group studies membrane receptor oligomers in live cells using pulsed interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS). Our aim is to characterize the composition, dynamic stability, and functional consequence of receptor oligomers in live cells. This detailed, molecular-level information will revolutionize our understanding of membrane receptor function and will directly impact drug design, where traditional receptor-ligand docking paradigms will be updated to recognize protein complexes as unique targets.
Lipid-protein interaction dynamics
Biological function at the plasma membrane is dependent on specific protein-lipid interactions. For example, many lipids play a central role in signal transduction, including protein kinase localization and activation. This localization occurs via protein domains that bind lipid head groups with high affinity. However, very little is known about the specificity of the interactions and the details of the bound protein-lipid complex. Using PIE-FCCS and single molecule imaging, my group studies the correlated diffusion of fluorescently labeled lipids with lipid binding proteins. Direct observation of correlated lipid-protein dynamics will provide unprecedented insight into a range of biological problems and will support the growing number of molecular dynamic simulations of proteins interacting with lipid bilayers.
- Huang, Y., Bharill, S., Karandur, D., Peterson, S. M., Marita, M., Shi, X., Kaliszewski, M. J., Smith, A. W.*, Isacoff, E. Y.*, Kuriyan, J.*, (2016) Molecular Basis for Multimerization in the Activation of the Epidermal Growth Factor Receptor. eLife, 5, e14107.
- 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.
- Grasse, E. K.; Torcasio, M. H.; Smith, A. W. (2016) Teaching UV–Vis Spectroscopy with a 3D-Printable Smartphone Spectrophotometer. J. Chem. Edu. 93, 146-151.
- Comar, W. D., Schubert, S. M., Jastrzebska, B., Palczewski, K. and Smith, A. W. (2014) Mobility and clustering of the opsin G protein-coupled receptor in live cells with time-resolved fluorescence spectroscopy. Journal of the American Chemical Society 136, 8342.
- Endres, N. F.*, Das, R.*, Smith, A. W.*, Arkhipov, A., Kovacs, E., Huang, Y., Pelton, J.G., Shan, Y., Shaw, D.E., Wemmer, D.E., Groves, J.T., Kuriyan, J. (2013) Conformational Coupling across the Plasma Membrane in Activation of the EGF Receptor, Cell 152, 543-546