Research Interests

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-lipid and protein-protein associations, but surprisingly limited information is available about the structure and dynamics of these interactions in situ. My research group will apply 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 systems. 

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. At this point, however, there is no consensus regarding the size, composition, and exact role of the oligomeric complexes. My research group will study membrane receptor oligomers in live cells using two-color time-correlated single photon counting (TCSPC) fluorescence microscopy. 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 dynamics of the bound protein-lipid complex. Using two-color TCSPC and single molecule imaging, my group will measure 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. 

Selected Publications

  1. Marita, M., Wang, Y, Comar, W. D., Shi, X., Dasari, P., Zhang, X., and Smith, A. W. Class A plexins are organized as preformed inactive dimers on the cell surface. (Submitted, in review).
  2. Shi, X., Li, X., Kaliszewski, M. J., Zhuang, X., and Smith, A. W. Tuning the mobility coupling of polycationic macromolecules and anionic phospholipids in supported lipid bilayers. (Submitted, in review).
  3. Smith, A. W. (2014) Detection of rhodopsin dimerization in situ by PIE-FCCS, a time-resolved fluorescence spectroscopy. Methods in Molecular Biology (in press)
  4. 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.
  5. 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.
    *Equal Contribution
  6. Triffo, S. B., Huang, H. H., Smith, A. W., Chou, E. T., Groves, J. T. (2012).  Monitoring Lipid Anchor Organization in Cell Membranes by PIE-FCCS.  Journal of the American Chemical Society 134, 10833–10842.
  7. Belardi, B., O’Donoghue, G. P., Smith, A. W., Groves, J. T., Bertozzi, C. R.  (2012). Investigating Cell Surface Galectin-Mediated Cross-Linking on Glycoengineered Cells. Journal of the American Chemical Society 134, 9549.
  8. Smith, A. W. (2012).  Invited Review:  Lipid-protein interactions in biological membranes: a dynamic perspective.  Biochimica et Biophysica Acta – Biomembranes 1818, 172.
  9. Smith, A. W., Smoligovets, A. A., and Groves, J. T. (2011). Patterned two-photon photoactivation illuminates spatial reorganization in live cells.  Journal of Physical Chemistry A, 115, 3867-3875.
  10. Smith, A. W., Lessing, J., Ganim, Z., Peng, C. S., Roy, S., Jansen, T. L. C., Knoester, J., and Tokmakoff, A. (2010).  Feature Article: Melting of a beta-hairpin peptide using isotope-edited 2D IR spectroscopy and simulations.  Journal of Physical Chemistry B. 114, 10913.