Interview for Faculty Position

Protein organization and dynamics in model membranes and cells

Suliana Manley

Cell Biology & Metabolism Branch
National Institute of Health

Cell membranes are characteristically heterogeneous, both structurally and dynamically. The spatial arrangement and dynamic movement of proteins in cell membranes are essential for coordinating many cellular functions, contributing to the specificity and sensitivity of a cell's response to its environment. I will discuss two routes toward understanding these heterogeneities, using either model membranes or mammalian cells. In the controlled environment of model membranes, we studied the influence of membrane-tethered proteins and lipid compositions on membrane organization. We found that the ordering of protein and lipid phases were closely interconnected. While heterogeneities in model membranes can be large enough to measure using diffraction-limited optical microscopy, heterogeneities in cell membranes generally exist on smaller scales. We addressed this by combining the super-resolution technique of photoactivated localization microscopy (PALM) with live cell single particle tracking (SPT). Photo-switchable, genetically expressed probes are used to create spatially resolved maps of single-molecule motions. We explored the capabilities of this method by imaging the membrane proteins Gag and VSVG, obtaining up to thousands of trajectories per cell, several orders of magnitude more than enabled by traditional SPT. By examining the behavior of dynamically or structurally distinct subsets of molecules, we can probe the origins of spatial and temporal heterogeneities within cell membranes.