Nano-Scale, Microsecond Diffusion Imaging of Membrane Protein - lipid Raft Interaction in the Plasma Membrane

Abstract

Spatial membrane domains, such as created by lipid rafts and the membrane cytoskeleton, influence membrane protein mobility and hence membrane bound processes, i.e. cell signaling. However, visualization of these lipid domains in intact cells is challenging because of their small dimension and dynamics. We have visualized lipid raft and cytoskeleton domains by tracking the diffusion of membrane proteins with thermal noise imaging (TNI). TNI tracks the diffusion of a colloid labeled membrane protein with microsecond and nanometer precision. In addition, an optical trap confines the diffusion to a small area of the membrane providing sufficient statistics for high resolutions maps of the diffusion. We observe millisecond transient confinement zones consistent with 10nm lipid rafts which redistribute after depolymerization of the actin cytoskeleton. Also, we observed larger (∼80nm) cytoskeleton caused confinement zones.