Transient confinement zones: A type of lipid raft?

Many important signaling events are initiated at the cell membrane. To facilitate efficient signal transduction upon stimulation, membrane microdomains, also known as lipid rafts, are postulated to serve as platforms to recruit components involved in the signaling complex, but few methods exist to study rafts in vivo. Single particle tracking provides an approach to study the plasma membrane of living cells on the nano-scale. The trajectories of single gold particles bound to membrane proteins and lipids are characterized in terms of both random and confined diffusion; the latter occurs in transient confinement zones. Here we review transient confinement zones and some of their implications for membrane structure and function.