Fig. 4

Actin cytoskeleton-dependent raft organization. a Topography of raft nanoclusters and macrodomains. Rafts occur as nanoclusters that are less than 20 nm in diameter, but can cluster to larger structures to include macrodomains that are microns in size. Both the nanoclusters and larger assembles form in an actin-dependent manner [29, 31, 129]. The macrodomains form as a result of signals that activate actin polymerization and attachment of actin filaments to cell membranes. Examples of raft macrodomains include immunological synapses that form in activated lymphocytes, cell–cell adhesion complexes, leading edge and uropod of migrating cells. b The cortical actin cytoskeleton is tethered to the plasma membrane through protein linkers, and these interactions likely structure rafts in the membrane. The meshwork of cortical actin filaments also compartmentalizes the membrane into areas approximately 50–200 nm in size. The compartments represent areas of transient and nonspecific membrane protein confinement by the underlying actin filaments