Figure 1
From: Endocytosis unplugged: multiple ways to enter the cell
Macroscale endocytic processes. (A) A simplified schematic representing molecular and membrane events occurring during macroscale endocytic processes. During phagocytic cup formation (left panel), sequential engagement of Fc-receptor initiates a zipper-like arrangement in opposition with bacterial surface. The process is orchestrated by stepwise involvement of GTPases and involves actin polymerization. Membrane remodeling during phagocytosis is accompanied with membrane addition to PM, in an AP1-dependent vesicular process. In trigger-type particle entry (right panel), the process involves injection of soluble effectors into cell, which, among other events, can activate Rho GTase effectors, and hence culminating in actin polymerization at the site of bacterial entry. Variations that exhibit intermediate forms, also exist, but have not been included here. (B) EGF-induced macropinocytosis–a most extensively studied example of macropinocytosis. Binding of EGF to EGF receptor triggers the intracellular signaling cascade and activation of downstream proteins, as indicated, eventually leading to actin-rich membrane ruffle formation. Collapse of ruffle on membrane is followed with macropinosome formation.
