Figure 11.

A model summarizing the proteins involved in macropinosomal formation and early maturation. RasS, PI 3-kinase, and PKB are hypothesized to play an important role in “building” the macropinosomal cup by activating and/or recruiting proteins that regulate membrane trafficking (Rabs and LmpA) and proteins that regulate F-actin formation and stability (profilin, Scar, coronin, etc.). Within 90 s of formation of a macropinosome, one group of proteins is removed (F-actin, coronin, PKB) and replaced by a second group of proteins, including Rab7, LmpA, and the proton pump.