The process of macropinocytosis begins with the reorganization of the actin cytoskeleton, leading to the formation of membrane ruffles or lamellipodia. These ruffles fold back onto the membrane, engulfing extracellular fluid and forming large, irregular vesicles called macropinosomes. These macropinosomes then undergo maturation through a series of fusion and fission events, eventually fusing with lysosomes for degradation of their contents.
