Macropinocytosis

Macropinocytosis is an actin-dependent, clathrin-independent endocytic process by which cells non-selectively internalize extracellular fluid and solutes into large vesicles called macropinosomes[1][4][7]. This process involves the formation of actin-driven membrane ruffles that close to engulf extracellular material. Macropinocytosis plays key roles in immune surveillance by dendritic cells and macrophages, nutrient uptake in unicellular organisms and cancer cells, and antigen presentation[1][3][6]. It is regulated by complex signaling pathways involving small GTPases (such as Rac and Ras), phosphoinositide 3-kinase (PI3K), lipid kinases/phosphatases, and actin regulatory proteins[1][2][6]. While it can be constitutive or induced by growth factor signaling, it is not itself a protein or receptor but rather a cellular pathway/process. Therefore, it should not be considered a direct therapeutic target like receptors or enzymes; instead, its regulation may be targeted indirectly for therapeutic purposes in diseases such as cancer or infection[6]. > "Macropinocytosis provides an important mechanism of immune surveillance by dendritic cells and macrophages but also serves as an essential nutrient uptake pathway for unicellular organisms and tumor cells."[1] > "This actin-driven endocytic process is not directly co-ordinated by the presence of cargo but can be induced upon activation of growth factor signalling pathways."[8] Because macropinocytosis refers to a biological process rather than a discrete molecule or receptor, it does not fit the definition of a canonical drug target, making this entry incorrect for most structured drug-target databases.

Other names

Fluid-phase endocytosis (context-dependent)