Table 1.

Overview of commonly used endocytic inhibitors, their effects and limitations [40,44,45,46].

Agent	Mechanism Affected 1	Effect	Limitation	Ref.
Low temp (4 degrees)	All energy dependent processes	Slows down/inhibits all energy dependent processes	Low temperature may influence fluidity of cell membrane	[47,48]
Sodium azide	All energy dependent processes	Inhibits respiratory system of cells	Toxic at higher concentrations	[49,50]
Chlorpromazine	CME	Translocates clathrin and AP2 from the cell surface to intracellular endosomes	Not efficient in all cell lines, might interfere with the biogenesis of intracellular vesicles	[51,52,53] [54] (pp. 19–20)
Cytosol acidification	CME	Inhibits the budding-off of clathrin- coated pits from the membrane	Interferes with macropinocytosis and the actin cytoskeleton	[54] (p. 19)
Hypertonic sucrose	CME	Removes plasma membrane-associated clathrin lattices	Nonspecific, interferes with fluid phase macropinocytosis	[54] (pp. 17–18) [55,56]
Monodansylcadaverine	CME	Stabilizes clathrin-coated pits	Induces global changes in actin dynamics	[54] (p. 20)
Phenylarsine oxide	CME	Mechanisms unknown, possibly a tyrosine phosphate inhibitor	Also inhibits micropinocytosis and is toxic at higher concentrations	[57,58]
Potassium depletion	CME	Removes plasma membrane-associated clathrin lattices	Nonspecific; affects actin cytoskeleton	[54] (p. 18) [59]
Dynasore	CME, CvME	Inhibitor of dynamin (small GTPase)	Has other off-target effects, including inhibition of membrane ruffling	[60,61]
Genistein	CvME	Inhibitor of several tyrosine kinases, causes disruption of the actin network	Affects several uptake processes	[62,63]
Okadaic acid	CvME	Phosphatase inhibitor, stimulates trafficking and internalization of caveolae	Nonspecific, off-target effects	[64]
Cholesterol inhibitors
Filipin	CvME, Lipid raft	Binds to cholesterol in the membrane	Unstable and toxic, cholesterol influences other endocytic pathways besides CvME	[54] (pp. 23–24) [65,66]
Statins	CvME, Lipid raft	Lowering of cholesterol formation by inhibiting the enzyme 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase	Nonspecific, many off-target effects	[54] (p. 22) [67,68]
Methyl-β-cyclodextrin	CvME, Lipid raft	Removes cholesterol out of the plasma membrane by forming soluble inclusion complexes with cholesterol	Nonspecific, interferes with fluid phase endocytosis and CME, might induce membrane curvature	[54] (pp. 22–23) [69,70]
Nystatin	CvME, Lipid raft	Binds to cholesterol in the membrane	Toxic	[54] (pp. 23–24)
(Endosome) acidification inhibitors
Monensin	Prevents acidification of endosomes	Acts as an ionophor, thereby inhibiting the acidification of endosomes		[71,72,73]
Nigericin	Prevents acidification of endosomes	Acts as an ionophor, thereby inhibiting the acidification of endosomes		[74,75]
Bafilomycin A1	Prevents acidification of endosomes	Inhibits the vacuolar ATPase endosomal proton pump.	Prevents maturation of autophagic vacuoles by inhibiting fusion between autophagosomes and lysosomes. Potentially inhibits Ca2+ pump SERCA	[76,77,78]
Chloroquine	Prevents acidification of endosomes	Increases pH of acidic vesicles (e.g., lysosomes), possibly inhibits some lysosomal hydrolases	Affects many other cellular processes	[79,80] (pp. 49–54)
Amiloride	Macropinocytosis	Inhibits macropinocytosis by lowering submembranous pH (cytosolic pH close to the membrane) and prevents Rac1 and Cdc42 signaling.		[81,82,83]
F-actin inhibitors
Cytochalasin D	Macropinocytosis	Inhibits actin polymerization and may thus lead to actin filament disassembly	Nonspecific, may affect other endocytic processes	[54] (p. 26) [84,85]
Jasplakinolide	Macropinocytosis	Stabilizes actin and promotes actin assembly	Various effects depending on cell line and assay conditions	[84,86]
Latrunculin	Macropinocytosis	Sequesters actin monomers, blocks actin polymerization and may thus lead to actin filament disassembly	Not necessarily efficient in adherent cells	[54] (p. 26) [87,88]
Swinholide A	Macropinocytosis	Has F-actin severing activity	Nonspecific, may affect other endocytic processes	[86,89]
Phosphoinositide 3-kinase inhibitors
LY294002	Macropinocytosis	Inhibits phosphatidylinositol 3-kinase class I and III	Nonspecific, also affects CME and CvME	[54] (pp. 26–27) [90,91]
Wortmannin	Macropinocytosis	Inhibits phosphatidylinositol 3-kinase class I and III	Nonspecific, also affects CME and CvME	[54] (pp. 26–27) [90,91]
3-methyladenine	Macropinocytosis	Inhibits phosphatidylinositol 3-kinase class III	Nonspecific, also affects CME and CvME	[54] (pp. 26–27) [92]

¹ Abbreviations: Clathrin-mediated endocytosis (CME), Caveolae-mediated endocytosis (CvME).