Table 1.
Mechanisms of endocytosis
| Pathway | Morphology and size | Coat | Small GTPase | Cargo | Function |
|---|---|---|---|---|---|
| Clathrin-mediateda | Vesicular 150–200 nm | Clathrin | Rab5 | RTKs, GPCR, TGF-ßR, Notch, TfR, LDLR, ß-arrestin, Wnt/ß-catenin | Cell signaling, vesicular transport |
| Caveolae-mediateda | Flask-shaped 50–120 nm | Caveolin 1 and 2 | Unclear | GPI-APs, TGF-ßR, CTxB, viruses, folic acid, IGF-1R, Wnt/ß-catenin | Cell signaling, lipid regulation, vesicular transport, transcytosis |
| CLIC/GEEC | Tubular | None | Cdc42 Arf1 | GPI-APs, glycosphingolipids, cholera toxin | Actin dynamics and cellular stress pathways, differentiation and apoptosis, focal adhesion, fluid-phase uptake, oncogenesis |
| Arf6-mediated | Tubular | None | Arf6 | ß-arrestins, MHC I-II | Membrane curvature |
| Flotillin-mediated | Vesicular | Flotillin 1 and 2 | None | CTxB, GPI-AP, proteoglycans | Lipid raft-mediated endocytosis, |
| IL-2Ra | Vesicular 50–100 nm | None | RhoA, Rac1 | IL-2Rß, yc cytokine receptor | IL-2R endocytosis and signaling |
| Macropinocytosisa | Ruffled | None | Rac1, Cdc42, Arf6, Rab5 | Fluid, RTKs, bacteria | Extracellular fluid uptake, actin dynamics |
| Phagocytosis | Cargo shaped | None | Rac1, RhoA, Cdc42 | Nutrients, pathogens, dead cells, and cellular debris | Uptake of nutrients, pathogens, and cellular debris by professional phagocytic cells; opsonization of foreign particles followed by actin rearrangements |
Arf, ADP rybosylation factor; GTPase, guanine triphosphate hydrolyze; Cdc42, cell division control protein 42 homolog; CLIC, clathrin-independent carriers; CTxB, cholera toxin B subunit; GEEC, GPI-AP-enriched early endosomal compartment; GPI-APs, glycosphingolipids anchored proteins; GPCR, G-protein coupled receptor; Rab, ras-associated binding protein; IGF-1R, insulin growth factor-1 receptor; IL-2R, interleukin 2 receptor beta; TRKs, receptor tyrosine kinases; TfR, transferring receptor; LDLR, low-density lipoprotein receptor; MHC, Major histocompatibility complex; RhoA, Ras homolog gene family, member A; Rac1, Ras-related C3 botulinum toxin substrate 1; TGF-ßR, transforming growth factor beta receptor
amarks the dynamin-dependent mechanisms; macropinocytosis requires dynamin only in some situations. The above information is based on references listed in this manuscript (most extensively reviewed in refs. [1, 2]. Only selected cargo and functions are listed