Table 1. Mechanisms of clathrin-independent endocytosis^*.

Characteristics	Caveolar‡	RhoA-regulated	CDC42-regulated	ARF6-regulated
Cargo§	Modified albumins	IL-2R-β	GPI-AP¶	MHC I
	GSL analogues	IL-2R-αβ	Fluid-phase markers	β1 integrin
	SV40; EV1	γc-cytokine receptor‖	CtxB¶	E-cadherin
	Some integrins (for example, β1)	IgE receptor‖	VacA toxin	GPI-AP
	CtxB¶		Aerolysin	CPE
	Ab-clustered GPI-AP#			IL-2R-α (Tac)
Structural components and machinery associated with pathway	CAV1	RhoA	CDC42	ARF6
	PV1	Dynamin	Flotillin-1**	Flotillin-1**
	Src		RAB5	RAB11
	PKC-α		PI3K	RAB22
	Dynamin		EEA1	PI3K
	RAB5
Primary carriers	50–80 nm diameter caveolin-coated vesicles and ‘grape-like’ aggregates	Uncoated vesicles	Clathrin- and dynamin-independent carriers (CLICs)	Unknown
Identity of earliest acceptor compartment	Caveosome or early endosome	Early endosome	GPI-AP enriched early endosomal compartments (GEECs)	Early tubular recycling compartment

Ab, antibody; ARF6, ADP-ribosylation factor-6; CAV1, caveolin-1; CPE, carboxypeptidase E; CtxB, cholera toxin B; EEA1, early endosomal antigen-1; EV1, Echo virus; GPI-AP, glycosyl phosphatidylinositol-anchored protein; GSL, glycosphingolipid; IgE, immunoglobulin E; IL-2R, interleukin-2 receptor; MHC I, major histocompatibility complex I; PI3K, phosphatidylinositol 3-kinase; PKC-α, protein kinase C-α; PV1, Polio virus; SV40, simian virus-40; VacA, Helicobacter pylori vacuolating toxin.

^*See Supplementary information S1 (table) for inhibitors and dominant negative proteins that are used to distinguish among the various clathrin-independent mechanisms.

^‡The best caveolar markers vary with cell type (see text).

^§See text for representative references for different cargo molecules.

^‖Although the specific requirements for endocytosis of molecules via a given pathway have not been rigorously established, available evidence suggests this classification.

^¶Originally described as a caveolar marker, but recent data suggests uptake by the CDC42-regulated pathway^31,33,104.

^#Crosslinking of GPI-APs shifts internalization from the CDC42-dependent pathway to the caveolar pathway^37,105,106.

^**Currently, it is not clear if flotillin-1 is part of one or both of these pathways (see text).