During endocytosis, extracellular material is transported into the cell through internalisation of plasma membrane. The internalisation is mostly mediated though clathrin, initiated by redistribution of membrane proteins into clathrin-coated pits. The internalised vesicle fuses with early endosome, a process regulated by small GTPase Rab5 (Bucci et al., 1992). During the maturation from early to late endosome, budding events occur, creating a collection of internal vesicles. Late endosome can receive digestive enzyme, fuse with lysosome or fuse with autophagosomes (Nixon, 2005).
Proper neuronal function requires endocytosis because its polarised shape, therefore, the need to communicate between synaptic active zones and perikaryon.
|Involvement in Alzheimer's disease|
Altered neuronal endocytosis is one of the earliest changes known to AD (Cataldo et al., 2000). Endocytosis can accelerates Aβ generation (Grbovic et al., 2003), as endosome can transport APP to undergo β-cleavage at a more distanced site, and early endosome may contain components of γ- secretase complex (Pasternak et al., 2003).
At the early stage of AD, the increase of soluble Aβ level is often companioned with enlarged Rab5-positive endosome (Cataldo et al., 2004). It seems that APP may also exert effect on endosome trafficking (Nixon, 2005).