Cell Biology

Endocytosis at the Hub

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Science  12 Nov 2004:
Vol. 306, Issue 5699, pp. 1103
DOI: 10.1126/science.306.5699.1103a

In clathrin-mediated endocytosis, a network of proteins assembles on the cytoplasmic surface of the plasma membrane and promotes the pinching off of a membrane-bounded clathrin-coated vesicle. Together, the proteins select cargoes that are carried either inside the vesicle or in its membrane, modify the shape of the membrane, and drive invagination, vesicle scission, and eventual uncoating. A key player in this process is the AP2 clathrin adaptor protein, which is involved in concentrating selected cargo in the newly forming clathrin-coated pits.

In protein interaction networks, hubs are proteins that have disproportionately high numbers of interaction partners; in biological processes, hubs provide a temporal or spatial ordering to protein interactions. Praefcke et al. treat clathrin-mediated endocytosis as a module of a network and show how the α-appendage part of the AP2 protein works as an interaction hub. Only after being concentrated at sites of endocytosis do the appendages provide a multivalent binding platform (hub) for interaction partners (i.e., endocytic cargoes or other cargo adaptors). Thus, the partners will then be represented according to their relative affinities and concentrations in endocytic clathrin-coated pits and vesicles, even though any individual interactions will have been transient. — SMH

EMBO J. 10.1038/sj.emboj.7600445 (2004).

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