Cell Biology

A Close-Up View of Endocytosis

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Science  31 Aug 2012:
Vol. 337, Issue 6098, pp. 1021
DOI: 10.1126/science.337.6098.1021-c

Clathrin-coated pits mediate the uptake of extracellular ligands into cells. Although this process is relatively well understood, questions still remain about how individual clathrin coated pits are initiated and precisely how the budding and scission process to form coated vesicles in the cytosol proceeds. Now, using mammalian live-cell and single-molecule imaging, Cocucci et al. provide a close-up view of the initiation process—the first 5 s in the life of a coated pit. Coated pits appeared to be initiated by the coordinated assembly of individual clathrin triskelions together with their AP2 adaptor proteins. The FCho proteins, known to play important roles in clathrin-coated vesicle assembly, were required for the sustained growth of the incipient coated pits. Working in yeast cells, Kikulski et al. used correlated fluorescence microscopy and electron tomography to look at individual endocytic events to reconstruct a virtual ultrastructural movie of membrane invagination. In this system, the coating of the membrane with clathrin was not sufficient to initiate budding—the actin network was required to promote the formation of invaginated tubules, which were severed from the surface once they had penetrated about 100 nm, which took about 9 s.

Cell 150, 495; 508 (2012).

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