Cells & molecules

Clathrin-mediated endocytosis

Cell biology · Membrane traffic

How does a cell take in something too big to fit through any of its doors?

Cells can swallow material by wrapping a patch of their own surface around it and pinching it off as a tiny bubble. To do this, proteins gather the things to be taken in, then a cage of three-legged protein units builds over the patch and curves it into a pit. A ring-shaped protein squeezes the neck of the pit until the bubble breaks free and carries its load into the cell.

Clathrin-mediated endocytosis is the main route by which animal cells take up specific receptors and their bound cargo from the cell surface. Adaptors link cargo to a self-assembling clathrin lattice that bends the membrane into a pit, dynamin pinches it off, and the uncoated vesicle delivers its contents to early endosomes for sorting.

Key facts

Coated vesicle diameter: ≈ 60–120 nm (cage); ≈ 40–80 nm membrane
Triskelion: 3 heavy chains (≈ 190 kDa) + 3 light chains (≈ 25 kDa); legs ≈ 50 nm
Coated-pit lifetime: ≈ 30–90 s from initiation to scission
Pentagons per closed cage: exactly 12 (with a variable number of hexagons)
Dynamin: ≈ 100 kDa GTPase; forms a helix ≈ 50 nm wide around the neck
Early endosome pH: ≈ 6.0–6.5

Parts you can explore (8)

Plasma membrane
Receptors & cargo
AP2 adaptors
Clathrin coat
Dynamin
Coated vesicle
Hsc70 & auxilin
Early endosome

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