Clathrin



Clathrin is a protein that is the major constituent of the 'coat' of the clathrin coated pits and coated vesicles formed during endocytosis of materials at the surface of cells.

Clathrin molecules are recruited with the aid of adaptor proteins to a membrane segment that is destined to be incorporated into a vesicle. In synaptic vesicle formation one such adaptor protein is AP180 (see here for micrographs of clathrin assembly). This protein both recruits clathrin to membranes and also promotes its polymerisation in a localized polyhedral lattice on the plasma membrane. Epsin can also recruit clathrin to membranes and promote its polymerisation and in this case the epsin helps deform the membrane and thus clathrin coated vesicles can bud (see here for micrographs of vesicle budding). After vesicle scission the coat quickly falls off and may then be reused to form fresh coated pits and vesicles. The un-coated vesicle then fuses with endosomes, delivering its contents to them; this membrane is ultimately returned to the cell surface. A similar process also buds membrane segments from intracellular organelles, such as in the formation of vesicles from the trans-Golgi network.

Clathrin was first isolated and named by Barbara Pearse in 1975.