Endocytosis, the uptake of material into a cell, often involves the structural protein clathrin. Clathrin forms a curved lattice on the plasma membrane that buds inward and eventually pinches off, carrying the material in a clathrin-coated vesicle. Last year, a group carefully measured the assembly and dynamics of clathrin structures and found that there are two distinct clathrin structures that are regulated differently, and interact with different cellular structures. Clathrin coated pits are the rapidly forming and sharply curved canonical structures of clathrin-mediated endocytosis, while clathrin coated plaques are longer-lived and less sharply curved structures. Electron microscopy image above shows both clathrin coated pits (top row) and plaques (bottom) in HeLa cells.
Reference: Saveez Saffarian, Emanuele Cocucci, Tomas Kirchhausen. Authors’ PLoS Biology paper can be found here.