Clathrin is a protein, which has the primary role of helping to form coated vesicles. A vesicle itself is a structure that can be within or outside a cell which consists of either a liquid or a cytoplasm enclosed by a lipid bilayer. Clathrin was originally identified and isolated in 1976 by Barbara Pearse, and is seen to be composed of a triskelion shape of three heavy chains and three light chains. Upon the interaction of the triskelia, a polyhedral lattice forms which then surrounds the vesicle, which is where Clathrin gets its name from, with the Latin clathrum meaning ‘lattice’.
As we have seen, it is composed of three clathrin heavy chains which interact at their C-termini. In essence, the three heavy chains work as a structural backbone for the lattice, and they are believed to help regulate the formation and subsequent disassembly of the lattice. For the light chains, there are two basic forms. The main clathrin heavy chain is found on chromosone 17 in human beings, and found in all cells in the body.
As for its function, Clathrin performs some critical roles: shaping rounded vesicles, helping intracellular trafficking, and sorting cargo at the cell membrane, trans-Golgi network, and endosomal compartments.
Another major function of Clathrin can be seen in non-dividing cells. During mitosis, Clathrin binds to a spindle apparatus along with two other proteins, and aids in the congression of chromosomes. It does this primarily by stabilising kinetochore fibers in the mitotic spindle. This process regulates many cellular processes.