Clathrins

Clathrins are a family of proteins that form cage-like structures called clathrin-coated pits and vesicles. These structures are involved in various cellular processes, including endocytosis, exocytosis, and intracellular transport. Clathrins are composed of three heavy chains (clathrin heavy chain, CHC) and three light chains (clathrin light chain, CLTC). The heavy chains form the triskelion structure, which assembles into a cage-like lattice, while the light chains stabilize and regulate the assembly of the heavy chains.

Clathrin-coated pits are invaginations of the plasma membrane that form at specific sites on the cell surface. These pits are coated with a lattice of clathrin triskelia, which helps to concentrate and sort cargo molecules for endocytosis. Once the cargo is internalized, the clathrin-coated pit pinches off to form a clathrin-coated vesicle, which then buds off from the membrane. The clathrin coat is then recycled back to the plasma membrane, ready to form another coated pit.

Clathrins play a crucial role in many cellular processes, including receptor-mediated endocytosis, where they help to internalize receptors and their ligands from the cell surface. They are also involved in the recycling of membrane proteins and lipids, as well as in the transport of vesicles within the cell. Dysregulation of clathrin-mediated endocytosis has been linked to various diseases, including neurodegenerative disorders, cancer, and infectious diseases. Therefore, understanding the molecular mechanisms of clathrin-mediated endocytosis is of great interest in the field of cell biology and medicine.