ClathrinCoated

Clathrin-coated refers to cellular structures that are enveloped by a lattice of the protein clathrin, most notably clathrin-coated pits on the plasma membrane and clathrin-coated vesicles in the endomembrane system. Clathrin coats arise from the polymerization of clathrin triskelions, which assemble into a polyhedral lattice that shapes membranes into vesicles during vesicular trafficking. The clathrin coat helps to select and concentrate cargo proteins for transport and to mold the membrane into a vesicle.

Cargo selection is mediated by adaptor protein complexes, especially AP-2 at the plasma membrane, which recognize sorting signals on transmembrane receptors and link them to the clathrin lattice. Other adaptors and accessory proteins regulate coat assembly, cargo density, and membrane curvature. Vesicle scission from the membrane is driven by the GTPase dynamin, which constricts the neck of the budding vesicle. Following scission, the clathrin coat is rapidly removed by uncoating factors such as Hsc70 and auxilin, allowing the vesicle to fuse with early endosomes or other target compartments.

Clathrin-coated structures are central to clathrin-mediated endocytosis, a major pathway for nutrient uptake, receptor internalization, and regulation of signaling. They also function in post-Golgi trafficking from the trans-Golgi network to endosomes. Disruptions to clathrin-mediated pathways can affect receptor recycling, lipid uptake, pathogen entry, and various cellular processes, highlighting the coat’s importance in cellular homeostasis.