Abstract

Vesicular traffic in the endocytic and secretory pathway is mediated by vesicles that carry cargo proteins. Clathrin-coated vesicles are responsible for a large fraction of the vescicular traffic that reaches the endosomal compartment, originating from the plasma membrane or from the TGN (trans-Golgi network). The assembly of the clathrin-coated vesicles is mediated by proteic adaptors, monomeric as AP180 and CALM or multimeric complexes like AP (Adaptor Protein) complexes. AP complexes are heterotetrameric proteins that simultaneously interact with clathrin and endocytic proteins: for example, the beta-subunit of AP-2 complex binds to clathrin, the mu-subunit interacts with Y-based sorting signal present in the cytosolic tails of membrane receptors and the alpha-subunit of AP-2 binds regulatory/accessory proteins involved in the control of clathrin coated vesicle formation.