Enter a novel COP I interactor: DSL1

Vesicular traffic in the secretory and endocytic pathways is mediated by the regulated assembly of cytoplasmic coat proteins on donor membranes. Once formed, transport vesicles dock at appropriate acceptor organelle membranes, the coat is shed and SNARE-mediated membrane fusion proceeds. To date, several coat proteins have been well characterized, including the hetero-tetrameric adaptor complexes (AP-1, AP-2, AP-3) and clathrin, and the COP I and COP II coats. COP I vesicles are involved in Golgi-to-endoplasmic reticulum and intra-Golgi retrograde traffic, COP II is in charge of ER-to-Golgi transport, and adaptors and clathrin mediate trafficking from the trans-Golgi complex and from the plasma membrane. All these coats are organized as multisubunit complexes, and their individual subunits are strictly conserved in evolution. In recent years, a large and growing number of auxiliary proteins have also been characterized that associate with subunits of the adaptors AP-1 and AP-2, or with clathrin, to effect cargo inclusion into coated vesicles or to regulate the vesicle budding event. Additionally, for some transport steps, ‘tethering factors’ have been identified that are required for vesicle delivery and thus contribute to the fidelity of fusion between membranes.