Adaptor autoregulation promotes coordinated binding within clathrin coats.

Membrane traffic is an essential process that allows protein and lipid exchange between the endocytic, lysosomal, and secretory compartments. Clathrin-mediated traffic between the trans-Golgi network and endosomes mediates responses to the environment through the sorting of biosynthetic and endocytic protein cargo. Traffic through this pathway is initiated by the controlled assembly of a clathrin-adaptor protein coat on the cytosolic surface of the originating organelle. In this process, clathrin is recruited by different adaptor proteins that act as a bridge between clathrin and the transmembrane cargo proteins to be transported. Interactions between adaptors and clathrin and between different types of adaptors lead to the formation of a densely packed protein network within the coat. A key unresolved issue is how the highly complex adaptor-clathrin interaction and adaptor-adaptor interaction landscape lead to the correct spatiotemporal assembly of the clathrin coat. Here we report the discovery of a new autoregulatory motif within the clathrin adaptor Gga2 that drives synergistic binding of Gga2 to clathrin and the adaptor Ent5. This autoregulation influences the temporal and/or spatial location of the Gga2-Ent5 interaction. We propose that this synergistic binding provides built-in regulation to ensure the correct assembly of clathrin coats.