WIP-1 and DBN-1 promote scission of endocytic vesicles by bridging actin and Dynamin-1 in the C. elegans intestine.

There has been a consensus that actin plays an important role in scission of the clathrin-coated pits (CCPs) together with large GTPases of the dynamin family in metazoan cells. However, the recruitment, regulation and functional interdependence of actin and dynamin during this process remain inadequately understood. Here, based on small-scale screening and in vivo live-imaging techniques, we identified a novel set of molecules underlying CCP scission in the multicellular organism Caenorhabditis elegans. We found that loss of Wiskott-Aldrich syndrome protein (WASP)-interacting protein (WIP-1) impaired CCP scission in a manner that is independent of the C. elegans homolog ofWASP/N-WASP (WSP-1) and is mediated by direct binding to G-actin. Moreover, the cortactin-binding domain of WIP-1 serves as the binding interface for DBN-1 (also known in other organisms as Abp1), another actin-binding protein. We demonstrate that the interaction between DBN-1 and F-actin is essential for Dynamin-1 (DYN-1) recruitment at endocytic sites. In addition, the recycling regulator RME-1, a homolog of mammalian Eps15 homology (EH) domain-containing proteins, is increasingly recruited at the arrested endocytic intermediates induced by F-actin loss or DYN-1 inactivation, which further stabilizes the tubular endocytic intermediates. Our study provides new insights into the molecular network underlying F-actin participation in the scission of CCPs.