Multi-functional protein that contributes to the endocytic process, but also to events that occur at the neck during budding and/or cytokinesis. Plays a role as an endocytic adapters with membrane-tubulation activity that associates with transmembrane cargo proteins and initiates the formation of endocytic sites. Contributes to the stabilization of the nascent clathrin-coated pit. Also plays a role in late endocytosis by mediating vesiculation. Involved in the regulation of cell cycle-dependent dynamics of the septin cytoskeleton by promoting septin turnover in different cell cycle stages. May act through the RHO2 signaling pathway to repolarize cortical actin patches in profilin-deficient cells. Interacts with CDC3, CDC10, CDC11, CDC12, EDE1 and EPS15. Concentrates at the mother-bud neck and at the tip of the forming bud. As the bud grows, abundant in the mother-bud neck and in the bud. At cytokinesis, found predominantly at the junction between the mother cell and the bud. Present at the base of shmoo projections. Present with 4280 molecules/cell in log phase SD medium. Belongs to the SYP1 family.