Enables identical protein binding activity. Acts upstream of or within regulation of protein localization. Located in ciliary membrane; clathrin-coated pit; and clathrin-coated vesicle. Part of AP-2 adaptor complex. Is expressed in several structures, including adrenal gland; alimentary system; heart; metanephros; and nervous system. Orthologous to human EPS15 (epidermal growth factor receptor pathway substrate 15). [provided by Alliance of Genome Resources, Apr 2022]