Enables low-density lipoprotein particle receptor binding activity and signal sequence binding activity. Involved in positive regulation of endocytosis; protein-containing complex assembly; and vesicle-mediated transport in synapse. Located in terminal bouton. Part of AP-2 adaptor complex. Is active in glutamatergic synapse. Human ortholog(s) of this gene implicated in autosomal dominant non-syndromic intellectual disability. Orthologous to human AP2M1 (adaptor related protein complex 2 subunit mu 1). [provided by Alliance of Genome Resources, Apr 2022]