Component of the adaptor complexes which link clathrin to receptors in coated vesicles (By similarity). Clathrin-associated protein complexes are believed to interact with the cytoplasmic tails of membrane proteins, leading to their selection and concentration (By similarity). AP50 is a subunit of the plasma membrane adaptor (By similarity). Essential wnt/egl-20 signaling protein that functions in wnt/egl-20-producing cells (PubMed:18160346, PubMed:18160347). Required for the AP-2 complex-mediated endocytosis of membrane proteins including wntless homolog mig-14 in egl-20-producing cells (PubMed:18160346, PubMed:18160347). During development, regulates the migration of HSN neurons and the left and right Q neuroblasts (QL and QR, respectively) and their descendants, possibly through hox gene and wnt/egl-20 gene target mab-5, and plays a role in establishing ALM and PLM neuronal cell polarity (PubMed:18160346). Required for the asymmetric divisions of V5 cells (PubMed:18160346). Adaptor protein complex 2 (AP-2) is a heterotetramer composed of two large adaptins (alpha-type subunit and beta-type subunits), a medium adaptin (mu-type subunit AP50) and a small adaptin (sigma-type subunit AP17). Component of the coat surrounding the cytoplasmic face of coated vesicles in the plasma membrane. Brain, heart, lung, liver, testis and spleen. Mutants display a squat body statue referred to as a dumpy phenotype and have defective HSN neuronal cell migration (PubMed:18160346). RNAi-mediated knockdown results in impaired function of the AP-2 complex and accumulation of the wntless homolog mig-14 at the cell membrane (PubMed:18160347). Belongs to the adaptor complexes medium subunit family.