Subunit of clathrin-associated adaptor protein complex 1 that plays a role in protein sorting in the trans-Golgi network (TGN) and endosomes. The AP complexes mediate the recruitment of clathrin to membranes and the recognition of sorting signals within the cytosolic tails of transmembrane cargo molecules. Belongs to the adaptor complexes medium subunit family. 2 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.
Biological Process: antigen processing and presentation of exogenous peptide antigen via MHC class II; intracellular protein transport; melanosome organization; neutrophil degranulation; regulation of defense response to virus by virus