Component of the adaptor protein complex 4 (AP-4). Adaptor protein complexes are vesicle coat components involved both in vesicle formation and cargo selection. They control the vesicular transport of proteins in different trafficking pathways (  ). AP-4 forms a non clathrin-associated coat on vesicles departing the trans-Golgi network (TGN) and may be involved in the targeting of proteins from the trans-Golgi network (TGN) to the endosomal-lysosomal system (, ). It is also involved in protein sorting to the basolateral membrane in epithelial cells and the proper asymmetric localization of somatodendritic proteins in neurons (By similarity). Within AP-4, the mu-type subunit AP4M1 is directly involved in the recognition and binding of tyrosine-based sorting signals found in the cytoplasmic part of cargos ( , ). The adaptor protein complex 4 (AP-4) may also recognize other types of sorting signal (By similarity).
Subcellular locations: Golgi apparatus, Trans-Golgi network membrane, Early endosome
Found in soma and dendritic shafts of neuronal cells.
Ubiquitous. Highly expressed in testis and lowly expressed in brain and lung.