The function of AP1S3 (adaptor related protein complex 1 subunit sigma 3, Ensembl gene identifier ENSG00000152056) is as follows. Subunit of clathrin-associated adaptor protein complex 1 that plays a role in protein sorting in the late-Golgi/trans-Golgi network (TGN) and/or endosomes. The AP complexes mediate both the recruitment of clathrin to membranes and the recognition of sorting signals within the cytosolic tails of transmembrane cargo molecules. Involved in TLR3 trafficking (PubMed:24791904). .