E3 ubiquitin-protein ligase that mediates ubiquitination of TFRC, CD86, FAS and MHC class II proteins, such as HLA-DR alpha and beta, and promotes their subsequent endocytosis and sorting to lysosomes via multivesicular bodies. By constitutively ubiquitinating MHC class II proteins in immature dendritic cells, down-regulates their cell surface localization thus sequestering them in the intracellular endosomal system.
Subcellular locations: Golgi apparatus, Trans-Golgi network membrane, Lysosome membrane, Cytoplasmic vesicle membrane, Late endosome membrane, Early endosome membrane, Cell membrane
Expressed in antigen presenting cells, APCs, located in lymph nodes and spleen. Also expressed in lung. Expression is high in follicular B-cells, moderate in dendritic cells and low in splenic T-cells.