Multifunctional protein that may be involved in endocytosis, multivesicular body biogenesis, membrane repair, cytokinesis, apoptosis and maintenance of tight junction integrity. Class E VPS protein involved in concentration and sorting of cargo proteins of the multivesicular body (MVB) for incorporation into intralumenal vesicles that are generated by invagination and scission from the limiting membrane of the endosome (By similarity). Binds to the phospholipid lysobisphosphatidic acid (LBPA) which is abundant in MVBs internal membranes. May play a role in the regulation of both apoptosis and cell proliferation. Regulates exosome biogenesis in concert with SDC1/4 and SDCBP. Ensures the proper assembly and positioning of actomyosin-tight junction complex at the apical sides of adjacent epithelial cells that defines a spatial membrane domain essential for the maintenance of epithelial cell polarity and barrier (By similarity). Component of the actomyosin-tight junction complex (By similarity). Phosphorylated on tyrosine residues. Extended N-terminus.