Multifunctional protein 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 (ILVs) that are generated by invagination and scission from the limiting membrane of the endosome. Binds to the phospholipid lysobisphosphatidic acid (LBPA) which is abundant in MVBs internal membranes. The MVB pathway requires the sequential function of ESCRT-O, -I,-II and -III complexes. The ESCRT machinery also functions in topologically equivalent membrane fission events, such as the terminal stages of cytokinesis. Adapter for a subset of ESCRT-III proteins, such as CHMP4, to function at distinct membranes. Required for completion of cytokinesis. May play a role in the regulation of both apoptosis and cell proliferation. Regulates exosome biogenesis in concert with SDC1/4 and SDCBP (By similarity). By interacting with F-actin, PARD3 and TJP1 secures 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). Self-associates (By similarity). Interacts with SH3KBP1 (PubMed:10858458). Interacts with PDCD6 in a calcium-dependent manner (By similarity). Interacts with TSG101 in a calcium-dependent manner; PDCD6IP homooligomerization may be required for TSG101-binding (By similarity). Interacts with SGSM3 (By similarity). Directly interacts with CHMP4A, CHMP4B and CHMP4C (By similarity). Directly interacts with CEP55 in a 1:2 stoechiometry; this interaction is required for PDCD6IP targeting to the midbody (By similarity). May interact with PDGFRB (By similarity). Interacts with SH3GL1 and SH3GL2/endophilin-1 (By similarity). Forms a complex with SDCBP and SDC2 (By similarity). Found in a complex with F-actin, TJP1/ZO-1 and PARD3 (By similarity). Interacts with CD2AP (By similarity). Interacts with ARRDC1 (By similarity). Colocalized with CEP55 in the midbody during cytokinesis and at centrosomes in non-dividing cells (By similarity). Component of the actomyosin-tight junction complex (By similarity). Expressed in astrocytes and glioma cells. May be phosphorylated on tyrosine residues by activated PDGFRB.