Functions as an adapter recruiting ubiquitin-protein ligases to their specific substrates. Through an ubiquitination-dependent mechanism plays for instance a role in the incorporation of SLC11A2 into extracellular vesicles. More generally, plays a role in the extracellular transport of proteins between cells through the release in the extracellular space of microvesicles. By participating in the ITCH-mediated ubiquitination and subsequent degradation of NOTCH1, negatively regulates the NOTCH signaling pathway. Interacts (via PPxY motifs) with ITCH (via WW domains); the interaction is direct and participates in the recruitment of the ubiquitin-protein ligase ITCH to the NOTCH1 receptor (By similarity). Interacts with ARRB1 and ARRB2; the interaction is direct (PubMed:23886940). Interacts with TSG101; may recruit TSG101 to the plasma membrane. Interacts (via PPxY motifs) with WWP2 (via WW domains); ubiquitinates ARRDC1. Interacts with SLC11A2; controls the incorporation of SLC11A2 into extracellular vesicles through an ubiquitination-dependent mechanism. Interacts with WWP1 (via WW domains). Interacts with NEDD4 (via WW domains). Interacts with PDCD6IP (By similarity). Also found in extracellular vesicles different from exosomes. The PPxY motifs mediate interaction with WW domain-containing ubiquitin-protein ligases. Ubiquitinated. Ubiquitination by WWP2; promotes localization to extracellular microvesicles. Ubiquitinated by WWP1. Belongs to the arrestin family. Extended N-terminus.