Component of the ESCRT-I complex, a regulator of vesicular trafficking process. Binds to ubiquitinated cargo proteins and is required for the sorting of endocytic ubiquitinated cargos into multivesicular bodies (MVBs). Component of an ESCRT-I complex (endosomal sorting complex required for transport I). Predominantly cytosolic. Recruited to endosomes as part of the ESCRT-I complex. The UMA domain mediates association with the ESCRT-I complex. Impaired motor neuron outgrowth, leading to decreased mobility and shorter lifespan (PubMed:31203368). Axon lengths is significantly shorter in motor neurons (PubMed:30929741, PubMed:31203368).