May function as a proteasomal ubiquitin receptor. May promote the deubiquitinating activity associated with the 26S proteasome (By similarity). Interacts with the 26S proteasome. In larvae, expressed in the central nervous system. The PH domain mediates interactions with PSMD1 and ubiquitin. Preferential binding to the proximal subunit of K48-linked diubiquitin allows UCHL5 access to the distal subunit (By similarity). Belongs to the ADRM1 family.