Component of the 26S proteasome, a multiprotein complex involved in the ATP-dependent degradation of ubiquitinated proteins (PubMed:16815440, PubMed:16906146, PubMed:16990800, PubMed:17139257, PubMed:18497817, PubMed:24752541, PubMed:25702870, PubMed:25702872). This complex plays a key role in the maintenance of protein homeostasis by removing misfolded or damaged proteins, which could impair cellular functions, and by removing proteins whose functions are no longer required (PubMed:16815440, PubMed:16906146, PubMed:16990800, PubMed:17139257, PubMed:18497817, PubMed:24752541, PubMed:25702870, PubMed:25702872). Therefore, the proteasome participates in numerous cellular processes, including cell cycle progression, apoptosis, or DNA damage repair (PubMed:16815440, PubMed:16906146, PubMed:16990800, PubMed:17139257, PubMed:18497817, PubMed:24752541, PubMed:25702870, PubMed:25702872). Within the complex, functions as a proteasomal ubiquitin receptor (PubMed:18497817). Engages and activates 19S-associated deubiquitinases UCHL5 and PSMD14 during protein degradation (PubMed:16906146, PubMed:16990800, PubMed:17139257, PubMed:24752541). UCHL5 reversibly associate with the 19S regulatory particle whereas PSMD14 is an intrinsic subunit of the proteasome lid subcomplex (PubMed:16906146, PubMed:16990800, PubMed:17139257, PubMed:24752541). Component of the 19S proteasome regulatory particle complex. The 26S proteasome consists of a 20S core particle (CP) and two 19S regulatory subunits (RP) (PubMed:16990800). Interacts with the proteasomal scaffolding protein PSMD1 (PubMed:16990800,PubMed:16815440, PubMed:16906146, PubMed:20471946). Interacts with deubiquitinase UCHL5; this interaction activates the auto-inhibited UCHL5 by deoligomerizing it (PubMed:17139257, PubMed:24752541, PubMed:25702870, PubMed:25702872). Interacts with UBQLN2 and ubiquitin (PubMed:27396824). The Pru (pleckstrin-like receptor for ubiquitin) domain mediates interactions with PSMD1 and ubiquitin. Preferential binding to the proximal subunit of 'Lys-48'-linked diubiquitin allows UCHL5 access to the distal subunit. Ubiquitinated by UBE3C in response to proteotoxic stress. Belongs to the ADRM1 family. Although initially described as a cell membrane glycoprotein, ADRM1 is intracellular and non-glycosylated, and has probably no direct role in cell adhesion.