Background: Ubiquilin-4 (UBQLN4) plays a role in the regulation of protein degradation via the ubiquitin-proteasome system (UPS). It mediates the proteasomal targeting of misfolded or accumulated proteins for degradation by binding (via UBA domain) to their polyubiquitin chains and by interacting (via ubiquitin-like domain) with the subunits of the proteasome. UBQLN4 Plays a role in the regulation of the proteasomal degradation of non-ubiquitinated GJA1 (By similarity). It acts as an adapter protein that recruits UBQLN1 to the autophagy machinery and mediates the association of UBQLN1 with autophagosomes and the autophagy-related protein LC3 (MAP1LC3A/B/C) and may assist in the maturation of autophagosomes to autolysosomes by mediating autophagosome-lysosome fusion (PubMed:23459205) [taken from NCBI Entrez Gene (Gene ID: 56893)].