Ubiquilin-1 (UBQLN1)

Plays an important role in the regulation of distinct protein degradation mechanisms and pathways including ubiquitin- proteasome system (UPS), autophagy and endoplasmic reticulum- associated protein degradation (ERAD) pathway. Mediates the proteasomal targeting of misfolded or accumulated proteins for degradation by binding (through UBA domain) for their polyubiquitin chains and by interacting (through ubiquitin-like domain) with the subunits of the proteasome (PubMed:15147878).

Plays a role in the ERAD pathway through its interaction with ER-localized proteins UBXN4, VCP and HERPUD1 and might form a link between the polyubiquitinated ERAD substrates and the proteasome (PubMed:19822669, PubMed:18307982). Isoform 1, isoform 2 and isoform 3 play a role in unfolded protein response (UPR) by attenuating the induction of UPR-inducible genes, DDTI3/CHOP, HSPA5 and PDIA2 during ER stress (PubMed:18953672).