Functional component of endoplasmic reticulum-associated degradation (ERAD) for misfolded lumenal glycoproteins, but not that of misfolded nonglycoproteins. May act by forming a channel that allows the retrotranslocation of misfolded glycoproteins into the cytosol where they are ubiquitinated and degraded by the proteasome. May mediate the interaction between VCP and misfolded glycoproteins. May also be involved in endoplasmic reticulum stress-induced pre-emptive quality control, a mechanism that selectively attenuates the translocation of newly synthesized proteins into the endoplasmic reticulum and reroutes them to the cytosol for proteasomal degradation. Forms homo- and heterooligomers with DERL3 and, to a lesser extent, with DERL1 (By similarity). Interacts with the SEL1L/SYVN1 and VCP/SELENOS protein complexes (PubMed:22016385). Mediates association between VCP and EDEM1, as well as that between VCP and the misfolded glycoproteins (By similarity). Interacts with OS9 (By similarity). Interacts with SELENOK and SELENOS (PubMed:22016385). Interacts with the signal recognition particle/SRP and the SRP receptor; in the process of endoplasmic reticulum stress-induced pre-emptive quality control (By similarity). Interacts with CCDC47 (PubMed:25009997). Widely expressed, with lowest levels in brain and heart. Up-regulated in response to endoplasmic reticulum stress via the ERN1-XBP1 pathway of the unfolded protein response (UPR). Belongs to the derlin family.