Involved in the degradation process of misfolded endoplasmic reticulum (ER) luminal proteins. Participates in the transfer of misfolded proteins from the ER to the cytosol, where they are destroyed by the proteasome in a ubiquitin-dependent manner. Probably acts by serving as a linker between DERL1, which mediates the retrotranslocation of misfolded proteins into the cytosol, and the ATPase complex VCP, which mediates the translocation and ubiquitination. Interacts with DERL1 and (via VIM motif) with VCP, suggesting that it forms a membrane complex with DERL1 that serves as a receptor for VCP. Also interacts with DERL2, DERL3 and SELENOK. The SELENOK-SELENOS complex interacts with VCP. Interacts with CCDC47 (By similarity). Truncated SELENOS proteins produced by failed UGA/Sec decoding are ubiquitinated by the CRL2(KLHDC2) and CRL2(KLHDC3) complexes, which recognizes the glycine (Gly) at the C-terminus of truncated SELENOS proteins (PubMed:26138980, PubMed:30526872). Truncated SELENOS proteins produced by failed UGA/Sec decoding are also ubiquitinated by the CRL5(KLHDC1) complex (PubMed:32200094). Belongs to the selenoprotein S family. Truncated C-terminus.