Surf4 collaborates with Derlin-2 and Derlin-1 to mediate Cyclooxygenase-2 translocation to the cytosol for degradation.

Abstract

Derlin family members participate in the retrotranslocation of endoplasmic reticulum (ER) lumen protein to the cytosol for ER-associated degradation (ERAD). However, the protein(s) facilitating their retrotranslocation remains to be explored. Using CRISPR library screening, we found that Derlin-2 and Surf4 were candidates to facilitate cyclooxygenase-2 (COX-2) degradation. Our results showed that Derlin-2 is the upstream of Derlin-1 and Surf4 is the downstream of Derlin-2 and Derlin-1 to facilitate COX-2 degradation. Knockdown of Derlin-2 or Surf4 impedes COX-2 ubiquitination and the interaction of COX-2 with caveolin-1 and p97 in cytosol. Additionally, COX-2 degradation is N-glycosylation-dependent. Although Derlin-2 facilitates N-glycosylated COX-2 degradation, the interaction of Derlin-2 with COX-2 is independent of COX-2 N-glycosylation. Derlin-1, Surf4 and p97 preferentially interact with non-glycosylated COX-2, while caveolin-1 preferentially interacts with N-glycosylated COX-2, regardless of the N-glycosylation patterns. Collectively, our results reveal that Surf4 collaborates with Derlin-2 and Derlin-1 to mediate COX-2 translocation from the ER lumen to the cytosol. The Derlin-2/Derlin-1/Surf4/Cav-1 machinery may represent a unique pathway to accelerate COX-2 degradation in ERAD.