Derlin family members participate in the retrotranslocation of endoplasmic reticulum (ER) lumen proteins to the cytosol for ER-associated degradation (ERAD); however, the proteins facilitating this retrotranslocation remain to be explored. Using CRISPR library screening, we have found that derlin-2 and surfeit locus protein 4 (Surf4) are candidates to facilitate degradation of cyclooxygenase-2 (COX-2, also known as PTGS2). Our results show that derlin-2 acts upstream of derlin-1 and that Surf4 acts downstream of derlin-2 and derlin-1 to facilitate COX-2 degradation. Knockdown of derlin-2 or Surf4 impedes the ubiquitylation of COX-2 and the interaction of COX-2 with caveolin-1 (Cav-1) and p97 (also known as VCP) in the cytosol. Additionally, COX-2 degradation is N-glycosylation dependent. Although derlin-2 facilitates degradation of N-glycosylated COX-2, the interaction between derlin-2 and COX-2 is independent of COX-2 N-glycosylation. Derlin-1, Surf4 and p97 preferentially interact with non-glycosylated COX-2, whereas Cav-1 preferentially interacts with N-glycosylated COX-2, regardless of the N-glycosylation pattern. 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 might represent a unique pathway to accelerate COX-2 degradation in ERAD.

中文翻译：

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Surf4 与 derlin-2 和 derlin-1 合作介导 cyclooxygenase-2 易位至胞质溶胶进行降解。

Derlin 家族成员参与内质网 (ER) 腔蛋白逆转位至胞质溶胶以进行 ER 相关降解 (ERAD)；然而，促进这种逆转位的蛋白质仍有待探索。通过 CRISPR 文库筛选，我们发现 derlin-2 和 surfeit 位点蛋白 4 (Surf4) 是促进环加氧酶 2 (COX-2，也称为 PTGS2) 降解的候选蛋白。我们的结果表明，derlin-2 作用于 derlin-1 上游，而 Surf4 作用于 derlin-2 和 derlin-1 下游，以促进 COX-2 降解。derlin-2 或 Surf4 的敲低会阻碍 COX-2 的泛素化以及 COX-2 与细胞质中的 Caveolin-1 (Cav-1) 和 p97（也称为 VCP）的相互作用。此外，COX-2 降解依赖于 N-糖基化。尽管 derlin-2 促进 N-糖基化 COX-2 的降解，但 derlin-2 和 COX-2 之间的相互作用独立于 COX-2 N-糖基化。Derlin-1、Surf4 和 p97 优先与非糖基化 COX-2 相互作用，而 Cav-1 优先与 N-糖基化 COX-2 相互作用，无论 N-糖基化模式如何。总的来说，我们的结果表明 Surf4 与 derlin-2 和 derlin-1 合作介导 COX-2 从 ER 腔到细胞质的易位。derlin-2-derlin-1-Surf4-Cav-1 机制可能代表了 ERAD 中加速 COX-2 降解的独特途径。