Bortezomib（bort）是多发性骨髓瘤（MM）患者的有效治疗药物，但大多数患者会出现耐药。自噬是一种高度保守的过程，通过溶酶体活性回收细胞质或整个细胞器，对于MM的生存、稳态和耐药性至关重要。越来越多的证据表明，三重蛋白质21（TRIM21）不仅与多种自噬调节因子相互作用，还参与多种癌症的耐药性。然而，迄今为止，TRIM21在MM中的直接底物和其他作用仍然未知。在本研究中，我们证明TRIM21表达低是MM复发的一个因素。TRIM21表达的减少使MM细胞对bort更加耐药，而TRIM21过表达会增加MM对bort的敏感性。 TRIM21 KD MM细胞的蛋白质组和磷酸化蛋白质组研究表明，bort抗药性与氧化应激的增加和升高的自噬有关。我们的结果表明，TRIM21 KD MM细胞系在bort治疗后诱导了利于生存的自噬，而通过3-甲基腺嘌呤处理或ATG5的短发夹RNA抑制自噬可以恢复bort敏感性。确实，TRIM21 KD和OE分别增加和减少了自噬相关基因5（ATG5）的表达。TRIM21通过K48泛素化ATG5进行蛋白酶体降解来影响自噬。重要的是，我们通过体外和体内实验证实了TRIM21可以增强bort的抗骨髓瘤效果。总体而言，我们的发现定义了TRIM21在MM bort耐药性中的关键作用，并为新的靶向治疗方法奠定了基础。版权所有©2023年美国血液学会。

Bortezomib (bort) is an effective therapeutic agent for multiple myeloma (MM) patients, however, the majority of patients develop drug resistance. Autophagy, a highly conserved process that recycles cytosol or entire organelles via lysosomal activity, is essential for the survival, homeostasis and drug resistance in MM. Growing evidence has highlighted the E3 ligase tripartite motif-containing protein 21 (TRIM21) not only interacts with multiple autophagy regulators but also participates in drug resistance in various cancers. However, to date, the direct substrates and additional roles of TRIM21 in MM remain unknown. In this study, we demonstrated that low TRIM21 expression was a factor for relapse in MM. TRIM21 knockdown (KD) made MM cells more resistant to bort, while TRIM21 overexpression (OE) resulted in increased MM sensitivity to bort. Proteomic and phospho-proteomic studies of TRIM21 KD MM cells showed bort resistance was associated with increased oxidative stress and elevated pro-survival autophagy. Our results provided that TRIM21 KD MM cell lines induced pro-survival autophagy after bort treatment, and suppressing autophagy by 3-methyladenine treatment or by the short hairpin RNA of ATG5 restored bort sensitivity. Indeed, autophagy-related gene 5 (ATG5) expression was increased and decreased by TRIM21 KD and OE, respectively. TRIM21 affected autophagy by ubiquitinating ATG5 through K48 for proteasomal degradation. Importantly, we confirmed that TRIM21 could potentiate the anti-myeloma effect of bort through in vitro and in vivo experiments. Overall, our findings define the key role for TRIM21 in MM bort resistance and provide the basis for a novel targeted therapeutic approach.Copyright © 2023 American Society of Hematology.