Proteasome Subunits Differentially Control Myeloma Cell Viability and Proteasome Inhibitor Sensitivity.
Proteasome Subunits Differentially Control Myeloma Cell Viability and Proteasome Inhibitor Sensitivity.
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DOI：
10.1158/1541-7786.mcr-19-1026
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发表时间：
2020-10
期刊：
影响因子：
--
通讯作者：
Stewart AK
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文献类型：
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作者：
Shi CX;Zhu YX;Bruins LA;Bonolo de Campos C;Stewart W;Braggio E;Stewart AK
我们产生了8个对硼替佐米（BTZ）耐药的多发性骨髓瘤（MM）细胞系; 5个获得性PSMB 5突变。在1,500名患者中，这种突变在临床上是罕见的。为了更好地理解蛋白酶体对MM活力和药物敏感性的破坏，我们系统地删除了主要的蛋白酶体催化亚基。没有PSMB 5的MM细胞是活的。通过PSMB 5缺失，耐药PSMB 5突变的细胞系对BTZ重新敏感，这意味着PSMB 5突变激活了其耐药功能。相反，PSMB 6敲除对MM细胞系是致命的。耗尽PSMB 6阻止了主要催化亚基PSMB 5、PSMB 7、PSMB 8和PSMB 10的剪接，然而，在没有剪接功能或催化活性的情况下工程化的PSMB 6也恢复了活力，推断PSMB 6对蛋白酶体结构的贡献比功能活性更重要。支持这一点，BTZ敏感性恢复在耐药MM细胞系的低水平表达的突变PSMB 6缺乏剪接功能。PSMB 8和PSMB 9的缺失既不致命也不恢复BTZ敏感性。观察到PSMB 5、PSMB 6和PSMB 7表达的显著共依赖性。我们证明了PSMB 6和7的水平升高，但不是8和9在一些，但不是全部，暴露于蛋白酶体抑制剂的系列患者样本。总之，我们表明PSMB 6和PSMB 7而不是PSMB 5是MM细胞存活所必需的，这种依赖性是结构性的，并且PSMB 5、6和7的上调或激活突变赋予蛋白酶体抑制剂抗性，而耗尽赋予敏感性。这些发现支持PSMB 5、PSMB 6或PSMB 7表达的调节作为新的治疗策略。
We generated eight multiple myeloma (MM) cell lines resistant to bortezomib (BTZ); five acquired PSMB5 mutations. In 1,500 patients such mutations were rare clinically. To better understand disruption of proteasomes on MM viability and drug sensitivity, we systematically deleted the major proteasome catalytic subunits. MM cells without PSMB5 were viable. Drug resistant, PSMB5 mutated, cell lines were re-sensitized to BTZ by PSMB5 deletion, implying PSMB5 mutation is activating in its drug resistance function. In contrast, PSMB6 knockout was lethal to MM cell lines. Depleting PSMB6 prevented splicing of the major catalytic subunits PSMB5, PSMB7, PSMB8 and PSMB10, however PSMB6 engineered without splicing function or catalytic activity, also restored viability, inferring the contribution of PSMB6 to proteasome structure to be more important than functional activity. Supporting this, BTZ sensitivity was restored in drug resistant MM cell lines by low level expression of mutated PSMB6 lacking splicing function. Loss of PSMB8 and PSMB9 was neither lethal nor restored BTZ sensitivity. Significant co-dependency of PSMB5, PSMB6 and PSMB7 expression was observed. We demonstrated elevated levels of PSMB6 and 7 but not 8 and 9 in some, but not all, serial patient samples exposed to proteasome inhibitors. In summary, we show PSMB6 and PSMB7 but not PSMB5 to be essential for MM cell survival, this dependency is structural and that up-regulation or activating mutation of PSMB5, 6 and 7 confers proteasome inhibitor resistance while depletion confers sensitivity. These findings support modulation of PSMB5, PSMB6 or PSMB7 expression as a new therapeutic strategy.