Phosphorylation of RNA helicase A by DNA-dependent protein kinase is indispensable for expression of the MDR1 gene product P-glycoprotein in multidrug-resistant human leukemia cells.
Phosphorylation of RNA helicase A by DNA-dependent protein kinase is indispensable for expression of the MDR1 gene product P-glycoprotein in multidrug-resistant human leukemia cells.
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DNA 依赖性蛋白激酶对 RNA 解旋酶 A 的磷酸化对于多重耐药人白血病细胞中 MDR1 基因产物 P-糖蛋白的表达是必不可少的。
DOI：
10.1021/bi700063b
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发表时间：
2007
期刊：
影响因子：
2.9
通讯作者：
Safa,AhmadR
中科院分区：
文献类型：
--
作者：
Zhong,Xiaoling;Safa,AhmadR
癌症中多药耐药（MDR）的发展通常涉及themdr1基因产物p -糖蛋白（P-gp）的过度表达，p -糖蛋白是一种严重阻碍化疗疗效的药物转运体。由于通过抑制P-gp的药物转运活性来确定逆转MDR的治疗方法的努力尚未取得成功，因此我们将重点放在靶向mdr1启动子激活以降低癌细胞中P-gp表达的替代策略上。我们最近发现，RNA解旋酶A （RHA）抑制是下调白血病细胞中P-gp的一种合理策略，表明RHA RNAi敲低可消除人白血病HL-60细胞MDR变体中P-gp的表达。在该报告中，我们还证明了RHA在MDR变异细胞中激活了themdr1启动子，但在药物敏感的对应细胞中却没有。这使我们假设RHA诱导P-gp需要与仅存在于MDR变体中的另一个因子合作。在这里，我们确定RHA协同因子为DNA-PK催化亚基（cs），我们发现DNA-PKcs与RHA一起存在于多蛋白复合物的themdr1启动子处。此外，靶向DNA-PKcs抑制消除了MDR变异细胞中P-gp的表达。研究人员发现，MDR突变体中的DNA-PKcs催化了构成性多位点RHA磷酸化，导致SDS - PAGE迁移迟缓，而在缺乏DNA-PKcs的亲本细胞中不会发生。DNA-PK在耐多药白血病细胞P-gp过表达中发挥了不可或缺的作用，本报告确定了靶向DNA-PK抑制是逆转癌症耐药的合理策略。
Development of multidrug resistance (MDR) in cancer frequently involves overexpression of theMDR1gene product P-glycoprotein (P-gp), a drug transporter which severely impedes the efficacy of chemotherapy. Because intensive efforts to identify therapeutics that reverse MDR by inhibiting the drug transport activity of P-gp have not yet met with success, we have focused on the alternative strategy of targetingMDR1promoter activation to knockdown P-gp expression in cancer cells. We recently identified RNA helicase A (RHA) inhibition as a rational strategy to downregulate P-gp in leukemia cells by showing that RHA RNAi knockdown abrogated P-gp expression in MDR variants of human leukemia HL-60 cells. In that report, we also demonstrated that RHA activated theMDR1promoter in the MDR variant cells but not in the drug-sensitive counterpart. This led us to hypothesize that P-gp induction by RHA required cooperation with another factor present only in the MDR variants. Here, we identify the RHA cooperating factor as DNA-PK catalytic subunit (cs), and we show that DNA-PKcs resides with RHA at theMDR1promoter in a multiprotein complex. Furthermore, targeted DNA-PKcs inhibition abrogated P-gp expression in the MDR variant cells. We demonstrate that constitutive multisite RHA phosphorylation producing retarded migration in SDS−PAGE is catalyzed by DNA-PKcs in the MDR variants, and does not occur in the parental cells, which are DNA-PKcs deficient. The indispensable role played by DNA-PK in P-gp overexpression in MDR leukemia cells in this report identifies targeted DNA-PK inhibition as a rational strategy to reverse drug resistance in cancer.