Li Lingzhi, Lu Yongju, Stemmer Paul M, Chen Fei
Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48201, USA.
The Proteomics Core and Institute of Environmental Health Sciences, School of Medicine, Wayne State University, Detroit, MI 48201, USA.
Oncotarget. 2015 May 20;6(14):12009-19. doi: 10.18632/oncotarget.3617.
We had previously reported that trivalent arsenic (As(3+)), a well-known environmental carcinogen, induces phosphorylation of several putative Akt substrates. In the present report, we characterized one of these substrates by immunoprecipitation and proteomics analysis. The results indicate that a cytoskeleton remodeling protein, filamin A, with a molecular weight around 280 kDa, is phosphorylated by Akt in HEK-293 cells treated with As(3+), which was also confirmed in human bronchial epithelial cell line, BEAS-2B cells. Additional biochemical and biological studies revealed that serine 2152 (S2152) of filamin A is phosphorylated by activated Akt in the cells treated with As(3+). To further confirm the importance of Akt-dependent filamin A S2152 phosphorylation in As(3+)-induced cell migration, we over-expressed either wild type filamin A or the mutated filamin A in which the S2152 was substituted with alanine (S2152A). The capability of cell migration was reduced significantly in the cells expressing the mutated filamin A (S2152A). Clinically, we found that increased expression of filamin A predicts poorer overall survival of the lung cancer patients with adenocarcinoma. Thus, these data suggest that Akt dependent filamin A phosphorylation is one of the key events in mediating As(3+)-induced carcinogenesis. Antagonizing Akt signaling can ameliorate As(3+)-induced filamin A phosphorylation and cell migration, which may serve as a molecular targeting strategy for malignancies associated with environmental As(3+) exposure.
我们之前曾报道，三价砷（As(3+)）作为一种著名的环境致癌物，可诱导多种假定的Akt底物发生磷酸化。在本报告中，我们通过免疫沉淀和蛋白质组学分析对其中一种底物进行了表征。结果表明，一种分子量约为280 kDa的细胞骨架重塑蛋白细丝蛋白A在经As(3+)处理的HEK-293细胞中被Akt磷酸化，这在人支气管上皮细胞系BEAS-2B细胞中也得到了证实。进一步的生化和生物学研究表明，在经As(3+)处理的细胞中，细丝蛋白A的丝氨酸2152（S2152）被活化的Akt磷酸化。为了进一步证实Akt依赖性细丝蛋白A S2152磷酸化在As(3+)诱导的细胞迁移中的重要性，我们过表达了野生型细丝蛋白A或S2152被丙氨酸取代的突变型细丝蛋白A（S2152A）。表达突变型细丝蛋白A（S2152A）的细胞的迁移能力显著降低。临床上，我们发现细丝蛋白A表达增加预示着腺癌肺癌患者的总体生存率较差。因此，这些数据表明Akt依赖性细丝蛋白A磷酸化是介导As(3+)诱导的致癌作用的关键事件之一。拮抗Akt信号传导可改善As(3+)诱导的细丝蛋白A磷酸化和细胞迁移，这可能作为与环境As(3+)暴露相关的恶性肿瘤的分子靶向策略。
