Huang Y, Zhao Q, Zhou C-X, Gu Z-M, Li D, Xu H-Z, Wiedmer T, Sims P J, Zhao K-W, Chen G-Q
Institute of Health Science, Shanghai Institutes for Biological Sciences and Graduate School of Chinese Academy of Sciences, Shanghai Jiao Tong University School of Medicine (SJTU-SM, formerly Shanghai Second Medical University), Shanghai, China.
Oncogene. 2006 Oct 26;25(50):6618-27. doi: 10.1038/sj.onc.1209677. Epub 2006 May 15.
Phospholipid scramblase 1 (PLSCR1) is a multiply palmitoylated protein which is localized in either the cell membrane or nucleus depending on its palmitoylated state. The increasing evidence showed the biological roles of PLSCR1 in cell signaling, maturation and apoptosis. To investigate the functions of PLSCR1 in leukemic cells, we generated an inducible PLSCR1-expressing cell line using myeloid leukemic U937 cells. In this cell line, PLSCR1 was tightly regulated and induced upon tetracycline withdrawal. Our results showed that inducible PLSCR1 expression arrested the proliferation of U937 cells at G1 phase. Meanwhile, PLSCR1-overexpressing U937 cells also underwent granulocyte-like differentiation with increased sensitivity to etoposide-induced apoptosis. Furthermore, we also found that PLSCR1 induction increased cyclin-dependent kinase inhibitors p27(Kip1) and p21(Cip1) proteins, together with downregulation of S phase kinase-associated protein 2 (SKP2), an F-box subunit of the ubiquitin-ligase complex that targets proteins for degradation. Additionally, PLSCR1 induction significantly decreased c-Myc protein and antiapoptotic Bcl-2 protein. Although the exact mechanism by which PLSCR1 regulates these cellular events and gene expression remains unresolved, our results suggest that PLSCR1 plays the antagonistic role regarding leukemia development. These data will shed new insights into understanding the biochemical and biological functions of PLSCR1 protein.
磷脂翻转酶1（PLSCR1）是一种多重棕榈酰化蛋白，根据其棕榈酰化状态定位于细胞膜或细胞核。越来越多的证据表明PLSCR1在细胞信号传导、成熟和凋亡中具有生物学作用。为了研究PLSCR1在白血病细胞中的功能，我们使用髓系白血病U937细胞构建了一种可诱导表达PLSCR1的细胞系。在该细胞系中，PLSCR1受到严格调控，并在撤除四环素后被诱导表达。我们的结果表明，可诱导的PLSCR1表达使U937细胞的增殖在G1期停滞。同时，过表达PLSCR1的U937细胞也经历了粒细胞样分化，对依托泊苷诱导的凋亡敏感性增加。此外，我们还发现PLSCR1的诱导增加了细胞周期蛋白依赖性激酶抑制剂p27（Kip1）和p21（Cip1）蛋白，同时下调了S期激酶相关蛋白2（SKP2），SKP2是泛素连接酶复合物的一个F-box亚基，负责靶向蛋白质进行降解。此外，PLSCR1的诱导显著降低了c-Myc蛋白和抗凋亡Bcl-2蛋白。虽然PLSCR1调节这些细胞事件和基因表达的确切机制仍未明确，但我们的结果表明PLSCR1在白血病发展中起拮抗作用。这些数据将为理解PLSCR1蛋白的生化和生物学功能提供新的见解。
