线粒体神经酰胺酶上调K562细胞Bcl-2蛋白表达水平(英文)

Mitochondrial Ceramidase Overexpression Up-regulates Bcl-2 Protein Level in K562 Cells, Probably Through Its Metabolite Sphingosine-1-phosphate

最近 ,克隆了一种新的选择性定位于线粒体的神经酰胺酶 ,提示线粒体存在着神经酰胺代谢途径 ,可能对线粒体的功能 ,特别对凋亡产生影响。本研究将线粒体神经酰胺酶基因转染到K5 6 2细胞 ,以此了解线粒体神经酰胺酶的细胞生物学效应。以脂质体介导将含有线粒体神经酰胺酶cDNA的pcDNA3.1 His CDase质粒转染到K5 6 2细胞 ,G4 18筛选阳性克隆 ,建立稳定表达线粒体神经酰胺酶的K5 6 2TC细胞株。用MTT法、annexinⅤ PI法、FCM及Westernblot分别检测K5 6 2与K5 6 2TC细胞在细胞毒药物抗性、血清剥夺耐受性及Bcl 2蛋白表达水平方面的差异。结果表明 :虽然K5 6 2TC与K5 6 2细胞对阿霉素、足叶乙甙及亚砷酸的敏感性没有差异 ,但是K5 6 2TC细胞Bcl 2蛋白水平明显升高 ,抗血清剥夺能力明显增强。以硫代反义寡核苷酸特异性封闭K5 6 2TC细胞线粒体神经酰胺酶 ,下调Bcl 2蛋白表达水平 ;二甲基鞘氨醇 (鞘氨醇激酶抑制剂 ,降低细胞内 1 磷酸鞘氨醇水平 )同样下调K5 6 2TC细胞Bcl 2蛋白表达水平 ,而 1 磷酸鞘氨醇明显上调K5 6 2细胞Bcl 2表达水平。结论 :线粒体神经酰胺酶将线粒体神经酰胺代谢为鞘氨醇 ,进而在鞘氨醇激酶作用下生成 1 磷酸鞘氨醇 ,此代谢途径上调K5 6 2细胞Bcl 2蛋白表达水平。

Recently, a mitochondrial ceramidase has been i dentified and cloned, whose mitochondrial localization str ongly suggests the existence of an unexpected mitochondrial pathway of ceramide metabolism that may play a key role in mitochondrial functions, especially in th e regulation of apoptosis. To explore the biological effect of mitochondrial cera midase on cells, pcDNA 3.1/His-CDase plasmid, containing mitochondrial c eramidase cDNA sequence, was transducted into K562 cells mediated by liposome, a nd G418 was used to screen for positive colonies. A stable transfected K562 cell line was established and named as ‘K562TC’. The difference between K562 and K 562TC cells in chemotheraputic cytotoxicity response and serum-withdrawal resistance and Bcl-2 protein expression were evaluated by MTT assay, annexin V/PI test, fl ow cytometry or Western blotting, respectively. The results showed that although survival was comparable between K562 and K562TC cells after exposed to adriamycin, etoposide or arseniou s acid, K562TC cells with elevated Bcl-2 protein expression level as identified by FCM or Western blotting revealed stronger resistance to apoptosis induced by seru m withdrawal than their parental cells. Inhibition of mitochondrial ceramidase e xpression in K562TC cells by its specific antisense oligodeoxynucleotide was cor related with a decrease in Bcl-2 protein level. N,N-dimethylsphingosine, a sph ingosine kinase inhibitor, depleted intracellular sphingosine-1-phosphate prod ucti on, also abrogated Bcl-2 protein expression in K562TC cells, while Bcl-2 prote in level in K562 cells was up-regulated by exogenous sphingosine-1-phosphate. It is concluded that mitochondrial ceramidase overexpression in K562 cells leads to markedly elevated level of Bcl-2 protein and results in more resistance to ser um withdrawal. This effect is initiated not by sphingosine, the direct metabolite of mitochondrial ceramidase, but via sphingosine-1-phosphate, its phosphorylat ed form. This is the first evidence that mitochondrial ceramidase, through its sph ingoid metabolite sphingosine-1-phosphate, up-regulates Bcl-2 protein expres sion in K562 cells.