Sphingosine kinase 1 expression is downregulated during differentiation of Friend cells due to decreased c-MYB.
Sphingosine kinase 1 expression is downregulated during differentiation of Friend cells due to decreased c-MYB.
复制标题
由于 c-MYB 减少，鞘氨醇激酶 1 表达在 Friend 细胞分化过程中下调。
DOI：
10.1016/j.bbamcr.2013.01.001
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Murate T.
中科院分区：
文献类型：
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作者：
Mizutani N;Kobayashi M;Sobue S;Ichihara M;Ito H;Tanaka K;Iwaki S,Fujii S,Ito Y;Tamiya-Koizumi K;Takagi A;Kojima T;Naoe T;Suzuki M;Nakamura M;Banno Y;Nozawa Y;Murate T.
鞘氨醇激酶1（SPHK 1）在恶性细胞中的过表达已有报道。与其他小鼠细胞系相比，小鼠Friend细胞显示出较高的SPHK 1表达，但SPHK 2表达不高。Sphk 1启动子分析表明-53bp和第一个外显子之间的区域是最小启动子。进一步的启动子截短揭示了MYB结合位点的重要性。用该区域作为探针的EMSA显示一条含有c-MYB蛋白的条带，并且在Friend细胞的红系分化的强力诱导剂六甲基二乙酰胺（HMBA）的红系分化过程中其强度降低。ChIP测定还揭示了c-MYB的体内结合。c-MYB过表达和针对c-Myb的siRNA影响SPHK 1的表达，证实了c-MYB在SPHK 1表达中的重要调节作用。HMBA迅速降低c-MYB表达。HMBA诱导分化引起SPHK 1 mRNA、蛋白和酶活性的显著和快速降低，导致细胞1-磷酸鞘氨醇水平的快速下降。此外，终末分化的细胞没有恢复SPHK 1的表达。与原始Friend细胞相比，野生型SPHK 1的稳定过表达显示更高的细胞增殖，抵抗血清耗竭引起的细胞死亡。有趣的是，HMBA诱导的这些细胞的分化被延迟，但没有完全抑制。相反，SPHK抑制剂及其siRNA抑制细胞生长并显著增强HMBA诱导的分化，表明SPHK 1通过其细胞增殖促进活性延迟HMBA诱导的分化。百日咳毒素、G蛋白偶联受体抑制剂和S1 P受体拮抗剂对Friend细胞生长和分化的影响可以忽略不计，表明细胞内SPHK 1/S1 P信号在Friend细胞中的重要性。
Sphingosine kinase 1 (SPHK1) overexpression in malignant cells has been reported. Mouse Friend cells showed higher SPHK1 but not SPHK2 expression compared with other mouse cell lines. A Sphk1 promoter analysis demonstrated the region between −53bp and the first exon as the minimal promoter. Further promoter truncation revealed the importance of a MYB-binding site. EMSA using this region as the probe demonstrated one band containing c-MYB protein, and its intensity decreased during erythroid differentiation with hexamethylane bisacetamide (HMBA), a potent inducer of erythroid differentiation of Friend cells. ChIP assay also revealed in vivo binding of c-MYB. c-MYB overexpression and siRNA for c-Myb affected SPHK1 expression, confirming the important regulatory role of c-MYB in SPHK1 expression. HMBA reduced c-MYB expression rapidly. Induced differentiation by HMBA caused a marked and rapid reduction of SPHK1 mRNA, protein and enzyme activity leading to the rapid decrease of cellular sphingosine 1-phosphate level. Moreover, terminally differentiated cells did not resume SPHK1 expression. Compared with original Friend cells, stable overexpression of wild-type SPHK1 showed higher cell proliferation, resistance to cell death by serum depletion. Interestingly, HMBA-induced differentiation of these cells was delayed but not completely suppressed. In contrast, SPHK inhibitor and its siRNA inhibited cell growth and enhanced HMBA-induced differentiation significantly, suggesting that SPHK1 delayed HMBA-induced differentiation by its cell proliferation-promoting activity. Effects of pertussis toxin, a G-protein-coupled receptor inhibitor, and S1P receptor antagonist on Friend cell growth and differentiation were negligible, suggesting the importance of the intracellular SPHK1/S1P signaling in Friend cells.