Fiume Roberta, Faenza Irene, Matteucci Alessandro, Astolfi Annalisa, Vitale Marco, Martelli Alberto Maria, Cocco Lucio
Department of Anatomical Sciences, Cellular Signaling Laboratory, University of Bologna, 40126 Bologna, Italy.
J Biol Chem. 2005 Jun 24;280(25):24221-6. doi: 10.1074/jbc.M411833200. Epub 2005 Apr 22.
Inositide-specific phospholipase C (PLC) beta1 is a key enzyme in nuclear lipid signal transduction affecting cell cycle progression and may be directly involved in regulation of gene expression and hematopoiesis. By microarrays, we compared the effect of nuclear PLCbeta1 overexpression with that of PLC M2b cytoplasmatic mutant, which is exclusively located in the cytoplasm, in murine erythroleukemia cells. Out of 9000 genes analyzed, the CD24 gene, coding for an antigen involved in differentiation and hematopoiesis as well, was up-regulated in cells overexpressing nuclear PLCbeta1 as compared with both cells overexpressing the M2b cytoplasmatic mutant and the wild type cells. Here we show that nuclear PLCbeta1 up-regulated the expression of CD24. The correlation was strengthened by the observation that when PLCbeta1 expression was silenced by means of small interfering RNA, CD24 expression was down-regulated. We also demonstrated that PLCbeta1-dependent up-modulation of CD24 was mediated, at least in part, at the transcriptional level, in that PLCbeta1 affected the CD24 promoter activity. Moreover, the up-regulation of CD24 was higher during erythroid differentiation of murine erythroleukemia cells. Altogether our findings, obtained by combining microarrays, phenotypic analysis, and small interfering RNA technology, identify CD24 as an molecular effector of nuclear PLCbeta1 signaling pathway in murine erythroleukemia cells and strengthen the contention that nuclear PLCbeta1 constitutes a key step in erythroid differentiation in vitro.
肌醇特异性磷脂酶C（PLC）β1是核脂质信号转导中的关键酶，影响细胞周期进程，可能直接参与基因表达调控和造血过程。通过微阵列技术，我们比较了核PLCβ1过表达与仅定位于细胞质的PLC M2b细胞质突变体在鼠红细胞白血病细胞中的作用。在分析的9000个基因中，编码一种也参与分化和造血的抗原的CD24基因，在过表达核PLCβ1的细胞中比过表达M2b细胞质突变体的细胞和野生型细胞上调。在此我们表明核PLCβ1上调了CD24的表达。当通过小干扰RNA使PLCβ1表达沉默时CD24表达下调这一观察结果进一步加强了这种相关性。我们还证明，PLCβ1依赖性的CD24上调至少部分是在转录水平介导的，因为PLCβ1影响CD24启动子活性。此外，在鼠红细胞白血病细胞的红系分化过程中CD24的上调更高。通过结合微阵列、表型分析和小干扰RNA技术获得的我们的研究结果共同确定CD24是鼠红细胞白血病细胞核PLCβ1信号通路的分子效应器，并强化了核PLCβ1构成体外红系分化关键步骤的论点。
