Nuclear phospholipase C beta1 (PLCbeta1) affects CD24 expression in murineerythroleukemia cells

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.