Molecular mechanisms for regulation and physiological role of phospholipase D

众所周知，磷脂酶D （PLD）参与多种信号转导途径，包括分泌、囊泡运输、有丝分裂和减数分裂。然而，PLD在细胞功能中的生理作用尚未阐明。在这个研究项目中，我们研究了PLD在细胞生长、分化和凋亡等多种细胞功能中的作用。从大鼠P012细胞中克隆了3个PLD基因（rPLD1a、1b、2），并采用荧光原位杂交（FISH）技术进行了染色体定位。研究了c2 -神经酰胺诱导大鼠嗜碱性白血病RBL细胞和胶质瘤C6细胞凋亡过程中PLD同工酶（rPLD1a、1b、2）mRNA的表达水平。PLD1a和PLD1b mRNA水平显著降低，PLD2 mRNA水平升高。两种形式的PLD （ARF依赖型PLD和油酸依赖型PLD）已被发现存在于从大鼠肝细胞分离的核中。adp核糖基化因子（ARF）依赖型PLD，但油酸依赖型PLD活性在部分肝切除术后再生的大鼠肝的s期增加，这表明核ARF依赖型PLD可能与细胞增殖有关。油酸依赖性PLD活性在大鼠P012细胞中大量存在，这可能受到[1202]刺激的丝裂原活化蛋白激酶的调节。放线菌素d诱导Jurkat T细胞凋亡过程中，油酸依赖的PLD活性也增加。这些结果表明不同的PLD同工酶可能参与不同的细胞功能。

It has been known that phospholipase D (PLD) has been implicated in a variety of signal transduction pathways, including secretion, vesicle trafficking, mitosis and meiosis. However, the physiological role of PLD in cell functions has not yet been elucidated. In this research project, we have investigated the role of PLD in various cell functions, such as cell growth, differentiation and apoptosis. We have cloned three PLD genes (rPLD1a, 1b, 2) from rat P012 cell and their chromosome mapping were performed by fluorescent in situ hybridization (FISH). The levels of mRNA of PLD isozymes (rPLD1a, 1b, 2) were examined in the course of the apoptotic process induced by C2-ceramide in rat basophilic leukemia RBL cells and glioma C6 cells. The mRNA levels of PLD1a, and PLD1b were greatly decreased whereas the level of PLD2 was in contrast increased. Two forms of PLD (ARF- and oleate-dependent PLDs) have been found to be present in nuclei isolated from rat hepatocytes The ADP-ribosylation factor (ARF)-dependent PLD, but not oleate-dependent PLD activity was increased in the S-phase of the regenerating rat liver after partial hepatectomy, suggesting that the nuclear ARF-dependent PLD may be associated with cell proliferation. The oleate-dependent PLD activity was abundantly present in rat P012 cells, which may be regulated by mitogen-activated protein kinase stimulated by [1202. The oleate-dependent PLD activity also was increased during Actinomycine D-induced Jurkat T cell apoptosis. These results suggest that distinct PLD isozymes may be involved in different cell functions.