STUDY ON FUNCTION OF PHOSPHOLIPASE D2 IN NEURITE REMODELING

哺乳动物磷脂酶D （PLD）是一种新型的信号转导酶，被认为在多种细胞功能中起着重要作用。已经鉴定出两种哺乳动物PLD同工酶，PLD1和PLD2。虽然PLD1的激活机制和生理功能已经有了很好的文献记载，但PLD2的激活机制和生理功能仍有待阐明。在本研究中，我们利用PC12细胞和原代培养的小脑颗粒神经元研究了PLD2是否参与轴突生长。(1)磷脂酶D2在l1刺激的小脑颗粒神经突生长中作为MAP激酶途径的下游信号分子：在出生后第8天的小鼠小脑中，PLD2蛋白丰富表达，而PLD1蛋白未检测到。脂酶缺陷（LD） PLD2的过度表达抑制了l1刺激的神经突生长。此外，我们发现L1刺激在CGNs中增加PLD活性，同时增加细胞外信号调节激酶（ERK）的磷酸化，这两者都被MAP激酶-ERK激酶（MEK）抑制剂抑制。这些结果证明，PLD2作为ERK的下游信号分子，介导了cgn的l1依赖性神经突生长，这一机制可能与酒精相关的神经发育障碍有关。(2)磷脂酶D2在NGF刺激下的PC12细胞神经突生长信号通路中的重要作用：在NGF刺激或MAP激酶ERK激酶活性形式（MEK-CA）的短暂表达诱导的PC12克隆细胞系中，野生型PLD2 （WT-PLD2）的表达增加，而WT-PLD1的表达不增加。相反，LD-PLD2的表达抑制了神经突的伸长。此外，MEK抑制剂抑制了诱导表达WT-PLD2的PC12细胞中NGF诱导的PLD2活化和增生性神经突延伸。MEK-CA刺激PLD2共表达的活性。这些结果证明PLD2作为ERK的下游信号分子在ngf诱导的pc12细胞神经突生长的信号通路中起作用。少

Mammalian phospholipase D (PLD) is a novel signal transducing enzyme, which is believed to play roles in a wide variety of cell functions. Two mammalian PLD isozymes, PLD1 and PLD2,have been identified. Although activation mechanisms and physiological functions of PLD1 have been well documented, those of PLD2 still remain to be clarified. In the present study, we investigated whether PLD2 is involved in axonal outgrowth using PC12 cells and primary cultured cerebellar granule neurons.(1)Phospholipase D2 Functions as a Downstream Signaling Molecule of MAP kinase Pathway in L1-Stimulated Neurite Outgrowth of Cerebellar Granule:In the cerebellum of postnatal day 8 mice, PLD2 protein was abundantly expressed, while PLD1 was not detected. The L1-stimulated neurite outgrowth was inhibited by overexpression of lipase-deficient (LD) PLD2. Furthermore, it was found that L1 stimulation in CGNs increased PLD activity concomitantly with phosphorylation of extracellular signal-regulated kinase (ERK … More ), both of which were inhibited by the MAP kinase-ERK kinase (MEK) inhibitor. These results provide evidence that PLD2 functions as a downstream signaling molecule of ERK to mediate the L1-dependent neurite outgrowth of CGNs, a mechanism that may be related to alcohol-related neurodevelopmental disorders.(2)Essential Role of Phospholipase D2 Activation Downstream of ERK MAP Kinase in the Signaling Pathway of NGF-Stimulated Neurite Outgrowth in PC12 Cells:Increased expression of wild type PLD2 (WT-PLD2), but not WT-PLD1,in a PC12 clonal cell line dramatically elongated neurites induced by NGF stimulation or transient expression of the active form of MAP kinase-ERK kinase (MEK-CA). In contrast, neurite elongation was inhibited by expression of LD-PLD2. Furthermore, the MEK inhibitor suppressed PLD2 activation and the hypertrophic neurite extension induced by NGF in PC12 cells inducibly expressing WT-PLD2. MEK-CA stimulated the activity of co-expressed PLD2. These results provide evidence that PLD2 functions as a downstream signaling molecule of ERK in the signaling pathway of the NGF-induced neurite outgrowth of PC 12 cells. Less