Mammalian Target of Rapamycin (mTOR) and S6 Kinase Down-regulate Phospholipase D2 Basal Expression and Function
Mammalian Target of Rapamycin (mTOR) and S6 Kinase Down-regulate Phospholipase D2 Basal Expression and Function
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DOI：
10.1074/jbc.m110.111542
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发表时间：
2010-06-18
影响因子：
4.8
通讯作者：
Gomez-Cambronero, Julian
中科院分区：
文献类型：
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作者：
Tabatabaian, Farnaz;Dougherty, Kevin;Gomez-Cambronero, Julian
哺乳动物雷帕霉素靶蛋白（mTOR）和S6激酶（S6 K）通路对细胞分化、生长和存活至关重要。磷脂酶D2（PLD 2）在mTOR/S6 K促有丝分裂信号传导中起关键作用。然而，PLD对mTOR/S6 K基因表达的影响尚不清楚。在这里，我们表明白细胞介素-8（IL-8）增加了PLD 2、mTOR和S6 K的mRNA表达水平，其中PLD 2在时间上先于mTOR/S6 K。PLD 2基因表达的沉默消除了IL-8诱导的mTOR/S6 K mRNA表达，而mTOR或S6 K基因表达的沉默导致PLD 2 RNA水平的大幅（分别>3倍和>5倍）增加，这被蛋白质表达和脂肪酶活性的增加所抵消。用0.5nM雷帕霉素处理细胞诱导了类似的趋势。这些结果表明，在基础条件下，PLD 2表达和伴随的活性受到mTOR/S6 K信号通路的负调控。在过度表达mTOR-野生型但不表达mTOR激酶死亡构建体的分化HL-60白细胞中证实了PLD 2的下调。在细胞水平上，mTOR-野生型的过表达导致较低的基底细胞迁移，这被用IL-8处理逆转。我们认为IL-8逆转了mTOR/S6 K诱导的PLD 2表达下调，使PLD 2能够充分发挥细胞迁移促进剂的作用。
The mammalian target of rapamycin (mTOR) and S6 kinase (S6K) pathway is essential for cell differentiation, growth, and survival. Phospholipase D2 (PLD2) plays a key role in mTOR/S6K mitogenic signaling. However, the impact of PLD on mTOR/S6K gene expression is not known. Here we show that interleukin-8 (IL-8) increases mRNA expression levels for PLD2, mTOR, and S6K, with PLD2 preceding mTOR/S6K in time. Silencing of PLD2 gene expression abrogated IL-8-induced mTOR/S6K mRNA expression, whereas silencing of mTOR or S6K gene expression resulted in large (>3-fold and >5-fold, respectively) increased levels of PLD2 RNA, which was paralleled by increases in protein expression and lipase activity. Treatment of cells with 0.5 nM rapamycin induced a similar trend. These results suggest that, under basal conditions, PLD2 expression and concomitant activity is negatively regulated by the mTOR/S6K signaling pathway. Down-regulation of PLD2 was confirmed in differentiated HL-60 leukocytes overexpressing an mTOR-wild type, but not an mTOR kinase-dead construct. At the cellular level, overexpression of mTOR-wild type resulted in lower basal cell migration, which was reversed by treatment with IL-8. We propose that IL-8 reverses an mTOR/S6K-led down-regulation of PLD2 expression and enables PLD2 to fully function as a facilitator for cell migration.