Regulation of neurogenin1 by phospholipase D1 via mTOR in H19-7 cells

초록

Phospholipase D (PLD) catalyzes the hydrolysys of phospholipids, mainly phosphatidylcoline (PC), resulting in formation of phosphatidic acid (PA). PA has been associated with many aspects of mammalian physiology, which include cell proliferation, survival, transformation, progression and differentiation. Recently, PA has been identified as a mitogenic activator of mTOR signaling pathway. PA binds to mTOR to promote various signals. We previously showed that PLD1 activity is upregulated during neurogenesis induced by basic fibroblast growth factor (bFGF) treatment in rat neuronal hippocampal progenitor cell line, H19-7 cells. Subsequently, we investigated the role of PLD in neurogenesis, specifically activation of neurogenin1 (Ngn1), bHLH family which plays critical role in regulation of neural stem cell differentiation. To figure out the effect of PLD1 on Ngn1 through mTOR signal, we treated natural PA to H19-7 cell under differentiation condition. Natural PA treatment upregulated mTOR and Ngn1 expressions. Furthermore, inhibition of PLD1 activity by PLD1 siRNA showed that expressions of mTOR and Ngn1 were completely inhibited. However, mTOR and Ngn1 expression levels were upregulated when PLD1 activity was increased by bFGF in H19-7 cells. To further confirm the role of PLD1 on Ngn1 through mTOR, we treated rapamycin to inhibit mTOR signal. Treatment of rapamycin showed completely inhibited Ngn1 expression and neurogenic morphological change. These results suggest that PLD1 regulate Ngn1 through mTOR signaling pathway during neurogenesis in H19-7 cell. This is important evidence that PLD1 regulates neurogenesis by producing PA to promote mTOR signaling and stimulate bHLH family, neurogenin1.