Mechanism for phosphatidic acid-induced Bcl-2 expression in HeLa cell

초록

Phosphatidic acid (PA), the product of PLD-mediated reaction, is lipid second messenger that participates in various intracellular signaling events and regulates a growing list of signaling protein, including several protein kinase and phosphatase. We found that Bcl-2, anti-apoptotic protein, was upregulated by PA treatment in HeLa cell. However, how PA upregulates Bcl-2 expression have not been studied yet. In this study, we tried to find out the mechanism of Bcl-2 up regulation by PA treatment in HeLa cell. Treatment with PA resulted in significantly increased expression of Bcl-2 in HeLa cell. Moreover PA-induced Bcl-2 expression was blocked by mepacrine, an inhibitor of phospholipase A2 (PLA2), whereas enhanced rather by propraonol, an inhibitor of PA phospholydrolase (PAP). These results indicated that PLA2 is very important enzyme for PA-induced expression of Bcl-2. Treatment of 1,2-Dipalmitoryl-sn-Glycero-3-phosphate (DPPA) instead of PA also increased Bcl-2 expression indicating that Bcl-2 expression is mediated though lysophosphatidic acid (LPA), not though arachidonic acid. Many biological function of lysophosphatidic acid (LPA) occur though four specific G-protein coupled receptor (GPCR) on the cell surface. To investigated the involvement of G-protein coupled receptor (GPCR), we used Gi -protein inhibitor, pertussis toxin (PTX). Pretreatment with PTX decreased PA-induced Bcl-2 expression in HeLa cell. This results indicated that GRCP is closely related with Bcl-2 expression and LPA signaling pathway. Moreover we found that ERK1/2 was activated by PA treatment. Treatment PD98059, an inhibitor of MEK, inhibited ERK1/2 activation as well as PA-induced Bcl-2 expression. These results suggesting that LPA-ERK1/2 pathway is related to PA- induced Bcl-2 expression. Taken together, PA important in Bcl-2 expression, which was mediated PLA2 and LPA-ERK1/2 pathway.