title: Overexpression of phospholipase D enhances Bcl-2 expression by activating STAT3 through independent activation of ERK and p38MAPK in HeLa cells.
abstract: The purpose of this study was to identify the role of phospholipase D (PLD) isozymes in Bcl-2 expression. Overexpression of PLD1 or PLD2 increased Bcl-2 expression and phosphatidic acid (PA), the product of PLDs, also upregulated Bcl-2 expression. Treatment with PA activated the phospholipase A(2) (PLA(2))/G(i)/ERK1/2, RhoA/Rho-associated kinase (ROCK)/p38 MAPK, and Rac1/p38 MAPK pathways. PA-induced phosphorylation of ERK1/2 was attenuated by a PLA(2) inhibitor (mepacrine) and, a G(i) protein inhibitor (pertussis toxin, PTX). On the other hand, p38 MAPK phosphorylation was attenuated by a dominant negative Rac1 and a specific Rho-kinase inhibitor (Y-27632). These results suggest that PLA(2)/G(i) acts at the upstream of ERK1/2, while Rac1 and RhoA/ROCK act upstream of p38 MAPK. We next, tried to determine which transcription factor is involved in PLD-related Bcl-2 expression. When signal transducer and activator of transcription 3 (STAT3) activity was blocked by a STAT3 specific siRNA, PA-induced Bcl-2 expression was remarkably decreased, suggesting that STAT3 is an essential transcription factor linking PLD to Bcl-2 upregulation. Taken together, these findings indicate that PLD acts as an important regulator in Bcl-2 expression by activating STAT3 involving the phosphorylation of Ser727 through the PLA(2)/G(i)/ERK1/2, RhoA/ROCK/p38 MAPK, and Rac1/p38 MAPK pathways.
authors.affiliation: Department of Biochemistry and Molecular Biology, College of Medicine, Hanyang University, Seoul, Republic of Korea.
authors.forename: Hye-Jin
authors.initials: HJ
authors.lastname: Choi
authors.forename: Joong-Soo
authors.initials: JS
authors.lastname: Han
mesh_terms: D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008954:Models, Biological; D010712:Phosphatidic Acids / Q000378:metabolism / Q000494:pharmacology; D010739:Phospholipase D / Q000378:metabolism*; D054467:Phospholipases A2 / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D054460:rho-Associated Kinases / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
chemical_list: D010712:Phosphatidic Acids; D019253:Proto-Oncogene Proteins c-bcl-2; C107953:RAC1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C066737:RHOA protein, human; D054460:rho-Associated Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D054467:Phospholipases A2; C105606:phospholipase D2; D010739:Phospholipase D; C106801:phospholipase D1; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein