Bcl-2 발현 및 bFGF에 의해 유도된 NT-3 발현과 신경분화에서의 phospholipase D의 역할규명

Abstract

The purpose of this study was to identify the role of phospholipase D (PLD) isozymes in Bcl-2 expression. Overexpression of PLD1or PLD2 increased Bcl-2 expression and phosphatidic acid (PA), the product of PLDs, also upregulated Bcl-2 expression. Treatment with PA activated the phospholipase A2 (PLA2)/Gi/ ERK1/2, RhoA/ Rho-associated kinase (ROCK)/p38 MAPK, and Rac1/ p38 MAPK pathways. PA-induced phosphorylation of ERK1/2 was attenuated by a PLA2 inhibitor (mepacrine) and, a Gi protein inhibitor (pertussis toxin, PTX). On the other hand, p38 MAPK phosphorylation was attenuated by a dominant negative Rac1 and RhoA as well as a specific Rho-kinase inhibitor (Y-27632). These results suggest that PLA2/Gi act 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 Ser 727 through the PLA2/Gi/ERK1/2, RhoA/ROCK-/p38 MAPK, and Rac1/p38 MAPK pathways

The purpose of this study was to identify the role of phospholipase D1 (PLD1) in basic fibroblast growth factor (bFGF)-induced neurotrophin-3 (NT-3) expression and neurite outgrowth in rat hippocampal neuronal progenitor, H19-7 cells. Overexpression of PLD1 increased bFGF -induced NT-3 expression, and DN-PLD1 or PLD1 siRNA abolished bFGF-induced NT-3 expression and neurite outgrowth. Treatment with bFGF activated the RhoA/ Rho-associated kinase (ROCK)/ c-jun N terminal kinase (JNK) pathway. bFGF-induced NT-3 expression was blocked by Y27632, an ROCK inhibitor, SP600125, an inhibitor of SAPK/JNK inhibitor. Furthermore, bFGF-induced JNK activation was also blocked by Y27632. These results indicate that RhoA/ROCK/JNK pathway acts as upstream signaling in bFGF -induced NT-3 expression. Also PA, the product of PLD, increased NT-3 expression. We found that PLD regulates the RhoA/ROCK/JNK pathway, which then led to Elk-1 transactivation. When Elk-1 activity was blocked by Elk-1 siRNA, bFGF-induced NT-3 expression and neurite outgrowth were decreased. Also we found that overexpression of NT-3 resulted in increased. Taken together, these results suggest that, PLD1 is an important regulator in bFGF-induced NT-3 expression and neurite outgrowth which are mediated by RhoA/ROCK/JNK pathway through activation of Elk-1 in H19-7 cells