Phospholipase D1 mediates bFGF-induced Bcl-2 expression leading to neurite outgrowth in H19-7 cells

Abstract

The purpose of the present study was to investigate the role of PLD (phospholipase D) in bFGF (basic fibroblast growth factor)-induced Bcl-2 expression and to examine whether overexpressed Bcl-2 influences neurite outgrowth in immortalized hippocampal progenitor cells (H19-7 cells). We found that Bcl-2 expression was maximally induced by bFGF within 24 h, and that this effect was reduced by inhibiting PLD1 expression with PLD1 small interfering RNA or by overexpressing DN (dominant-negative)-PLD1, whereas PLD1 overexpression markedly induced Bcl-2 expression. bFGF treatment activated Ras, Src, PI3K (phosphoinositide 3-kinase), PLCγ (phospholipase Cγ) and PKCα (protein kinase Cα). Among these molecules, Src and PKCα were not required for Bcl-2 expression. PLD activity was decreased by Ras, PI3K or PLCγ inhibitor, suggesting that PLD1 activation occurred through Ras, PI3K or PLCγ. We found that Ras was the most upstream molecule among these proteins, followed by the PI3K/PLCγ pathway, indicating that bFGF-induced PLD activation took place through the Ras/PI3K/PLCγ pathway. Furthermore, PLD1 was required for activation of JNK (c-Jun N-terminal kinase), which led to activation of STAT3 (signal transducer and activator of transcription 3) and finally Bcl-2 expression. When Bcl-2 was overexpressed, neurite outgrowth was stimulated along with induction of neurotrophic factors such as brain-derived neurotrophic factor and neurotrophin 4/5. In conclusion, PLD1 acts as a downstream effector of bFGF/Ras/PI3K/PLCγ signalling and regulates Bcl-2 expression through JNK/STAT3, which leads to neurite outgrowth in H19-7 cells.

Hippocalcin Promotes Neuronal Differentiation and Inhibits Astrocytic Differentiation in Neural Stem Cells

“…We previously reported that PLD1 is involved in various neuronal signaling pathways and is an important regulator of neuron function (Yoon et al., 2006, Yoon et al., 2012). We also showed that HPCA increased the activity and expression of PLD in various cell types (Hyun et al., 2000, Oh et al., 2006).…”

“…Thus, further studies are needed to clarify the relationship between HPCA and PDK1 signaling during neuronal differentiation in NSCs; this could be important for a complete understanding of HPCA-mediated signaling cascade in neurogenesis of NSCs. Our previous studies showed that HPCA played a role in Ca 2+ -dependent PLD activation (Hyun et al., 2000), and PLD1 promotes neurite outgrowth in H19-7 cells (Yoon et al., 2012). As expected, PLD1 is involved in HPCA-mediated neurogenesis and its activation is regulated by HPCA.…”

“…Recent studies have reported that PLD plays a key role in neuronal differentiation of cells such as PC12 cells (Banno et al., 2008) and cerebellar granule neurons (Watanabe et al., 2004). We have also reported that it has a critical role in the neuronal differentiation of rat NSCs (Yoon et al., 2005) and H19-7 cells (Yoon et al., 2012). However, the relevance of PLD1 signaling in neuronal differentiation remains unclear.…”

Phospholipase D Signaling Pathways and Phosphatidic Acid as Therapeutic Targets in Cancer

“…H19-7 rat embryonic hippocampal cells increase Bcl-2 expression when stimulated by fibroblast growth factor (FGF). Dominantnegative PLD and PLD siRNA inhibit the FGF-induced increase in Bcl-2, suggesting that PLD activity is required for Bcl-2 expression (Yoon et al, 2012). Both studies demonstrate that Bcl-2 transcription increases through the STAT3 transcription factor in a mechanism that requires MAPK activity.…”

Use of Retinal Explants to Examine the Effect of Granulocyte-Macrophage Colony-Stimulating Factor on Neurite Growth

“…Thus, the JAK/STAT and mTOR signaling pathways have been implicated in long-distance CNS regeneration. A downstream effector of these pathways is the anti-apoptotic protein Bcl-2 (Sepúlveda et al, 2007;Asomugha et al, 2010;Choi et al, 2011;Yoon et al, 2012). The sustained axonal growth ability observed in retina-superior colliculus cocultures from Bcl-2 transgenic mice translated to the in vivo setting.…”