Involvement of Cytosolic Phospholipase A2 in Nerve Growth Factor-Mediated Neurite Outgrowth of PC12 Cells

Abstract

The nerve growth factor (NGF) induces neuronal differentiation and neurite outgrowth of PC12 cells, whereas epidermal growth factors (EGF) stimulate growth and proliferation of the cells. In spite of this difference, NGF-or EGF-treated PC12 cells share various properties in cellularsignaling pathways. These include the activation of the phosphoinositide (PI)-3 kinase, 70 kDa S6 kinase, and in the mitogen-activated protein (MAP) kinase pathway, following the binding of these growth factors to intrinsic receptor tyrosine kinases (RTKs). Therefore, many studies have been atkempted to access the critical signaling events in determining the differentiation and proliferation of PC12 cells. In this study, we investigated the cytoso6c phospholipase A₂ (cPLA₂) in neurite behavior in order to identify the differences of signaling pathways between the NFF-induced differentiation and the EGF-induced proliferation of PC12 cells. We have showed here that the cPLA₂ was translocated from cytosol to membrane only in NGF-treated cells. We also demonstrated that this translocation is associated with NGF-induced activation of phospholipase C-γ(PLC-γ), which elevates intracellular Ca^(2+) concentration. These results reveal that the translocation of cPLA₂ may be a requisite event in the neuronal differentiation of PC12 cells. Various phospholipase inhibitors were used to confirm the importance of these enzymes in the differentiation of PC12 cells. Neomycin B, a PLC inhibitor, dramatically inhibited the neurite outgrowth, and two distinct PLA₂ inhibitors, 4-bromophenacyl bromide (BPB) and arachidonyltritluoro-methyl ketone (AACOCF₃) also suppressed the neurite outgrowth of the cells, as well. Taken together, these data indicated that cPLA₂ is involved in NGF-induced neuronal differentiation and neurite outgrowth of PC12 cells.