FGF2-mediated signal transduction in human SH-SY5Y neuroblastoma cells involves cross-talk between the ERK1/2 pathway and protein kinase C
Dokas LA, Watson SJ, Akil H
Society for Neuroscience. 2015.
The SH-SY5Y human neuroblastoma cell line is an appropriate model system in which to examine FGF2-mediated signal transduction. Coupling of the FGF receptor (FGFR) to the extracellular signal-regulated kinase (ERK1/2) pathway in these cells results in rapid ERK1/2 phosphorylation in response to FGF2 that is blocked by the FGFR inhibitor, PD 173074. SH-SY5Y cells are of the N (neuron)-type and they can be further differentiated to a mature catecholaminergic phenotype by the combination of FGF2 and a phorbol ester that activates protein kinase C (PKC). Cells differentiated in this manner assume a phenotype characterized by increased expression of tyrosine hydroxylase (TH) and of GAP-43, a neuron-specific protein that is a major PKC substrate. Induced morphological changes include elaboration of long processes with varicosities and growth cone-like terminals. Increased GAP-43 expression is primarily caused by activation of PKC while that of TH is more responsive to FGF2. Thus, it is of interest to determine whether and how the ERK1/2 and PKC pathways interact to mediate the cell signaling underlying such effects and to compare these interactions in undifferentiated and differentiated cells. Either FGF2 or the phorbol ester, phorbol 12, 13-dibutyrate (PDB), increases ERK1/2 phosphorylation in SH-SY5Y cells but not in an additive manner. Preincubation of cells with the PKC inhibitor, GF 109203X, not only reduces PDB-stimulated ERK1/2 phosphorylation to basal levels as expected, but also causes a nearly-complete inhibition of ERK1/2 phosphorylation elicited by FGF2. These results suggest a considerable degree of cross-talk between the ERK1/2 and PKC pathways. Cells differentiated with FGF2 and PDB contain higher levels of phosphorylated ERK1/2 than control cells. However, once differentiated, SH-SY5Y cells lose the ability to activate ERK1/2 phosphorylation upon retesting with FGF2, an alteration that is only seen when cells are differentiated with the combination of PDB and FGF2. The overall conclusion derived from these experiments is that both ERK1/2 and PKC activities are essential components of normal FGF2-mediated signaling in SH-SY5Y neuroblastoma cells and during the differentiation process.