Stimulation of the Epidermal Growth Factor Receptor Induces Glial-Specific Protein Expression in the Human DAOY Neuroectodermal Cell Line

Abstract

Central nervous system (CNS) stem cells require epidermal growth factor (EGF) to survive and express glial-specific proteins (GSPs) under its influence. EGF and its receptor (EGF-R) therefore are involved in gliogenesis. We hypothesize that EGF selectively modulates GSP expression in pluripotential CNS cells and this effect is dependent on the degree of EGF-R activation (i.e., the amount of both EGF and the EGF-R present). In order to explore this, we investigated the effects of EGF on the expression of glial- and neuronal-specific proteins in the pluripotential human neuroectodermal cell line, DAOY. DAOY clones expressing different EGF-R levels were treated with EGF. The expression of glial fibrillary acid protein (GFAP), glutamine synthetase (GS) and neuron-specific enolase (NSE) were measured by ELISA. In a clone with low EGF-R levels (clone DAOY-YS-15), EGF selectively stimulated GSPs. In cells which express twice the EGF-R level, EGF (10^–8 M) stimulated both glial and neuronal proteins nonspecifically. In cells with higher EGF-R numbers, EGF suppressed both glial and neuronal proteins. These effects were not due to the negligible growth influences of EGF on the cells. In clone DAOY- YS-15, selective GSP expression was observed as early as 2 days after exposure to EGF (10^–9 M). In these cells, GFAP induction was also shown at the transcriptional level using a quantitative reverse transcriptase-polymerase chain reaction. This suggests one mechanism for EGF action. Our findings are therefore consistent with the hypothesis that the selective induction of GSPs in pluripotent cells is dependent on the EGF-R level and the degree of EGF-R activation.