Growth factor signals in neural cells: coherent patterns of interaction control multiple levels of molecular and phenotypic responses.
Individual neurons express receptors for several different growth factors that influence the survival, growth, neurotransmitter phenotype, and other properties of the cell. Although there has been considerable progress in elucidating the molecular signal transduction pathways and physiological responses of neurons and other cells to individual growth factors, little is known about if and how signals from different growth factors are integrated within a neuron. In this study, we determined the interactive effects of nerve growth factor, insulin-like growth factor 1, and epidermal growth factor on the activation status of downstream kinase cascades and transcription factors, cell survival, and neurotransmitter production in neural cells that express receptors for all three growth factors. We document considerable differences in the quality and quantity of intracellular signaling and eventual phenotypic responses that are dependent on whether cells are exposed to a single or multiple growth factors. Dual stimulations that generated the greatest antagonistic or synergistic actions, compared with a theoretically neutral summation of their two activities, yielded the largest eventual change of neuronal phenotype indicated by the ability of the cell to produce norepinephrine or resist oxidative stress. Combined activation of insulin-like growth factor 1 and epidermal growth factor receptors was particularly notable for antagonistic interactions at some levels of signal transduction and norepinephrine production, but potentiation at other levels of signaling and cytoprotection. Our findings suggest that in true physiological settings where multiple growth factors are present, activation of one receptor type may result in molecular and phenotypic responses that are different from that observed in typical experimental paradigms in which cells are exposed to only a single growth factor at a time.
Martin
Bronwen
B
Laboratory of Neurosciences, Research Resources Branch, NIA, Intramural Research Program, National Institutes of Health, Baltimore, Maryland 21224, USA.
Brenneman
Randall
R
Golden
Erin
E
Walent
Tom
T
Becker
Kevin G
KG
Prabhu
Vinayakumar V
VV
Wood
William
W
Ladenheim
Bruce
B
Cadet
Jean-Lud
JL
Maudsley
Stuart
S
D000818:Animals; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008024:Ligands; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism*; D016716:PC12 Cells; D010641:Phenotype; D011485:Protein Binding; D014176:Protein Biosynthesis; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D014158:Transcription, Genetic / Q000235:genetics
D008024:Ligands; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D020794:Receptor Protein-Tyrosine Kinases