Cross talk among tyrosine kinase receptors in PC12 cells: desensitization of mitogenic epidermal growth factor receptors by the neurotrophic factors, nerve growth factor and basic fibroblast growth factor.
AUTOR(ES)
Mothe, I
RESUMO
We have studied the effects of nerve growth factor (NGF) and basic fibroblast growth factor (bFGF) on epidermal growth factor (EGF) binding to PC12 cells. We show that NGF and bFGF rapidly induce a reduction in 125I-EGF binding to PC12 cells in a dose-dependent manner. This decrease amounts to 50% for NGF and 35% for bFGF. Both factors appear to act through a protein kinase C(PKC)-independent pathway, because their effect persists in PKC-downregulated PC12 cells. Scatchard analysis indicates that NGF and bFGF decrease the number of high affinity EGF binding sites. In addition to their effect on EGF binding, NGF and bFGF activate in intact PC12 cells one or several serine/threonine kinases leading to EGF receptor threonine phosphorylation. Using an in vitro phosphorylation system, we show that NGF- or bFGF-activated extracellular regulated kinase 1 (ERK1) is able to phosphorylate a kinase-deficient EGF receptor. Phosphoamino acid analysis indicates that this phosphorylation occurs mainly on threonine residues. Furthermore, two comparable phosphopeptides are observed in the EGF receptor, phosphorylated either in vivo after NGF treatment or in a cell-free system by NGF-activated ERK1. Finally, a good correlation was found between the time courses of ERK1 activation and 125I-EGF binding inhibition after NGF or bFGF treatment. In conclusion, in PC12 cells the NGF- and bFGF-stimulated ERK1 appears to be involved in the induction of the threonine phosphorylation of the EGF receptor and the decrease in the number of high affinity EGF binding sites.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=300983Documentos Relacionados
- Activation of phosphatidylinositol 3-kinase by epidermal growth factor, basic fibroblast growth factor, and nerve growth factor in PC12 pheochromocytoma cells.
- Early changes in protein synthesis induced by basic fibroblast growth factor, nerve growth factor, and epidermal growth factor in PC12 pheochromocytoma cells.
- Carbachol stimulates a different phospholipid metabolism than nerve growth factor and basic fibroblast growth factor in PC12 cells.
- Nerve growth factor receptors on PC12 cells: ligand-induced conversion from low- to high-affinity states.
- The internalization of nerve growth factor by high-affinity receptors on pheochromocytoma PC12 cells.
