Abstract
In this study, we have shown that nerve growth factor (NGF)-dependent activation of the p42/p44 mitogen-activated protein kinase (p42/p44 MAPK) pathway in PC12 cells can be partially blocked by pertussis toxin (which inactivates the G proteins Gi/o). This suggests that the Trk A receptor may use a G protein-coupled receptor pathway to signal to p42/p44 MAPK. This was supported by data showing that the NGF-dependent activation of p42/p44 MAPK is potentiated in cells transfected with G protein-coupled receptor kinase 2 (GRK2) or β-arrestin I. Moreover, GRK2 is constitutively bound with the Trk A receptor, whereas NGF stimulates the pertussis toxin-sensitive binding of β-arrestin I to the TrkA receptor-GRK2 complex. Both GRK2 and β-arrestin I are involved in clathrin-mediated endocytic signaling to p42/p44 MAPK. Indeed, inhibitors of clathrin-mediated endocytosis (e.g., monodansylcadaverine, concanavalin A, and hyperosmolar sucrose) reduced the NGF-dependent activation of p42/p44 MAPK. Finally, we have found that the G protein-coupled receptor-dependent component regulating p42/p44 MAPK is required for NGF-induced differentiation of PC12 cells. Thus, NGF-dependent inhibition of DNA synthesis was partially blocked by PD098059 (inhibitor of MAPK kinase-1 activation) and pertussis toxin. Our findings are the first to show that the Trk A receptor uses a classic G protein-coupled receptor-signaling pathway to promote differentiation of PC12 cells.
Abbreviations
- NGF
- nerve growth factor
- MAPK
- mitogen-activated protein kinase
- IGF
- insulin-like growth factor
- GRK
- G protein-coupled receptor kinase
- Grb-2
- growth factor receptor binding protein
- PI3K
- phosphoinositide 3-kinase
- LPA
- lysophosphatidic acid
- PDGF
- platelet-derived growth factor
- Gi
- inhibitory G protein
- Gab1
- growth factor receptor binding protein associated binder
- HRP
- horseradish peroxidase
- DMEM
- Dulbecco's modified Eagle's medium
- FCS
- fetal calf serum
- NP-40
- Nonidet P-40
- EGF
- epidermal growth factor
- GPCR
- G protein-coupled receptor
- mSos
- son of sevenless
- c-Src
- cellular Src tyrosine kinase
- MDC
- monodansylcadaverine
- Received August 25, 2000.
- Accepted February 9, 2001.
- The American Society for Pharmacology and Experimental Therapeutics
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