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Growth factor-like effects mediated by muscarinic receptors in PC12M1 cells
R Pinkas-Kramarski1, R Stein, L Lindenboim
1Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel.
Abstract:
Rat pheochromocytoma (PC12) cells stably expressing cloned m1 muscarinic acetylcholine receptors (PC12M1) undergo morphological changes when stimulated by muscarinic agonists. These changes, which include the outgrowth of neurite-like processes, are blocked by the muscarinic antagonist atropine and are not observed in PC12 cells. The observed morphological changes, which are independent of RNA and protein synthesis, are blocked by the methylation inhibitor 5'-deoxy-5'-methylthioadenosine, suggesting that methylation plays a role in this process. Analysis of cyclic AMP accumulation and phosphoinositide turnover reveals that both processes are enhanced on activation by muscarinic agonist. Our data suggest, however, that the muscarinic-dependent neurite-like outgrowth processes are not mediated by cyclic AMP, Ca2+, or protein kinase C pathways. The muscarinic-dependent neurite outgrowth effect is enhanced by nerve growth factor, with a resulting increase in both the number of neurite-extending cells and the length of the neurite. In addition, activation of muscarinic receptors in PC12M1 cells stimulates the induction of marker genes for neuronal differentiation. Muscarinic receptors may therefore mediate growth factor-like effects in these cells.
Insights
Muscarinic acetylcholine receptors in PC12M1 cells trigger neurite outgrowth, independent of RNA/protein synthesis. This process involves methylation and mimics growth factor effects, inducing neuronal differentiation markers.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Rat pheochromocytoma (PC12) cells are a model for neuronal differentiation.
- Muscarinic acetylcholine receptors (mAChRs) are key neurotransmitter receptors.
- PC12M1 cells stably express cloned m1 muscarinic acetylcholine receptors.
Purpose of the Study:
- To investigate the role of m1 mAChRs in PC12M1 cell morphology.
- To elucidate the signaling pathways involved in mAChR-mediated neurite outgrowth.
- To explore the interaction between muscarinic signaling and nerve growth factor (NGF).
Main Methods:
- Stimulation of PC12M1 cells with muscarinic agonists and antagonists.
- Assessment of morphological changes, including neurite outgrowth.
- Analysis of RNA/protein synthesis, methylation, cyclic AMP, phosphoinositide turnover, and protein kinase C pathways.
- Evaluation of gene expression for neuronal differentiation markers.
- Co-application of muscarinic agonists and nerve growth factor (NGF).
Main Results:
- Muscarinic agonist stimulation induced neurite-like outgrowth in PC12M1 cells, blocked by atropine.
- Morphological changes were independent of RNA and protein synthesis but sensitive to methylation inhibition.
- Muscarinic activation enhanced cyclic AMP and phosphoinositide turnover but did not mediate outgrowth via these pathways or PKC.
- NGF potentiated muscarinic-dependent neurite outgrowth.
- Activation of muscarinic receptors induced neuronal differentiation marker genes.
Conclusions:
- M1 muscarinic receptor activation in PC12M1 cells promotes neurite outgrowth and neuronal differentiation.
- Methylation, but not cyclic AMP, Ca2+, or PKC, appears to mediate this process.
- Muscarinic receptors can exert growth factor-like effects, potentially interacting with NGF signaling.