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Extracellular ATP triggers two functionally distinct calcium signalling pathways in PC12 cells
1AFRC Laboratory of Molecular Signalling, Department of Zoology, University of Cambridge, UK.
Journal of Cell Science
|February 1, 1994
Summary
Extracellular adenosine triphosphate (ATP) triggers distinct calcium (Ca2+) signals in PC12 cells via multiple receptors. Only ATP-induced Ca2+ influx, not intracellular Ca2+ release, stimulates dopamine secretion.
Area of Science:
- Cell biology
- Neuroscience
- Biochemistry
Background:
- Extracellular signaling molecules play crucial roles in cellular communication.
- Adenosine triphosphate (ATP) is increasingly recognized as a key extracellular messenger.
- Understanding ATP's signaling pathways is vital for deciphering cellular responses, including secretion.
Purpose of the Study:
- To investigate the distinct effects of extracellular ATP on intracellular calcium (Ca2+) signaling in rat pheochromocytoma (PC12) cells.
- To elucidate the relationship between ATP-evoked Ca2+ signaling and the secretion of neurotransmitters.
- To differentiate the mechanisms underlying ATP-induced Ca2+ mobilization and Ca2+ influx.
Main Methods:
- Single-cell calcium imaging to observe spatiotemporal dynamics of intracellular Ca2+ concentration ([Ca2+]i).
- Application of extracellular nucleotides (ATP and UTP) to stimulate specific cell surface receptors.
- Measurement of inositol phosphate production to assess receptor-mediated signaling.
- Assessment of [3H]dopamine secretion in response to nucleotide stimulation.
- Use of pharmacological agents (e.g., nifedipine) to probe Ca2+ channel involvement.
Main Results:
- Extracellular ATP evoked two distinct subcellular Ca2+ distributions, differing from UTP-induced responses, indicating multiple ATP receptors.
- ATP and UTP were equipotent in mobilizing intracellular Ca2+ via inositol phosphate production.
- ATP, but not UTP, induced divalent cation (Ca2+/Mn2+) entry, independent of intracellular Ca2+ release and phosphoinositide turnover.
- ATP-induced Ca2+ influx, not intracellular Ca2+ release, was essential for triggering [3H]dopamine secretion.
- Nifedipine showed minimal inhibition of ATP-induced Ca2+ rise, suggesting limited involvement of L-type voltage-operated Ca2+ channels.
Conclusions:
- Extracellular ATP activates distinct Ca2+ signaling pathways in PC12 cells through different receptors.
- ATP-induced Ca2+ influx, mediated by a distinct receptor-operated channel, is critical for neurotransmitter secretion.
- Different extracellular stimuli can generate functionally distinct Ca2+ signals within the same cell.