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Voltage-dependent phosphorylation may recruit Ca2+ current facilitation in chromaffin cells
C R Artalejo1, S Rossie, R L Perlman
1Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637.
Nature
|July 2, 1992
Summary
Bovine chromaffin cells exhibit two Ca2+ currents. Voltage-dependent phosphorylation regulates the recruitment of facilitation Ca2+ currents, a key finding for understanding ion channel modulation.
Area of Science:
- Neuroscience
- Cell Biology
- Ion Channel Physiology
Background:
- Bovine chromaffin cells possess distinct whole-cell Ca2+ currents: standard and facilitation components.
- Facilitation Ca2+ currents are typically quiescent but can be activated by specific depolarization patterns.
- Protein kinase A activation suggests a role for phosphorylation in Ca2+ current facilitation.
Purpose of the Study:
- To investigate the role of protein phosphorylation in recruiting facilitation Ca2+ currents.
- To elucidate the mechanisms underlying voltage-dependent recruitment of these currents.
Main Methods:
- Utilized bovine chromaffin cells.
- Applied pre-pulses and repetitive depolarizations to study Ca2+ current recruitment.
- Investigated the effects of protein phosphorylation inhibitors and phosphatase 2A injection.
- Examined the reversibility of recruitment under different conditions.
Main Results:
- Depolarization-induced recruitment of facilitation Ca2+ current is a rapid, first-order process.
- Inhibitors of protein phosphorylation and phosphatase 2A suppressed recruitment.
- Voltage-dependent recruitment, normally reversible, became irreversible with phosphatase inhibitors.
Conclusions:
- Voltage-dependent phosphorylation of the Ca2+ channel or associated proteins mediates the recruitment of facilitation Ca2+ currents.
- This phosphorylation mechanism allows membrane potential to modulate ion channel activity.
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