Cations Residing at the Selectivity Filter of the Voltage-Gated Ca2+-Channel Modify Fusion-Pore Kinetics
| Autor: | Ariel Sebag, Merav Marom, Daphne Atlas |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
inorganic chemicals
Chromaffin Cells Kinetics Biophysics Analytical chemistry chemistry.chemical_element Biochemistry Membrane Potentials Catecholamines Lanthanum Cations Animals Fusion Polyglutamate Voltage-gated ion channel Chemistry Calcium channel Depolarization Membrane Models Chemical Barium Synapses Calcium Cattle Calcium Channels Signal Transduction |
| Zdroj: | Channels. 1:377-386 |
| ISSN: | 1933-6969 1933-6950 |
| DOI: | 10.4161/chan.5398 |
| Popis: | Strontium (Sr(2+)), Barium (Ba(2+)) and Lanthanum (La(3+)) can substitute for Ca(2+) in driving synaptic transmission during membrane depolarization. Ion recognition at the polyglutamate motif (EEEE), comprising the channel selectivity-filter, during voltage-driven transitions, controls the kinetics of the voltage-gated calcium channel (VGCC) and its interactions with the synaptic proteins. We tested the effect of different charge carriers on evoked-release, as a means of exploring the involvement of VGCC in the fusion pore configuration. Employing amperometry recordings in single bovine chromaffin cells we show that the size of the fusion pore, designated by the 'foot'-amplitude, was increased when Ba(2+) substituted for Ca(2+) and decreased, with La(3+). The fusion pore stability, indicated by 'foot'-width, was decreased in La(3+). Also, the mean open time of the fusion pore (tau(fp)) was significantly lower in Sr(2+) and La(3+) compared to Ba(2+) and Ca(2+). These cations when occupying the selectivity filter reduced the spike frequency in the order of Ca(2+)Sr(2+)Ba(2+)La(3+), which is parallel to the reduction in total catecholamine release. The correlation between ion binding at the selectivity filter and fusion pore properties supports a model in which the Ca(2+) channel regulates secretion through a site at the selectivity filter, upstream to cation entry into the cell. |
| Databáze: | OpenAIRE |
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