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Dissection of Local Ca2+ Signals in Cultured Cells by Membrane-targeted Ca2+ Indicators
Published on: March 22, 2019
Exocytosis, dependent on Ca2+ release from Ca2+ stores, is regulated by Ca2+ microdomains
Jiun T Low1, Alka Shukla, Natasha Behrendorff
1School of Biomedical Sciences, University of Queensland, Brisbane, QLD 4072, Australia.
Journal of Cell Science
|August 26, 2010
Summary
Cellular calcium (Ca2+) signals regulate exocytosis. This study shows Ca2+ release from intracellular stores controls secretion via microdomain cytosolic Ca2+ concentration, not localized hot-spots.
Area of Science:
- Cell Biology
- Biophysics
- Physiology
Background:
- Cellular calcium (Ca2+) signals are crucial for regulating exocytosis, the process of secretory vesicle fusion.
- The kinetics and magnitude of the secretory response are determined by the relationship between Ca2+ signals and exocytosis.
Purpose of the Study:
- To investigate how Ca2+ release from intracellular stores controls exocytosis.
- To determine if secretion is regulated by Ca2+ concentration within microdomains.
Main Methods:
- Live-cell two-photon microscopy was used to simultaneously record Ca2+ signals and exocytic responses.
- Investigated Ca2+ dependence, latency, and spatial distribution of exocytosis.
Main Results:
- Exocytosis exhibited long latencies (>2 seconds) after Ca2+ rise.
- Secretion occurred throughout the cell, not clustered at Ca2+ release sites.
- Exocytosis showed high affinity Ca2+ dependence (Kd=1.75 microM) and was reduced by EGTA.
- Endoplasmic reticulum spatially excluded secretory granules from the cell membrane.
- Local Ca2+ responses could not trigger exocytosis.
Conclusions:
- Cellular secretion controlled by intracellular Ca2+ stores is regulated by cytosolic Ca2+ concentration within microdomains.
- Exocytosis is not triggered by localized Ca2+ hot-spots but by broader microdomain Ca2+ changes.
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