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Imaging the hierarchical Ca2+ signalling system in HeLa cells
M Bootman1, E Niggli, M Berridge
1Department of Physiology, University of Bern, Switzerland.
The Journal of Physiology
|March 1, 1997
Summary
This study reveals a hierarchy of calcium (Ca2+) signals in non-excitable cells, from elementary Ca2+ blips and puffs to complex Ca2+ waves. These findings provide a prototype for understanding Ca2+ signal transduction in these cell types.
Area of Science:
- Cellular Biology
- Biophysics
- Physiology
Background:
- Calcium ions (Ca2+) are crucial intracellular second messengers.
- Understanding Ca2+ signaling in non-excitable cells is vital for various physiological processes.
- The endoplasmic reticulum (ER) is a primary storage site for intracellular Ca2+.
Purpose of the Study:
- To investigate hormone-induced subcellular Ca2+ release signals from the ER in HeLa cells.
- To characterize the elementary Ca2+ signals (blips and puffs) and their relationship to Ca2+ waves.
- To elucidate the mechanisms of Ca2+ wave propagation.
Main Methods:
- Confocal microscopy was employed to visualize and quantify Ca2+ signals.
- Histamine was used as a stimulus to evoke Ca2+ release.
- Analysis of Ca2+ signal kinetics, amplitude, and spatial spreading.
Main Results:
- Two types of elementary Ca2+ signals were identified: Ca2+ blips (from single channels) and Ca2+ puffs (from multiple channels).
- Ca2+ waves originated from stable initiation sites and their characteristics depended on the number of recruited puffs.
- Wave propagation involves diffusion and regeneration, with threshold stimulation leading to abortive waves.
Conclusions:
- A hierarchical model of Ca2+ signaling (blips -> puffs -> waves) is proposed for non-excitable cells.
- This signaling cascade is analogous to Ca2+ events observed in cardiac muscle cells.
- The findings offer insights into Ca2+ signal transduction mechanisms in a broad range of cell types.