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Subcellular Ca2+ signals underlying waves and graded responses in HeLa cells
1Babraham Institute Laboratory of Molecular Signalling, Department of Zoology, University of Cambridge, UK. mdb@mole.bio.cam.ac.uk
Current Biology : CB
|July 1, 1996
Summary
Intracellular calcium (Ca2+) signals in HeLa cells originate from discrete units, generating localized signals. Sequential activation of these units leads to Ca2+ waves and graded signal amplitudes.
Area of Science:
- Cellular biology
- Biophysics
- Calcium signaling
Background:
- Agonist-evoked intracellular Ca2+ signals exhibit complex spatio-temporal patterns like spikes and waves.
- Understanding the intracellular Ca2+ pool's functional structure is key to explaining these signals.
- Previous studies in large cells identified subcellular elementary Ca2+ signals from discrete release sites, but their role in smaller cells was unknown.
Purpose of the Study:
- To investigate the existence and characteristics of subcellular Ca2+ signals in smaller cells (HeLa cells).
- To determine how these subcellular signals contribute to global Ca2+ spikes and waves.
- To elucidate the functional architecture of the intracellular Ca2+ pool in HeLa cells.
Main Methods:
- Utilized Fura2-based calcium imaging in single HeLa cells.
- Stimulated cells with histamine to evoke intracellular Ca2+ responses.
- Analyzed the spatio-temporal properties of Ca2+ signals at the subcellular level.
Main Results:
- Detected subcellular Ca2+ signals in HeLa cells responding to histamine.
- Observed spatio-temporal similarities between these signals and elementary Ca2+ signals in other cell types.
- Found subcellular signals prominent during the 'pacemaker' rise preceding Ca2+ waves and during post-wave increases and low-amplitude responses.
Conclusions:
- The intracellular Ca2+ pool in HeLa cells comprises numerous functionally discrete units.
- Stimulation leads to localized Ca2+ signals from these units.
- Sequential activation and summation of these units drive Ca2+ wave propagation, with differential recruitment potentially explaining graded signal amplitudes.