Elementary [Ca2+]i signals generated by electroporation functionally mimic those evoked by hormonal stimulation.
The generation of oscillations and global Ca2+ waves relies on the spatio-temporal recruitment of elementary Ca2+ signals, such as 'Ca2+ puffs'. Each elementary signal contributes a small amount of Ca2+ into the cytoplasm, progressively promoting neighboring Ca2+ release sites into an excitable state. Previous studies have indicated that increases in frequency or amplitude of such hormone-evoked elementary Ca2+ signals are necessary to initiate Ca2+ wave propagation. In the present study, an electroporation device was used to rapidly and reversibly permeabilize the plasma membrane of HeLa cells and to allow a limited influx of Ca2+. With low field intensities (100-500 V/cm), brief (50-100 micros) electroporation triggered localized Ca2+ signals that resembled hormone-evoked Ca2+ puffs, but not global signals. With such low intensity electroporative pulses, the Ca2+ influx component was usually undetectable, confirming that the electroporation-induced local signals represented Ca2+ puffs arising from the opening of intracellular Ca2+ release channels. Increasing either the frequency at which low-intensity electroporative pulses were applied, or the intensity of a single electroporative pulse (>500 V/cm), resulted in caffeine-sensitive regenerative Ca2+ waves. We suggest that Ca2+ puffs caused by electroporation functionally mimic hormone-evoked elementary events and can activate global Ca2+ signals if they provide a sufficient trigger.
Bobanović
F
F
Laboratory of Molecular Signalling, Babraham Institute, Cambridge, England, UK.
Bootman
M D
MD
Berridge
M J
MJ
Parkinson
N A
NA
Lipp
P
P
D002118:Calcium / Q000502:physiology*; D004594:Electrophysiology; D018274:Electroporation; D006367:HeLa Cells; D006728:Hormones / Q000494:pharmacology; D006801:Humans; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology*