title: Elementary [Ca2+]i signals generated by electroporation functionally mimic those evoked by hormonal stimulation.
abstract: 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.
authors.affiliation: Laboratory of Molecular Signalling, Babraham Institute, Cambridge, England, UK.
authors.forename: F
authors.initials: F
authors.lastname: Bobanović
authors.forename: M D
authors.initials: MD
authors.lastname: Bootman
authors.forename: M J
authors.initials: MJ
authors.lastname: Berridge
authors.forename: N A
authors.initials: NA
authors.lastname: Parkinson
authors.forename: P
authors.initials: P
authors.lastname: Lipp
mesh_terms: 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*