Imaging the hierarchical Ca2+ signalling system in HeLa cells.
1. Confocal microscopy was used to investigate hormone-induced subcellular Ca2+ release signals from the endoplasmic reticulum (ER) in a prototype non-excitable cell line (HeLa cells). 2. Histamine application evoked two types of elementary Ca2+ signals: (i) Ca2+ blips arising from single ER Ca2+ release channels (amplitude, 30 nM; lateral spreading, 1.3 microns); (ii) Ca2+ puffs resulting from the concerted activation of several Ca2+ blips (amplitude, 170 nM; spreading, 4 microns). 3. Ca2+ waves in the HeLa cells arose from a variable number of initiation sites, but for individual cells, the number and subcellular location of the initiation sites were constant. The kinetics and amplitude of global Ca2+ signals were directly proportional to the number of initiation sites recruited. 4. Reduction of the feedback inherent in intracellular Ca2+ release caused saltatoric Ca2+ waves, revealing the two principal steps underlying wave propagation: diffusion and regeneration. Threshold stimulation evoked abortive Ca2+ waves, caused by the limited recruitment of Ca2+ puffs. 5. The hierarchy of Ca2+ signalling events, from fundamental levels (blips) to intermediate levels (puffs) to Ca2+ waves, is a prototype for Ca2+ signal transduction for non-excitable cells, and is also analogous to the Ca2+ quarks, Ca2+ sparks and Ca2+ waves in cardiac muscle cells.
Bootman
M
M
Department of Physiology, University of Bern, Switzerland.
Niggli
E
E
Berridge
M
M
Lipp
P
P
D000814:Aniline Compounds; D002118:Calcium / Q000502:physiology*; D005071:Evoked Potentials; D005456:Fluorescent Dyes; D006367:HeLa Cells; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D018613:Microscopy, Confocal; D010716:Phosphatidylinositols / Q000378:metabolism; D015398:Signal Transduction; D014966:Xanthenes
D000814:Aniline Compounds; D005456:Fluorescent Dyes; D010716:Phosphatidylinositols; D014966:Xanthenes; C059715:Fluo-3; D006632:Histamine; D002118:Calcium