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Microdomain Ca2+ activation during exocytosis in Paramecium cells : superposition of local subplasmalemmal calcium store activation by local Ca2+ influx

Microdomain Ca2+ activation during exocytosis in Paramecium cells : superposition of local subplasmalemmal calcium store activation by local Ca2+ influx

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ERXLEBEN, Christian, Norbert KLAUKE, Matthias FLÖTENMEYER, Marie-Pierre BLANCHARD, Claudia BRAUN, Helmut PLATTNER, 1997. Microdomain Ca2+ activation during exocytosis in Paramecium cells : superposition of local subplasmalemmal calcium store activation by local Ca2+ influx. In: Journal of Cell Biology. 136(3), pp. 597-607. ISSN 0021-9525

@article{Erxleben1997Micro-7589, title={Microdomain Ca2+ activation during exocytosis in Paramecium cells : superposition of local subplasmalemmal calcium store activation by local Ca2+ influx}, year={1997}, doi={10.1083/jcb.136.3.597}, number={3}, volume={136}, issn={0021-9525}, journal={Journal of Cell Biology}, pages={597--607}, author={Erxleben, Christian and Klauke, Norbert and Flötenmeyer, Matthias and Blanchard, Marie-Pierre and Braun, Claudia and Plattner, Helmut} }

eng Microdomain Ca2+ activation during exocytosis in Paramecium cells : superposition of local subplasmalemmal calcium store activation by local Ca2+ influx Klauke, Norbert Braun, Claudia 2011-03-24T17:35:36Z Braun, Claudia deposit-license Plattner, Helmut 1997 application/pdf Blanchard, Marie-Pierre Plattner, Helmut Erxleben, Christian In Paramecium tetraurelia, polyamine-triggered exocytosis is accompanied by the activation of Ca2+-activated currents across the cell membrane (Erxleben, C., and H. Plattner. 1994. J. Cell Biol. 127:935- 945). We now show by voltage clamp and extracellular recordings that the product of current × time (As) closely parallels the number of exocytotic events. We suggest that Ca2+ mobilization from subplasmalemmal storage compartments, covering almost the entire cell surface, is a key event. In fact, after local stimulation, Ca2+ imaging with high time resolution reveals rapid, transient, local signals even when extracellular Ca2+ is quenched to or below resting intracellular Ca2+ concentration ([Ca2+]e =< [Ca2+]i). Under these conditions, quenched-flow/freeze-fracture analysis shows that membrane fusion is only partially inhibited. Increasing [Ca2+]e alone, i.e., without secretagogue, causes rapid, strong cortical increase of [Ca2+]i but no exocytosis. In various cells, the ratio of maximal vs. minimal currents registered during maximal stimulation or single exocytotic events, respectively, correlate nicely with the number of Ca stores available. Since no quantal current steps could be observed, this is again compatible with the combined occurrence of Ca2+ mobilization from stores (providing close to threshold Ca2+ levels) and Ca2+ influx from the medium (which per se does not cause exocytosis). This implies that only the combination of Ca2+ flushes, primarily from internal and secondarily from external sources, can produce a signal triggering rapid, local exocytotic responses, as requested for Paramecium defense. Flötenmeyer, Matthias 2011-03-24T17:35:36Z Klauke, Norbert Erxleben, Christian Flötenmeyer, Matthias First publ. in: Journal of Cell Biology 136 (1997), 3, pp. 597-607 Blanchard, Marie-Pierre

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