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Microdomain Ca(2+) Activation during Exocytosis in Paramecium Cells. Superposition of Local Subplasmalemmal Calcium Store Activation by Local Ca(2+) Influx
In Paramecium tetraurelia, polyamine-triggered exocytosis is accompanied by the activation of Ca(2+)-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 ×...
Autores principales: | , , , , , |
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Formato: | Texto |
Lenguaje: | English |
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The Rockefeller University Press
1997
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2134299/ https://www.ncbi.nlm.nih.gov/pubmed/9024690 |
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author | Erxleben, Christian Klauke, Norbert Flötenmeyer, Matthias Blanchard, Marie-Pierre Braun, Claudia Plattner, Helmut |
author_facet | Erxleben, Christian Klauke, Norbert Flötenmeyer, Matthias Blanchard, Marie-Pierre Braun, Claudia Plattner, Helmut |
author_sort | Erxleben, Christian |
collection | PubMed |
description | In Paramecium tetraurelia, polyamine-triggered exocytosis is accompanied by the activation of Ca(2+)-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 Ca(2+) mobilization from subplasmalemmal storage compartments, covering almost the entire cell surface, is a key event. In fact, after local stimulation, Ca(2+) imaging with high time resolution reveals rapid, transient, local signals even when extracellular Ca(2+) is quenched to or below resting intracellular Ca(2+) concentration ([Ca(2+)](e) ⩽ [Ca(2+)](i)). Under these conditions, quenched-flow/freeze-fracture analysis shows that membrane fusion is only partially inhibited. Increasing [Ca(2+)](e) alone, i.e., without secretagogue, causes rapid, strong cortical increase of [Ca(2+)](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 Ca(2+) mobilization from stores (providing close to threshold Ca(2+) levels) and Ca(2+) influx from the medium (which per se does not cause exocytosis). This implies that only the combination of Ca(2+) flushes, primarily from internal and secondarily from external sources, can produce a signal triggering rapid, local exocytotic responses, as requested for Paramecium defense. |
format | Text |
id | pubmed-2134299 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 1997 |
publisher | The Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-21342992008-05-01 Microdomain Ca(2+) Activation during Exocytosis in Paramecium Cells. Superposition of Local Subplasmalemmal Calcium Store Activation by Local Ca(2+) Influx Erxleben, Christian Klauke, Norbert Flötenmeyer, Matthias Blanchard, Marie-Pierre Braun, Claudia Plattner, Helmut J Cell Biol Article In Paramecium tetraurelia, polyamine-triggered exocytosis is accompanied by the activation of Ca(2+)-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 Ca(2+) mobilization from subplasmalemmal storage compartments, covering almost the entire cell surface, is a key event. In fact, after local stimulation, Ca(2+) imaging with high time resolution reveals rapid, transient, local signals even when extracellular Ca(2+) is quenched to or below resting intracellular Ca(2+) concentration ([Ca(2+)](e) ⩽ [Ca(2+)](i)). Under these conditions, quenched-flow/freeze-fracture analysis shows that membrane fusion is only partially inhibited. Increasing [Ca(2+)](e) alone, i.e., without secretagogue, causes rapid, strong cortical increase of [Ca(2+)](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 Ca(2+) mobilization from stores (providing close to threshold Ca(2+) levels) and Ca(2+) influx from the medium (which per se does not cause exocytosis). This implies that only the combination of Ca(2+) flushes, primarily from internal and secondarily from external sources, can produce a signal triggering rapid, local exocytotic responses, as requested for Paramecium defense. The Rockefeller University Press 1997-02-10 /pmc/articles/PMC2134299/ /pubmed/9024690 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/). |
spellingShingle | Article Erxleben, Christian Klauke, Norbert Flötenmeyer, Matthias Blanchard, Marie-Pierre Braun, Claudia Plattner, Helmut Microdomain Ca(2+) Activation during Exocytosis in Paramecium Cells. Superposition of Local Subplasmalemmal Calcium Store Activation by Local Ca(2+) Influx |
title | Microdomain Ca(2+) Activation during Exocytosis in Paramecium Cells. Superposition of Local Subplasmalemmal Calcium Store Activation by Local Ca(2+) Influx |
title_full | Microdomain Ca(2+) Activation during Exocytosis in Paramecium Cells. Superposition of Local Subplasmalemmal Calcium Store Activation by Local Ca(2+) Influx |
title_fullStr | Microdomain Ca(2+) Activation during Exocytosis in Paramecium Cells. Superposition of Local Subplasmalemmal Calcium Store Activation by Local Ca(2+) Influx |
title_full_unstemmed | Microdomain Ca(2+) Activation during Exocytosis in Paramecium Cells. Superposition of Local Subplasmalemmal Calcium Store Activation by Local Ca(2+) Influx |
title_short | Microdomain Ca(2+) Activation during Exocytosis in Paramecium Cells. Superposition of Local Subplasmalemmal Calcium Store Activation by Local Ca(2+) Influx |
title_sort | microdomain ca(2+) activation during exocytosis in paramecium cells. superposition of local subplasmalemmal calcium store activation by local ca(2+) influx |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2134299/ https://www.ncbi.nlm.nih.gov/pubmed/9024690 |
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