We have investigated the consequences of having multiple fusion complexes on exocytotic granules, and have identified a new principle for interpreting the calcium dependence of calcium-triggered exocytosis. Strikingly different physiological responses to calcium are expected when active fusion complexes are distributed between granules in a deterministic or probabilistic manner. We have modeled these differences, and compared them with the calcium dependence of sea urchin egg cortical granule exocytosis. From the calcium dependence of cortical granule exocytosis, and from the exposure time and concentration dependence of N-ethylmaleimide inhibition, we determined that cortical granules do have spare active fusion complexes that are randomly distributed as a Poisson process among the population of granules. At high calcium concentrations, docking sites have on average nine active fusion complexes.
Article|
July 15 1996
Poisson-distributed active fusion complexes underlie the control of the rate and extent of exocytosis by calcium.
S S Vogel,
S S Vogel
Laboratory of Theoretical and Physical Biology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA. Steven_Vogel@nih.gov
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P S Blank,
P S Blank
Laboratory of Theoretical and Physical Biology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA. Steven_Vogel@nih.gov
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J Zimmerberg
J Zimmerberg
Laboratory of Theoretical and Physical Biology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA. Steven_Vogel@nih.gov
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S S Vogel
Laboratory of Theoretical and Physical Biology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA. Steven_Vogel@nih.gov
P S Blank
Laboratory of Theoretical and Physical Biology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA. Steven_Vogel@nih.gov
J Zimmerberg
Laboratory of Theoretical and Physical Biology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA. Steven_Vogel@nih.gov
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1996) 134 (2): 329–338.
Citation
S S Vogel, P S Blank, J Zimmerberg; Poisson-distributed active fusion complexes underlie the control of the rate and extent of exocytosis by calcium.. J Cell Biol 15 July 1996; 134 (2): 329–338. doi: https://doi.org/10.1083/jcb.134.2.329
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