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A novel Ca 2+ ‐dependent step in exocytosis subsequent to vesicle fusion
Author(s) -
Hartmann Jana,
Lindau Manfred
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)00318-4
Subject(s) - exocytosis , vesicle , biophysics , chemistry , cytoplasm , fusion , conductance , vesicle fusion , membrane , biochemistry , biology , physics , synaptic vesicle , linguistics , philosophy , condensed matter physics
Exocytosis begins with formation of a small fusion pore which then expands allowing rapid release of granular contents. We studied the influence of cytoplasmic free Ca 2+ ([Ca 2+ ] i ) on the conductance of the initial pore and on the dynamics of subsequent expansion in horse eosinophils using the patch clamp technique. The mean initial conductance is ∼200 pS independent of [Ca 2+ ] i . This value is close to that previously found in beige mouse mast cells. The pore subsequently expands by 18 nS/s at [Ca 2+ ] i < 10 nM, by 40 nS/s at [Ca 2+ ] i = 1.5 μ M and by 90 nS/s at [Ca 2+ ] i = 10 μ M. These results show that the structure of the initial fusion pore is independent of cytoplasmic Ca 2+ . However, the pore expansion is a Ca 2+ ‐dependent process modulating secretion at a step later than vesicle‐plasma membrane fusion.