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Differential Properties of GTP‐ and Ca 2+ ‐Stimulated Exocytosis from Large Dense Core Vesicles
Author(s) -
Bai Li,
Zhu Dan,
Zhou Keming,
Zhou Wei,
Li Dongdong,
Wang Yan,
Zhang Rongying,
Xu Tao
Publication year - 2006
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2006.00394.x
Subject(s) - exocytosis , vesicle , mastoparan , gtp' , lipid bilayer fusion , vesicle fusion , biophysics , biology , microbiology and biotechnology , membrane , biochemistry , g protein , signal transduction , synaptic vesicle , enzyme
Many cells utilize a GTP‐dependent pathway to trigger exocytosis in addition to Ca 2+ ‐triggered exocytosis. However, little is known about the mechanism by which GTP triggers exocytosis independent of Ca 2+ . We used dual‐color evanescent field microscopy to compare the motion and fusion of large dense core vesicles stimulated by either mastoparan (Mas) in Ca 2+ ‐free conditions or high K + in the presence of Ca 2+ . We demonstrate that Mas is hardly effective in triggering the fusion of the predocked vesicles but predominantly mobilizes cytosolic vesicles. In contrast, Ca 2+ ‐dependent exocytosis is largely due to predocked vesicles. Fusion kinetics analysis and carbon‐fiber amperometry reveal that Mas induces a brief ‘kiss‐and‐run’ fusion and releases only a small amount of the cargo, whereas Ca 2+ stimulates a more persistent opening of the fusion pore and larger release of the contents. Furthermore, we show that Mas‐released vesicles require a much shorter time to reach fusion competence once they approach the plasma membrane. Our data suggest the involvement of different mechanisms not only in triggering and fusion but also in the docking and priming process for Ca 2+ ‐ and GTP‐dependent exocytosis.