| Autor: |
Chih-Tien Wang, Jihong Bai, Chang, Payne Y., Chapman, Edwin R., Jackson, Meyer B. |
| Předmět: |
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| Zdroj: |
Journal of Physiology; Jan2006, Vol. 570 Issue 2, p295-307, 13p, 1 Diagram, 1 Chart, 6 Graphs |
| Abstrakt: |
Synaptotagmin I (Syt I), the putative Ca2+ sensor in regulated exocytosis, has two Ca2+-binding modules, the C2A and C2B domains, and a number of putative effectors to which Syt I binds in a Ca2+-dependent fashion. The role of Ca2+ binding to these domains remains unclear, as efforts to address questions about Ca2+-triggered effector interactions have led to conflicting results. We have studied the effects of Ca2+ on fusion pores using amperometry to follow the exocytosis of single vesicles in real time and analyse the kinetics of fusion pore transitions. Elevating [Ca2+] in permeabilized cells reduced the fusion pore lifetime, indicating an action of Ca2+ during the actual fusion process. Analysing the Ca2+ dependence of the fusion pore lifetime, together with the frequency of pore openings and the proportion of openings that close without dilating (kiss-and-run events) enabled us to resolve exocytosis into a sequence of kinetic steps representing functional transitions in the fusion pore. Fusion pore opening and dilation were both accelerated by Ca2+, indicating separate Ca2+ control over each of these steps. Ca2+ ligand mutations in either the C2A or C2B domains of Syt I reduced fusion pore opening, but had opposite actions on the rate of fusion pore closure. These studies resolve two separate and distinct Ca2+-triggered steps during regulated exocytosis. The C2A and C2B domains of Syt I have different actions during these steps, and these actions may be linked to their distinctive effector interactions. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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