期刊
JOURNAL OF GENERAL PHYSIOLOGY
卷 122, 期 3, 页码 265-276出版社
ROCKEFELLER UNIV PRESS
DOI: 10.1085/jgp.200308855
关键词
chromaffin cell; membrane fusion; neurosecretion; capacitance measurement; amperometry
类别
We tested the long-standing hypothesis that synaptotagmin 1 is the Ca2+ sensor for fast neurosecretion by analyzing the intracellular Ca2+ dependence of large dense-core vesicle exocytosis in a mouse strain carrying a mutated synaptotagmin C2A domain. The mutation (R233Q) causes a twofold increase in the K-D of Ca2+ dependent phospholipid binding to the double C2A-C2B domain of synaptotagmin. Using photolysis of caged calcium and capacitance measurements we found that secretion from mutant cells had lower secretory rates, longer secretory delays, and a higher intracellular Ca2+-threshold for secretion due to a twofold increase in the apparent K-D of the Ca2+ sensor for fast exocytosis. Single amperometric fusion events were unchanged. We conclude that Ca2+-dependent phospholipid binding to synaptotagmin 1 mirrors the intracellular Ca2+ dependence of exocytosis.
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