Click
here to close Hello! We notice that
you are using Internet Explorer, which is not supported by Echinobase
and may cause the site to display incorrectly. We suggest using a
current version of Chrome,
FireFox,
or Safari.
J Gen Physiol
1998 Nov 01;1125:559-67. doi: 10.1085/jgp.112.5.559.
Show Gene links
Show Anatomy links
Submaximal responses in calcium-triggered exocytosis are explained by differences in the calcium sensitivity of individual secretory vesicles.
Blank PS
,
Cho MS
,
Vogel SS
,
Kaplan D
,
Kang A
,
Malley J
,
Zimmerberg J
.
???displayArticle.abstract???
A graded response to calcium is the defining feature of calcium-regulated exocytosis. That is, there exist calcium concentrations that elicit submaximal exocytotic responses in which only a fraction of the available population of secretory vesicles fuse. The role of calcium-dependent inactivation in defining the calcium sensitivity of sea urchin eggsecretory vesicle exocytosis in vitro was examined. The cessation of fusion in the continued presence of calcium was not due to calcium-dependent inactivation. Rather, the calcium sensitivity of individual vesicles within a population of exocytotic vesicles is heterogeneous. Any specific calcium concentration above threshold triggered subpopulations of vesicles to fuse and the size of the subpopulations was dependent upon the magnitude of the calcium stimulus. The existence of multiple, stable subpopulations of vesicles is consistent with a fusion process that requires the action of an even greater number of calcium ions than the numbers suggested by models based on the assumption of a homogeneous vesicle population.
Figure 2. (A) Percent fusion vs. time, species differences. For comparable extents of fusion, L. pictus requires higher calcium concentration than S. purpuratus. The data were collected using a sample time of 0.02 (L. pictus) and 0.1 (S. purpuratus) s. (B) Rate, d(%fusion)/dt vs. time in the continued presence of calcium. The maximum rate of fusion is larger and occurs earlier in L. pictus compared with S. purpuratus. The data were low-pass filtered with a 1.0 Hz cutoff frequency before calculating the derivative using third order forward differences.
Figure 3. 30-min exposure to elevated calcium with S. purpuratus. Submaximal responses were maintained during the exposure of cortices to solutions containing 5 or 16 μM. The upward arrows signify addition of calcium. The smaller arrow represents the addition of either 5 or 16 μM calcium while the larger arrow represents the calcium concentration (>300 μM) used to fuse all the remaining vesicles. The presence of elevated calcium for 30 min had no effect on subsequent fusion resulting from exposure to a higher concentration of calcium. The sample time was 0.3 s.
Figure 4. Multiple calcium challenges. Enhanced fusion does not occur when cortices are challenged with a second application of 24 μM calcium, S. purpuratus. Cortices were washed and incubated in zero calcium for 0.5, 1.0, 3.0, 10.0, and 30 min (A–E) before the second calcium challenge. The upward and downward arrows signify addition and removal of calcium, respectively. The largest arrow represents the calcium concentration (>300 μM) used to fuse all remaining vesicles. The sample time was 0.15 s.
Figure 5. Additivity in the extent of fusion, S. purpuratus. The final extent of fusion is independent of the sequence of concentrations used to elicit the response. The upward and downward arrow signifies addition and removal of calcium. The calcium concentrations were 14, 24, and >300 μM (DP); 24 and >300 μM (SP). For clarity, only every 10th data point was plotted for SP. The sample time was 0.15 s.
Figure 7. (A) Calcium activation curves for S. purpuratus and L. pictus, average values (± SEM). Unchallenged cortices are represented by solid symbols and previously challenged cortices are represented by open symbols. The solid lines are the log-normal cumulative distribution function, %fusion = 50 · erfc{[pCa + log (10−6 M)]/\documentclass[10pt]{article}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{pmc}
\usepackage[Euler]{upgreek}
\pagestyle{empty}
\oddsidemargin -1.0in
\begin{document}
\begin{equation*}(\sqrt{2}{\cdot}W)\}\end{equation*}\end{document} , with W = 0.23 ± 0.02 and 0.24 ± 0.02 and midpoint M = 18.2 ± 0.6 and 44.8 ± 1.2 μM for S. purpuratus and L. pictus, respectively. (B) Distribution of calcium thresholds (probability density function) for S. purpuratus and L. pictus derived from the derivative of the log-normal cumulative distribution function. The total area under each curve is one, corresponding to 100% fusion.
Figure 6. (A) Fusion can occur during solution exchange, before establishing the stable, submaximal response, which is independent of the presence or absence of calcium. The upward and downward arrows signify addition and removal of 24 μM calcium, S. purpuratus. The absence of abrupt changes in fusion (inset) indicates that the solution exchange occurred during a time when previously activated vesicles are now fusing. T1 and T2 label the times of solution exchange. The sample time was 0.15 s. (B) Abrupt changes in fusion are observed only when calcium is removed before irreversible commitment to the fusion process. The upward and downward arrows signify addition and removal (Interrupted) of 70 μM calcium, S. purpuratus. The sample times were 0.15 and 0.05 s for Uninterrupted and Interrupted, respectively.
Augustine,
Calcium dependence of presynaptic calcium current and post-synaptic response at the squid giant synapse.
1986, Pubmed
Augustine,
Calcium dependence of presynaptic calcium current and post-synaptic response at the squid giant synapse.
1986,
Pubmed
Baker,
Influence of ATP and calcium on the cortical reaction in sea urchin eggs.
1978,
Pubmed
,
Echinobase
Baker,
Calcium control of exocytosis and endocytosis in bovine adrenal medullary cells.
1981,
Pubmed
Berstein,
Effect of the lipid environment on the differential affinity of purified cerebral and atrial muscarinic acetylcholine receptors for pirenzepine.
1989,
Pubmed
Chernomordik,
Lipids in biological membrane fusion.
1995,
Pubmed
Chess,
Molecular biology of smell: expression of the multigene family encoding putative odorant receptors.
1992,
Pubmed
Dodge,
Co-operative action a calcium ions in transmitter release at the neuromuscular junction.
1967,
Pubmed
Heinemann,
Kinetics of the secretory response in bovine chromaffin cells following flash photolysis of caged Ca2+.
1994,
Pubmed
Heinemann,
A two-step model of secretion control in neuroendocrine cells.
1993,
Pubmed
Kaplan,
Single cell fusion events induced by influenza hemagglutinin: studies with rapid-flow, quantitative fluorescence microscopy.
1991,
Pubmed
Kaplan,
A rapid-flow perfusion chamber for high-resolution microscopy.
1996,
Pubmed
,
Echinobase
Knight,
Gaining access to the cytosol: the technique and some applications of electropermeabilization.
1986,
Pubmed
Knight,
Exocytosis from the vesicle viewpoint: an overview.
1987,
Pubmed
Knight,
Calcium-dependence of catecholamine release from bovine adrenal medullary cells after exposure to intense electric fields.
1982,
Pubmed
Littleton,
Synaptotagmin controls and modulates synaptic-vesicle fusion in a Ca(2+)-dependent manner.
1995,
Pubmed
Llinás,
Presynaptic calcium currents and their relation to synaptic transmission: voltage clamp study in squid giant synapse and theoretical model for the calcium gate.
1976,
Pubmed
Llinás,
Relationship between presynaptic calcium current and postsynaptic potential in squid giant synapse.
1981,
Pubmed
McLaughlin,
Cations that alter surface potentials of lipid bilayers increase the calcium requirement for exocytosis in sea urchin eggs.
1988,
Pubmed
,
Echinobase
Moy,
Calcium-mediated release of glucanase activity from cortical granules of sea urchin eggs.
1983,
Pubmed
,
Echinobase
Ninomiya,
Kinetic diversity in the fusion of exocytotic vesicles.
1997,
Pubmed
Sarafian,
Loss of proteins from digitonin-permeabilized adrenal chromaffin cells essential for exocytosis.
1987,
Pubmed
Sasaki,
Cortical vesicle exocytosis in isolated cortices of sea urchin eggs: description of a turbidometric assay and its utilization in studying effects of different media on discharge.
1983,
Pubmed
,
Echinobase
Shen,
Mechanisms of calcium regulation in sea urchin eggs and their activities during fertilization.
1995,
Pubmed
,
Echinobase
Simon,
Compartmentalization of the submembrane calcium activity during calcium influx and its significance in transmitter release.
1985,
Pubmed
Tsien,
Neutral carrier ion-selective microelectrodes for measurement of intracellular free calcium.
1980,
Pubmed
Vacquier,
The isolation of intact cortical granules from sea urchin eggs: calcium lons trigger granule discharge.
1975,
Pubmed
,
Echinobase
Vogel,
The sea urchin cortical reaction. A model system for studying the final steps of calcium-triggered vesicle fusion.
1991,
Pubmed
,
Echinobase
Vogel,
Lysophosphatidylcholine reversibly arrests exocytosis and viral fusion at a stage between triggering and membrane merger.
1993,
Pubmed
,
Echinobase
Vogel,
Poisson-distributed active fusion complexes underlie the control of the rate and extent of exocytosis by calcium.
1996,
Pubmed
,
Echinobase
Zimmerberg,
Mechanisms of membrane fusion.
1993,
Pubmed
Zimmerberg,
Exocytosis of sea urchin egg cortical vesicles in vitro is retarded by hyperosmotic sucrose: kinetics of fusion monitored by quantitative light-scattering microscopy.
1985,
Pubmed
,
Echinobase
Zucker,
Relationship between transmitter release and presynaptic calcium influx when calcium enters through discrete channels.
1986,
Pubmed
