cn6b00350_si_001.pdf (3.4 MB)
Extracellular Osmotic Stress Reduces the Vesicle Size while Keeping a Constant Neurotransmitter Concentration
journal contribution
posted on 2016-12-14, 00:00 authored by Hoda Fathali, Johan Dunevall, Soodabeh Majdi, Ann-Sofie CansSecretory
cells respond to hypertonic stress by cell shrinking,
which causes a reduction in exocytosis activity and the amount of
signaling molecules released from single exocytosis events. These
changes in exocytosis have been suggested to result from alterations
in biophysical properties of cell cytoplasm and plasma membrane, based
on the assumption that osmotic stress does not affect the secretory
vesicle content and size prior to exocytosis. To further investigate
whether vesicles in secretory cells are affected by the osmolality
of the extracellular environment, we used intracellular electrochemical
cytometry together with transmission electron microscopy imaging to
quantify and determine the catecholamine concentration of dense core
vesicles in situ before and after cell exposure to
osmotic stress. In addition, single cell amperometry recordings of
exocytosis at chromaffin cells were used to monitor the effect on
exocytosis activity and quantal release when cells were exposed to
osmotic stress. Here we show that hypertonic stress hampers exocytosis
secretion after the first pool of readily releasable vesicles have
been fused and that extracellular osmotic stress causes catecholamine
filled vesicles to shrink, mainly by reducing the volume of the halo
solution surrounding the protein matrix in dense core vesicles. In
addition, the vesicles demonstrate the ability to perform adjustments
in neurotransmitter content during shrinking, and intracellular amperometry
measurements in situ suggest that vesicles reduce
the catecholamine content to maintain a constant concentration within
the vesicle compartment. Hence, the secretory vesicles in the cell
cytoplasm are highly affected and respond to extracellular osmotic
stress, which gives a new perspective to the cause of reduction in
quantal size by these vesicles when undergoing exocytosis.
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core vesiclesintracellular electrochemical cytometryhypertonic stresscell amperometry recordingsConstant Neurotransmitter Concentration Secretory cellsExtracellular Osmotic Stresscell cytoplasmstress causes catecholamineintracellular amperometry measurementssecretory vesicle contenttransmission electron microscopy imagingexocytosis activity
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