Dynamic interaction between plasmamembrane structures and intracellu-lar calcium stores in drg neurons
I.V. Stepanova, P.G. Kostyuk, E.P. Kostyuk
О.О. Bogomolets Institute of Physiology, National Academyof Sciences of Ukraine, KyivInternational Centre for Molecular Physiology, Kyiv
We studied the dynamic contribution of endoplasmic reticulum
and mitochondria to depolarization-induced Ca2+ transients in
small (18-24 µm) DRG neurons of rats. We have used the
application of 10 µM of mitochondrial protonophore CCCP
for switching off the calcium uptake by mitochondrial
uniporter. For depletion of the store of endoplasmic reticulum
we applied 1 µM of thapsigargin. Depolarization-induced tran-
sients in control conditions and in conditions when one of the
mechanisms (mitochondria or endoplasmic reticulum) does
not participate in the forming of the shape of Ca2+ transient
have been studied. This allowed us to clarify the kinetics of
mitochondrial and endoplasmic reticulum uptake and release
of calcium in the process of the neuronal activity. We have
determined the main characteristics of functioning of above-
named calcium stores in the process of cell excitation, such as
time of the beginning of uptake, time and duration of maximum
activity etc. We concluded, that mitochondria and endoplas-
mic reticulum are acting in opposite directions at least in the
phase of the beginning of the transient. Mitochondria are
limiting the amplitude of the transient during depolarization,
at the same time the endoplasmic reticulum is increasing the
amplitude of the transient by CICR (calcium-induced calcium
release) mechanism. Mitochondria store calcium released from
endoplasmic reticulum by application of 30 mM caffeine. In-
hibition of the mitochondrial uniporter results in reduction of
amplitude of repetitive caffeine application compared with
control conditions. We have compared the kinetics of mito-
chondrial participation in the formation of calcium signal when
the initial sources of calcium ions were different. Our results
allow us to suggest a close functional dynamic interactions
between mitochondria and endoplasmic reticulum during
calcium signaling in sensory neurons.
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