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Expanding the neuron's calcium signaling repertoire: intracellular calcium release via voltage-induced PLC and IP3R activation.

Ryglewski S, Pflueger HJ, Duch C - PLoS Biol. (2007)

Bottom Line: Specific and independent regulation of these vital cellular processes is achieved by a rich bouquet of different calcium signaling mechanisms within the neuron, which either can operate independently or may act in concert.This study demonstrates the existence of a novel calcium signaling mechanism by simultaneous patch clamping and calcium imaging from acutely isolated central neurons.This allows neurons to monitor activity by intracellular calcium release without relying on calcium as the input signal and opens up new insights into intracellular signaling, developmental regulation, and information processing in neuronal compartments lacking calcium channels.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biology/Neurobiology, Free University of Berlin, Berlin, Germany.

ABSTRACT
Neuronal calcium acts as a charge carrier during information processing and as a ubiquitous intracellular messenger. Calcium signals are fundamental to numerous aspects of neuronal development and plasticity. Specific and independent regulation of these vital cellular processes is achieved by a rich bouquet of different calcium signaling mechanisms within the neuron, which either can operate independently or may act in concert. This study demonstrates the existence of a novel calcium signaling mechanism by simultaneous patch clamping and calcium imaging from acutely isolated central neurons. These neurons possess a membrane voltage sensor that, independent of calcium influx, causes G-protein activation, which subsequently leads to calcium release from intracellular stores via phospholipase C and inositol 1,4,5-trisphosphate receptor activation. This allows neurons to monitor activity by intracellular calcium release without relying on calcium as the input signal and opens up new insights into intracellular signaling, developmental regulation, and information processing in neuronal compartments lacking calcium channels.

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Related in: MedlinePlus

Voltage Dependence of the Calcium Signal(A) Acutely isolated DUM neurons are maintained in calcium-free saline containing TTX and TEA, and clamped to a holding potential of −60 mV followed by command potentials of −50, −40, −30, and 0 mV. The amplitudes of the resulting intracellular calcium signals change as a function of the command potential.(B) Percent change (means and standard deviations from three neurons) in intracellular calcium levels (y-axis) plotted as a function of command voltage (x-axis).
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pbio-0050066-g006: Voltage Dependence of the Calcium Signal(A) Acutely isolated DUM neurons are maintained in calcium-free saline containing TTX and TEA, and clamped to a holding potential of −60 mV followed by command potentials of −50, −40, −30, and 0 mV. The amplitudes of the resulting intracellular calcium signals change as a function of the command potential.(B) Percent change (means and standard deviations from three neurons) in intracellular calcium levels (y-axis) plotted as a function of command voltage (x-axis).

Mentions: In a final set of experiments, we determined the voltage dependency of this novel calcium-release pathway. In order to avoid depletion of internal calcium stores during the course of the experiments, in a first set of measurements, the activation voltage was roughly narrowed down, and in a second set of measurements, the voltage dependency was determined more accurately within the pre-determined voltage range. First, in calcium-free saline, neurons were clamped to −90 mV followed by test steps to −60 mV, −30mV, and 0 mV. Calcium signals were not caused by depolarizations to −60 mV, but by those to −30 mV and to 0 mV (unpublished data). Second, in calcium-free saline neurons were clamped to −60 mV, followed by test pulses to −50, −40, −30, and 0 mV (Figure 6A), and the percentage increase in fluorescence was averaged over three neurons and plotted as a function of the command voltage (Figure 6B). The threshold for G-protein–PLC-IP3–mediated calcium release without calcium influx was between −60 mV and −50 mV. This was followed by a nearly linear increase of the calcium signal amplitude for command potentials between −50 mV and 0 mV. Command potentials more positive than −30 mV did not further increase the calcium signal amplitude (Figure 6B).


Expanding the neuron's calcium signaling repertoire: intracellular calcium release via voltage-induced PLC and IP3R activation.

Ryglewski S, Pflueger HJ, Duch C - PLoS Biol. (2007)

Voltage Dependence of the Calcium Signal(A) Acutely isolated DUM neurons are maintained in calcium-free saline containing TTX and TEA, and clamped to a holding potential of −60 mV followed by command potentials of −50, −40, −30, and 0 mV. The amplitudes of the resulting intracellular calcium signals change as a function of the command potential.(B) Percent change (means and standard deviations from three neurons) in intracellular calcium levels (y-axis) plotted as a function of command voltage (x-axis).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1808487&req=5

pbio-0050066-g006: Voltage Dependence of the Calcium Signal(A) Acutely isolated DUM neurons are maintained in calcium-free saline containing TTX and TEA, and clamped to a holding potential of −60 mV followed by command potentials of −50, −40, −30, and 0 mV. The amplitudes of the resulting intracellular calcium signals change as a function of the command potential.(B) Percent change (means and standard deviations from three neurons) in intracellular calcium levels (y-axis) plotted as a function of command voltage (x-axis).
Mentions: In a final set of experiments, we determined the voltage dependency of this novel calcium-release pathway. In order to avoid depletion of internal calcium stores during the course of the experiments, in a first set of measurements, the activation voltage was roughly narrowed down, and in a second set of measurements, the voltage dependency was determined more accurately within the pre-determined voltage range. First, in calcium-free saline, neurons were clamped to −90 mV followed by test steps to −60 mV, −30mV, and 0 mV. Calcium signals were not caused by depolarizations to −60 mV, but by those to −30 mV and to 0 mV (unpublished data). Second, in calcium-free saline neurons were clamped to −60 mV, followed by test pulses to −50, −40, −30, and 0 mV (Figure 6A), and the percentage increase in fluorescence was averaged over three neurons and plotted as a function of the command voltage (Figure 6B). The threshold for G-protein–PLC-IP3–mediated calcium release without calcium influx was between −60 mV and −50 mV. This was followed by a nearly linear increase of the calcium signal amplitude for command potentials between −50 mV and 0 mV. Command potentials more positive than −30 mV did not further increase the calcium signal amplitude (Figure 6B).

Bottom Line: Specific and independent regulation of these vital cellular processes is achieved by a rich bouquet of different calcium signaling mechanisms within the neuron, which either can operate independently or may act in concert.This study demonstrates the existence of a novel calcium signaling mechanism by simultaneous patch clamping and calcium imaging from acutely isolated central neurons.This allows neurons to monitor activity by intracellular calcium release without relying on calcium as the input signal and opens up new insights into intracellular signaling, developmental regulation, and information processing in neuronal compartments lacking calcium channels.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biology/Neurobiology, Free University of Berlin, Berlin, Germany.

ABSTRACT
Neuronal calcium acts as a charge carrier during information processing and as a ubiquitous intracellular messenger. Calcium signals are fundamental to numerous aspects of neuronal development and plasticity. Specific and independent regulation of these vital cellular processes is achieved by a rich bouquet of different calcium signaling mechanisms within the neuron, which either can operate independently or may act in concert. This study demonstrates the existence of a novel calcium signaling mechanism by simultaneous patch clamping and calcium imaging from acutely isolated central neurons. These neurons possess a membrane voltage sensor that, independent of calcium influx, causes G-protein activation, which subsequently leads to calcium release from intracellular stores via phospholipase C and inositol 1,4,5-trisphosphate receptor activation. This allows neurons to monitor activity by intracellular calcium release without relying on calcium as the input signal and opens up new insights into intracellular signaling, developmental regulation, and information processing in neuronal compartments lacking calcium channels.

Show MeSH
Related in: MedlinePlus