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Ryanodine Receptor Activation Induces Long-Term Plasticity of Spine Calcium Dynamics.

Johenning FW, Theis AK, Pannasch U, Rückl M, Rüdiger S, Schmitz D - PLoS Biol. (2015)

Bottom Line: Ca2+ is a major upstream effector in this transduction cascade, serving both as a depolarising electrical charge carrier at the membrane and an intracellular second messenger.We demonstrate that RyRs can form specific Ca2+ signalling nanodomains within single spines.Functionally, RyR mediated Ca2+ release in these nanodomains induces a new form of Ca2+ transient plasticity that constitutes a spine specific storage mechanism of neuronal suprathreshold activity patterns.

View Article: PubMed Central - PubMed

Affiliation: Neuroscience Research Center, Charité-Universitätsmedizin, Berlin, Germany; Berlin Institute of Health (BIH), Berlin, Germany.

ABSTRACT
A key feature of signalling in dendritic spines is the synapse-specific transduction of short electrical signals into biochemical responses. Ca2+ is a major upstream effector in this transduction cascade, serving both as a depolarising electrical charge carrier at the membrane and an intracellular second messenger. Upon action potential firing, the majority of spines are subject to global back-propagating action potential (bAP) Ca2+ transients. These transients translate neuronal suprathreshold activation into intracellular biochemical events. Using a combination of electrophysiology, two-photon Ca2+ imaging, and modelling, we demonstrate that bAPs are electrochemically coupled to Ca2+ release from intracellular stores via ryanodine receptors (RyRs). We describe a new function mediated by spine RyRs: the activity-dependent long-term enhancement of the bAP-Ca2+ transient. Spines regulate bAP Ca2+ influx independent of each other, as bAP-Ca2+ transient enhancement is compartmentalized and independent of the dendritic Ca2+ transient. Furthermore, this functional state change depends exclusively on bAPs travelling antidromically into dendrites and spines. Induction, but not expression, of bAP-Ca2+ transient enhancement is a spine-specific function of the RyR. We demonstrate that RyRs can form specific Ca2+ signalling nanodomains within single spines. Functionally, RyR mediated Ca2+ release in these nanodomains induces a new form of Ca2+ transient plasticity that constitutes a spine specific storage mechanism of neuronal suprathreshold activity patterns.

No MeSH data available.


Enhancement of bAP-Ca2+ transients in dendritic spines.(a1) Illustration of recording pipette positioning in layer 2 of the MEC (black) and in the hippocampal CA1 region (green). (a2) Experimental paradigm for enhancement of bAP-Ca2+ transients. Top: Test stimulus AP doublets evoked by current injection before (pre, grey) and after (post, black) 5 AP bursts (bold black). Bottom: Experimental timeline, vertical bars correspond to test stimulus AP doublet (short bars) and 5 APs (long bars). Doublet test stimuli were delivered every 60 s. After a 6 min baseline measurement, we applied a bursting paradigm consisting of 5 APs delivered every 30 s for 5 min. After the bursting paradigm, we again measured the bAP-Ca2+ transient evoked by the doublet test stimulus. Grey box illustrates the interval 15 to 20 min after bAP stimulation onset which is compared to baseline stimulation to quantify enhancement. (b1) Z-projection of the imaged dendritic segment (scale bar corresponds to 2 μm). Asterisks mark imaged spine and dendritic segment. (b2) bAP Ca2+ transient enhancement in a cortical neuron. Averaged fluorescence traces of Ca2+ transients in spine (top) and dendrite (middle). Representative AP traces from the time intervals averaged for Ca2+ imaging (bottom). (c1) Z-projection of the imaged dendritic segment in a hippocampal CA1 pyramidal cell. (scale bar corresponds to 2 μm). Asterisks mark imaged spine and dendritic segment. (c2) Overlay of averaged fluorescence traces 0–5 (grey) and 15–20 min after bAP stimulation onset in a CA1 pyramidal cell spine (green) and the adjacent dendrite (red). (c3) Time plot of normalized single sweep amplitudes. (d) Cumulative distribution plot of normalized bAP Ca2+ transient enhancement in spines of MEC layer 2 cortical neurons (19 ± 4%, n = 92/43 spines/cells, black) and hippocampal CA1 pyramidal cells (8 ± 4%, n = 59/22 spines/cells, green), comparison did not reach significance (n.s., Mann Whitney U Test). (e) Bar graph illustrates percentage of spines displaying bAP-Ca2+ transient enhancement >20% in MEC layer 2 cells (42%, 39/27 out of 92/43 spines/cells, black) and in hippocampal CA1 pyramidal cells (24%, 14/8 out of 59/22 measured spines/cells, green).
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pbio.1002181.g002: Enhancement of bAP-Ca2+ transients in dendritic spines.(a1) Illustration of recording pipette positioning in layer 2 of the MEC (black) and in the hippocampal CA1 region (green). (a2) Experimental paradigm for enhancement of bAP-Ca2+ transients. Top: Test stimulus AP doublets evoked by current injection before (pre, grey) and after (post, black) 5 AP bursts (bold black). Bottom: Experimental timeline, vertical bars correspond to test stimulus AP doublet (short bars) and 5 APs (long bars). Doublet test stimuli were delivered every 60 s. After a 6 min baseline measurement, we applied a bursting paradigm consisting of 5 APs delivered every 30 s for 5 min. After the bursting paradigm, we again measured the bAP-Ca2+ transient evoked by the doublet test stimulus. Grey box illustrates the interval 15 to 20 min after bAP stimulation onset which is compared to baseline stimulation to quantify enhancement. (b1) Z-projection of the imaged dendritic segment (scale bar corresponds to 2 μm). Asterisks mark imaged spine and dendritic segment. (b2) bAP Ca2+ transient enhancement in a cortical neuron. Averaged fluorescence traces of Ca2+ transients in spine (top) and dendrite (middle). Representative AP traces from the time intervals averaged for Ca2+ imaging (bottom). (c1) Z-projection of the imaged dendritic segment in a hippocampal CA1 pyramidal cell. (scale bar corresponds to 2 μm). Asterisks mark imaged spine and dendritic segment. (c2) Overlay of averaged fluorescence traces 0–5 (grey) and 15–20 min after bAP stimulation onset in a CA1 pyramidal cell spine (green) and the adjacent dendrite (red). (c3) Time plot of normalized single sweep amplitudes. (d) Cumulative distribution plot of normalized bAP Ca2+ transient enhancement in spines of MEC layer 2 cortical neurons (19 ± 4%, n = 92/43 spines/cells, black) and hippocampal CA1 pyramidal cells (8 ± 4%, n = 59/22 spines/cells, green), comparison did not reach significance (n.s., Mann Whitney U Test). (e) Bar graph illustrates percentage of spines displaying bAP-Ca2+ transient enhancement >20% in MEC layer 2 cells (42%, 39/27 out of 92/43 spines/cells, black) and in hippocampal CA1 pyramidal cells (24%, 14/8 out of 59/22 measured spines/cells, green).

Mentions: To quantify spine-specific enhancement, bAP-Ca2+ transient amplitudes following a 15 min stimulation paradigm (Fig 2A2) were normalized to the baseline amplitudes (Fig 3C; see Methods and S6 Fig on amplitude measurements). In layer 2 cells of the MEC, a population of 92 spines from 43 cells fulfilled our quality criteria for long-term measurements (see Methods). As opposed to our fluo-5F control doublet timelines from Fig 1C, enhancement under these conditions was significantly different from a theoretical median of 0% change in the time interval 15 to 20 min after the onset of stimulation (p < 0.0001, Wilcoxon-signed rank test). This new protocol enabled us to study enhancement in a more systematic fashion with a larger effect size in a shorter experimental time window. 42% of the spines could be classified as plastic, which means they displayed bAP-Ca2+ transient enhancement by >20%. Spines with changes of the bAP-Ca2+ transient of <20% were defined as static spines.


Ryanodine Receptor Activation Induces Long-Term Plasticity of Spine Calcium Dynamics.

Johenning FW, Theis AK, Pannasch U, Rückl M, Rüdiger S, Schmitz D - PLoS Biol. (2015)

Enhancement of bAP-Ca2+ transients in dendritic spines.(a1) Illustration of recording pipette positioning in layer 2 of the MEC (black) and in the hippocampal CA1 region (green). (a2) Experimental paradigm for enhancement of bAP-Ca2+ transients. Top: Test stimulus AP doublets evoked by current injection before (pre, grey) and after (post, black) 5 AP bursts (bold black). Bottom: Experimental timeline, vertical bars correspond to test stimulus AP doublet (short bars) and 5 APs (long bars). Doublet test stimuli were delivered every 60 s. After a 6 min baseline measurement, we applied a bursting paradigm consisting of 5 APs delivered every 30 s for 5 min. After the bursting paradigm, we again measured the bAP-Ca2+ transient evoked by the doublet test stimulus. Grey box illustrates the interval 15 to 20 min after bAP stimulation onset which is compared to baseline stimulation to quantify enhancement. (b1) Z-projection of the imaged dendritic segment (scale bar corresponds to 2 μm). Asterisks mark imaged spine and dendritic segment. (b2) bAP Ca2+ transient enhancement in a cortical neuron. Averaged fluorescence traces of Ca2+ transients in spine (top) and dendrite (middle). Representative AP traces from the time intervals averaged for Ca2+ imaging (bottom). (c1) Z-projection of the imaged dendritic segment in a hippocampal CA1 pyramidal cell. (scale bar corresponds to 2 μm). Asterisks mark imaged spine and dendritic segment. (c2) Overlay of averaged fluorescence traces 0–5 (grey) and 15–20 min after bAP stimulation onset in a CA1 pyramidal cell spine (green) and the adjacent dendrite (red). (c3) Time plot of normalized single sweep amplitudes. (d) Cumulative distribution plot of normalized bAP Ca2+ transient enhancement in spines of MEC layer 2 cortical neurons (19 ± 4%, n = 92/43 spines/cells, black) and hippocampal CA1 pyramidal cells (8 ± 4%, n = 59/22 spines/cells, green), comparison did not reach significance (n.s., Mann Whitney U Test). (e) Bar graph illustrates percentage of spines displaying bAP-Ca2+ transient enhancement >20% in MEC layer 2 cells (42%, 39/27 out of 92/43 spines/cells, black) and in hippocampal CA1 pyramidal cells (24%, 14/8 out of 59/22 measured spines/cells, green).
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pbio.1002181.g002: Enhancement of bAP-Ca2+ transients in dendritic spines.(a1) Illustration of recording pipette positioning in layer 2 of the MEC (black) and in the hippocampal CA1 region (green). (a2) Experimental paradigm for enhancement of bAP-Ca2+ transients. Top: Test stimulus AP doublets evoked by current injection before (pre, grey) and after (post, black) 5 AP bursts (bold black). Bottom: Experimental timeline, vertical bars correspond to test stimulus AP doublet (short bars) and 5 APs (long bars). Doublet test stimuli were delivered every 60 s. After a 6 min baseline measurement, we applied a bursting paradigm consisting of 5 APs delivered every 30 s for 5 min. After the bursting paradigm, we again measured the bAP-Ca2+ transient evoked by the doublet test stimulus. Grey box illustrates the interval 15 to 20 min after bAP stimulation onset which is compared to baseline stimulation to quantify enhancement. (b1) Z-projection of the imaged dendritic segment (scale bar corresponds to 2 μm). Asterisks mark imaged spine and dendritic segment. (b2) bAP Ca2+ transient enhancement in a cortical neuron. Averaged fluorescence traces of Ca2+ transients in spine (top) and dendrite (middle). Representative AP traces from the time intervals averaged for Ca2+ imaging (bottom). (c1) Z-projection of the imaged dendritic segment in a hippocampal CA1 pyramidal cell. (scale bar corresponds to 2 μm). Asterisks mark imaged spine and dendritic segment. (c2) Overlay of averaged fluorescence traces 0–5 (grey) and 15–20 min after bAP stimulation onset in a CA1 pyramidal cell spine (green) and the adjacent dendrite (red). (c3) Time plot of normalized single sweep amplitudes. (d) Cumulative distribution plot of normalized bAP Ca2+ transient enhancement in spines of MEC layer 2 cortical neurons (19 ± 4%, n = 92/43 spines/cells, black) and hippocampal CA1 pyramidal cells (8 ± 4%, n = 59/22 spines/cells, green), comparison did not reach significance (n.s., Mann Whitney U Test). (e) Bar graph illustrates percentage of spines displaying bAP-Ca2+ transient enhancement >20% in MEC layer 2 cells (42%, 39/27 out of 92/43 spines/cells, black) and in hippocampal CA1 pyramidal cells (24%, 14/8 out of 59/22 measured spines/cells, green).
Mentions: To quantify spine-specific enhancement, bAP-Ca2+ transient amplitudes following a 15 min stimulation paradigm (Fig 2A2) were normalized to the baseline amplitudes (Fig 3C; see Methods and S6 Fig on amplitude measurements). In layer 2 cells of the MEC, a population of 92 spines from 43 cells fulfilled our quality criteria for long-term measurements (see Methods). As opposed to our fluo-5F control doublet timelines from Fig 1C, enhancement under these conditions was significantly different from a theoretical median of 0% change in the time interval 15 to 20 min after the onset of stimulation (p < 0.0001, Wilcoxon-signed rank test). This new protocol enabled us to study enhancement in a more systematic fashion with a larger effect size in a shorter experimental time window. 42% of the spines could be classified as plastic, which means they displayed bAP-Ca2+ transient enhancement by >20%. Spines with changes of the bAP-Ca2+ transient of <20% were defined as static spines.

Bottom Line: Ca2+ is a major upstream effector in this transduction cascade, serving both as a depolarising electrical charge carrier at the membrane and an intracellular second messenger.We demonstrate that RyRs can form specific Ca2+ signalling nanodomains within single spines.Functionally, RyR mediated Ca2+ release in these nanodomains induces a new form of Ca2+ transient plasticity that constitutes a spine specific storage mechanism of neuronal suprathreshold activity patterns.

View Article: PubMed Central - PubMed

Affiliation: Neuroscience Research Center, Charité-Universitätsmedizin, Berlin, Germany; Berlin Institute of Health (BIH), Berlin, Germany.

ABSTRACT
A key feature of signalling in dendritic spines is the synapse-specific transduction of short electrical signals into biochemical responses. Ca2+ is a major upstream effector in this transduction cascade, serving both as a depolarising electrical charge carrier at the membrane and an intracellular second messenger. Upon action potential firing, the majority of spines are subject to global back-propagating action potential (bAP) Ca2+ transients. These transients translate neuronal suprathreshold activation into intracellular biochemical events. Using a combination of electrophysiology, two-photon Ca2+ imaging, and modelling, we demonstrate that bAPs are electrochemically coupled to Ca2+ release from intracellular stores via ryanodine receptors (RyRs). We describe a new function mediated by spine RyRs: the activity-dependent long-term enhancement of the bAP-Ca2+ transient. Spines regulate bAP Ca2+ influx independent of each other, as bAP-Ca2+ transient enhancement is compartmentalized and independent of the dendritic Ca2+ transient. Furthermore, this functional state change depends exclusively on bAPs travelling antidromically into dendrites and spines. Induction, but not expression, of bAP-Ca2+ transient enhancement is a spine-specific function of the RyR. We demonstrate that RyRs can form specific Ca2+ signalling nanodomains within single spines. Functionally, RyR mediated Ca2+ release in these nanodomains induces a new form of Ca2+ transient plasticity that constitutes a spine specific storage mechanism of neuronal suprathreshold activity patterns.

No MeSH data available.