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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.


Electrochemical coupling of bAPs and intracellular Ca2+ store release in dendritic spines.(a) Top: Illustration of recording pipette positioning in layer 2 of the MEC. Bottom: Representative voltage trace of an AP doublet (100 Hz) evoked by current injection to induce the bAP-Ca2+ transients displayed in b2. (b1) Z-projection of the imaged dendritic segments in MEC layer 2 under control conditions (top), with CPA wash-in (middle), and with ryanodine wash-in (bottom; scale bars correspond to 2 μm). Asterisks mark imaged spines. (b2) Averaged traces (corresponding to consecutive 5 min recording intervals) of a control spine (black, top), a spine in the presence of 30 μM CPA as indicated by the red bar (red, middle), and a spine in the presence of 10 μM ryanodine (blue, bottom). (c1) Time plot of normalized doublet evoked bAP-Ca2+ amplitudes comparing control (black), CPA wash-in (red), and ryanodine wash-in (blue) after 5 min of baseline (indicated by the red bar). One doublet was applied every 60 s; the data is plotted in 3 min bins. Interval used for normalized post/pre ratios of bAP-Ca2+ is shaded in grey. (c2) Cumulative distribution plot of the averaged bAP-Ca2+ amplitudes 20 to 25 min after stimulation onset (corresponding to 16 to 21 min after drug wash-in; grey area in c1) normalized to baseline. Reduction by CPA (red, -21 ± 3%, n = 16/3 spines/cells) and ryanodine (blue, -10 ± 5%, n = 21/5 spines/cells) is significant when compared to the same time interval under control conditions (black, +11 ± 6%, n = 12/3 spines/cells, CPA versus control: p < 0.001, ryanodine versus control: p < 0.01, ANOVA with Bonferroni's Multiple Comparison Test). (d1) Time plot of normalized single AP-evoked bAP-Ca2+ amplitudes comparing control (black), CPA wash-in (red), and ryanodine wash-in (blue) after 5 min of baseline (indicated by red bar). One AP was applied every 60 s; the data is plotted in 3 min bins. Interval used for normalized post/pre ratios of bAP-Ca2+ in d2 is shaded in grey. (d2) Cumulative distribution plot of the averaged bAP-Ca2+ amplitudes 15 to 20 min after drug wash-in (grey area in d1) normalized to baseline. Reduction by CPA (red, n = 21/5 spines/cells) and ryanodine (blue, n = 19/6 spines/cells) is not significant when compared to the same time interval under control conditions (black, n = 21/5 spines/cells, not significant (n.s.), ANOVA with Bonferroni's Multiple Comparison Test). (e1) Representative voltage trace of a single AP evoked by current injection to induce the bAP-Ca2+ transient displayed in e3. (e2) Z-projection of the imaged dendritic segment (scale bar corresponds to 2 μm). Asterisk marks imaged spine. (e3) Averaged single AP-traces before and after wash-in of 10 μM ryanodine as indicated by the blue bar. (f) Cumulative distribution plot of the averaged single bAP-Ca2+ amplitudes in the first 5 min of drug wash-in (blue area in d1) normalized to baseline. The increase in the initial phase of ryanodine wash-in (+10 ± 6%, n = 34/8 spines/cells) is significant when compared to the same time interval under control conditions (-4 ± 4%, n = 31/7 spines/cells, p < 0.05, one-tailed Mann Whitney U test). (g) Bar graph of the fraction of spines responding with an effect size >1 standard deviation than the time-matched controls for 1 bAP during the first 5 min of ryanodine wash-in (35%, light blue), 2 bAPs 20 to 25 min after stimulation onset with ryanodine (38%, dark blue) and CPA (44%, red) wash-in. Data are expressed as mean standard error of the mean (SEM) * p < 0.05; ** p < 0.01; *** p < 0.001.
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pbio.1002181.g001: Electrochemical coupling of bAPs and intracellular Ca2+ store release in dendritic spines.(a) Top: Illustration of recording pipette positioning in layer 2 of the MEC. Bottom: Representative voltage trace of an AP doublet (100 Hz) evoked by current injection to induce the bAP-Ca2+ transients displayed in b2. (b1) Z-projection of the imaged dendritic segments in MEC layer 2 under control conditions (top), with CPA wash-in (middle), and with ryanodine wash-in (bottom; scale bars correspond to 2 μm). Asterisks mark imaged spines. (b2) Averaged traces (corresponding to consecutive 5 min recording intervals) of a control spine (black, top), a spine in the presence of 30 μM CPA as indicated by the red bar (red, middle), and a spine in the presence of 10 μM ryanodine (blue, bottom). (c1) Time plot of normalized doublet evoked bAP-Ca2+ amplitudes comparing control (black), CPA wash-in (red), and ryanodine wash-in (blue) after 5 min of baseline (indicated by the red bar). One doublet was applied every 60 s; the data is plotted in 3 min bins. Interval used for normalized post/pre ratios of bAP-Ca2+ is shaded in grey. (c2) Cumulative distribution plot of the averaged bAP-Ca2+ amplitudes 20 to 25 min after stimulation onset (corresponding to 16 to 21 min after drug wash-in; grey area in c1) normalized to baseline. Reduction by CPA (red, -21 ± 3%, n = 16/3 spines/cells) and ryanodine (blue, -10 ± 5%, n = 21/5 spines/cells) is significant when compared to the same time interval under control conditions (black, +11 ± 6%, n = 12/3 spines/cells, CPA versus control: p < 0.001, ryanodine versus control: p < 0.01, ANOVA with Bonferroni's Multiple Comparison Test). (d1) Time plot of normalized single AP-evoked bAP-Ca2+ amplitudes comparing control (black), CPA wash-in (red), and ryanodine wash-in (blue) after 5 min of baseline (indicated by red bar). One AP was applied every 60 s; the data is plotted in 3 min bins. Interval used for normalized post/pre ratios of bAP-Ca2+ in d2 is shaded in grey. (d2) Cumulative distribution plot of the averaged bAP-Ca2+ amplitudes 15 to 20 min after drug wash-in (grey area in d1) normalized to baseline. Reduction by CPA (red, n = 21/5 spines/cells) and ryanodine (blue, n = 19/6 spines/cells) is not significant when compared to the same time interval under control conditions (black, n = 21/5 spines/cells, not significant (n.s.), ANOVA with Bonferroni's Multiple Comparison Test). (e1) Representative voltage trace of a single AP evoked by current injection to induce the bAP-Ca2+ transient displayed in e3. (e2) Z-projection of the imaged dendritic segment (scale bar corresponds to 2 μm). Asterisk marks imaged spine. (e3) Averaged single AP-traces before and after wash-in of 10 μM ryanodine as indicated by the blue bar. (f) Cumulative distribution plot of the averaged single bAP-Ca2+ amplitudes in the first 5 min of drug wash-in (blue area in d1) normalized to baseline. The increase in the initial phase of ryanodine wash-in (+10 ± 6%, n = 34/8 spines/cells) is significant when compared to the same time interval under control conditions (-4 ± 4%, n = 31/7 spines/cells, p < 0.05, one-tailed Mann Whitney U test). (g) Bar graph of the fraction of spines responding with an effect size >1 standard deviation than the time-matched controls for 1 bAP during the first 5 min of ryanodine wash-in (35%, light blue), 2 bAPs 20 to 25 min after stimulation onset with ryanodine (38%, dark blue) and CPA (44%, red) wash-in. Data are expressed as mean standard error of the mean (SEM) * p < 0.05; ** p < 0.01; *** p < 0.001.

Mentions: We performed two-photon Ca2+ imaging of bAP-Ca2+ transients in spines and adjacent dendritic segments. In acute brain slices, we studied cortical neurons in layer 2 of the medial entorhinal cortex (MEC) using fluo-5F (500 μM) as a Ca2+ indicator (Fig 1A). The contribution of RyR-mediated Ca2+ release to doublet bAP-Ca2+ transients was analysed using different pharmacological approaches (Fig 1B and 1E).


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)

Electrochemical coupling of bAPs and intracellular Ca2+ store release in dendritic spines.(a) Top: Illustration of recording pipette positioning in layer 2 of the MEC. Bottom: Representative voltage trace of an AP doublet (100 Hz) evoked by current injection to induce the bAP-Ca2+ transients displayed in b2. (b1) Z-projection of the imaged dendritic segments in MEC layer 2 under control conditions (top), with CPA wash-in (middle), and with ryanodine wash-in (bottom; scale bars correspond to 2 μm). Asterisks mark imaged spines. (b2) Averaged traces (corresponding to consecutive 5 min recording intervals) of a control spine (black, top), a spine in the presence of 30 μM CPA as indicated by the red bar (red, middle), and a spine in the presence of 10 μM ryanodine (blue, bottom). (c1) Time plot of normalized doublet evoked bAP-Ca2+ amplitudes comparing control (black), CPA wash-in (red), and ryanodine wash-in (blue) after 5 min of baseline (indicated by the red bar). One doublet was applied every 60 s; the data is plotted in 3 min bins. Interval used for normalized post/pre ratios of bAP-Ca2+ is shaded in grey. (c2) Cumulative distribution plot of the averaged bAP-Ca2+ amplitudes 20 to 25 min after stimulation onset (corresponding to 16 to 21 min after drug wash-in; grey area in c1) normalized to baseline. Reduction by CPA (red, -21 ± 3%, n = 16/3 spines/cells) and ryanodine (blue, -10 ± 5%, n = 21/5 spines/cells) is significant when compared to the same time interval under control conditions (black, +11 ± 6%, n = 12/3 spines/cells, CPA versus control: p < 0.001, ryanodine versus control: p < 0.01, ANOVA with Bonferroni's Multiple Comparison Test). (d1) Time plot of normalized single AP-evoked bAP-Ca2+ amplitudes comparing control (black), CPA wash-in (red), and ryanodine wash-in (blue) after 5 min of baseline (indicated by red bar). One AP was applied every 60 s; the data is plotted in 3 min bins. Interval used for normalized post/pre ratios of bAP-Ca2+ in d2 is shaded in grey. (d2) Cumulative distribution plot of the averaged bAP-Ca2+ amplitudes 15 to 20 min after drug wash-in (grey area in d1) normalized to baseline. Reduction by CPA (red, n = 21/5 spines/cells) and ryanodine (blue, n = 19/6 spines/cells) is not significant when compared to the same time interval under control conditions (black, n = 21/5 spines/cells, not significant (n.s.), ANOVA with Bonferroni's Multiple Comparison Test). (e1) Representative voltage trace of a single AP evoked by current injection to induce the bAP-Ca2+ transient displayed in e3. (e2) Z-projection of the imaged dendritic segment (scale bar corresponds to 2 μm). Asterisk marks imaged spine. (e3) Averaged single AP-traces before and after wash-in of 10 μM ryanodine as indicated by the blue bar. (f) Cumulative distribution plot of the averaged single bAP-Ca2+ amplitudes in the first 5 min of drug wash-in (blue area in d1) normalized to baseline. The increase in the initial phase of ryanodine wash-in (+10 ± 6%, n = 34/8 spines/cells) is significant when compared to the same time interval under control conditions (-4 ± 4%, n = 31/7 spines/cells, p < 0.05, one-tailed Mann Whitney U test). (g) Bar graph of the fraction of spines responding with an effect size >1 standard deviation than the time-matched controls for 1 bAP during the first 5 min of ryanodine wash-in (35%, light blue), 2 bAPs 20 to 25 min after stimulation onset with ryanodine (38%, dark blue) and CPA (44%, red) wash-in. Data are expressed as mean standard error of the mean (SEM) * p < 0.05; ** p < 0.01; *** p < 0.001.
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pbio.1002181.g001: Electrochemical coupling of bAPs and intracellular Ca2+ store release in dendritic spines.(a) Top: Illustration of recording pipette positioning in layer 2 of the MEC. Bottom: Representative voltage trace of an AP doublet (100 Hz) evoked by current injection to induce the bAP-Ca2+ transients displayed in b2. (b1) Z-projection of the imaged dendritic segments in MEC layer 2 under control conditions (top), with CPA wash-in (middle), and with ryanodine wash-in (bottom; scale bars correspond to 2 μm). Asterisks mark imaged spines. (b2) Averaged traces (corresponding to consecutive 5 min recording intervals) of a control spine (black, top), a spine in the presence of 30 μM CPA as indicated by the red bar (red, middle), and a spine in the presence of 10 μM ryanodine (blue, bottom). (c1) Time plot of normalized doublet evoked bAP-Ca2+ amplitudes comparing control (black), CPA wash-in (red), and ryanodine wash-in (blue) after 5 min of baseline (indicated by the red bar). One doublet was applied every 60 s; the data is plotted in 3 min bins. Interval used for normalized post/pre ratios of bAP-Ca2+ is shaded in grey. (c2) Cumulative distribution plot of the averaged bAP-Ca2+ amplitudes 20 to 25 min after stimulation onset (corresponding to 16 to 21 min after drug wash-in; grey area in c1) normalized to baseline. Reduction by CPA (red, -21 ± 3%, n = 16/3 spines/cells) and ryanodine (blue, -10 ± 5%, n = 21/5 spines/cells) is significant when compared to the same time interval under control conditions (black, +11 ± 6%, n = 12/3 spines/cells, CPA versus control: p < 0.001, ryanodine versus control: p < 0.01, ANOVA with Bonferroni's Multiple Comparison Test). (d1) Time plot of normalized single AP-evoked bAP-Ca2+ amplitudes comparing control (black), CPA wash-in (red), and ryanodine wash-in (blue) after 5 min of baseline (indicated by red bar). One AP was applied every 60 s; the data is plotted in 3 min bins. Interval used for normalized post/pre ratios of bAP-Ca2+ in d2 is shaded in grey. (d2) Cumulative distribution plot of the averaged bAP-Ca2+ amplitudes 15 to 20 min after drug wash-in (grey area in d1) normalized to baseline. Reduction by CPA (red, n = 21/5 spines/cells) and ryanodine (blue, n = 19/6 spines/cells) is not significant when compared to the same time interval under control conditions (black, n = 21/5 spines/cells, not significant (n.s.), ANOVA with Bonferroni's Multiple Comparison Test). (e1) Representative voltage trace of a single AP evoked by current injection to induce the bAP-Ca2+ transient displayed in e3. (e2) Z-projection of the imaged dendritic segment (scale bar corresponds to 2 μm). Asterisk marks imaged spine. (e3) Averaged single AP-traces before and after wash-in of 10 μM ryanodine as indicated by the blue bar. (f) Cumulative distribution plot of the averaged single bAP-Ca2+ amplitudes in the first 5 min of drug wash-in (blue area in d1) normalized to baseline. The increase in the initial phase of ryanodine wash-in (+10 ± 6%, n = 34/8 spines/cells) is significant when compared to the same time interval under control conditions (-4 ± 4%, n = 31/7 spines/cells, p < 0.05, one-tailed Mann Whitney U test). (g) Bar graph of the fraction of spines responding with an effect size >1 standard deviation than the time-matched controls for 1 bAP during the first 5 min of ryanodine wash-in (35%, light blue), 2 bAPs 20 to 25 min after stimulation onset with ryanodine (38%, dark blue) and CPA (44%, red) wash-in. Data are expressed as mean standard error of the mean (SEM) * p < 0.05; ** p < 0.01; *** p < 0.001.
Mentions: We performed two-photon Ca2+ imaging of bAP-Ca2+ transients in spines and adjacent dendritic segments. In acute brain slices, we studied cortical neurons in layer 2 of the medial entorhinal cortex (MEC) using fluo-5F (500 μM) as a Ca2+ indicator (Fig 1A). The contribution of RyR-mediated Ca2+ release to doublet bAP-Ca2+ transients was analysed using different pharmacological approaches (Fig 1B and 1E).

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.