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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.


Stores play a role in induction but not in expression of bAP-Ca2+ transient enhancement.(a1) Z-projection of the imaged dendritic segment (scale bar corresponds to 2 μm). Asterisk marks imaged spine. (a2) Averaged traces of spine bAP-Ca2+ transients: baseline (grey, 0 to 5 min after onset of the experiment), pre-CPA wash-in (black, 10 to 15 min after onset), and post-CPA wash-in (red, 16 to 20, 21 to 25 and 26 to 30 min after the onset of the experiment). Red line indicates wash-in of 30 μM CPA. (b1) Time plot of preselected enhanced spines (enhancement >20% between 15 and 20 min after starting the experiment) comparing controls (black) and spines with CPA wash-in (red) 15 min after the onset of the experiment. Interval used for comparison between control spines and spines where CPA was washed in is shaded in grey. (b2) Cumulative distribution plot of normalized bAP-Ca2+ transient enhancement in time-matched controls and 10 min after CPA and combined CPA and ryanodine wash-in in spines (corresponds to grey area in b1). Control spine enhancement (black, +63 ± 11%, n = 14/10 spines/cells) is not significantly different from spines treated with 30 μM CPA alone (red, +42 ± 11%, n = 17/13 spines/cells, p = 0.07, one-tailed Mann Whitney U test). Combined treatment with CPA and ryanodine was tested in a small population of spines (+57 ± 23%, n = 6/3 spines/cells, magenta). Data are expressed as mean SEM.
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pbio.1002181.g007: Stores play a role in induction but not in expression of bAP-Ca2+ transient enhancement.(a1) Z-projection of the imaged dendritic segment (scale bar corresponds to 2 μm). Asterisk marks imaged spine. (a2) Averaged traces of spine bAP-Ca2+ transients: baseline (grey, 0 to 5 min after onset of the experiment), pre-CPA wash-in (black, 10 to 15 min after onset), and post-CPA wash-in (red, 16 to 20, 21 to 25 and 26 to 30 min after the onset of the experiment). Red line indicates wash-in of 30 μM CPA. (b1) Time plot of preselected enhanced spines (enhancement >20% between 15 and 20 min after starting the experiment) comparing controls (black) and spines with CPA wash-in (red) 15 min after the onset of the experiment. Interval used for comparison between control spines and spines where CPA was washed in is shaded in grey. (b2) Cumulative distribution plot of normalized bAP-Ca2+ transient enhancement in time-matched controls and 10 min after CPA and combined CPA and ryanodine wash-in in spines (corresponds to grey area in b1). Control spine enhancement (black, +63 ± 11%, n = 14/10 spines/cells) is not significantly different from spines treated with 30 μM CPA alone (red, +42 ± 11%, n = 17/13 spines/cells, p = 0.07, one-tailed Mann Whitney U test). Combined treatment with CPA and ryanodine was tested in a small population of spines (+57 ± 23%, n = 6/3 spines/cells, magenta). Data are expressed as mean SEM.

Mentions: We next asked whether the contribution of stores to bAP-Ca2+ transient enhancement results from store activation during induction or whether store activation underlies the expression of enhancement. To test the hypothesis that the expression of bAP-Ca2+ transient enhancement is mediated by recruitment of intracellular Ca2+ stores, 30 μM CPA was washed in after 15 min. This permitted to assess enhancement during our defined time interval for quantification of enhancement (Fig 3C) without an appreciable effect of CPA, as Fig 1C demonstrates that the first 5 min of CPA wash-in did not have an effect. We preselected for enhanced spines (enhancement >20% between 15 and 20 min after starting the experiment; as doublet application has been demonstrated to be sufficient in inducing enhancement, some enhancement can already be observed at the end of our 6 min baseline measurement when only the enhanced spines are plotted). In enhanced spines, 10 min of CPA application resulted in a small reduction of enhancement which was not significant when compared to enhanced control spines in the same time interval (Fig 7B). From Fig 1C, we can see that this 10 min wash-in of CPA already has a significant effect on the bAP-Ca2+ transient measured with 500 μM fluo-5F (CPA: -18 ± 3%, n = 17/3 spines/cells; control: +6 ± 5%, n = 13/3 spines/cells, p < 0.01, Mann Whitney U test). In a smaller subset of spines, we also washed in a combination of CPA and ryanodine aiming at a stronger inhibition of store release. This resulted in no appreciable reduction compared to controls (Fig 7B). The small trend towards reduction by CPA corresponds to the effect size observed in Fig 1, but cannot explain the expression level of enhancement reached in our experiments. We conclude that RyR mediated Ca2+ release from intracellular stores is a requirement during induction, but is not involved in the expression of enhancement.


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)

Stores play a role in induction but not in expression of bAP-Ca2+ transient enhancement.(a1) Z-projection of the imaged dendritic segment (scale bar corresponds to 2 μm). Asterisk marks imaged spine. (a2) Averaged traces of spine bAP-Ca2+ transients: baseline (grey, 0 to 5 min after onset of the experiment), pre-CPA wash-in (black, 10 to 15 min after onset), and post-CPA wash-in (red, 16 to 20, 21 to 25 and 26 to 30 min after the onset of the experiment). Red line indicates wash-in of 30 μM CPA. (b1) Time plot of preselected enhanced spines (enhancement >20% between 15 and 20 min after starting the experiment) comparing controls (black) and spines with CPA wash-in (red) 15 min after the onset of the experiment. Interval used for comparison between control spines and spines where CPA was washed in is shaded in grey. (b2) Cumulative distribution plot of normalized bAP-Ca2+ transient enhancement in time-matched controls and 10 min after CPA and combined CPA and ryanodine wash-in in spines (corresponds to grey area in b1). Control spine enhancement (black, +63 ± 11%, n = 14/10 spines/cells) is not significantly different from spines treated with 30 μM CPA alone (red, +42 ± 11%, n = 17/13 spines/cells, p = 0.07, one-tailed Mann Whitney U test). Combined treatment with CPA and ryanodine was tested in a small population of spines (+57 ± 23%, n = 6/3 spines/cells, magenta). Data are expressed as mean SEM.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4476683&req=5

pbio.1002181.g007: Stores play a role in induction but not in expression of bAP-Ca2+ transient enhancement.(a1) Z-projection of the imaged dendritic segment (scale bar corresponds to 2 μm). Asterisk marks imaged spine. (a2) Averaged traces of spine bAP-Ca2+ transients: baseline (grey, 0 to 5 min after onset of the experiment), pre-CPA wash-in (black, 10 to 15 min after onset), and post-CPA wash-in (red, 16 to 20, 21 to 25 and 26 to 30 min after the onset of the experiment). Red line indicates wash-in of 30 μM CPA. (b1) Time plot of preselected enhanced spines (enhancement >20% between 15 and 20 min after starting the experiment) comparing controls (black) and spines with CPA wash-in (red) 15 min after the onset of the experiment. Interval used for comparison between control spines and spines where CPA was washed in is shaded in grey. (b2) Cumulative distribution plot of normalized bAP-Ca2+ transient enhancement in time-matched controls and 10 min after CPA and combined CPA and ryanodine wash-in in spines (corresponds to grey area in b1). Control spine enhancement (black, +63 ± 11%, n = 14/10 spines/cells) is not significantly different from spines treated with 30 μM CPA alone (red, +42 ± 11%, n = 17/13 spines/cells, p = 0.07, one-tailed Mann Whitney U test). Combined treatment with CPA and ryanodine was tested in a small population of spines (+57 ± 23%, n = 6/3 spines/cells, magenta). Data are expressed as mean SEM.
Mentions: We next asked whether the contribution of stores to bAP-Ca2+ transient enhancement results from store activation during induction or whether store activation underlies the expression of enhancement. To test the hypothesis that the expression of bAP-Ca2+ transient enhancement is mediated by recruitment of intracellular Ca2+ stores, 30 μM CPA was washed in after 15 min. This permitted to assess enhancement during our defined time interval for quantification of enhancement (Fig 3C) without an appreciable effect of CPA, as Fig 1C demonstrates that the first 5 min of CPA wash-in did not have an effect. We preselected for enhanced spines (enhancement >20% between 15 and 20 min after starting the experiment; as doublet application has been demonstrated to be sufficient in inducing enhancement, some enhancement can already be observed at the end of our 6 min baseline measurement when only the enhanced spines are plotted). In enhanced spines, 10 min of CPA application resulted in a small reduction of enhancement which was not significant when compared to enhanced control spines in the same time interval (Fig 7B). From Fig 1C, we can see that this 10 min wash-in of CPA already has a significant effect on the bAP-Ca2+ transient measured with 500 μM fluo-5F (CPA: -18 ± 3%, n = 17/3 spines/cells; control: +6 ± 5%, n = 13/3 spines/cells, p < 0.01, Mann Whitney U test). In a smaller subset of spines, we also washed in a combination of CPA and ryanodine aiming at a stronger inhibition of store release. This resulted in no appreciable reduction compared to controls (Fig 7B). The small trend towards reduction by CPA corresponds to the effect size observed in Fig 1, but cannot explain the expression level of enhancement reached in our experiments. We conclude that RyR mediated Ca2+ release from intracellular stores is a requirement during induction, but is not involved in the expression of enhancement.

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.