Limits...
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.


bAP-Ca2+ transient enhancement depends on neuronal output.(a) Raster plot of a 10 min in vivo extracellular recording from a freely moving p19 rat in layer 2 of the MEC. Grey bars correspond to single spikes. AP doublets with frequencies >100 Hz are indicated in red. (b) Diagram of experimental timelines. Grey and black vertical bars correspond to test stimulus doublets (short bars) and the ten 5 AP bursts administered after baseline (long bars). Dark green vertical bars depict doublet test stimuli delivered every 60 s. A 6 min baseline measurement was followed by a stimulus-free interval of 5 min. We then again measured the bAP-Ca2+ transients evoked by the doublet test stimulus. Light green bars correspond to three doublet test stimuli delivered at an interval of 120s and followed by a 10 min stimulus-free interval. After that, six doublets were measured at a 60 s interval. Shorter pink horizontal bars correspond to singlets. For baseline measurements, three singlet test stimuli were delivered at an interval of 120 s and followed by a 10 min stimulus-free interval. After that, six singlets were measured at a 60 s interval. Interval used for normalized post/pre ratios of bAP-Ca2+ transient enhancement is shaded in grey. (c1) Z-projection of the imaged dendritic segment (scale bar corresponds to 1 μm). (c2) Singlet evoked averaged bAP-Ca2+ transients from two neighbouring spines (top and middle). Bottom trace refers to representative underlying APs. (d1) Plot of normalized bAP-Ca2+ transient enhancement 15 to 20 min after bAP stimulation onset in spines with baseline ∆G/R <0.041. In the singlet experiments, the doublet response was measured at 20 min to permit grouping for comparison with the other doublet responses. bAP-Ca2+ transient enhancement in the control group (black, n = 53/31 spines/cells) is significantly larger than in the spine group where singlets were applied (-16.5%, n = 16/11 spines/cells, magenta, p < 0.001, Kruskal Wallis Test with Dunn’s posthoc comparison). Reduced enhancement upon application of doublets when 5 AP bursts were omitted (27 ± 8%, n = 10/6 spines/cells, dark green) and doublet number further reduced (14 ± 5%, n = 16/12 spines cells, light green). Both conditions were not significantly different from controls (n.s., Kruskal Wallis Test with Dunn’s posthoc comparison). (d2) Cumulative distribution plot of normalized bAP-Ca2+ transient enhancement. Dataset corresponds to d1. Data are expressed as mean SEM *** P < 0.001.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4476683&req=5

pbio.1002181.g004: bAP-Ca2+ transient enhancement depends on neuronal output.(a) Raster plot of a 10 min in vivo extracellular recording from a freely moving p19 rat in layer 2 of the MEC. Grey bars correspond to single spikes. AP doublets with frequencies >100 Hz are indicated in red. (b) Diagram of experimental timelines. Grey and black vertical bars correspond to test stimulus doublets (short bars) and the ten 5 AP bursts administered after baseline (long bars). Dark green vertical bars depict doublet test stimuli delivered every 60 s. A 6 min baseline measurement was followed by a stimulus-free interval of 5 min. We then again measured the bAP-Ca2+ transients evoked by the doublet test stimulus. Light green bars correspond to three doublet test stimuli delivered at an interval of 120s and followed by a 10 min stimulus-free interval. After that, six doublets were measured at a 60 s interval. Shorter pink horizontal bars correspond to singlets. For baseline measurements, three singlet test stimuli were delivered at an interval of 120 s and followed by a 10 min stimulus-free interval. After that, six singlets were measured at a 60 s interval. Interval used for normalized post/pre ratios of bAP-Ca2+ transient enhancement is shaded in grey. (c1) Z-projection of the imaged dendritic segment (scale bar corresponds to 1 μm). (c2) Singlet evoked averaged bAP-Ca2+ transients from two neighbouring spines (top and middle). Bottom trace refers to representative underlying APs. (d1) Plot of normalized bAP-Ca2+ transient enhancement 15 to 20 min after bAP stimulation onset in spines with baseline ∆G/R <0.041. In the singlet experiments, the doublet response was measured at 20 min to permit grouping for comparison with the other doublet responses. bAP-Ca2+ transient enhancement in the control group (black, n = 53/31 spines/cells) is significantly larger than in the spine group where singlets were applied (-16.5%, n = 16/11 spines/cells, magenta, p < 0.001, Kruskal Wallis Test with Dunn’s posthoc comparison). Reduced enhancement upon application of doublets when 5 AP bursts were omitted (27 ± 8%, n = 10/6 spines/cells, dark green) and doublet number further reduced (14 ± 5%, n = 16/12 spines cells, light green). Both conditions were not significantly different from controls (n.s., Kruskal Wallis Test with Dunn’s posthoc comparison). (d2) Cumulative distribution plot of normalized bAP-Ca2+ transient enhancement. Dataset corresponds to d1. Data are expressed as mean SEM *** P < 0.001.

Mentions: Next, we wanted to see whether enhancement conforms to realistic neuronal firing patterns and scales with AP output. Bursts of 5 APs in the 100 Hz range were not observed in a 10 min in vivo spike train from an MEC layer 2 cell displaying grid cell firing in a freely moving p19 rat (Fig 4A). As the in vivo spike train contained several 100 Hz doublets (Fig 4A), we investigated whether more physiological doublet firing induces a significant enhancement (ten doublets in 15 min, Fig 4B). Indeed, we still observed enhancement, which was not significantly different from control conditions using additional 5 AP bursts (Fig 4D).


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)

bAP-Ca2+ transient enhancement depends on neuronal output.(a) Raster plot of a 10 min in vivo extracellular recording from a freely moving p19 rat in layer 2 of the MEC. Grey bars correspond to single spikes. AP doublets with frequencies >100 Hz are indicated in red. (b) Diagram of experimental timelines. Grey and black vertical bars correspond to test stimulus doublets (short bars) and the ten 5 AP bursts administered after baseline (long bars). Dark green vertical bars depict doublet test stimuli delivered every 60 s. A 6 min baseline measurement was followed by a stimulus-free interval of 5 min. We then again measured the bAP-Ca2+ transients evoked by the doublet test stimulus. Light green bars correspond to three doublet test stimuli delivered at an interval of 120s and followed by a 10 min stimulus-free interval. After that, six doublets were measured at a 60 s interval. Shorter pink horizontal bars correspond to singlets. For baseline measurements, three singlet test stimuli were delivered at an interval of 120 s and followed by a 10 min stimulus-free interval. After that, six singlets were measured at a 60 s interval. Interval used for normalized post/pre ratios of bAP-Ca2+ transient enhancement is shaded in grey. (c1) Z-projection of the imaged dendritic segment (scale bar corresponds to 1 μm). (c2) Singlet evoked averaged bAP-Ca2+ transients from two neighbouring spines (top and middle). Bottom trace refers to representative underlying APs. (d1) Plot of normalized bAP-Ca2+ transient enhancement 15 to 20 min after bAP stimulation onset in spines with baseline ∆G/R <0.041. In the singlet experiments, the doublet response was measured at 20 min to permit grouping for comparison with the other doublet responses. bAP-Ca2+ transient enhancement in the control group (black, n = 53/31 spines/cells) is significantly larger than in the spine group where singlets were applied (-16.5%, n = 16/11 spines/cells, magenta, p < 0.001, Kruskal Wallis Test with Dunn’s posthoc comparison). Reduced enhancement upon application of doublets when 5 AP bursts were omitted (27 ± 8%, n = 10/6 spines/cells, dark green) and doublet number further reduced (14 ± 5%, n = 16/12 spines cells, light green). Both conditions were not significantly different from controls (n.s., Kruskal Wallis Test with Dunn’s posthoc comparison). (d2) Cumulative distribution plot of normalized bAP-Ca2+ transient enhancement. Dataset corresponds to d1. Data are expressed as mean SEM *** P < 0.001.
© Copyright Policy
Related In: Results  -  Collection

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

pbio.1002181.g004: bAP-Ca2+ transient enhancement depends on neuronal output.(a) Raster plot of a 10 min in vivo extracellular recording from a freely moving p19 rat in layer 2 of the MEC. Grey bars correspond to single spikes. AP doublets with frequencies >100 Hz are indicated in red. (b) Diagram of experimental timelines. Grey and black vertical bars correspond to test stimulus doublets (short bars) and the ten 5 AP bursts administered after baseline (long bars). Dark green vertical bars depict doublet test stimuli delivered every 60 s. A 6 min baseline measurement was followed by a stimulus-free interval of 5 min. We then again measured the bAP-Ca2+ transients evoked by the doublet test stimulus. Light green bars correspond to three doublet test stimuli delivered at an interval of 120s and followed by a 10 min stimulus-free interval. After that, six doublets were measured at a 60 s interval. Shorter pink horizontal bars correspond to singlets. For baseline measurements, three singlet test stimuli were delivered at an interval of 120 s and followed by a 10 min stimulus-free interval. After that, six singlets were measured at a 60 s interval. Interval used for normalized post/pre ratios of bAP-Ca2+ transient enhancement is shaded in grey. (c1) Z-projection of the imaged dendritic segment (scale bar corresponds to 1 μm). (c2) Singlet evoked averaged bAP-Ca2+ transients from two neighbouring spines (top and middle). Bottom trace refers to representative underlying APs. (d1) Plot of normalized bAP-Ca2+ transient enhancement 15 to 20 min after bAP stimulation onset in spines with baseline ∆G/R <0.041. In the singlet experiments, the doublet response was measured at 20 min to permit grouping for comparison with the other doublet responses. bAP-Ca2+ transient enhancement in the control group (black, n = 53/31 spines/cells) is significantly larger than in the spine group where singlets were applied (-16.5%, n = 16/11 spines/cells, magenta, p < 0.001, Kruskal Wallis Test with Dunn’s posthoc comparison). Reduced enhancement upon application of doublets when 5 AP bursts were omitted (27 ± 8%, n = 10/6 spines/cells, dark green) and doublet number further reduced (14 ± 5%, n = 16/12 spines cells, light green). Both conditions were not significantly different from controls (n.s., Kruskal Wallis Test with Dunn’s posthoc comparison). (d2) Cumulative distribution plot of normalized bAP-Ca2+ transient enhancement. Dataset corresponds to d1. Data are expressed as mean SEM *** P < 0.001.
Mentions: Next, we wanted to see whether enhancement conforms to realistic neuronal firing patterns and scales with AP output. Bursts of 5 APs in the 100 Hz range were not observed in a 10 min in vivo spike train from an MEC layer 2 cell displaying grid cell firing in a freely moving p19 rat (Fig 4A). As the in vivo spike train contained several 100 Hz doublets (Fig 4A), we investigated whether more physiological doublet firing induces a significant enhancement (ten doublets in 15 min, Fig 4B). Indeed, we still observed enhancement, which was not significantly different from control conditions using additional 5 AP bursts (Fig 4D).

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.