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Pro-aggregant Tau impairs mossy fiber plasticity due to structural changes and Ca(++) dysregulation.

Decker JM, Krüger L, Sydow A, Zhao S, Frotscher M, Mandelkow E, Mandelkow EM - Acta Neuropathol Commun (2015)

Bottom Line: Both pre-and postsynaptic structural deficits are preventable by inhibition of Tau(RDΔ) aggregation.In N2a cells we observed this even in cells without tangle load, whilst in primary hippocampal neurons transient Tau(RDΔ) expression alone caused similar Ca(++) dysregulation.We conclude that oligomer formation by Tau(RDΔ) causes pre- and postsynaptic structural deterioration and Ca(++) dysregulation which leads to synaptic plasticity deficits.

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: We used an inducible mouse model expressing the Tau repeat domain with the pro-aggregant mutation ΔK280 to analyze presynaptic Tau pathology in the hippocampus.

Results: Expression of pro-aggregant Tau(RDΔ) leads to phosphorylation, aggregation and missorting of Tau in area CA3. To test presynaptic pathophysiology we used electrophysiology in the mossy fiber tract. Synaptic transmission was severely disturbed in pro-aggregant Tau(RDΔ) and Tau-knockout mice. Long-term depression of the mossy fiber tract failed in pro-aggregant Tau(RDΔ) mice. We observed an increase in bouton size, but a decline in numbers and presynaptic markers. Both pre-and postsynaptic structural deficits are preventable by inhibition of Tau(RDΔ) aggregation. Calcium imaging revealed progressive calcium dysregulation in boutons of pro-aggregant Tau(RDΔ) mice. In N2a cells we observed this even in cells without tangle load, whilst in primary hippocampal neurons transient Tau(RDΔ) expression alone caused similar Ca(++) dysregulation. Ultrastructural analysis revealed a severe depletion of synaptic vesicles pool in accordance with synaptic transmission impairments.

Conclusions: We conclude that oligomer formation by Tau(RDΔ) causes pre- and postsynaptic structural deterioration and Ca(++) dysregulation which leads to synaptic plasticity deficits.

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Expression of pro-aggregant TauRDΔimpairs Ca++regulation in primary hippocampal cell culture and N2a cells. (a) Intracellular Ca++ concentrations in primary hippocampal cell culture transfected with GFP only (white arrow) before membrane depolarization by high KCl. Ca++ levels are depicted by false color coding according to Fura2 intensity (scale bar in (d)). (b) Same neuron as in (a) after high KCl stimulation. (c) Intracellular Ca++ levels in a hippocampal neuron expressing pro-aggregant TauRDΔ and GFP (white arrow). (d) Same neuron as in (c) after membrane depolarization. (e) Quantification of Ca++ imaging experiments demonstrating a reduction of calcium influx after high KCl application in pro-aggregant TauRDΔ expressing cells. Pictures in (a)-(d) are background subtracted at the indicated location (BG1). (f) Bright field image of a N2a control cell culture not expressing pro-aggregant TauRDΔ. (g) Bright field image of a N2a cell culture expressing pro-aggregant TauRDΔ. (h)Post-hoc staining after Ca++ imaging experiment of the same cells as in (g) by washing in 0.0001% ThioflavineS (ThS) for 5 minutes. ThS enables to distinguish between N2a cells expressing pro-aggregant TauRDΔ without neurofibrillary tangles (NFT, red circle), N2a cells with NFTs (green circle) and cells with NFT and destroyed membranes (white arrow). (i) Quantification of the maximum Ca++ influx after KCl stimulation in N2a cells loaded with Fura2AM. Cell populations introduced in (f) and (g) demonstrating that cells expressing pro-aggregant TauRDΔ with no ThS positive staining (pro; red column) are already severely impaired but cells with visible tangle load (pro + ThS, green column) are more impaired in Ca++ influx. N2a cells expressing anti-aggregant TauRDΔPP (anti, blue column) do not show reduced calcium influx compared to control cells. Values represent at least three independent experiments. Error bars represent SEM. * p-value < 0.05; ** p-value < 0.01; *** p- value < 0.001.
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Fig8: Expression of pro-aggregant TauRDΔimpairs Ca++regulation in primary hippocampal cell culture and N2a cells. (a) Intracellular Ca++ concentrations in primary hippocampal cell culture transfected with GFP only (white arrow) before membrane depolarization by high KCl. Ca++ levels are depicted by false color coding according to Fura2 intensity (scale bar in (d)). (b) Same neuron as in (a) after high KCl stimulation. (c) Intracellular Ca++ levels in a hippocampal neuron expressing pro-aggregant TauRDΔ and GFP (white arrow). (d) Same neuron as in (c) after membrane depolarization. (e) Quantification of Ca++ imaging experiments demonstrating a reduction of calcium influx after high KCl application in pro-aggregant TauRDΔ expressing cells. Pictures in (a)-(d) are background subtracted at the indicated location (BG1). (f) Bright field image of a N2a control cell culture not expressing pro-aggregant TauRDΔ. (g) Bright field image of a N2a cell culture expressing pro-aggregant TauRDΔ. (h)Post-hoc staining after Ca++ imaging experiment of the same cells as in (g) by washing in 0.0001% ThioflavineS (ThS) for 5 minutes. ThS enables to distinguish between N2a cells expressing pro-aggregant TauRDΔ without neurofibrillary tangles (NFT, red circle), N2a cells with NFTs (green circle) and cells with NFT and destroyed membranes (white arrow). (i) Quantification of the maximum Ca++ influx after KCl stimulation in N2a cells loaded with Fura2AM. Cell populations introduced in (f) and (g) demonstrating that cells expressing pro-aggregant TauRDΔ with no ThS positive staining (pro; red column) are already severely impaired but cells with visible tangle load (pro + ThS, green column) are more impaired in Ca++ influx. N2a cells expressing anti-aggregant TauRDΔPP (anti, blue column) do not show reduced calcium influx compared to control cells. Values represent at least three independent experiments. Error bars represent SEM. * p-value < 0.05; ** p-value < 0.01; *** p- value < 0.001.

Mentions: For comparison we looked at the immediate effect of pro-aggregant TauRDΔ expression on depolarization induced Ca++ influx in rat primary hippocampal neuronal cell cultures. We transiently transfected neurons to express pro-aggregant TauRDΔ plus GFP, compared with neurons expressing GFP only (Figure 8a-d). There was a pronounced reduction (−60%) of KCl-induced Ca++ in TauRDΔ + GFP expressing neurons (GFP only: 263.4 ± 18.6%; n = 7 and pro-aggregant TauRDΔ + GFP: 203.4 ± 19.7%; n = 7; p = 0.014, paired T-test; Figure 8e). This confirms that intracellular TauRDΔ impairs the influx of Ca++ after membrane depolarization, both in slices and in primary neurons.Figure 8


Pro-aggregant Tau impairs mossy fiber plasticity due to structural changes and Ca(++) dysregulation.

Decker JM, Krüger L, Sydow A, Zhao S, Frotscher M, Mandelkow E, Mandelkow EM - Acta Neuropathol Commun (2015)

Expression of pro-aggregant TauRDΔimpairs Ca++regulation in primary hippocampal cell culture and N2a cells. (a) Intracellular Ca++ concentrations in primary hippocampal cell culture transfected with GFP only (white arrow) before membrane depolarization by high KCl. Ca++ levels are depicted by false color coding according to Fura2 intensity (scale bar in (d)). (b) Same neuron as in (a) after high KCl stimulation. (c) Intracellular Ca++ levels in a hippocampal neuron expressing pro-aggregant TauRDΔ and GFP (white arrow). (d) Same neuron as in (c) after membrane depolarization. (e) Quantification of Ca++ imaging experiments demonstrating a reduction of calcium influx after high KCl application in pro-aggregant TauRDΔ expressing cells. Pictures in (a)-(d) are background subtracted at the indicated location (BG1). (f) Bright field image of a N2a control cell culture not expressing pro-aggregant TauRDΔ. (g) Bright field image of a N2a cell culture expressing pro-aggregant TauRDΔ. (h)Post-hoc staining after Ca++ imaging experiment of the same cells as in (g) by washing in 0.0001% ThioflavineS (ThS) for 5 minutes. ThS enables to distinguish between N2a cells expressing pro-aggregant TauRDΔ without neurofibrillary tangles (NFT, red circle), N2a cells with NFTs (green circle) and cells with NFT and destroyed membranes (white arrow). (i) Quantification of the maximum Ca++ influx after KCl stimulation in N2a cells loaded with Fura2AM. Cell populations introduced in (f) and (g) demonstrating that cells expressing pro-aggregant TauRDΔ with no ThS positive staining (pro; red column) are already severely impaired but cells with visible tangle load (pro + ThS, green column) are more impaired in Ca++ influx. N2a cells expressing anti-aggregant TauRDΔPP (anti, blue column) do not show reduced calcium influx compared to control cells. Values represent at least three independent experiments. Error bars represent SEM. * p-value < 0.05; ** p-value < 0.01; *** p- value < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4384391&req=5

Fig8: Expression of pro-aggregant TauRDΔimpairs Ca++regulation in primary hippocampal cell culture and N2a cells. (a) Intracellular Ca++ concentrations in primary hippocampal cell culture transfected with GFP only (white arrow) before membrane depolarization by high KCl. Ca++ levels are depicted by false color coding according to Fura2 intensity (scale bar in (d)). (b) Same neuron as in (a) after high KCl stimulation. (c) Intracellular Ca++ levels in a hippocampal neuron expressing pro-aggregant TauRDΔ and GFP (white arrow). (d) Same neuron as in (c) after membrane depolarization. (e) Quantification of Ca++ imaging experiments demonstrating a reduction of calcium influx after high KCl application in pro-aggregant TauRDΔ expressing cells. Pictures in (a)-(d) are background subtracted at the indicated location (BG1). (f) Bright field image of a N2a control cell culture not expressing pro-aggregant TauRDΔ. (g) Bright field image of a N2a cell culture expressing pro-aggregant TauRDΔ. (h)Post-hoc staining after Ca++ imaging experiment of the same cells as in (g) by washing in 0.0001% ThioflavineS (ThS) for 5 minutes. ThS enables to distinguish between N2a cells expressing pro-aggregant TauRDΔ without neurofibrillary tangles (NFT, red circle), N2a cells with NFTs (green circle) and cells with NFT and destroyed membranes (white arrow). (i) Quantification of the maximum Ca++ influx after KCl stimulation in N2a cells loaded with Fura2AM. Cell populations introduced in (f) and (g) demonstrating that cells expressing pro-aggregant TauRDΔ with no ThS positive staining (pro; red column) are already severely impaired but cells with visible tangle load (pro + ThS, green column) are more impaired in Ca++ influx. N2a cells expressing anti-aggregant TauRDΔPP (anti, blue column) do not show reduced calcium influx compared to control cells. Values represent at least three independent experiments. Error bars represent SEM. * p-value < 0.05; ** p-value < 0.01; *** p- value < 0.001.
Mentions: For comparison we looked at the immediate effect of pro-aggregant TauRDΔ expression on depolarization induced Ca++ influx in rat primary hippocampal neuronal cell cultures. We transiently transfected neurons to express pro-aggregant TauRDΔ plus GFP, compared with neurons expressing GFP only (Figure 8a-d). There was a pronounced reduction (−60%) of KCl-induced Ca++ in TauRDΔ + GFP expressing neurons (GFP only: 263.4 ± 18.6%; n = 7 and pro-aggregant TauRDΔ + GFP: 203.4 ± 19.7%; n = 7; p = 0.014, paired T-test; Figure 8e). This confirms that intracellular TauRDΔ impairs the influx of Ca++ after membrane depolarization, both in slices and in primary neurons.Figure 8

Bottom Line: Both pre-and postsynaptic structural deficits are preventable by inhibition of Tau(RDΔ) aggregation.In N2a cells we observed this even in cells without tangle load, whilst in primary hippocampal neurons transient Tau(RDΔ) expression alone caused similar Ca(++) dysregulation.We conclude that oligomer formation by Tau(RDΔ) causes pre- and postsynaptic structural deterioration and Ca(++) dysregulation which leads to synaptic plasticity deficits.

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: We used an inducible mouse model expressing the Tau repeat domain with the pro-aggregant mutation ΔK280 to analyze presynaptic Tau pathology in the hippocampus.

Results: Expression of pro-aggregant Tau(RDΔ) leads to phosphorylation, aggregation and missorting of Tau in area CA3. To test presynaptic pathophysiology we used electrophysiology in the mossy fiber tract. Synaptic transmission was severely disturbed in pro-aggregant Tau(RDΔ) and Tau-knockout mice. Long-term depression of the mossy fiber tract failed in pro-aggregant Tau(RDΔ) mice. We observed an increase in bouton size, but a decline in numbers and presynaptic markers. Both pre-and postsynaptic structural deficits are preventable by inhibition of Tau(RDΔ) aggregation. Calcium imaging revealed progressive calcium dysregulation in boutons of pro-aggregant Tau(RDΔ) mice. In N2a cells we observed this even in cells without tangle load, whilst in primary hippocampal neurons transient Tau(RDΔ) expression alone caused similar Ca(++) dysregulation. Ultrastructural analysis revealed a severe depletion of synaptic vesicles pool in accordance with synaptic transmission impairments.

Conclusions: We conclude that oligomer formation by Tau(RDΔ) causes pre- and postsynaptic structural deterioration and Ca(++) dysregulation which leads to synaptic plasticity deficits.

Show MeSH
Related in: MedlinePlus