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Selective regulation of NR2B by protein phosphatase-1 for the control of the NMDA receptor in neuroprotection.

Farinelli M, Heitz FD, Grewe BF, Tyagarajan SK, Helmchen F, Mansuy IM - PLoS ONE (2012)

Bottom Line: The protective effect of PP1 is associated with a selective dephosphorylation on a residue phosphorylated by CaMKIIα on the NMDA receptor subunit NR2B, which promotes pro-survival pathways and associated transcriptional programs.These results reveal a novel contributor to the mechanisms of neuroprotection and underscore the importance of PP1-dependent dephosphorylation in these mechanisms.They provide a new target for the development of potential therapeutic treatment of neurodegeneration.

View Article: PubMed Central - PubMed

Affiliation: Brain Research Institute, University of Zürich, Zürich, Switzerland.

ABSTRACT
An imbalance between pro-survival and pro-death pathways in brain cells can lead to neuronal cell death and neurodegeneration. While such imbalance is known to be associated with alterations in glutamatergic and Ca(2+) signaling, the underlying mechanisms remain undefined. We identified the protein Ser/Thr phosphatase protein phosphatase-1 (PP1), an enzyme associated with glutamate receptors, as a key trigger of survival pathways that can prevent neuronal death and neurodegeneration in the adult hippocampus. We show that PP1α overexpression in hippocampal neurons limits NMDA receptor overactivation and Ca(2+) overload during an excitotoxic event, while PP1 inhibition favors Ca(2+) overload and cell death. The protective effect of PP1 is associated with a selective dephosphorylation on a residue phosphorylated by CaMKIIα on the NMDA receptor subunit NR2B, which promotes pro-survival pathways and associated transcriptional programs. These results reveal a novel contributor to the mechanisms of neuroprotection and underscore the importance of PP1-dependent dephosphorylation in these mechanisms. They provide a new target for the development of potential therapeutic treatment of neurodegeneration.

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PP1α expression and CaMIIα inhibition normalize NR2B-containing NMDAR-mediated currents after excitotoxicity.(a) Significant enhancement of NMDAR currents following 4 min OGD in control slices (control, n = 6). Expression of PP1α (n = 5), ifenprodil treatment (n = 8), and KN-93 treatment (n = 6) led to a full recovery of NMDAR currents 6 min after the end of OGD. NVP-AAM077 (n = 5) has no effect on NMDAR currents that remain potentiated throughout recording. Top left, Schematic representation of an organotypic hippocampal slice showing the positioning of the recording patch-clamp electrode and the puffing pipette. Top right, Individual responses from single CA1 pyramidal neurons before (1), during (2) and 10 min after (3) OGD. (b) Time course of OGD mean effect on NMDAR currents. +++p<0.001, ***p<0.001.
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pone-0034047-g005: PP1α expression and CaMIIα inhibition normalize NR2B-containing NMDAR-mediated currents after excitotoxicity.(a) Significant enhancement of NMDAR currents following 4 min OGD in control slices (control, n = 6). Expression of PP1α (n = 5), ifenprodil treatment (n = 8), and KN-93 treatment (n = 6) led to a full recovery of NMDAR currents 6 min after the end of OGD. NVP-AAM077 (n = 5) has no effect on NMDAR currents that remain potentiated throughout recording. Top left, Schematic representation of an organotypic hippocampal slice showing the positioning of the recording patch-clamp electrode and the puffing pipette. Top right, Individual responses from single CA1 pyramidal neurons before (1), during (2) and 10 min after (3) OGD. (b) Time course of OGD mean effect on NMDAR currents. +++p<0.001, ***p<0.001.

Mentions: NR2B Ser1303 phosphorylation is associated with increased [Ca2+]i, and Ca2+ is known to modulate NMDAR activity. Therefore, we examined whether NMDAR currents are altered by OGD. Isolated post-synaptic NMDAR currents were induced by pressure application of NMDA onto CA1 neurons and recorded in voltage clamp whole-cell configuration. In control slices, NMDAR currents progressively increased during the 4-min OGD and reached a plateau at about 168% of baseline, 2 min after the end of OGD (Figure 5a, b). This increase was stable (over 25 min), indicating a persistent potentiation of NMDAR currents by OGD, consistent with previous reports [37]. While NVP-AAM077 had no effect on the potentiation of NMDAR currents, ifenprodil abolished this potentiation and induced a full recovery of NMDAR currents a few minutes after OGD (Figure 5a, b). These results confirm that NR2B underlies the prolonged potentiation of NMDAR currents induced by excitotoxicity.


Selective regulation of NR2B by protein phosphatase-1 for the control of the NMDA receptor in neuroprotection.

Farinelli M, Heitz FD, Grewe BF, Tyagarajan SK, Helmchen F, Mansuy IM - PLoS ONE (2012)

PP1α expression and CaMIIα inhibition normalize NR2B-containing NMDAR-mediated currents after excitotoxicity.(a) Significant enhancement of NMDAR currents following 4 min OGD in control slices (control, n = 6). Expression of PP1α (n = 5), ifenprodil treatment (n = 8), and KN-93 treatment (n = 6) led to a full recovery of NMDAR currents 6 min after the end of OGD. NVP-AAM077 (n = 5) has no effect on NMDAR currents that remain potentiated throughout recording. Top left, Schematic representation of an organotypic hippocampal slice showing the positioning of the recording patch-clamp electrode and the puffing pipette. Top right, Individual responses from single CA1 pyramidal neurons before (1), during (2) and 10 min after (3) OGD. (b) Time course of OGD mean effect on NMDAR currents. +++p<0.001, ***p<0.001.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3316588&req=5

pone-0034047-g005: PP1α expression and CaMIIα inhibition normalize NR2B-containing NMDAR-mediated currents after excitotoxicity.(a) Significant enhancement of NMDAR currents following 4 min OGD in control slices (control, n = 6). Expression of PP1α (n = 5), ifenprodil treatment (n = 8), and KN-93 treatment (n = 6) led to a full recovery of NMDAR currents 6 min after the end of OGD. NVP-AAM077 (n = 5) has no effect on NMDAR currents that remain potentiated throughout recording. Top left, Schematic representation of an organotypic hippocampal slice showing the positioning of the recording patch-clamp electrode and the puffing pipette. Top right, Individual responses from single CA1 pyramidal neurons before (1), during (2) and 10 min after (3) OGD. (b) Time course of OGD mean effect on NMDAR currents. +++p<0.001, ***p<0.001.
Mentions: NR2B Ser1303 phosphorylation is associated with increased [Ca2+]i, and Ca2+ is known to modulate NMDAR activity. Therefore, we examined whether NMDAR currents are altered by OGD. Isolated post-synaptic NMDAR currents were induced by pressure application of NMDA onto CA1 neurons and recorded in voltage clamp whole-cell configuration. In control slices, NMDAR currents progressively increased during the 4-min OGD and reached a plateau at about 168% of baseline, 2 min after the end of OGD (Figure 5a, b). This increase was stable (over 25 min), indicating a persistent potentiation of NMDAR currents by OGD, consistent with previous reports [37]. While NVP-AAM077 had no effect on the potentiation of NMDAR currents, ifenprodil abolished this potentiation and induced a full recovery of NMDAR currents a few minutes after OGD (Figure 5a, b). These results confirm that NR2B underlies the prolonged potentiation of NMDAR currents induced by excitotoxicity.

Bottom Line: The protective effect of PP1 is associated with a selective dephosphorylation on a residue phosphorylated by CaMKIIα on the NMDA receptor subunit NR2B, which promotes pro-survival pathways and associated transcriptional programs.These results reveal a novel contributor to the mechanisms of neuroprotection and underscore the importance of PP1-dependent dephosphorylation in these mechanisms.They provide a new target for the development of potential therapeutic treatment of neurodegeneration.

View Article: PubMed Central - PubMed

Affiliation: Brain Research Institute, University of Zürich, Zürich, Switzerland.

ABSTRACT
An imbalance between pro-survival and pro-death pathways in brain cells can lead to neuronal cell death and neurodegeneration. While such imbalance is known to be associated with alterations in glutamatergic and Ca(2+) signaling, the underlying mechanisms remain undefined. We identified the protein Ser/Thr phosphatase protein phosphatase-1 (PP1), an enzyme associated with glutamate receptors, as a key trigger of survival pathways that can prevent neuronal death and neurodegeneration in the adult hippocampus. We show that PP1α overexpression in hippocampal neurons limits NMDA receptor overactivation and Ca(2+) overload during an excitotoxic event, while PP1 inhibition favors Ca(2+) overload and cell death. The protective effect of PP1 is associated with a selective dephosphorylation on a residue phosphorylated by CaMKIIα on the NMDA receptor subunit NR2B, which promotes pro-survival pathways and associated transcriptional programs. These results reveal a novel contributor to the mechanisms of neuroprotection and underscore the importance of PP1-dependent dephosphorylation in these mechanisms. They provide a new target for the development of potential therapeutic treatment of neurodegeneration.

Show MeSH
Related in: MedlinePlus