Inhibiting pro-death NMDA receptor signaling dependent on the NR2 PDZ ligand may not affect synaptic function or synaptic NMDA receptor signaling to gene expression

Center for Integrative Physiology, University of Edinburgh, Edinburgh, UK.
Channels (Austin, Tex.) (Impact Factor: 2.32). 02/2009; 3(1):12-5. DOI: 10.4161/chan.3.1.7864
Source: PubMed


NMDA receptors (NMDARs) mediate ischemic brain damage, in part through interactions of the PDZ ligand of NR2 subunits with the PDZ domain proteins PSD-95 and neuronal nitric oxide synthase located within the NMDAR signaling complex. We have recently shown that this PDZ ligand-dependent pathway promotes neuronal death via p38 activation. A peptide mimetic of the NR2B PDZ ligand (TAT-NR2B9c) reduces p38-mediated death in vitro and p38-dependent ischemic damage in vivo. In the absence of the PDZ ligand-p38 pathway, such as in TAT-NR2B9c-treated neurons, or in NMDAR-expressing non-neuronal cells, NMDAR-dependent excitotoxicity is mediated largely by JNK and requires greater Ca2+ influx. A major reason for blocking pro-death signaling events downstream of the NMDAR as an anti-excitotoxic strategy is that it may spare physiological synaptic function and signaling. We find that neuroprotective doses of TAT-NR2B9c do not alter the frequency of spontaneous synaptic events within networks of cultured cortical neurons nor is mini-EPSC frequency altered. Furthermore, TAT-NR2B9c does not inhibit the capacity of synaptic NMDAR activity to promote neuroprotective changes in gene expression, including the upregulation of PACAP via CREB, and suppression of the pro-oxidative FOXO target gene Txnip. Thus, while the NR2 PDZ ligand does not account for all the excitotoxic effects of excessive NMDAR activity, these findings underline the value of the specific targeting of death pathways downstream of the NMDAR.

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    • "ressing pro - death p38 signal - ling and CREB shut - off ( Aarts et al . , 2002 ; Martel et al . , 2012 ; Soriano et al . , 2008 ) . Also , unlike conventional NMDAR antagonists , NA - 1 / Tat - NR2B9c did not interfere with activity - dependent synaptic potentiation , nor synaptic NMDAR - dependent neuroprotective sig - nalling via Akt or CREB ( Martel et al . , 2009a ; Soriano et al . , 2008 ) . Moreover NA - 1 / Tat - NR2B9c was shown to be effective post - treatment in reducing lesion size and improving outcome follow - ing stroke in the non - human primate brain ( Cook et al . , 2012 ) . NA - 1 has also advanced to human clinical trials for iatrogenic stroke after endovascular aneurysm repair ( H"
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    • "Interestingly, this agrees with the finding that Tat-NR2B9c application caused a small yet significant potentiating effect on CRE-dependent reporter gene expression (Martel et al. 2009) downstream of NMDAR activation. Thus, Tat- NR2B9c may provide significant neuroprotection by maintaining trophic, CREB-dependent transcription during ischaemia. "
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    Full-text · Article · Aug 2009 · Channels (Austin, Tex.)
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