Calmodulin kinase IV-dependent CREB activation is required for neuroprotection via NMDA receptor-PSD95 disruption.
NMDA-type glutamate receptors mediate both trophic and excitotoxic signalling in CNS neurons. We have previously shown that blocking NMDAR- post-synaptic density-95 (PSD95) interactions provides significant protection from excitotoxicity and in vivo ischaemia; however, the mechanism of neuroprotection is unclear. Here, we report that blocking PSD-95 interactions with the Tat-NR2B9c peptide enhances a Ca²⁺-dependent protective pathway converging on cAMP Response Element binding protein (CREB) activation. We provide evidence that Tat-NR2B9c neuroprotection from oxygen glucose deprivation and NMDA toxicity occurs in parallel with the activation of calmodulin kinase signalling and is dependent on a sustained phosphorylation of the CREB transcription factor and its activator CaMKIV. Tat-NR2B9c-dependent neuroprotection and CREB phosphorylation are blocked by coapplication of CaM kinase (KN93 and STO-609) or CREB (KG-501) inhibitors, and by siRNA knockdown of CaMKIV. These results are mirrored in vivo in a rat model of permanent focal ischaemia. Tat-NR2B9c application significantly reduces infarct size and causes a selective and sustained elevation in CaMKIV phosphorylation; effects which are blocked by coadministration of KN93. Thus, calcium-dependent nuclear signalling via CaMKIV and CREB is critical for neuroprotection via NMDAR-PSD95 blockade, both in vitro and in vivo. This study highlights the importance of maintaining neuronal function following ischaemic injury. Future stroke research should target neurotrophic and pro-survival signal pathways in the development of novel neuroprotective strategies.
Department of Biological Sciences, University of Toronto, Scarborough, Ontario, Canada.
Karen F S
KF
Bell
Russell J
RJ
Bent
Saira
S
Meese-Tamuri
Alicia
A
Ali
Joan P
JP
Forder
Michelle M
MM
Aarts
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D020520:Brain Infarction / Q000209:etiology / Q000517:prevention & control*; D050882:CREB-Binding Protein / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4 / Q000378:metabolism*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D004195:Disease Models, Animal; D000076122:Disks Large Homolog 4 Protein; D004622:Embryo, Mammalian; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005947:Glucose / Q000172:deficiency; D000860:Hypoxia / Q000473:pathology; D066298:In Vitro Techniques; D020244:Infarction, Middle Cerebral Artery / Q000150:complications; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D009553:Nimodipine / Q000494:pharmacology; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D013997:Time Factors
D002121:Calcium Channel Blockers; D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D016194:Receptors, N-Methyl-D-Aspartate; D009553:Nimodipine; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D050882:CREB-Binding Protein; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D005947:Glucose
NMDA; PSD-95; calcium signaling; calmodulin kinase; neuroprotection; trophic signaling