Disassembly of Death-associated Protein Kinase and DANGER Interaction Mediates Hippocampal CA1 Neuron Death in Rat Cerebral Ischemic Reperfusion.

Death-associated protein kinase (DAPK) is a Ca2+/CaM-regulated protein kinase that is involved in cell death processes by multiple pathways. It has been reported that DAPK may play a role in brain ischemia-induced neuronal death, but this mechanism is not well understood. DANGER, a membrane-associated protein that binds to DAPK physiologically, inhibits DAPK activation. In the present study, we used a transient global brain ischemia and reperfusion (I/R) rat model to investigate whether the interaction between DAPK and DANGER is involved in neuronal cell death following brain ischemia, and to reveal the mechanism of action. Our results indicate that the DAPK/DANGER interaction in the hippocampal CA1 region was significantly reduced after I/R with a peak reduction at 6 h. We further demonstrate that the NMDA inhibitor MK-801, DAPK inhibitor, or calcineurin inhibitor FK-506 prevented the dissociation of DANGER from DAPK 6 h after I/R. This was accompanied by a significantly decreased I/R-induced dephosphorylation of DAPK(ser-308), inhibiting DAPK catalytic activity. Moreover, the expression of DANGER and the interaction between DANGER and IP3R on the endoplasmic reticulum was significantly increased at I/R 6 h, which may be related to a reduction of DAPK/DANGER binding under I/R condition. Furthermore, MK-801, DAPK inhibitor and FK-506 had neuroprotective effects against hippocampal CA1 neuronal death 5 days after I/R. In conclusion, our data suggest that the dissociation of DANGER from DAPK may mediate DAPK activation, which is involved in DAPK-related neuronal death following I/R injury.

PDZ1 inhibitor peptide protects neurons against ischemia via inhibiting GluK2-PSD-95-module-mediated Fas signaling pathway.

Respecting the selective inhibition of peptides on protein-protein interactions, they might become potent methods in ischemic stroke therapy. In this study, we investigated the effect of PDZ1 inhibitor peptide on ischemic neuron apoptosis and the relative mechanism. Results showed that PDZ1 inhibitor peptide, which significantly disrupted GluK2-PSD-95 interaction, efficiently protected neuron from ischemia/reperfusion-induced apoptosis. Further, PDZ1 inhibited FasL expression, DISC assembly and activation of Caspase 8, Bid, Caspase 9 and Caspase 3 after global brain ischemia. Based on our previous report that GluK2-PSD-95 pathway increased FasL expression after global brain ischemia, the neuron protection effect of PDZ1 inhibitor peptide was considered to be achieved by disrupting GluK2-PSD-95 interaction and subsequently inhibiting FasL expression and Fas apoptosis pathway.