nNOS downregulation attenuates neuronal apoptosis by inhibiting nNOS-GluR6 interaction and GluR6 nitrosylation in cerebral ischemic reperfusion.

Glutamate receptor 6 (GluR6) is well documented to play a pivotal role in ischemic brain injury, which is mediated by the GluR6·PSD95·MLK3 signaling module and subsequent c-Jun N-terminal kinase (JNK) activation. Our recent studies show that GluR6 is S-nitrosylated in the early stages of ischemia-reperfusion. NO (Nitric Oxide) is mainly generated from neuronal nitric oxide synthase (nNOS) in cerebral neurons during the early stages of reperfusion. Here, the effect of nNOS downregulation on GluR6 S-nitrosylation and GluR6-mediated signaling was investigated in cerebral ischemia and reperfusion. Administration of nNOS oligonucleotides confirmed that GluR6 nitrosylation is induced by nNOS-derived endogenous NO and further activates the GluR6·PSD95·MLK3 signaling module and JNK signaling pathway. Moreover, this study revealed for the first time that nNOS can bind with GluR6 during ischemic reperfusion, and PSD95 is involved in this interaction. In summary, our results suggest that nNOS binds with GluR6 via PSD95 and then produces endogenous NO to S-nitrosylate GluR6 in cerebral ischemia-reperfusion, which provides a new approach for stroke therapy.