Postsynaptic density protein 95 mediates Ca2+/calmodulin-dependent protein kinase II-activated serine phosphorylation of neuronal nitric oxide synthase during brain ischemia in rat hippocampus.

Recent study has indicated that postsynaptic density protein 95 (PSD95) promotes Ca2+/calmodulin-dependent protein kinase II (CaMKII)-mediated serine phosphorylation of neuronal nitric oxide synthase (nNOS). To investigate whether PSD95 is involved in the brain ischemia-induced enhancement of serine phosphorylation of nNOS by CaMKII in rat hippocampus, we examined the interactions among CaMKIIalpha, PSD95 and nNOS, and the effects of suppression of PSD95 expression on both the increased serine phosphorylation of nNOS and the interactions mentioned above by immunoprecipitation and immunoblotting. The following results were observed: (1) brain ischemia increased markedly the interactions of CaMKIIalpha and nNOS with PSD95. (2) Intracerebroventricular infusion of PSD95 antisense oligodeoxynucleotides, but not missense oligodeoxynucleotides or vehicle, not only significantly decreased the protein level of PSD95 but also attenuated the elevated serine phosphorylation of nNOS and the interactions among CaMKIIalpha, PSD95 and nNOS induced by 15 min ischemia. These data suggested that PSD95 is important for facilitating nNOS serine phosphorylation by CaMKII.