kn-93 and Ischemic-Attack--Transient

Although recent results suggest that GluR6 serine phosphorylation plays a prominent role in brain ischemia/reperfusion-mediated neuronal injury, little is known about the precise mechanisms regulating GluR6 receptor phosphorylation. Our present study shows that the assembly of the GluR6-PSD95-CaMKII signaling module induced by brain ischemia facilitates the serine phosphorylation of GluR6 and further induces the activation of c-Jun NH2-terminal kinase JNK. More important, a selective CaMKII inhibitor KN-93 suppressed the increase of the GluR6-PSD95-CaMKII signaling module assembly and GluR6 serine phosphorylation as well as JNK activation. Such effects were similar to be observed by NMDA receptor antagonist MK801 and L-type Ca(2+) channel (L-VGCC) blocker Nifedipine. These results demonstrate that NMDA receptors and L-VGCCs depended-CaMKII functionally modulated the phosphorylation of GluR6 via the assembly of GluR6-PSD95-CaMKII signaling module in cerebral ischemia injury.

Topics: Analysis of Variance; Animals; Benzylamines; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Disease Models, Animal; Disks Large Homolog 4 Protein; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; GluK2 Kainate Receptor; Immunoprecipitation; In Situ Nick-End Labeling; Injections, Intraventricular; Intracellular Signaling Peptides and Proteins; Ischemic Attack, Transient; Male; Membrane Proteins; Nifedipine; Phosphorylation; Protein Kinase Inhibitors; Rats; Rats, Sprague-Dawley; Receptors, Kainic Acid; Serine; Signal Transduction; Sulfonamides

The authors previously demonstrated that Ca2+/calmodulin (CaM)-dependent protein kinase IIalpha (CaM-KIIalpha) can phosphorylate neuronal nitric oxide synthase (nNOS) at Ser847 and attenuate NOS activity in neuronal cells. In the present study, they established that forebrain ischemia causes an increase in the phosphorylation of nNOS at Ser847 in the hippocampus. This nNOS phosphorylation appeared to be catalyzed by CaM-KII: (1) it correlated with the autophosphorylation of CaM-KIIalpha; (2) it was blocked by the CaM-KII inhibitor, KN-93; and (3) nNOS and CaM-KIIalpha were found to coexist in the hippocampus. Examination of the spatial relation between nNOS and CaM-KIIalpha in the brain revealed coexistence in the hippocampus but not in the cortex during reperfusion, with a concomitant increase in autophosphorylation of CaM-KIIalpha. The phosphorylation of nNOS at Ser847 probably takes place in nonpyramidal hippocampal neurons, which increased after 30 minutes of reperfusion in the hippocampus, whereas no significant increase was detected in the cortex. An intraventricular injection of KN-93 significantly decreased the phosphorylation of nNOS in the hippocampus. These results point to CaM-KII as a protein kinase, which by its colocalization may attenuate the activity of nNOS through its Ser847 phosphorylation, and may thus contribute to promotion of tolerance to postischemic damage in hippocampal neurons.

Topics: Animals; Benzylamines; Blood Pressure; Body Temperature; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Calcium-Calmodulin-Dependent Protein Kinases; Carbon Dioxide; Disease Models, Animal; Enzyme Inhibitors; Functional Laterality; Hippocampus; Injections, Intraventricular; Ischemic Attack, Transient; Male; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Oxygen; Phosphorylation; Phosphoserine; Protein Kinase Inhibitors; Rats; Rats, Sprague-Dawley; Reference Values; Reperfusion; Sulfonamides; Time Factors