Protein kinase M zeta regulation of Na/K ATPase: a persistent neuroprotective mechanism of ischemic preconditioning in hippocampal slice cultures.
In ischemic preconditioning, a sublethal ischemic insult protects neurons from subsequent ischemia. In organotypic hippocampal slice cultures a sublethal 5-minute hypoxia-hypoglycemia treatment prevented neuronal loss after a 10-minute experimental ischemic (EI) treatment of hypoxia-hypoglycemia. Whereas preconditioning protected against EI given 24 h later, it did not protect when EI was given 2 h later, suggesting a slow development of neuroprotection. This model identified two regulators of ischemic preconditioning: the atypical protein kinase M zeta (PKMzeta), and the Na/K ATPase. Two hours following preconditioning, when there was no neuroprotection, Na/K ATPase activity was unchanged. In contrast, Na/K ATPase activity significantly increased 24 h after the preconditioning treatment. Elevated Na/K ATPase activity was accompanied by increased surface expression of the alpha1 and alpha2 isoforms of the Na/K ATPase. Similarly, active PKMzeta levels were increased at 24 h, but not 2 h, after preconditioning. PKMzeta overexpression by sindbis virus vectors also increased Na/K ATPase activity. To examine PKMzeta regulation of Na/K ATPase, occlusion experiments were performed using marinobufagenin to inhibit alpha1, dihydroouabain to inhibit alpha2/3 and a zeta-pseudosubstrate peptide to inhibit PKMzeta. These experiments showed that PKMzeta regulated both the activity and surface expression of the alpha1 isoform of the Na/K ATPase. Marinobufagenin, dihydroouabain, and zeta-pseudosubstrate peptide were used to determine if PKMzeta or the alpha1 and alpha2 Na/K ATPase isoforms protected neurons. All three compounds blocked neuroprotection following ischemic preconditioning. PKMzeta levels were elevated 3 days after ischemic preconditioning. These data indicate key roles of PKMzeta and Na/K ATPase in ischemic preconditioning.
Tian
Dezhi
D
Program in Neural and Behavioral Science, The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York-Downstate Medical Center, Brooklyn, NY 11203, USA.
Dmitrieva
Renata I
RI
Doris
Peter A
PA
Crary
John F
JF
Sondhi
Rachna
R
Sacktor
Todd C
TC
Bergold
Peter J
PJ
D000818:Animals; D000831:Animals, Newborn; D019921:Biotinylation; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000502:physiology; D006624:Hippocampus / Q000378:metabolism*; D007003:Hypoglycemia / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D000860:Hypoxia / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D047468:Immunoprecipitation; D019194:Ischemic Preconditioning / Q000379:methods*; D011189:Potassium Chloride / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013997:Time Factors; D046509:Tissue Culture Techniques
D011189:Potassium Chloride; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase