Effect of brain ischemia on protein kinase C.
We examined the influence of brain ischemia on the activity and subcellular distribution of protein kinase C (PKC). Two different models of ischemic brain injury were used: postdecapitative ischemia in rat forebrain and transient (6-min) cerebral ischemia in gerbil hippocampus. In the rat forebrain model, at 5 and 15 min postdecapitation there was a steady decrease of total PKC activity to 60% of control values. This decrease occurred without changes in the proportion of the particulate to the soluble enzyme pools. Isolated rat brain membranes also exhibited a concomitant decrease of [3H]phorbol 12,13-dibutyrate ([3H]PDBu) binding with an apparent increase of the ligand affinity to the postischemic membranes. On the other hand, the ischemic gerbil hippocampus model displayed a 40% decrease of total PKC activity, which was accompanied by a relative increase of PKC activity in its membrane-bound form. This resulted in an increase in the membrane/total activity ratio, indicating a possible enzyme translocation from cytosol to the membranes after ischemia. Moreover, after 1 day of recovery, a statistically significant enhancement of membrane-bound PKC activity resulted in a further increase of its relative activity up to 162% of control values. In vitro experiments using a synaptoneurosomal particulate fraction were performed to clarify the mechanism of the rapid PKC inhibition observed in cerebral tissue after ischemia. These experiments showed a progressive, Ca(2+)-dependent, antiprotease-insensitive down-regulation of PKC during incubation. This down-regulation was significantly enhanced by prior phorbol (PDBu) treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Domańska-Janik
K
K
Department of Neurochemistry, Polish Academy of Sciences, Warsaw.
Zalewska
T
T
D000818:Animals; D001921:Brain / Q000201:enzymology; D002545:Brain Ischemia / Q000201:enzymology*; D002118:Calcium / Q000494:pharmacology; D003655:Decerebrate State; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005849:Gerbillinae; D008297:Male; D015240:Phorbol 12,13-Dibutyrate / Q000378:metabolism; D010766:Phosphorylation; D011480:Protease Inhibitors / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000201:enzymology
D011480:Protease Inhibitors; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; D002118:Calcium