Reduced protein kinase C activity in ischemic spinal cord.
Protein phosphorylation was evaluated in a rabbit spinal cord ischemia model under conditions where cyclic AMP-dependent protein kinase (PK-A) and calcium/phospholipid-dependent protein kinase (PK-C) were activated. One hour of ischemia did not affect PK-A activity significantly; however, PK-C activity was reduced by more than 60%. In vitro phosphorylation of endogenous proteins by endogenous PK-C revealed that eight particulate and five cytosolic proteins showed stimulated phosphorylation by PK-C activators in control tissue, although this stimulation was virtually absent in ischemic samples. When control and ischemic particulate fractions were combined, the endogenous protein phosphorylation pattern under PK-C-activating conditions was similar to the ischemic sample, which suggests that inhibitory molecules may be present in the ischemic particulate fraction. In vitro phosphorylation of endogenous proteins under PK-A-activating conditions in ischemic tissue was similar to that in control tissue. The results suggest that the PK-C phosphorylation system is selectively impaired in ischemic spinal cord. In addition to reduced PK-C-dependent phosphorylation, an Mr 64,000 protein was phosphorylated in ischemic cytosolic samples, but not in control samples. The phosphorylation of the Mr 64,000 protein was neither PK-C-dependent nor PK-A-dependent. These altered phosphorylation reactions may play critical roles in neuronal death during the course of ischemia.
Kochhar
A
A
Department of Neurosciences, School of Medicine, University of California--San Diego, La Jolla 92093.
Saitoh
T
T
Zivin
J
J
D000818:Animals; D000242:Cyclic AMP / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D007511:Ischemia / Q000201:enzymology*; D008297:Male; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010718:Phosphatidylserines / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism; D011817:Rabbits; D013116:Spinal Cord / Q000098:blood supply* / Q000201:enzymology / Q000648:ultrastructure; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D009419:Nerve Tissue Proteins; D010718:Phosphatidylserines; D010750:Phosphoproteins; D000242:Cyclic AMP; D011494:Protein Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate