Hippocampal long-term potentiation: transient increase but no persistent translocation of protein kinase C isoenzymes alpha and beta.
Using a monoclonal antibody the translocation of the Ca(2+)-dependent protein kinase C (PKC) isoenzymes alpha/beta was studied in hippocampal slices after stimulation of glutamate receptors or induction of long-term potentiation. In submerged slices preincubated for 60 min in a medium usually used in electrophysiological studies, cytosolic PKC was not detectable and the amount of membrane-associated enzyme was increased. The treatment of these slices with 10(-6) M phorbol-12,13-dibutyrate induced a time-dependent translocation of alpha/beta PKC from the membrane-associated into the membrane-inserted state. The glutamatergic agonists N-methyl-D-aspartate, quisqualate and trans-ACPD did not cause a membrane insertion of alpha/beta PKC as observed for the phorbol ester when applied alone or in combination. Furthermore, 2 min and 15 min after induction of LTP in the Schaffer collateral-CA1 pathway the distribution of alpha/beta PKC between the two membrane fractions remained unchanged. An increase in the total amount of PKC immunoreactivity was measured immediately after tetanization (142.6% of controls). The data suggest that a membrane insertion of alpha/beta PKC is not a prerequisite for the LTP-induced increased phosphorylation of PKC substrates and that the enzyme might be recruited from a previously inactive pool.
Staak
S
S
Federal Institute for Neurobiology, Laboratory for Cellular Signalling, Magdeburg, Germany.
Behnisch
T
T
Angenstein
F
F
D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000502:physiology; D004558:Electric Stimulation; D004591:Electrophoresis, Polyacrylamide Gel; D006624:Hippocampus / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000378:metabolism*; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D017470:Receptors, Glutamate / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology; D013569:Synapses / Q000502:physiology
D007527:Isoenzymes; D017470:Receptors, Glutamate; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; D002118:Calcium