Transient translocation of protein kinase Cgamma in hippocampal long-term potentiation depends on activation of metabotropic glutamate receptors

• Published in: Neuroscience Vol. 93; no. 4; pp. 1289 - 1295
• Main Authors: Angenstein, F, Riedel, G, Reyman, K G, Staak, S
• Format: Journal Article
• Language: English
• Published: United States 1999
• Subjects: Animals; Benzoates - pharmacology; Dentate Gyrus - chemistry; Dentate Gyrus - enzymology; Electric Stimulation; Excitatory Amino Acid Antagonists - pharmacology; Glycine - analogs & derivatives; Glycine - pharmacology; Isoenzymes - metabolism; Long-Term Potentiation - physiology; Male; Protein Kinase C - metabolism; Protein Kinase C beta; Protein Kinase C-alpha; Rats; Rats, Wistar; Receptors, Metabotropic Glutamate - antagonists & inhibitors; Receptors, Metabotropic Glutamate - physiology; Subcellular Fractions - enzymology
• ISSN: 0306-4522

Protein kinase C has been implicated in long-term regulation of cellular functions including induction and maintenance of hippocampal long-term potentiation. In the present study the time-course of long-term potentiation-induced translocation of Ca(2+)-dependent protein kinase C isoenzymes (PKCalpha/beta and PKCgamma) was investigated. Quantitative immunoblot analysis was used to measure translocation of these isoenzymes between cytosolic, membrane-associated and membrane-inserted fraction at 5, 15 and 60 min after induction of long-term potentiation in the dentate gyrus in vivo. To investigate the involvement of metabotropic glutamate receptors in protein kinase C regulation during long-term potentiation induction, additional animals were treated before tetanization with (R,S)-alpha-methyl-4-carboxyphenylglycine, an antagonist of metabotropic glutamate receptors. Brief tetanic stimulation of the perforant path resulted in a 100-150% increase in the population spike amplitude in response to test stimuli 5, 15 or 60 min after stimulation in both untreated and (R,S)-alpha-methyl-4-carboxyphenylglycine-treated animals. Only those rats showing clear potentiation were selected for further biochemical analysis of the potentiated dentate gyrus. Five minutes after high-frequency stimulation the subcellular distribution of all studied protein kinase C isoenzymes was unchanged compared with controls. PKC-gamma translocated into the cytosol 15 min after tetanization and this redistribution was blocked by (R,S)-alpha-methyl-4-carboxyphenylgly-cine pretreatment. By contrast, PKC alpha/beta levels increased in the cytosolic fraction only 60 min after tetanization, but in a (R,S)-alpha-methyl-4-carboxyphenylglycine-independent manner. In an additional set of experiments it was shown that (R,S)-alpha-methyl-4-carboxyphenylglycine alone applied intraventricularly had no effect on the subcellular distribution of the studied isoenzymes. The data suggest that PKCalpha/beta and PKCgamma are activated during different post-tetanic phases and metabotropic glutamate receptor activation might be essential for tetanus-induced translocation of postsynaptic PKCgamma only.