Protein kinase C and the regulation of glutamate exocytosis from cerebrocortical synaptosomes.
The role of protein kinase C (PKC) in the regulation of transmitter glutamate release from rat cerebral cortical synaptosomes is investigated. Two depolarization protocols are used: first, elevated KCl, which produces a clamped depolarization, and second, 4-aminopyridine, which evokes spontaneous "action potentials" allowing any potential modulation of Na+ or K+ channels to influence release. Although the PKC inhibitor Ro 31-8220 prevents both the depolarization-evoked and phorbol dibutyrate (PDBu)-evoked phosphorylation of the major presynaptic PKC substrate, myristoylated alanine-rich C kinase substrate, it is without effect on KCl-evoked Ca(2+)-dependent glutamate release. Ro 31-8220 totally inhibits the Ca(2+)-dependent 4-aminopyridine-evoked release of glutamate in the presence and absence of PDBu and again decreases the phosphorylation of myristoylated alanine-rich C kinase substrate. Ro 31-8220 strongly inhibits the 4-aminopyridine-evoked increase in [Ca2+] both in the presence and absence of PDBu and antagonizes the PDBu enhancement of depolarization. This indicates that PKC isoforms activatable by PDBu and sensitive to Ro 31-8220 play no discernable role in Ca(2+)-secretion coupling per se in cerebral cortical glutamatergic nerve terminals, but that the kinase plays a major role in regulating the depolarization of the terminal.
Coffey
E T
ET
Department of Biochemistry, University of Dundee, Scotland, United Kingdom.
Sihra
T S
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Nicholls
D G
DG
D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005089:Exocytosis; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D007211:Indoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008564:Membrane Potentials; D008565:Membrane Proteins; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010766:Phosphorylation; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
D005971:Glutamates; D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D015221:Potassium Channels; D011506:Proteins; D015222:Sodium Channels; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D015240:Phorbol 12,13-Dibutyrate; D018698:Glutamic Acid; D011189:Potassium Chloride; D015761:4-Aminopyridine; D011493:Protein Kinase C; D002118:Calcium; C064758:Ro 31-8220