Ca/calmodulin-dependent kinase II inhibitor KN62 attenuates glutamate release by inhibiting voltage-dependent Ca(2+)-channels.
The effect of KN62 (1-[N,O-bis(5-isoquinolinesulphonyl)-N -methyl-L-tyrosyl]-4-phenylpiperazine), a putative inhibitor of Ca/calmodulin-dependent kinase II (Ca/CaM-K II), on glutamate release from isolated nerve-terminals (synaptosomes) was examined. The drug caused a potent inhibition of KCl- and 4-aminopyridine-evoked glutamate release from isolated nerve-terminals (synaptosomes). Examination of the effect of the inhibitor on Ca(2+)-influx revealed that the diminution of glutamate release could be attributed to a decrease in cytosolic Ca. A direct effect of KN62 on synaptosomal Ca(2+)-channels was confirmed in experiments where Ba, which does not support CaM-dependent processes, was used in place of Ca. Additionally, whole-cell patch-clamping of cerebellar granule neurones directly demonstrated inhibition of Ca-currents by KN62. We therefore suggest that, in cellular systems, conclusions based on the use of KN62 as a Ca/CaM-K II blocker may be ambiguous and should be viewed with caution unless the effect of the drug on Ca-influx has also been quantified. The effect of KN62 on Ca(2+)-influx appears to be specific to slowly-or non-inactivating conductances, and therefore presents KN62 as a potentially useful tool in this context.
Sihra
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TS
Department of Pharmacology, Royal Free Hospital School of Medicine, University of London, U.K.
Pearson
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HA
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects*; D002147:Calmodulin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D018698:Glutamic Acid / Q000378:metabolism*; D007546:Isoquinolines / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D011494:Protein Kinases / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000378:metabolism; D013997:Time Factors
D015220:Calcium Channels; D002147:Calmodulin; D004791:Enzyme Inhibitors; D007546:Isoquinolines; D010879:Piperazines; D018698:Glutamic Acid; C063302:KN 62; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011494:Protein Kinases; D002118:Calcium