Regulatory roles of Ca2+/calmodulin-dependent protein kinase II and protein phosphatase 2A on the quisqualic acid-induced K+-current response in identified neurons of Aplysia.
In identified B6 neurons of Aplysia buccal ganglia under voltage-clamp, application of quisqualic acid (QA) induces a unique slow K(+)-current response independent of G-protein. The response was augmented by raising the temperature in a similar fashion to the Phe-Met-Arg-Phe-NH(2)-induced K(+)-current response mediated by Gi/o. The QA-induced K(+)-current response markedly increased during the perfusion with Ca(2+)-free solution or after the application of W-7, a calmodulin (CaM) inhibitor. It was also enhanced by intracellular application either of H-7, a serine/threonine protein kinase inhibitor, or of KN-93, a Ca(2+)/CaM-dependent kinase II (CaMKII) inhibitor. Furthermore, the QA-induced response was markedly augmented by pre-treatment with 2,3-butanedione monoxime, an inorganic phosphatase. Intracellular application of protein phosphatase 2A (PP2A) significantly augmented the QA-induced response although neither protein phosphatase 1 nor protein phosphatase 2B altered the response. Application of either okadaic acid or calyculin A, protein phosphatase inhibitors, only slightly depressed the QA-induced response. Surprisingly, W-7 had no augmenting effect on the QA-induced response when examined after the application of either okadaic acid or calyculin A. These results suggest that the K(+)-current response is reciprocally but sequentially regulated by PP2A and CaMKII, the response of which the former is facilitating and the latter is inhibiting.
Kimura
Shingo
S
Department of Physiology, School of Medicine, Iwate Medical University, Morioka 020-8505, Japan. skimura@iwate-med.ac.jp
Kawasaki
Satoshi
S
Watanabe
Shuji
S
Fujita
Reiko
R
Sasaki
Kazuhiko
K
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001048:Aplysia / Q000166:cytology / Q000378:metabolism*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009420:Nervous System / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000502:physiology*; D016318:Quisqualic Acid / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D015221:Potassium Channels; D016318:Quisqualic Acid; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D054648:Protein Phosphatase 2