Modulation of calcium-mediated inactivation of ionic currents by Ca2+/calmodulin-dependent protein kinase II.
Iontophoretic injection of Ca2+ causes reduction of I0A (an early rapidly activating and inactivating K+ current) and I0C (a late Ca2+-dependent K+ current) measured across the isolated type B soma membrane (Alkon et al., 1984, 1985; Alkon and Sakakibara, 1984, 1985). Similarly, voltage-clamp conditions which cause elevation of [Ca2+]i are followed by reduction of I0A and I0C lasting 1-3 min. Iontophoretic injection of highly purified Ca2+/CaM-dependent protein kinase II (CaM kinase II) isolated from brain tissue (Goldenring et al., 1983) enhanced and prolonged this Ca2+-mediated reduction of I0A and I0C. ICa2+, a voltage-dependent Ca2+ current, also showed some persistent reduction under these conditions. Iontophoretic injection of heat-inactivated enzyme had no effect. Agents that inhibit or block Ca2+/CaM-dependent phosphorylation produced increased I0A and I0C amplitudes and prevented the effects of CaM kinase II injection. The results reported here and in other studies implicate Ca2+-stimulated phosphorylation in the regulation of type B soma ionic currents.
D000818:Animals; D001921:Brain / Q000201:enzymology; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D004947:Esophagus / Q000294:innervation; D005399:Fishes; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008027:Light; D008564:Membrane Potentials; D010786:Photoreceptor Cells / Q000502:physiology; D011188:Potassium / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*
D007473:Ion Channels; D011494:Protein Kinases; D011188:Potassium; D002118:Calcium