Protein kinase C inhibition of cloned inward rectifier (HRK1/KIR2.3) K+ channels expressed in Xenopus oocytes.
1. The effect of protein kinase activators on cloned inward rectifier channels expressed in Xenopus oocytes was examined using a two-electrode voltage clamp. PKA activators caused no change in KIR1.1, KIR2.1, or KIR2.3 current. The PKC activators phorbol 12-myristate 14-acetate (PMA) and phorbol 12, 13-dibutyrate (PDBu) inhibited KIR2.3 currents, but not KIR2.1 or KIR1.1 current. This inhibition was blocked by staurosporine. An inactive phorbol ester, 4 alpha-phorbol 12, 13-didecanoate (4 alpha-PDD), had no effect on KIR2.3. 2. Upon changing solution from 2 to 98 microM K+, KIR2.3 but not KIR1.1 or KIR2.1 currents typically 'ran down' over 5 min to 60-80% of maximum amplitude. Rundown occurred even if PMA was applied before changing to high [K+] solution, indicating that rundown was independent of PKC activity. Rundown was evoked by substituting NMG+ for Na+, showing that it results from low [Na+] and not from high [K+]. 3. These results suggest that KIR2.3, but not KIR1.1 or KIR2.1, is subject to regulation, both by PKC activation and as a consequence of low [Na+]o. The difference in secondary regulation may account for specific responses to PKC stimulation of tissues expressing otherwise nearly identical KIR channels.
Henry
P
P
Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO 63110, USA.
Pearson
W L
WL
Nichols
C G
CG
D000818:Animals; D003001:Cloning, Molecular; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D008564:Membrane Potentials; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D019311:Staurosporine / Q000494:pharmacology; D014981:Xenopus
D004791:Enzyme Inhibitors; C099489:KCNJ4 protein, human; D010703:Phorbol Esters; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D012964:Sodium; D011493:Protein Kinase C; D019311:Staurosporine; D011188:Potassium