Modulation by protein kinase C activation of rat brain delayed-rectifier K+ channel expressed in Xenopus oocytes.
The modulation by protein kinase C (PKC) of the RCK1 K+ channel was investigated in Xenopus oocytes by integration of two-electrode voltage clamp, site-directed mutagenesis and SDS-PAGE analysis techniques. Upon application of beta-phorbol 12-myristate 13-acetate (PMA) the current was inhibited by 50-90%. No changes in the voltage sensitivity of the channel, changes in membrane surface area or selective elimination of RCK1 protein from the plasma membrane could be detected. The inhibition was mimicked by 1-oleoyl-2-acetyl-rac-glycerol (OAG) but not by alphaPMA, and was blocked by staurosporine and calphostin C. Upon deletion of most of the N-terminus a preceding enhancement of about 40% of the current was prominent in response to PKC activation. Its physiological significance is discussed. The N-terminus deletion eliminated 50% of the inhibition. However, phosphorylation of none of the ten classical PKC phosphorylation sites on the channel molecule could account, by itself or in combination with others, for the inhibition. Thus, our results show that PKC activation can modulate the channel conductance in a bimodal fashion. The N-terminus is involved in the inhibition, however, not via its direct phosphorylation.
Peretz
T
T
Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Ramat Aviv, Israel.
Levin
G
G
Moran
O
O
Thornhill
W B
WB
Chikvashvili
D
D
Lotan
I
I
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D017931:DNA Primers; D004075:Diglycerides / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008961:Models, Structural; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009281:Naphthalenes / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism*; D017433:Protein Structure, Secondary; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013997:Time Factors; D014982:Xenopus laevis
D000470:Alkaloids; D017931:DNA Primers; D004075:Diglycerides; D004791:Enzyme Inhibitors; D009281:Naphthalenes; D015221:Potassium Channels; D011994:Recombinant Proteins; C038237:1-oleoyl-2-acetylglycerol; D011493:Protein Kinase C; D019311:Staurosporine; C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate