Constitutive activity of inwardly rectifying K+ channel at physiological [Ca]i is mediated by Ca2+/CaMK II pathway in opossum kidney proximal tubule cells.
Using patch-clamp technique, we studied the role of the Ca2+/calmodulin kinase II (CaMK II)-mediated phosphorylation process on the K+ channel with an inward conductance of 90 pS in opossum kidney proximal tubule cells (OKPCs). The intracellular Ca2+ concentration ([Ca]i) was measured by use of the fluorescent dye fura 2. The following results were obtained: (i) In cell-attached patches, the channel activity was inhibited by a decrease in [Ca]i induced by perfusion with low Ca2+ (10(-8) M), La3+ (100 microM), or EGTA/AM (100 microM) contained in the bath solution. The application of KN-62 (10 microM) or KN-93 (5 microM), inhibitors of CaMK II, also inhibited the channel activity. (ii) The membrane potential measured with nystatin-perforated patches was significantly decreased by the fall in [Ca]i induced by the perfusion with EGTA- or La(3+)-containing solution. Also, the application of KN-62 (10 microM) or KN-93 (5 microM) to the bath significantly decreased the membrane potential. (iii) In inside-out patches, the channel activity was significantly stimulated by the application of CaMK II (300 pM) at 10(-7) M Ca2+ in the bath. Furthermore, the application of KN-62 (10 microM) to the bath significantly decreased the channel activity. Our findings show that the constitutive activity of inwardly rectifying K+ channel at physiological [Ca]i is mediated by the Ca2+/CaMK II pathway in OKPCs.
Mori
Yoshiaki
Y
Department of Physiology, Osaka Medical College, Takatsuki, Osaka 569-8686, Japan.
Yoshida
Hideyo
H
Miyamoto
Manabu
M
Sohma
Yoshiro
Y
Kubota
Takahiro
T
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism; D002147:Calmodulin / Q000494:pharmacology; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009893:Opossums; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*
D002147:Calmodulin; D004791:Enzyme Inhibitors; D024661:Potassium Channels, Inwardly Rectifying; C063302:KN 62; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D002118:Calcium