The effect of rapamycin on single ENaC channel activity and phosphorylation in A6 cells.
Rapamycin and FK-506 are immunosuppressive drugs that bind a ubiquitous immunophilin, FKBP12, but immunosuppressive mechanisms and side effects appear to be different. Rapamycin binds renal FKBP12 to change renal transport. We used cell-attached patch clamp to examine rapamycin's effect on Na(+) channels in A6 cells. Channel NP(o) was 0.5 +/- 0.08 (n = 6) during the first 5 min but fell close to zero after 20 min. Application of 1 microM rapamycin reactivated Na(+) channels (NP(o) = 0.47 +/- 0.1; n=6), but 1 microM FK-506 did not. Also, GF-109203X, a protein kinase C (PKC) inhibitor, mimicked the rapamycin-induced reactivation in a nonadditive manner. However, rapamycin did not reactivate Na(+) channels if cells were exposed to 1 microM FK-506 before rapamycin. In PKC assays, rapamycin was as effective as the PKC inhibitor; however, epithelial Na(+) channel (ENaC) phosphorylation was low under baseline conditions and was not altered by PKC inhibitors or activators. These results suggest that rapamycin activates Na(+) channels by binding FKBP12 and inhibiting PKC, and, in renal cells, despite binding the same immunophilin, rapamycin and FK-506 activate different intracellular signaling pathways.
Yue
G
G
Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Edinger
R S
RS
Bao
H F
HF
Johnson
J P
JP
Eaton
D C
DC
D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053503:Epithelial Sodium Channels; D020104:Immunophilins / Q000235:genetics; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D020123:Sirolimus / Q000494:pharmacology*; D015222:Sodium Channels / Q000187:drug effects* / Q000378:metabolism* / Q000502:physiology; D016559:Tacrolimus / Q000494:pharmacology; D022021:Tacrolimus Binding Proteins; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D004791:Enzyme Inhibitors; D053503:Epithelial Sodium Channels; D007166:Immunosuppressive Agents; D007211:Indoles; D008301:Maleimides; D015222:Sodium Channels; D011493:Protein Kinase C; D022021:Tacrolimus Binding Proteins; D020104:Immunophilins; C070515:bisindolylmaleimide I; D013755:Tetradecanoylphorbol Acetate; D020123:Sirolimus; D016559:Tacrolimus