Effect of FK506 on ATP-induced intracellular calcium oscillations in cow tracheal epithelium.
To elucidate the effect of FK506 on Ca2+ oscillations in airway epithelium, we investigated cultured cow tracheal epithelial cells with a Ca2+ image-analysis system. ATP (1 microM) induced long-lasting Ca2+ oscillations, having nearly constant peak values (300-400 nM) and intervals (20-40 s) in subconfluent cells but not in confluent cells. These responses were gradually attenuated and abolished by the addition of FK506. Rapamycin, which binds the FK506-binding protein (FKBP), likewise inhibited Ca2+ oscillations, whereas cyclosporin A, a calcineurin inhibitor, did not. Treatment of cells with FK506 decreased Ca2+ content in thapsigargin-sensitive stores, suggesting that the partial depletion of the stores causes the inhibition of Ca2+ oscillations. Immunocytochemistry revealed the existence of cytoplasmic FKBP-like immunoreactivities. The expression of a 12-kDa FKBP was greater in subconfluent cells than in confluent cells as determined by Western blotting, suggesting that the 12-kDa FKBP may be one of the factors that regulates Ca2+ oscillations. Therefore, FK506 possesses an inhibitory action on the Ca2+ response via intracellular FKBP but not via calcineurin, which may result in modification of airway epithelial functions.
Kanoh
S
S
Third Department of Medicine, National Defense Medical College, Saitama 359, Tokyo Women's Medical College, Tokyo 162, Japan.
Kondo
M
M
Tamaoki
J
J
Shirakawa
H
H
Aoshiba
K
K
Miyazaki
S
S
Kobayashi
H
H
Nagata
N
N
Nagai
A
A
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005260:Female; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000378:metabolism*; D009991:Oscillometry; D016559:Tacrolimus / Q000494:pharmacology*; D019284:Thapsigargin / Q000494:pharmacology; D014132:Trachea / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D004791:Enzyme Inhibitors; D007166:Immunosuppressive Agents; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D002118:Calcium; D016559:Tacrolimus