Okadaic acid-sensitive activation of Maxi Cl(-) channels by triphenylethylene antioestrogens in C1300 mouse neuroblastoma cells.
1. The regulation of Maxi Cl(-) channels by 17beta-oestradiol and non-steroidal triphenylethylene antioestrogens represents a rapid, non-classical effect of these compounds. In the present study we have investigated the signalling pathways used for the regulation of Maxi Cl(-) channel activity by oestrogens and antioestrogens in C1300 neuroblastoma cells. 2. Whole-cell Maxi Cl(-) currents were readily and reversibly activated by tamoxifen, toremifene and the membrane-impermeant ethyl-bromide tamoxifen, only when applied to the extracellular medium. 3. Pre-treatment of C1300 cells with oestrogen or cAMP prevented the antioestrogen-induced activation of Maxi Cl(-) channels. The inhibitory effect of 17beta-oestradiol and cAMP was abolished by the kinase inhibitor staurosporine. 4. Current activation was unaffected by the removal of intracellular Ca(2+) and Mg(2+), but was completely abolished in the presence of okadaic acid. These results are consistent with the participation of an okadaic acid-sensitive serine/threonine protein phosphatase in the activation of Maxi Cl(-) channels. However, neither oestrogen or antioestrogen treatment modified the total activity of the two major serine/threonine phosphatases, PP1 and PP2A, in C1300 cells. 5. Although the role of these Maxi Cl(-) channels remains unknown, our findings suggest strongly that their modulation by oestrogens and antioestrogens is linked to intracellular signalling pathways.
Diaz
M
M
Departamento de Biología Animal, Universidad de la Laguna, Tenerife, Spain.
Bahamonde
M I
MI
Lock
H
H
Muñoz
F J
FJ
Hardy
S P
SP
Posas
F
F
Valverde
M A
MA
D000818:Animals; D002273:Carcinogens / Q000494:pharmacology*; D018118:Chloride Channels / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D051379:Mice; D009447:Neuroblastoma; D019319:Okadaic Acid / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D020845:Selective Estrogen Receptor Modulators / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D019311:Staurosporine / Q000494:pharmacology; D013267:Stilbenes / Q000494:pharmacology*; D013629:Tamoxifen / Q000494:pharmacology; D017312:Toremifene / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D002273:Carcinogens; D018118:Chloride Channels; D002712:Chlorides; D004791:Enzyme Inhibitors; D004965:Estrogen Antagonists; D020845:Selective Estrogen Receptor Modulators; D013267:Stilbenes; D013629:Tamoxifen; D019319:Okadaic Acid; D004958:Estradiol; D017312:Toremifene; D000242:Cyclic AMP; D010749:Phosphoprotein Phosphatases; D019311:Staurosporine; C037749:triphenylethylene