Up-regulation of cell surface sodium channels by cyclosporin A, FK506, and rapamycin in adrenal chromaffin cells.
Treatment of cultured bovine adrenal chromaffin cells with cyclosporin A (CsA) increased cell surface [(3)H]saxitoxin ([(3)H]STX) binding by 56% in a time (t(1/2) = 15.2 h)- and concentration (EC(50) = 2.9 microM)-dependent manner but did not change the K(d) value. In CsA-treated cells, veratridine-induced (22)Na(+) influx was augmented with no change in the EC(50) of veratridine; also, alpha- and beta-scorpion venom and Ptychodiscus brevis toxin-3 enhanced veratridine-induced (22)Na(+) influx in a more than additive manner, as in nontreated cells. CsA treatment for 1 to 24 h inhibited calcineurin activity, measured by the in vitro assay, with the IC(50) of 0.6 microM but did not alter cellular level of calcineurin. FK506 or rapamycin elevated [(3)H]STX binding by 36 or 25%, whereas GPI-1046, an immunophilin ligand incapable to inhibit calcineurin, or okadaic acid, an inhibitor of protein phosphatases 1 and 2A, had no increasing effect. The rise of [(3)H]STX binding by CsA was attenuated by the coincident treatment with brefeldin A (BFA), an inhibitor of vesicular exit from the trans-Golgi network. The internalization rate of cell surface Na(+) channels, as determined in the presence of BFA, was decreased in CsA (but not rapamycin)-treated cells (t(1/2) = 20.3 h), compared with nontreated cells (t(1/2) = 13.7 h). CsA treatment, however, did not elevate cellular levels of Na(+) channel alpha-subunit and Na(+) channel alpha- and beta(1)-subunit mRNAs. In CsA-treated cells, veratridine-induced (45)Ca(2+) influx via voltage-dependent Ca(2+) channels and catecholamine secretion were enhanced, whereas high K(+)-induced (45)Ca(+) influx was not. Thus, the inhibition of calcineurin or rapamycin-binding protein causes up-regulation of cell surface functional Na(+) channels via modulating externalization and internalization of Na(+) channels, thus enhancing Ca(2+) channel gating and catecholamine secretion.
Shiraishi
S
S
Department of Pharmacology, Miyazaki Medical College, Kiyotake, Miyazaki, Japan.
Yanagita
T
T
Kobayashi
H
H
Uezono
Y
Y
Yokoo
H
H
Minami
S I
SI
Takasaki
M
M
Wada
A
A
D000311:Adrenal Glands / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D015152:Blotting, Northern; D019703:Calcineurin / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects*; D016572:Cyclosporine / Q000494:pharmacology*; D015151:Immunoblotting; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D008387:Marine Toxins / Q000494:pharmacology; D009466:Neuromuscular Blocking Agents / Q000494:pharmacology; D035964:Oxocins; D012604:Scorpion Venoms / Q000494:pharmacology; D020123:Sirolimus / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000187:drug effects*; D016559:Tacrolimus / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects; D014701:Veratridine / Q000494:pharmacology; D000095702:Polyether Toxins
D019703:Calcineurin; D002118:Calcium; D002395:Catecholamines; D016572:Cyclosporine; D007166:Immunosuppressive Agents; D008387:Marine Toxins; D009466:Neuromuscular Blocking Agents; D035964:Oxocins; D012604:Scorpion Venoms; D020123:Sirolimus; D012964:Sodium; D015222:Sodium Channels; D016559:Tacrolimus; D014701:Veratridine; C041017:brevetoxin T17; D000095702:Polyether Toxins