Direct evidence that FK506 inhibition of FcεRI-mediated exocytosis from RBL mast cells involves calcineurin

被引:0
作者
T. Hultsch
P. Brand
S. Lohmann
J. Saloga
R. L. Kincaid
J. Knop
机构
[1] Department of Dermatology,
[2] University of Mainz,undefined
[3] Langenbeckstrasse 1,undefined
[4] D-55101 Mainz,undefined
[5] Germany e-mail HULTSCH@goofy.ZDV.UNI-MAINZ.DE Fax +49-6131-176614,undefined
[6] Veritas Inc.,undefined
[7] 679 Southlawn Lane,undefined
[8] Rockville,undefined
[9] MD 20850,undefined
[10] USA,undefined
来源
Archives of Dermatological Research | 1998年 / 290卷
关键词
Key words Mast cells; FK506; Signalling; Exocytosis; FcɛRI;
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摘要
εRI-mediated exocytosis of preformed mediators from mast cells and basophils (e.g. histamine, serotonin, beta-hexosaminidase) is sensitive to the immunosuppressants cyclosporin A and FK506 (IC50 200 and 4 nM, respectively) but not rapamycin. The mechanism of inhibition does not appear to involve tyrosine phosphorylation, hydrolysis of inositol phosphates or calcium flux. Here we report experiments using a molecular approach to assess the role of calcineurin, a serine/threonine phosphatase thought to be the primary pharmacological target of these drugs. Calcineurin’s activity requires association of its catalytic (A) subunit with an intrinsic regulatory (B) subunit. We hypothesized that calcineurin-sensitive signalling events should be affected by the depletion of calcineurin B subunits, thereby reducing the number of active A:B complexes. We therefore transfected rat basophilic leukemia (RBL) cells with an inhibitory (dominant negative) form of the calcineurin A subunit, which binds the calcineurin B subunit with high affinity but does not possess catalytic activity (B subunit knock-out, BKO). In these transfected cells, the dose-response curve for the inhibition of FcεRI-mediated exocytosis by FK506 was shifted to the left, indicating an increased drug sensitivity of BKO-transfected cells. We conclude that FK506 inhibition of FcεRI-mediated exocytosis in mast cells specifically targets calcineurin activity.
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页码:258 / 263
页数:5
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