Calcineurin phosphatase activity: activation by glucocorticoids and role of intracellular calcium1
- 1 January 2004
- journal article
- immunobiology
- Published by Wolters Kluwer Health in Transplantation
- Vol. 77 (2) , 259-267
- https://doi.org/10.1097/01.tp.0000099267.05131.11
Abstract
Background. Glucocorticoids stimulate release of intracellular calcium in peripheral lymphocytes, but their effects on calcineurin phosphatase activity are unknown. Methods. Calcineurin phosphatase activity was measured in permeabilized Jurkat T cells using a specific orthophosphate substrate. Changes in intracellular calcium were measured by FURA-2 fluorescence. Inositol triphosphate levels were measured by radioimmunoassay. Transfection with luciferase reporter plasmids linked to glucocorticoid response elements were used to evaluate glucocorticoid receptor function in Jurkat T cells. Results. Dexamethasone significantly (P P 3) and intracellular calcium within 15 sec. Cells incubated with U-73122 (a nonspecific phospholipase C [PLC] antagonist) completely blocked dexamethasone-induced activation of calcineurin, whereas U-73343 failed to block enzyme activation. Dexamethasone-induced activation of calcineurin activity stimulates dephosphorylation of the proapoptotic protein BAD and augments apoptosis through a calcineurin-dependent pathway. Conclusion. Dexamethasone rapidly increases calcineurin activity through a transcription-independent mechanism involving activation of phospholipase C and the release of IP3-dependent calcium stores.Keywords
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