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Paper Information

Title: 

MOLECULAR MECHANISM OF GLUCOCORTICOID ACTION ON ION CHANNELS

Type: SPEECH
Author(s): ATARZADEH YAZDI GH.*,SHIPSTON M.J.,ANTONI F.
 
 *VETERINARY BIOMEDICAL SCIENCE, EDINBURGH UNIVERSITY, SUMMERHALL, EH9 1QH, DIVISION OF NEUROSCIENCE, EDINBURGH UNIVERSITY, EH8 9JZ, MEMBRANE BIOLOGY GROUP, UNIVERSITY OF EDINBURGH MEDICAL SCHOOL, HUGH ROBSON BUILDING, EDINBURGH, EH8 9XD, UK
 
Name of Seminar: IRANIAN CONGRESS OF PHYSIOLOGY AND PHARMACOLOGY
Type of Seminar:  CONGRESS
Sponsor:  PHYSIOLOGY AND PHARMACOLOGY SOCIETY, MASHHAD UNIVERSITY OF MEDICAL SCIENCE
Date:  2007Volume 18
 
 
Abstract: 

Adrenal corteroids are involved in multiple aspects of homeostatic control. The early delayed (<2h) action of glucocorticoids is mediated by rapid induction of mRNA and protein synthesis. Within this time-frame, glucocorticoids potently modify the electrical excitability of target cells through regulation of ion channels. Increasing evidence suggests that in neurones and endocrine cells, large conductance calcium- and voltage-activated potassium channels (BK channels) are important targets for glucocorticoid action. The aim of this thesis project was to investigate the mechanisms by which glucocorticoid hormones regulate the activity of BK channels in human embryonic kidney 293 (HEK 293) cells as the model system for glucocorticoid-action. It was shown that glucocorticoids act via endogenously expressed type II receptors in a concentration- and time-dependent manner in these cells. The data also showed that dexamethasone (100nM) had no significant effect on Dexras1 mRNA but significantly increased serum- and glucocorticoid-induced protein kinase 1 (SGK-1) mRNA and protein. Immunoprecipitations of BK channel -subunits showed that protein phosphatase 2A (PP2A) but not SGK-1 is constitutively associated with the STREX as well as the ZERO variant BK channel. Dexamethasone failed to change the apparent amount of immunoreactive PP2A co-immunoprecipitating with the BK channel. Then the regulation of BK channels by glucocorticoid is likely to be due to changes in the enzymatic activity of the associated PP2A rather than the recruitment of more PP2A catalytic subunits to BK channels. Furthermore, the cytoplasmic C-terminal segment of the STREX-BK channel was necessary for cell-surface expression of the channel and the association of the channel with PP2A.

 
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