HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 93/6/3146    most recent 00865.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Denson, D. D. Articles by Eaton, D. C. Search for Related Content PubMed PubMed Citation Articles by Denson, D. D. Articles by Eaton, D. C.

Activation of BK Channels in GH3 Cells by a c-PLA₂-Dependent G-Protein Signaling Pathway

¹Departments of Anesthesiology and ²Physiology and ³The Center for Cellular and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia

Submitted 23 August 2004; accepted in final form 10 January 2005

BK-channels in GH3 cells are activated by arachidonic acid produced by c-PLA₂. -adrenergic agonists also activate BK channels and were presumed to do so via production of cAMP. We, however, show for the first time in GH3 cells that a -adrenergic agonist activates a pertussis-toxin-sensitive G protein that activates c-PLA₂. The arachidonic acid produced by c-PLA₂ then activates BK channels. We examined BK channels in cell-attached patches and in excised patches from untreated GH3 cells and from GH3 cells exposed to c-PLA₂ antisense oligonucleotides. For the cell-attached patch experiments, physiologic pipette and bath solutions were used. For the excised patches, 150 mM KCl was used in both the pipette and bath solutions, and the cytosolic surface contained 1 µM free Ca²⁺ (buffered with 5 mM K₂EGTA). Treatment of GH3 cells with the G protein activator, fluoroaluminate, (AlF₄^–) produced an increase in the P_o of BK channels of 177 ± 41% (mean ± SD) in cell-attached patches. Because G proteins are membrane associated, we also added an activator of G proteins, 100 µM GTP--S, to the cytosolic surface of excised patches. This treatment leads to an increase in P_o of 50 ± 9%. Similar treatment of excised patches with GDP--S had no effect on P_o. Isoproterenol (1 µM), an activator of -adrenergic receptors and, consequently, some G proteins, increased BK channel activity 229 ± 37% in cell-attached patches from cultured GH3 cells. Western blot analysis showed that GH3 cells have -adrenergic receptor protein and that isoproterenol acts through these receptors because the -adrenergic receptor antagonist, propanolol, blocks the action of isoproterenol. To test whether G protein activation of BK channels involves c-PLA₂, we studied the effects of GTP--S on excised patches and isoproterenol on cell attached patches from GH3 cells previously treated with c-PLA₂ antisense oligonucleotides or pharmacological inhibitors of c-PLA₂. Neither isoproterenol nor GTP--S had any effect on P_o in these patches. Similarly, neither isoproterenol nor GTP--S had any effect on P_o in cultured GH3 cells pretreated with pertussis toxin. Isoproterenol also significantly increased the rate of arachidonic production in GH3 cells. These results show that some receptor-linked, pertussis-toxin-sensitive G protein in GH3 cells can activate c-PLA₂ to increase the amount of arachidonic acid present and ultimately increase BK-channel activity.

This article has been cited by other articles:

				A. Roch, V. Shlyonsky, A. Goolaerts, F. Mies, and S. Sariban-Sohraby Halothane Directly Modifies Na+ and K+ Channel Activities in Cultured Human Alveolar Epithelial Cells Mol. Pharmacol., May 1, 2006; 69(5): 1755 - 1762. [Abstract] [Full Text] [PDF]