AJP - Cell Physiology, Vol 263, Issue 1 C172-C175, Copyright © 1992 by American Physiological Society
Regulation of an epithelial chloride channel by direct phosphorylation and dephosphorylation
A. L. Finn, M. L. Gaido, M. Dillard and D. L. Brautigan
Department of Medicine, University of North Carolina, Chapel Hill 27599.
A native chloride channel in Necturus gallbladder epithelial cells is
opened by a theophylline-induced rise in cellular cyclic AMP and is closed
by removal of theophylline or by addition of specific antibody; however, it
does not close if okadaic acid, an inhibitor of protein phosphatases 1 and
2A, is added. The purified channel reconstituted into lipid bilayers closes
upon the addition of protein phosphatase 2A and is reopened by the addition
of Mg-ATP and the catalytic subunit of cyclic AMP-dependent protein kinase.
These results indicate that the channel protein is purified in a
phosphorylated state and that its functional characteristics are at least
partly controlled by direct phosphorylation and dephosphorylation.
