Phosphorylation Regulates an Inwardly Rectifying ATP-sensitive K + - Conductance in Proximal Tubule Cells of Frog Kidney

Phosphorylation Regulates an Inwardly Rectifying ATP-sensitive K + - Conductance in Proximal... K+ channels in the renal proximal tubule play an important role in salt reabsorption. Cells of the frog proximal tubule demonstrate an inwardly rectifying, ATP-sensitive K+ conductance that is inhibited by Ba2+, G Ba. In this paper we have investigated the importance of phosphorylation state on the activity of G Ba in whole-cell patches. In the absence of ATP, G Ba decreased over time; this fall in G Ba involved phosphorylation, as rundown was inhibited by alkaline phosphatase and was accelerated by the phosphatase inhibitor F−(10 mM). Activation of PKC using the phorbol ester PMA accelerated rundown via a mechanism that was dependent on phosphorylation. In contrast, the inactive phorbol ester PDC slowed rundown. Inclusion of the PKC inhibitor PKC-ps in the pipette inhibited rundown. These data indicate that PKC-mediated phosphorylation promotes channel rundown. Rundown was prevented by the inclusion of PIP-2 in the pipette. PIP-2 also abrogated the PMA-mediated increase in rundown, suggesting that regulation of G Ba by PIP-2 occurred downstream of PKC-mediated phosphorylation. G-protein activation inhibited G Ba, with initial currents markedly reduced in the presence of GTPγs. These properties are consistent with G Ba being a member of the ATP-sensitive K+ channel family. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Phosphorylation Regulates an Inwardly Rectifying ATP-sensitive K + - Conductance in Proximal Tubule Cells of Frog Kidney

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Publisher
Springer-Verlag
Copyright
Copyright © 2005 by Springer Science+Business Media, Inc.
Subject
Life Sciences; Human Physiology; Biochemistry, general
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-005-0811-2
Publisher site
See Article on Publisher Site

Abstract

K+ channels in the renal proximal tubule play an important role in salt reabsorption. Cells of the frog proximal tubule demonstrate an inwardly rectifying, ATP-sensitive K+ conductance that is inhibited by Ba2+, G Ba. In this paper we have investigated the importance of phosphorylation state on the activity of G Ba in whole-cell patches. In the absence of ATP, G Ba decreased over time; this fall in G Ba involved phosphorylation, as rundown was inhibited by alkaline phosphatase and was accelerated by the phosphatase inhibitor F−(10 mM). Activation of PKC using the phorbol ester PMA accelerated rundown via a mechanism that was dependent on phosphorylation. In contrast, the inactive phorbol ester PDC slowed rundown. Inclusion of the PKC inhibitor PKC-ps in the pipette inhibited rundown. These data indicate that PKC-mediated phosphorylation promotes channel rundown. Rundown was prevented by the inclusion of PIP-2 in the pipette. PIP-2 also abrogated the PMA-mediated increase in rundown, suggesting that regulation of G Ba by PIP-2 occurred downstream of PKC-mediated phosphorylation. G-protein activation inhibited G Ba, with initial currents markedly reduced in the presence of GTPγs. These properties are consistent with G Ba being a member of the ATP-sensitive K+ channel family.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Jan 1, 2005

References

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