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J Biol Chem. 2007 Apr 6;282(14):10585-93. Epub 2007 Feb 12.

Identification of a pool of non-pumping Na/K-ATPase.

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1
Department of Physiology, Pharmacology, Metabolism, and Cardiovascular Sciences, University of Toledo Health Science Campus, Toledo, Ohio 43614, USA.

Abstract

Recent studies have ascribed many non-pumping functions to the Na/K-ATPase. Here, we present experimental evidence demonstrating that over half of the plasma membrane Na/K-ATPase in LLC-PK1 cells is performing cellular functions other than ion pumping. This "non-pumping" pool of Na/K-ATPase, like the pumping pump, binds ouabain. Depletion of either cholesterol or caveolin-1 moves some of the "non-pumping" Na/K-ATPase into the pumping pool. Graded knock-down of the alpha1 subunit of the Na/K-ATPase eventually results in loss of this "non-pumping" pool while preserving the pumping pool. Our prior studies indicate that a loss of the non-pumping pool is associated with a loss of receptor function as evidenced by the failure of ouabain administration to induce the activation of Src and/or ERK. Therefore, our new findings suggest that a substantial amount of surface-expressed Na/K-ATPase, at least in some types of cells, may function as non-canonical ouabain-binding receptors.

PMID:
17296611
DOI:
10.1074/jbc.M609181200
[Indexed for MEDLINE]
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