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Originally published as MBC in Press, 10.1091/mbc.E08-10-0999 on December 24, 2008

Vol. 20, Issue 4, 1132-1140, February 15, 2009

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A Link between FXYD3 (Mat-8)-mediated Na,K-ATPase Regulation and Differentiation of Caco-2 Intestinal Epithelial Cells

Stéphanie Bibert, David Aebischer, Florian Desgranges, Sophie Roy, Danièle Schaer, Solange Kharoubi-Hess, Jean-Daniel Horisberger, and Käthi Geering

Department of Pharmacology, University of Lausanne, 1005 Lausanne, Switzerland

Submitted October 7, 2008; Revised December 5, 2008; Accepted December 8, 2008
Monitoring Editor: Keith E. Mostov

FXYD3 (Mat-8) proteins are regulators of Na,K-ATPase. In normal tissue, FXYD3 is mainly expressed in stomach and colon, but it is also overexpressed in cancer cells, suggesting a role in tumorogenesis. We show that FXYD3 silencing has no effect on cell proliferation but promotes cell apoptosis and prevents cell differentiation of human colon adenocarcinoma cells (Caco-2), which is reflected by a reduction in alkaline phosphatase and villin expression, a change in several other differentiation markers, and a decrease in transepithelial resistance. Inhibition of cell differentiation in FXYD3-deficient cells is accompanied by an increase in the apparent Na+ and K+ affinities of Na,K-ATPase, reflecting the absence of Na,K-pump regulation by FXYD3. In addition, we observe a decrease in the maximal Na,K-ATPase activity due to a decrease in its turnover number, which correlates with a change in Na,K-ATPase isozyme expression that is characteristic of cancer cells. Overall, our results suggest an important role of FXYD3 in cell differentiation of Caco-2 cells. One possibility is that FXYD3 silencing prevents proper regulation of Na,K-ATPase, which leads to perturbation of cellular Na+ and K+ homeostasis and changes in the expression of Na,K-ATPase isozymes, whose functional properties are incompatible with Caco-2 cell differentiation.

This was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E08-10-0999) on December 24, 2008.

Address correspondence to: Käthi Geering (Kaethi.Geering{at}unil.ch).






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