title: A link between FXYD3 (Mat-8)-mediated Na,K-ATPase regulation and differentiation of Caco-2 intestinal epithelial cells.
abstract: 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.
authors.affiliation: Department of Pharmacology, University of Lausanne, 1005 Lausanne, Switzerland.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Bibert
authors.forename: David
authors.initials: D
authors.lastname: Aebischer
authors.forename: Florian
authors.initials: F
authors.lastname: Desgranges
authors.forename: Sophie
authors.initials: S
authors.lastname: Roy
authors.forename: Danièle
authors.initials: D
authors.lastname: Schaer
authors.forename: Solange
authors.initials: S
authors.lastname: Kharoubi-Hess
authors.forename: Jean-Daniel
authors.initials: JD
authors.lastname: Horisberger
authors.forename: Käthi
authors.initials: K
authors.lastname: Geering
mesh_terms: D017209:Apoptosis; D018938:Caco-2 Cells; D002454:Cell Differentiation; D049109:Cell Proliferation; D015536:Down-Regulation; D004847:Epithelial Cells / Q000166:cytology* / Q000201:enzymology*; D020868:Gene Silencing; D006801:Humans; D007422:Intestines / Q000166:cytology*; D007527:Isoenzymes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: C091777:FXYD3 protein, human; D007527:Isoenzymes; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium