Selective basolateral localization of overexpressed Na-K-ATPase beta1- and beta2- subunits is disrupted by butryate treatment of MDCK cells.
The exclusive basolateral localization of the Na-K-ATPase in kidney epithelium is a critical aspect of nephron function. It has been suggested that mislocalized delivery of the Na-K-ATPase to the apical surface in autosomal dominant polycystic kidney disease (ADPKD) is due to the inappropriate expression of an alternative isoform of the beta-subunit, the beta(2)-isoform. It has been reported that heterologous expression of this beta(2)-isoform in Madin-Darby canine kidney (MDCK) cells results in apical delivery of the Na-K-ATPase. We created a MDCK cell line containing a tetracycline-inducible promoter and expressed either myc-tagged beta(2)- or flag-tagged beta(1)-subunits to study the surface localization of these beta-subunit isoforms in polarized monolayers. We find that the beta(2)-isoform is targeted to the basolateral surface of the plasma membrane in a polarization pattern indistinguishable from the beta(1)-isoform. However, inclusion of butyrate in the growth medium leads to upregulation of overexpressed beta(1)- or beta(2)-subunits and to their appearance at the apical surface. The beta(2)-isoform expressed in MDCK cells does not assemble into alpha(1)beta(2) heterodimers with the endogenous alpha(1). Our findings demonstrate that expression of the beta(2)-isoform does not lead to apical localization of the Na-K-ATPase in MDCK cells and provides evidence for an unexpected effect of butyrate on the trafficking of Na pump subunits.
Laughery
Melissa D
MD
Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago 60607-7170, USA.
Clifford
Rebecca J
RJ
Chi
Yiqing
Y
Kaplan
Jack H
JH
D000818:Animals; D001710:Biotin / Q000378:metabolism; D015153:Blotting, Western; D002087:Butyrates / Q000494:pharmacology*; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D004285:Dogs; D016259:Genes, myc / Q000187:drug effects; D047468:Immunoprecipitation; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D007668:Kidney / Q000201:enzymology*; D018613:Microscopy, Confocal; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D013752:Tetracycline / Q000494:pharmacology
D002087:Butyrates; D007527:Isoenzymes; D011500:Protein Synthesis Inhibitors; D001710:Biotin; D000254:Sodium-Potassium-Exchanging ATPase; D013752:Tetracycline