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First published online 8 December 2005
doi: 10.1242/jcs.02706

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Deglycosylation of Na⁺/K⁺-ATPase causes the basolateral protein to undergo apical targeting in polarized hepatic cells

¹ Institute of Microbiology and Immunology, National Yang-Ming University, 155 Sec. 2 Linong Street, Taipei 112, Taiwan
² Department of Life Science, National Yang-Ming University, 155 Sec. 2 Linong Street, Taipei 112, Taiwan
³ Institute of Biophotonics Engineering, National Yang-Ming University, 155 Sec. 2 Linong Street, Taipei 112, Taiwan
⁴ Department of Surgery, Veteran General Hospital, 201 Sec. 2 Shih-Pai Road, Taipei 112, Taiwan

^* Author for correspondence (e-mail: linch{at}ym.edu.tw)

Accepted 21 September 2005

Polarized epithelia, such as hepatocytes, target their integral membrane proteins to specific apical or basolateral membrane domains during or after biogenesis. The roles played by protein glycosylation in this sorting process remain controversial. We report here that deglycosylation treatments in well-polarized hepatic cells by deglycosylation drugs, or by site-directed mutagenesis of the N-linked-glycosylation residues, all cause the Na⁺/K⁺-ATPase ß-subunit to traffic from the native basolateral to the apical/canalicular domain. Deglycosylated ß-subunits are still able to bind and therefore transport the catalytic -subunits to the aberrant apical location. Such apical targeting is mediated via the indirect transcytosis pathway. Cells containing apical Na⁺/K⁺-ATPase appear to be defective in maintaining the ionic gradient across the plasma membrane and in executing hepatic activities that are dependent upon the ionic homeostasis such as canalicular excretion.

Key words: Glycosylation, Protein targeting, Na⁺/K⁺-ATPase, Liver