Inverse correlation between the extent of N-glycan branching and intercellular adhesion in epithelia. Contribution of the Na,K-ATPase beta1 subunit.
The majority of cell adhesion molecules are N-glycosylated, but the role of N-glycans in intercellular adhesion in epithelia remains ill-defined. Reducing N-glycan branching of cellular glycoproteins by swainsonine, the inhibitor of N-glycan processing, tightens and stabilizes cell-cell junctions as detected by a 3-fold decrease in the paracellular permeability and a 2-3-fold increase in the resistance of the adherens junction proteins to extraction by non-ionic detergent. In addition, exposure of cells to swainsonine inhibits motility of MDCK cells. Mutagenic removal of N-glycosylation sites from the Na,K-ATPase beta(1) subunit impairs cell-cell adhesion and decreases the effect of swainsonine on the paracellular permeability of the cell monolayer and also on detergent resistance of adherens junction proteins, indicating that the extent of N-glycan branching of this subunit is important for intercellular adhesion. The N-glycans of the Na,K-ATPase beta(1) subunit and E-cadherin are less complex in tight renal epithelia than in the leakier intestinal epithelium. The complexity of the N-glycans linked to these proteins gradually decreases upon the formation of a tight monolayer from dispersed MDCK cells. This correlates with a cell-cell adhesion-induced increase in expression of GnT-III (stops N-glycan branching) and a decrease in expression of GnTs IVC and V (promote N-glycan branching) as detected by real-time quantitative PCR. Consistent with these results, partial silencing of the gene encoding GnT-III increases branching of N-glycans linked to the Na,K-ATPase beta(1) subunit and other glycoproteins and results in a 2-fold increase in the paracellular permeability of MDCK cell monolayers. These results suggest epithelial cells can regulate tightness of cell junctions via remodeling of N-glycans, including those linked to the Na,K-ATPase beta(1)-subunit.
Vagin
Olga
O
Department of Physiology, School of Medicine, University of California, Los Angeles, Veterans Administration Greater Los Angeles Health Care System, Los Angeles, California 90073, USA. olgav@ucla.edu
Tokhtaeva
Elmira
E
Yakubov
Iskandar
I
Shevchenko
Eugenia
E
Sachs
George
G
D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000201:enzymology*; D004848:Epithelium / Q000201:enzymology; D005936:Glucans / Q000096:biosynthesis*; D007365:Intercellular Junctions / Q000378:metabolism*; D017351:N-Acetylglucosaminyltransferases / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D025942:Oligosaccharides, Branched-Chain / Q000096:biosynthesis*; D046188:Protein Modification, Translational / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*; D017026:Swainsonine / Q000494:pharmacology
D015815:Cell Adhesion Molecules; D004791:Enzyme Inhibitors; D005936:Glucans; D025942:Oligosaccharides, Branched-Chain; D017351:N-Acetylglucosaminyltransferases; D000254:Sodium-Potassium-Exchanging ATPase; D017026:Swainsonine