FXYD5 O- glycosylated ectodomain impairs adhesion by disrupting cell-cell trans -dimerization of Na,K-ATPase β1 subunits

• Published in: Journal of cell science
• Main Authors: Tokhtaeva, Elmira, Sun, Haying, Deiss-Yehiely, Nimrod, Wen, Yi, Soni, Pritin N., Gabrielli, Nieves M., Marcus, Elizabeth A., Ridge, Karen M., Sachs, George, Vazquez-Levin, Mónica, Sznajder, Jacob I., Vagin, Olga, Dada, Laura A.
• Format: Journal Article
• Language: English
• Published: 01.01.2016
• ISSN: 0021-9533; 1477-9137
• DOI: 10.1242/jcs.186148

FXYD5/Dysadherin, a regulatory subunit of the Na,K-ATPase, impairs intercellular adhesion by a poorly understood mechanism. Here, we determined whether FXYD5 disrupts the trans-dimerization of Na,K-ATPase molecules located in neighboring cells. Mutagenesis of the Na,K-ATPase β1 subunit identified four conserved residues, including Y199, that are critical for the intercellular Na,K-ATPase trans-dimerization and adhesion. Modulation of expression of FXYD5 or of β1 subunit with intact or mutated β1:β1 binding sites demonstrated that the anti-adhesive effect of FXYD5 depends on the presence Y199 in the β1 subunit. Immunodetection of the plasma membrane FXYD5 was prevented by the presence of O-glycans. Partial FXYD5 deglycosylation enabled antibody binding and showed that the protein level and the degree of O-glycosylation were greater in cancer than in normal cells. FXYD5-induced impairment of adhesion was abolished by both genetic and pharmacological inhibition of FXYD5 O-glycosylation. Therefore, the extracellular O-glycosylated domain of FXYD5 impairs adhesion by interfering with intercellular β1:β1 interactions, suggesting that the ratio between FXYD5 and α1-β1 heterodimer determines whether the Na,K-ATPase acts as a positive or negative regulator of intercellular adhesion.