Mouse Na+/K+-ATPase beta1-subunit has a K+-dependent cell adhesion activity for beta-GlcNAc-terminating glycans.

Abstract

A 48-kDa beta-N-acetylglucosamine (GlcNAc)-binding protein was isolated from mouse brain by GlcNAc-agarose column chromatography. The N-terminal amino acid residues showed the protein to be a mouse Na(+)/K(+)-ATPase beta1-subunit. When the recombinant FLAG-beta1-subunit expressed in Sf-9 cells was applied to a GlcNAc-agarose column, only the glycosylated 38- and 40-kDa proteins bound to the column. In the absence of KCl, little of the proteins bound to a GlcNAc-agarose column, but the 38- and 40-kDa proteins bound in the presence of KCl at concentrations above 1 mM. Immunohistochemical study showed that the beta1-subunit and GlcNAc-terminating oligosaccharides are at the cell contact sites. Inclusion of anti-beta1-subunit antibody or chitobiose in cell aggregation assays using mouse neural cells resulted in inhibition of cell aggregation. These results indicate that the Na(+)/K(+)-ATPase beta1-subunit is a potassium-dependent lectin that binds to GlcNAc-terminating oligosaccharides: it may be involved in neural cell interactions.