The roles of the NaKATPase beta 1 subunit in pum

Authors: Olga Vagin George Sachs Elmira Tokhtaeva

Publish Date: 2007/11/14

Volume: 39, Issue: 5-6, Pages: 367-372

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Abstract

In epithelial MDCK cells the NaKATPase is colocalized with adherens junctions in all stages of monolayer formation starting from initiation of cell–cell contact The NaKATPase and adherens junction proteins stay partially colocalized even after internalization due to disruption of intercellular contacts by Ca2+ deprivation Similar to adherens junction proteins the NaKATPase is resistant to extraction with nonionic detergent suggesting pump association with the cytoskeleton In contrast the heterodimer formed by expressed unglycosylated NaKATPase β1 subunit and the endogenous α1 subunit is easily dissociated from the adherens junctions and cytoskeleton by detergent extraction The MDCK cells in which half of the endogenous β1 subunits in the lateral membrane are substituted by unglycosylated β1 subunits display a slower rate of celltocell contact formation and decreased ability to both spread over the surface and migrate The lack of Nglycans in the NaKATPase β1 subunit results in an impairment of mature cell–cell junctions as detected by an increase in the paracellular permeability of the MDCK cell monolayers and by a decrease in resistance of adherens junction proteins to extraction by a nonionic detergent Therefore the Nglycans of the NaKATPase β1 subunit are important for retention of the pump at the sites of cell–cell contact Moreover they are important for the integrity and stability of cell–cell junctions in mature epithelia In addition Nglycans contribute to the formation of cell–cell contacts between surfaceattached dispersed cells by mediating lamellipodia formation and stabilizing the newly formed adherens junctions

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