Identification of the amino acid region involved in the intercellular interaction between the ?1 subunits of Na+/K+ -ATPase.

ABSTRACT: Epithelial junctions depend on intercellular interactions between ?(1) subunits of the Na(+)/K(+)-ATPase molecules of neighboring cells. The interaction between dog and rat subunits is less effective than the interaction between two dog ?(1) subunits, indicating the importance of species-specific regions for ?(1)-?(1) binding. To identify these regions, the species-specific amino acid residues were mapped on a high-resolution structure of the Na(+)/K(+)-ATPase ?(1) subunit to select those exposed towards the ?(1) subunit of the neighboring cell. These exposed residues were mutated in both dog and rat YFP-linked ?(1) subunits (YFP-?(1)) and also in the secreted extracellular domain of the dog ?(1) subunit. Five rat-like mutations in the amino acid region spanning residues 198-207 of the dog YFP-?(1) expressed in Madin-Darby canine kidney (MDCK) cells decreased co-precipitation of the endogenous dog ?(1) subunit with YFP-?(1) to the level observed between dog ?(1) and rat YFP-?(1). In parallel, these mutations impaired the recognition of YFP-?(1) by the dog-specific antibody that inhibits cell adhesion between MDCK cells. Accordingly, dog-like mutations in rat YFP-?(1) increased both the (YFP-?(1))-?(1) interaction in MDCK cells and recognition by the antibody. Conversely, rat-like mutations in the secreted extracellular domain of the dog ?(1) subunit increased its interaction with rat YFP-?(1) in vitro. In addition, these mutations resulted in a reduction of intercellular adhesion between rat lung epithelial cells following addition of the secreted extracellular domain of the dog ?(1) subunit to a cell suspension. Therefore, the amino acid region 198-207 is crucial for both trans-dimerization of the Na(+)/K(+)-ATPase ?(1) subunits and cell-cell adhesion.

SUBMITTER: Tokhtaeva E 

PROVIDER: S-EPMC3336383 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature