Identification of the amino acid region involved in the intercellular interaction between the β1 subunits of Na+/K+ -ATPase.
Epithelial junctions depend on intercellular interactions between β(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 β(1) subunits, indicating the importance of species-specific regions for β(1)-β(1) binding. To identify these regions, the species-specific amino acid residues were mapped on a high-resolution structure of the Na(+)/K(+)-ATPase β(1) subunit to select those exposed towards the β(1) subunit of the neighboring cell. These exposed residues were mutated in both dog and rat YFP-linked β(1) subunits (YFP-β(1)) and also in the secreted extracellular domain of the dog β(1) subunit. Five rat-like mutations in the amino acid region spanning residues 198-207 of the dog YFP-β(1) expressed in Madin-Darby canine kidney (MDCK) cells decreased co-precipitation of the endogenous dog β(1) subunit with YFP-β(1) to the level observed between dog β(1) and rat YFP-β(1). In parallel, these mutations impaired the recognition of YFP-β(1) by the dog-specific antibody that inhibits cell adhesion between MDCK cells. Accordingly, dog-like mutations in rat YFP-β(1) increased both the (YFP-β(1))-β(1) interaction in MDCK cells and recognition by the antibody. Conversely, rat-like mutations in the secreted extracellular domain of the dog β(1) subunit increased its interaction with rat YFP-β(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 β(1) subunit to a cell suspension. Therefore, the amino acid region 198-207 is crucial for both trans-dimerization of the Na(+)/K(+)-ATPase β(1) subunits and cell-cell adhesion.
Department of Physiology, School of Medicine, UCLA and Veterans Administration Greater Los Angeles Health Care System, Los Angeles, VAGLAHS/West LA, Building 113, Room 324, 11301 Wilshire Boulevard, Los Angeles, CA 90073,  USA.
Elmira
E
Tokhtaeva
George
G
Sachs
Haiying
H
Sun
Laura A
LA
Dada
Jacob I
JI
Sznajder
Olga
O
Vagin
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D000818:Animals; D002450:Cell Communication / Q000502:physiology*; D002460:Cell Line; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology / Q000201:enzymology*; D008969:Molecular Sequence Data; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary / Q000235:genetics; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
D000596:Amino Acids; C503554:Atp1b1 protein, rat; D000254:Sodium-Potassium-Exchanging ATPase