Na, K ATPase beta3 subunit (CD298): association with alpha subunit and expression on peripheral blood cells

Beta3 subunit is described as one of the Na, K ATPase subunits. Recently, we generated a monoclonal antibody (mAb), termed P-3E10. This mAb was shown to react with the Na, K ATPase beta3 subunit or CD298. By immunofluorescence analysis using mAb P-3E10, it was found that all peripheral blood leukocytes express Na, K ATPase beta3. The presence of beta3 subunit on leukocytes is not in a quantitative polymorphic manner. Upon phytohemagglutinin or phorbol myristate acetate activation, the expression level of the Na, K ATPase beta3 subunit on activated peripheral blood mononuclear cells was not altered in comparison with those of unstimulated cells. Red blood cells (RBCs) of healthy donors showed negative reactivity with mAb P-3E10. However, more than 80% of thalassemic RBCs showed positive reactivity. By immunoprecipitation, moreover, a protein band of 55-65 kDa was precipitated from normal RBC membrane using mAb P-3E10. These results evidenced that the beta3 subunit of Na, K ATPase is expressed on RBC membrane but the epitope recognized by mAb P-3E10 is hidden in normal RBCs. Furthermore, we showed the association of beta3 subunit and alpha subunit of Na, K ATPase. This information is important for further understanding of the functional roles of this molecule.