Cystic fibrosis transmembrane conductance regulator in human and mouse red blood cell membranes and its interaction with ecto-apyrase.

Elevated blood ATP and increased red blood cell (RBC) ATP transport is associated with cystic fibrosis (CF). In this report, we demonstrate the presence of the wild-type and the DeltaF508 mutant form of the CF transmembrane conductance regulator protein in RBC membranes and its putative interaction with ecto-apyrase, an ATP hydrolyzing enzyme also present in the RBC membrane. RBC membranes of control and DeltaF508 individuals and of wild-type and CF transmembrane conductance regulator-knockout mice were examined by immunoblot using several antibodies directed against different epitopes of this protein. These experiments indicated that human RBC membranes contain comparable amounts of the wild-type CF transmembrane conductance regulator protein and the DeltaF508 mutant form of the protein, respectively. CF transmembrane conductance regulator protein was also detected in wild-type mouse RBC membranes but not in the gene knockout mouse RBC membranes. Antibodies directed against ecto-apyrase co-immunoprecipitated CF transmembrane conductance regulator protein of human RBC membranes indicating a physical interaction between these two membrane proteins consistent with ATP transport and extracellular hydrolysis. We conclude that RBCs are a significant repository of CF transmembrane conductance regulator protein and should provide a novel system for evaluating its expression and function.