Erythrocyte membrane ATP binding cassette (ABC) proteins: MRP1 and CFTR aswell as CD39 (ecto-apyrase) involved in RBC ATP transport and elevated blood plasma ATP of cystic fibrosis

In addition to the better-known roles of the erythrocyte in the transport o f oxygen and carbon dioxide, the concept that the red blood cell is involve d in the transport and release of ATP has been evolving (J. Luthje, Blut 59 , 367, 1989; G. R. Bergfeld and T. Forrester, Cardiovasc. Res. 26, 40, 1992 ; M. L. Ellsworth et al., Am. J. Physiol. 269, H2155, 1995; R. S. Sprague e t al., Am. J. Physiol. 275, H1726, 1998). Membrane proteins involved in the release of ATP from erythrocytes now appear to include members of the ATP binding cassette (ABC) family (C. F. Higgins, Annu. Rev. Cell Biol. 8, 67, 1992; C. F. Higgins, Cell 82, 693, 1995). In addition to defining physiolog ically the presence of ABC proteins in RBCs, accumulating gel electrophoret ic evidence suggests that the cystic fibrosis transmembrane conductance reg ulator (CE;TR) and the multidrug resistance-associated protein (MRP1), resp ectively, constitute significant proteins in the red blood cell membrane. A s such, this finding makes the mature erythrocyte compartment a major mamma lian repository of these important ABC proteins. Because of its relative st ructural simplicity and ready accessibility, the erythrocyte offers an idea l system to explore details of the physiological functions of ABC proteins. Moreover, the presence of different ABC proteins in a single membrane impl ies that interaction among these proteins and with other membrane proteins may be the norm and not the exception in terms of modulation of their funct ions, (C) 2001 Academic Press.