Cellular and biophysical evidence for interactions between adenosine triphosphate and P-glycoprotein substrates: Functional implications for adenosine triphosphate/drug cotransport in P-glycoprotein overexpressing tumor cells and in P-glycoprotein low-level expressing erythrocytes

Edward H. Abraham, Brij Shrivastav, Anna Y. Salikhova, Kenneth M. Sterling, Nicholas Johnston, Guido Guidotti, Stefania Scala, Thomas Litman, King C. Chan, Robert J. Arceci, Kim Steiglitz, Laurie Herscher, Paul Okunieff

Research output: Contribution to journalArticle

Abstract

P-glycoprotein is involved with the removal of drugs, most of them cations, from the plasma membrane and cytoplasm. Pgp is also associated with movement of ATP, an anion, from the cytoplasm to the extracellular space. The central question of this study is whether drug and ATP transport associated with the expression of Pgp are in any way coupled. We have measured the stoichiometry of transport coupling between drug and ATP release. The drug and ATP transport that is inhibitable by the sulfonylurea compound, glyburide (P. E. Golstein, A. Boom, J. van Geffel, P. Jacobs, B. Masereel, and R. Beauwens, Pfluger's Arch. 437, 652, 1999), permits determination of the transport coupling ratio, which is close to 1:1. In view of this result, we asked whether ATP interacts directly with Pgp substrates. We show by measuring the movement of Pgp substrates in electric fields that ATP and drug movement are coupled. The results are compatible with the view that substrates for Pgp efflux are driven by the movement of ATP through electrostatic interaction and effective ATP-drug complex formation with net anionic character. This mechanism not only pertains to drug efflux from tumor cells overexpressing Pgp, but also provides a framework for understanding the role of erythrocytes in drug resistance. The erythrocyte consists of a membrane surrounding a millimolar pool of ATP. Mammalian RBCs have no nucleus or DNA drug/toxin targets. From the perspective of drug/ATP complex formation, the RBC serves as an important electrochemical sink for toxins. The presence in the erythrocyte membrane of approximately 100 Pgp copies per RBC provides a mechanism for eventual toxin clearance. The RBC transport of toxins permits their removal from sensitive structures and ultimate clearance from the organism via the liver and/or kidneys.

Original languageEnglish
Pages (from-to)181-200
Number of pages20
JournalBlood cells, molecules & diseases
Volume27
Issue number1
DOIs
Publication statusPublished - 2001

Keywords

  • ABC proteins
  • Adriamycin
  • Apyrase
  • ATP (adenosine triphosphate)
  • ATP transporter
  • Camptothecin
  • Capillary electrophoresis
  • CD39
  • Colchicine
  • Cotransport
  • Doxorubicin
  • Electrophoresis
  • Erythrocyte
  • Knockout mice
  • MDR (multidrug resistance protein)
  • Pgp (P-glycoprotein)
  • Pgp drug substrates
  • Plasma ATP
  • RBC
  • Stoichiometry of coupling
  • Taxol
  • Verapamil

ASJC Scopus subject areas

  • Molecular Biology
  • Molecular Medicine
  • Hematology

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