TY - JOUR

T1 - Cellular and biophysical evidence for interactions between adenosine triphosphate and P-glycoprotein substrates

T2 - functional implications for adenosine triphosphate/drug cotransport in P-glycoprotein overexpressing tumor cells and in P-glycoprotein low-level expressing erythrocytes

AU - Abraham, E H

AU - Shrivastav, B

AU - Salikhova, A Y

AU - Sterling, K M

AU - Johnston, N

AU - Guidotti, G

AU - Scala, S

AU - Litman, Thomas

AU - Chan, K C

AU - Arceci, R J

AU - Steiglitz, K

AU - Herscher, L

AU - Okunieff, P

N1 - Copyright 2001 Academic Press.

PY - 2001/5/19

Y1 - 2001/5/19

N2 - 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.

AB - 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.

KW - ATP-Binding Cassette Transporters

KW - Adenosine Triphosphate

KW - Animals

KW - Antibiotics, Antineoplastic

KW - Antineoplastic Agents

KW - Drug Interactions

KW - Erythrocytes

KW - Humans

KW - Ion Transport

KW - Kinetics

KW - Ligands

KW - Mice

KW - Mice, Knockout

KW - Models, Chemical

KW - P-Glycoprotein

KW - Transfection

KW - Tumor Cells, Cultured

U2 - 10.1006/bcmd.2000.0373

DO - 10.1006/bcmd.2000.0373

M3 - Journal article

C2 - 11358379

VL - 27

SP - 181

EP - 200

JO - Blood Cells, Molecules and Diseases

JF - Blood Cells, Molecules and Diseases

SN - 1079-9796

IS - 1

ER -