title: Evidence for multidrug resistance-1 P-glycoprotein-dependent regulation of cellular ATP permeability.
abstract: The mechanisms responsible for regulating epithelial ATP permeability and purinergic signaling are not well defined. Based on the observations that members of the ATP-binding cassette (ABC)1 family of proteins may contribute to ATP release, the purpose of these studies was to assess whether multidrug resistance-1 (MDR1) proteins are involved in ATP release from HTC hepatoma cells. Using a bioluminescence assay to detect extracellular ATP, increases in cell volume increased ATP release approximately 3-fold. The MDR1 inhibitors cyclosporine A (10 microm) and verapramil (10 microm) inhibited ATP release by 69% and 62%, respectively (p < 0.001). Similarly, in whole-cell patch-clamp recordings, intracellular dialysis with C219 antibodies to inhibit MDR1 decreased ATP-dependent volume-sensitive Cl- current density from -33.1 +/- 12.5 pA/pF to -2.0 +/- 0.3 pA/pF (-80 mV, p < or = 0.02). In contrast, overexpression of MDR1 in NIH 3T3 cells increased ATP release rates. Inhibition of ATP release by Gd3+ had no effect on transport of the MDR1 substrate rhodamine-123; and alteration of MDR1-substrate selectivity by mutation of G185 to V185 had no effect on ATP release. Since the effects of P-glycoproteins on ATP release can be dissociated from P-glycoprotein substrate transport, MDR1 is not likely to function as an ATP channel, but instead serves as a potent regulator of other cellular ATP transport pathways.
authors.affiliation: Department of Medicine, University of Colorado Health Sciences Center, Campus Box B-158, Denver, CO 80262, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Roman
authors.forename: N
authors.initials: N
authors.lastname: Lomri
authors.forename: G
authors.initials: G
authors.lastname: Braunstein
authors.forename: A P
authors.initials: AP
authors.lastname: Feranchak
authors.forename: L A
authors.initials: LA
authors.lastname: Simeoni
authors.forename: A K
authors.initials: AK
authors.lastname: Davison
authors.forename: E
authors.initials: E
authors.lastname: Mechetner
authors.forename: E M
authors.initials: EM
authors.lastname: Schwiebert
authors.forename: J G
authors.initials: JG
authors.lastname: Fitz
mesh_terms: D016475:3T3 Cells / Q000166:cytology; D018435:ATP Binding Cassette Transporter, Subfamily B / Q000378:metabolism*; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology*; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured / Q000166:cytology; D002712:Chlorides / Q000378:metabolism*; D016572:Cyclosporine / Q000494:pharmacology; D006801:Humans; D051379:Mice; D051381:Rats; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology; D000097202:ATP-Binding Cassette Sub-Family B Member 4
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000255:Adenosine Triphosphate; D000906:Antibodies; D002712:Chlorides; D016572:Cyclosporine; D014700:Verapamil; D000097202:ATP-Binding Cassette Sub-Family B Member 4