Cholesterol-Mediated Activation of P-Glycoprotein: Distinct Effects on Basal and Drug-Induced ATPase Activities
| Autor: | Priska M. Elsener, Sara Belli, Heidi Wunderli-Allenspach, Stefanie D. Krämer |
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| Rok vydání: | 2009 |
| Předmět: |
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2-Dipalmitoylphosphatidylcholine ATPase Lipid Bilayers alpha-Tocopherol Pharmaceutical Science ATP-binding cassette transporter Vinblastine Excipients Propanolamines Mice chemistry.chemical_compound Cell Line Tumor Membrane fluidity medicine Animals ATP Binding Cassette Transporter Subfamily B Member 1 Lipid bilayer P-glycoprotein Adenosine Triphosphatases biology Cholesterol Membranes Artificial Calcium Channel Blockers Antineoplastic Agents Phytogenic Sterol Verapamil Biochemistry chemistry Enzyme Induction Liposomes biology.protein Biophysics Anisotropy lipids (amino acids peptides and proteins) Adrenergic alpha-Agonists medicine.drug |
| Zdroj: | Journal of Pharmaceutical Sciences. 98:1905-1918 |
| ISSN: | 0022-3549 |
| DOI: | 10.1002/jps.21558 |
| Popis: | Cholesterol promotes basal and verapamil-induced ATPase activity of P-glycoprotein (P-gp). We investigated whether these effects are related to each other and to the impact of the sterol on bilayer fluidity and verapamil membrane affinity. P-gp was reconstituted in egg-phosphatidylcholine (PhC) liposomes with or without cholesterol, 1,2-dipalmitoyl-phosphatidylcholine (DPPC), alpha-tocopherol (alpha-Toc) or 2,2,5,7,8-pentamethyl-6-chromanol (PMC). Basal and verapamil-induced ATPase activities were studied with an enzymatic assay. Membrane fluidity was characterized with diphenyl-hexatriene anisotropy measurements and membrane affinity by equilibrium dialysis. DPPC (70% mol/mol) decreased the fluidity of PhC bilayers to the same level as 20% cholesterol. PMC (20%) and alpha-Toc (20%) decreased the fluidity to lesser extents. alpha-Toc and PMC, but not DPPC increased the verapamil membrane affinity. While 20% cholesterol strikingly enhanced the basal ATPase activity, none of the other constituents had a similar effect. In contrast, verapamil stimulation of P-gp ATPase activity was not only enabled by cholesterol but also by alpha-Toc and DPPC. PMC had no effect. In conclusion, cholesterol exerts distinct effects on basal and verapamil-induced ATPase activity. The influence on basal ATPase activity is sterol-specific while its effect on verapamil-induced ATPase activity is unspecific and not related to its influence on membrane fluidity and on verapamil membrane affinity. |
| Databáze: | OpenAIRE |
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