title: Functional modulation of ATPase of P-glycoprotein by C219, a monoclonal antibody against P-glycoprotein.
abstract: P-glycoprotein functions as an ATP-driven efflux pump for antitumor agents. C219 is a monoclonal antibody which recognizes regions near both ATP binding domains in each half of P-glycoprotein. In this study, we have demonstrated that C219 inhibits the ATPase activity of P-glycoprotein based on the following findings: 1) the inhibition of total ATPase activity by C219 was selective to P-glycoprotein-positive membranes; 2) the C219-sensitive fraction of ATPase correlated the expression of P-glycoprotein; and 3) modulators of P-glycoprotein ATPase, verapamil and cyclosporin A, affected the C219-sensitive fraction of ATPase. The photolabeling of P-glycoprotein with 8-azido-[alpha-32P]ATP was inhibited by C219, suggesting that the inhibition of ATP binding by C219 reduced the activity. Since C219 interacts with P-glycoprotein ATPase, C219 might become a useful tool for studying the role of P-glycoprotein ATPase.
authors.affiliation: Oncology/Hematology Unit, Pharmacology Department, Sandoz Tsukuba Research Institute, Tsukuba-shi, Ibaraki, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Kokubu
authors.forename: D
authors.initials: D
authors.lastname: Cohen
authors.forename: T
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000276:immunology* / Q000378:metabolism*; D000230:Adenocarcinoma; D000251:Adenosine Triphosphatases / Q000276:immunology / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D001665:Binding Sites; D001943:Breast Neoplasms; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D016572:Cyclosporine / Q000494:pharmacology; D004317:Doxorubicin / Q000633:toxicity; D019008:Drug Resistance, Neoplasm; D005260:Female; D006801:Humans; D007700:Kinetics; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal; D004317:Doxorubicin; D016572:Cyclosporine; D000255:Adenosine Triphosphate; D014700:Verapamil; D000251:Adenosine Triphosphatases