title: Molecular interactions of cyclosporin A with P-glycoprotein. Photolabeling with cyclosporin derivatives.
abstract: The interaction between P-glycoprotein (140-180 kDa) from the multidrug-resistant Chinese hamster ovary cell line CHRC5 and cyclosporin A was characterized using three different photoactivable cyclosporin A analogs. Two monoclonal antibodies, which are able to discriminate between two major domains of cyclosporin A (the cyclophilin and calcineurin binding domains), were used to detect the photolabeled proteins. A protein of 155 kDa corresponding to P-glycoprotein was much more strongly photolabeled in membranes of CHRC5 cells than in membranes of their drug-sensitive parent cell line AuxB1. The antitumor drug vinblastine and the reversal agents verapamil and cyclosporin A inhibited the photolabeling, and the nonimmunosuppressive derivative PSC-833 caused a stronger inhibition than cyclosporin A. P-glycoprotein photolabeled with cyclosporin A analogs was only detected with the monoclonal antibody that recognizes cyclosporin A and its metabolites, indicating that the calcineurin binding domain recognized specifically by the other antibody is not exposed. These results suggest that the portion of cyclosporin A that binds to calcineurin plays a role in the interaction of cyclosporin A with P-glycoprotein.
authors.affiliation: Laboratoire d'Oncologie Moléculaire, Département de Chimie-biochimie, Université du Québec-Hopital Ste-Justine, Montréal, Québec H3C 3P8, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Demeule
authors.forename: R M
authors.initials: RM
authors.lastname: Wenger
authors.forename: R
authors.initials: R
authors.lastname: Béliveau
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry*; D000818:Animals; D000911:Antibodies, Monoclonal; D001389:Azirines / Q000737:chemistry; D001665:Binding Sites; D001667:Binding, Competitive; D015153:Blotting, Western; D016466:CHO Cells; D006224:Cricetinae; D016572:Cyclosporine / Q000737:chemistry*; D010777:Photochemistry
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal; D001389:Azirines; D016572:Cyclosporine