title: Cyclophilin binds to the region of cyclosporine involved in its immunosuppressive activity.
abstract: Although several cytosolic proteins including calmodulin and cyclophilin have been shown to bind cyclosporine, the direct involvement of these proteins in the immunosuppressive activity of cyclosporine remains to be established. In the present study, a quantitative immunoassay for cyclophilin was developed which made it possible to compare its relative affinity for cyclosporine and any of its analogues. The binding of cyclophilin to cyclosporine coated on a solid phase was revealed by anti-cyclophilin rabbit antiserum followed by antiglobulin-enzyme conjugate. This reaction could be inhibited by addition of free cyclosporine or certain cyclosporine analogues. By studying the binding of cyclophilin to more than fifty cyclosporine derivatives modified singly on each of the eleven amino acid residues, it could be shown that cyclophilin binds to the residues of cyclosporine known to be critical for its immunosuppressive activity. These data identify cyclophilin as a highly discriminating stereospecific binding protein for cyclosporine.
authors.affiliation: Laboratoire d'Immunochimie, Institut de Biologie Moléculaire et Cellulaire du CNRS, Strasbourg, France.
authors.forename: V F
authors.initials: VF
authors.lastname: Quesniaux
authors.forename: M H
authors.initials: MH
authors.lastname: Schreier
authors.forename: R M
authors.initials: RM
authors.lastname: Wenger
authors.forename: P C
authors.initials: PC
authors.lastname: Hiestand
authors.forename: M W
authors.initials: MW
authors.lastname: Harding
authors.forename: M H
authors.initials: MH
authors.lastname: Van Regenmortel
mesh_terms: D002147:Calmodulin / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D003524:Cyclosporins / Q000378:metabolism* / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008958:Models, Molecular; D019696:Peptidylprolyl Isomerase; D011485:Protein Binding; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D002147:Calmodulin; D002352:Carrier Proteins; D003524:Cyclosporins; D007166:Immunosuppressive Agents; D019696:Peptidylprolyl Isomerase