Cyclophilin A-deficient mice are resistant to immunosuppression by cyclosporine.
Cyclosporine is an immunosuppressive drug that is widely used to prevent organ transplant rejection. Known intracellular ligands for cyclosporine include the cyclophilins, a large family of phylogenetically conserved proteins that potentially regulate protein folding in cells. Immunosuppression by cyclosporine is thought to result from the formation of a drug-cyclophilin complex that binds to and inhibits calcineurin, a serine/threonine phosphatase that is activated by TCR engagement. Amino acids within the cyclophilins that are critical for binding to cyclosporine have been identified. Most of these residues are highly conserved within the 15 mammalian cyclophilins, suggesting that many are potential targets for the drug. We examined the effects of cyclosporine on immune cells and mice lacking Ppia, the gene encoding the prototypical cyclophilin protein cyclophilin A. TCR-induced proliferation and signal transduction by Ppia(-/-) CD4(+) T cells were resistant to cyclosporine, an effect that was attributable to diminished calcineurin inhibition. Immunosuppressive doses of cyclosporine failed to block the responses of Ppia(-/-) mice to allogeneic challenge. Rag2(-/-) mice reconstituted with Ppia(-/-) splenocytes were also cyclosporine resistant, indicating that this property is intrinsic to Ppia(-/-) immune cells. Thus, among multiple potential ligands, CypA is the primary mediator of immunosuppression by cyclosporine.
Colgan
John
J
Department of Microbiology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
Asmal
Mohammed
M
Yu
Bin
B
Luban
Jeremy
J
D000818:Animals; D019703:Calcineurin / Q000502:physiology; D065095:Calcineurin Inhibitors; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D021984:Cyclophilin A / Q000172:deficiency* / Q000235:genetics* / Q000502:physiology; D016572:Cyclosporine / Q000008:administration & dosage* / Q000494:pharmacology; D004351:Drug Resistance / Q000235:genetics* / Q000276:immunology*; D020868:Gene Silencing / Q000187:drug effects / Q000276:immunology; D007111:Immunity, Cellular / Q000187:drug effects / Q000235:genetics; D007166:Immunosuppressive Agents / Q000008:administration & dosage* / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D012513:Sarcoma, Experimental / Q000201:enzymology / Q000235:genetics / Q000276:immunology; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000637:transplantation; D013601:T-Lymphocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism
D065095:Calcineurin Inhibitors; D007166:Immunosuppressive Agents; D016572:Cyclosporine; D019703:Calcineurin; D021984:Cyclophilin A