title: Calcineurin mutants render T lymphocytes resistant to cyclosporin A.
abstract: The immunosuppressants cyclosporin A (CsA) and FK506 have been widely used to prevent and treat graft rejection after human organ and tissue transplantations. CsA and FK506 associate with intracellular binding proteins (i.e., CsA with cyclophilin A and FK506 with FKBP12) to form protein/drug complexes that suppress the immune system by preventing activation of T cells in response to antigen presentation. The common target of CsA and FK506 is calcineurin, a Ca2+/calmodulin-regulated, serine/threonine-specific protein phosphatase that regulates the nuclear import of a transcription factor, NF-AT, required for expression of T cell activation genes. In previous studies, we identified calcineurin mutations that block binding by the cyclophilin A/CsA or FKBP12/FK506 complexes and thereby render yeast cells resistant to the antifungal effects of CsA or FK506. In this report, we demonstrate that the corresponding mutations in murine calcineurin render the T cell receptor signal transduction cascade CsA resistant in human Jurkat T cells. Our findings support the recently determined calcineurin X-ray crystal structure, provide evidence that calcineurin is the only CsA-sensitive component limiting signaling from the T cell receptor to the nucleus, and suggest a means to render cells and tissues resistant to the toxic side effects of CsA and FK506.
authors.affiliation: Department of Genetics, Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: D
authors.initials: D
authors.lastname: Zhu
authors.forename: M E
authors.initials: ME
authors.lastname: Cardenas
authors.forename: J
authors.initials: J
authors.lastname: Heitman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000957:Antigens, Viral, Tumor / Q000096:biosynthesis; D001483:Base Sequence; D019703:Calcineurin; D002148:Calmodulin-Binding Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D017124:Conserved Sequence; D016572:Cyclosporine / Q000494:pharmacology*; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism; D004351:Drug Resistance / Q000502:physiology; D005658:Fungi / Q000378:metabolism; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D015458:Leukemia, T-Cell; D008213:Lymphocyte Activation; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010749:Phosphoprotein Phosphatases / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013539:Simian virus 40 / Q000235:genetics; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000957:Antigens, Viral, Tumor; D002148:Calmodulin-Binding Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D007166:Immunosuppressive Agents; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D016572:Cyclosporine; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases