title: Interaction of FKBP12-FK506 with calcineurin A at the B subunit-binding domain.
abstract: Calcineurin is a calcium-dependent protein phosphatase that plays a pivotal role in antigen-stimulated T cell activation. The complexes formed between the immunosuppressants cyclosporin A and FK506 and their respective intracellular binding proteins (immunophilins) block T cell activation by binding to calcineurin. Recent studies have shown that the immunophilin-immunosuppressant complexes interact with the latch region of the calcineurin B subunit (Milan, D., Griffith, J., Su, M., Price, E. R., and McKeon, F. (1994) Cell 79, 437-447). Mutations in the B subunit-binding domain of the calcineurin A subunit result in a reduction of calcineurin activity that correlates with B binding affinity. Calcineurin A subunit mutants D348A, F350A, W352A, S353A, and E359A lost greater than 90% of their activity to activate the transcription factor NF kappa B in Jurkat T cells. Furthermore, calcineurin A subunit mutants of residues Thr351, Leu354, and Lys360 showed NF kappa B transactivation activity and phosphatase activity with increased resistance to FKBP12-FK506 but displayed no or minimal increase in resistance for cyclosporin A inhibition. Together, these results strongly suggest that the B subunit-binding domain is required for calcineurin activity intracellulary and interacts with the FKBP12-FK506 complex.
authors.affiliation: Vertex Pharmaceuticals Incorporated, Cambridge, Massachusetts 02139-4211, USA.
authors.forename: A
authors.initials: A
authors.lastname: Kawamura
authors.forename: M S
authors.initials: MS
authors.lastname: Su
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D019703:Calcineurin; D002148:Calmodulin-Binding Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D016559:Tacrolimus / Q000378:metabolism*; D022021:Tacrolimus Binding Proteins; D015533:Transcriptional Activation
chemical_list: D002148:Calmodulin-Binding Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D016328:NF-kappa B; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D010744:Phosphoric Monoester Hydrolases; D022021:Tacrolimus Binding Proteins; D016559:Tacrolimus