Immunophilins interact with calcineurin in the absence of exogenous immunosuppressive ligands

EMBO J. 1994 Dec 15;13(24):5944-57.


The peptidyl-prolyl isomerases FKBP12 and cyclophilin A (immunophilins) form complexes with the immunosuppressants FK506 and cyclosporin A that inhibit the phosphatase calcineurin. With the yeast two hybrid system, we detect complexes between FKBP12 and the calcineurin A catalytic subunit in both the presence and absence of FK506. Mutations in FKBP12 surface residues or the absence of the calcineurin B regulatory subunit perturb the FK506-dependent, but not the ligand-independent, FKBP12-calcineurin complex. By affinity chromatography, both FKBP12 and cyclophilin A bind calcineurin A in the absence of ligand, and FK506 and cyclosporin A respectively potentiate these interactions. Both in vivo and in vitro, the peptidyl-prolyl isomerase active sites are dispensable for ligand-independent immunophilin-calcineurin complexes. Lastly, by genetic analyses we demonstrate that FKBP12 modulates calcineurin functions in vivo. These findings reveal that immunophilins interact with calcineurin in the absence of exogenous ligands and suggest that immunosuppressants may take advantage of the inherent ability of immunophilins to interact with calcineurin.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Isomerases / genetics
  • Amino Acid Isomerases / metabolism*
  • Base Sequence
  • Calcineurin
  • Calmodulin-Binding Proteins / metabolism*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Chromatography, Affinity
  • Cyclosporine / genetics
  • Cyclosporine / metabolism*
  • Cyclosporine / pharmacology
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Dose-Response Relationship, Drug
  • Drug Resistance, Microbial
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / metabolism*
  • Ligands
  • Lithium Chloride / pharmacology
  • Mating Factor
  • Molecular Sequence Data
  • Peptides / pharmacology
  • Peptidylprolyl Isomerase
  • Phosphoprotein Phosphatases / metabolism*
  • Protein Binding
  • Recombinant Proteins / metabolism
  • Signal Transduction
  • Structure-Activity Relationship
  • Tacrolimus / metabolism*
  • Tacrolimus / pharmacology
  • Tacrolimus Binding Proteins
  • Yeasts / growth & development


  • Calmodulin-Binding Proteins
  • Carrier Proteins
  • DNA-Binding Proteins
  • Heat-Shock Proteins
  • Ligands
  • Peptides
  • Recombinant Proteins
  • Mating Factor
  • Cyclosporine
  • Calcineurin
  • Phosphoprotein Phosphatases
  • Amino Acid Isomerases
  • Tacrolimus Binding Proteins
  • Peptidylprolyl Isomerase
  • Lithium Chloride
  • Tacrolimus