title: FKBP51, a novel T-cell-specific immunophilin capable of calcineurin inhibition.
abstract: The immunosuppressive drugs FK506 and cyclosporin A block T-lymphocyte proliferation by inhibiting calcineurin, a critical signaling molecule for activation. Multiple intracellular receptors (immunophilins) for these drugs that specifically bind either FK506 and rapamycin (FK506-binding proteins [FKBPs]) or cyclosporin A (cyclophilins) have been identified. We report the cloning and characterization of a new 51-kDa member of the FKBP family from murine T cells. The novel immunophilin, FKBP51, is distinct from the previously isolated and sequenced 52-kDa murine FKBP, demonstrating 53% identity overall. Importantly, Western blot (immunoblot) analysis showed that unlike all other FKBPs characterized to date, FKBP51 expression was largely restricted to T cells. Drug binding to recombinant FKBP51 was demonstrated by inhibition of peptidyl prolyl isomerase activity. As judged from peptidyl prolyl isomerase activity, FKBP51 had a slightly higher affinity for rapamycin than for FK520, an FK506 analog. FKBP51, when complexed with FK520, was capable of inhibiting calcineurin phosphatase activity in an in vitro assay system. Inhibition of calcineurin phosphatase activity has been implicated both in the mechanism of immunosuppression and in the observed toxic side effects of FK506 in nonlymphoid cells. Identification of a new FKBP that can mediate calcineurin inhibition and is restricted in its expression to T cells suggests that new immunosuppressive drugs may be identified that, by virtue of their specific interaction with FKBP51, would be targeted in their site of action.
authors.affiliation: Regulatory Biology Laboratory, Salk Institute for Biological Studies, San Diego, California 92186-5800, USA.
authors.forename: G
authors.initials: G
authors.lastname: Baughman
authors.forename: G J
authors.initials: GJ
authors.lastname: Wiederrecht
authors.forename: N F
authors.initials: NF
authors.lastname: Campbell
authors.forename: M M
authors.initials: MM
authors.lastname: Martin
authors.forename: S
authors.initials: S
authors.lastname: Bourgeois
mesh_terms: D000591:Amino Acid Isomerases / Q000037:antagonists & inhibitors; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D019703:Calcineurin; D002148:Calmodulin-Binding Proteins / Q000037:antagonists & inhibitors*; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D019696:Peptidylprolyl Isomerase; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D011090:Polyenes / Q000378:metabolism; D011485:Protein Binding; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D020123:Sirolimus; D013601:T-Lymphocytes / Q000378:metabolism*; D016559:Tacrolimus / Q000031:analogs & derivatives / Q000378:metabolism; D022021:Tacrolimus Binding Proteins; D014018:Tissue Distribution
chemical_list: D002148:Calmodulin-Binding Proteins; D002352:Carrier Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D011090:Polyenes; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D000591:Amino Acid Isomerases; D022021:Tacrolimus Binding Proteins; D019696:Peptidylprolyl Isomerase; D020123:Sirolimus; D016559:Tacrolimus