Noncatalytic role of the FKBP52 peptidyl-prolyl isomerase domain in the regulation of steroid hormone signaling.
Hormone-dependent transactivation by several of the steroid hormone receptors is potentiated by the Hsp90-associated cochaperone FKBP52, although not by the closely related FKBP51. Here we analyze the mechanisms of potentiation and the functional differences between FKBP51 and FKBP52. While both have peptidyl-prolyl isomerase activity, this is not required for potentiation, as mutations abolishing isomerase activity did not affect potentiation. Genetic selection in Saccharomyces cerevisiae for gain of potentiation activity in a library of randomly mutated FKBP51 genes identified a single residue at position 119 in the N-terminal FK1 domain as being a critical difference between these two proteins. In both the yeast model and mammalian cells, the FKBP51 mutation L119P, which is located in a hairpin loop overhanging the catalytic pocket and introduces the proline found in FKBP52, conferred significant potentiation activity, whereas the converse P119L mutation in FKBP52 decreased potentiation. A second residue in this loop, A116, also influences potentiation levels; in fact, the FKBP51-A116V L119P double mutant potentiated hormone signaling as well as wild-type FKBP52 did. These results suggest that the FK1 domain, and in particular the loop overhanging the catalytic pocket, is critically involved in receptor interactions and receptor activity.
Riggs
Daniel L
DL
Mayo Clinic Arizona, 13400 E. Shea Blvd., Scottsdale, AZ 85259, USA.
Cox
Marc B
MB
Tardif
Heather L
HL
Hessling
Martin
M
Buchner
Johannes
J
Smith
David F
DF
D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D004357:Drug Synergism; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000302:isolation & purification / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D019696:Peptidylprolyl Isomerase / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012641:Selection, Genetic; D015398:Signal Transduction / Q000187:drug effects*; D013256:Steroids / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D022021:Tacrolimus Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D000099159:Tacrolimus Binding Protein 5
D050505:Mutant Proteins; D019696:Peptidylprolyl Isomerase; D011993:Recombinant Fusion Proteins; D013256:Steroids; D022021:Tacrolimus Binding Proteins; D000099159:Tacrolimus Binding Protein 5; C403485:tacrolimus binding protein 4