title: Cyclophilin 40 (CyP-40), mapping of its hsp90 binding domain and evidence that FKBP52 competes with CyP-40 for hsp90 binding.
abstract: The structurally related immunophilins cyclophilin 40 (CyP-40) and FKBP52 have been identified as components of the unactivated estrogen receptor. Both immunophilins have a similar molecular architecture that includes a C-terminal segment with a tetratricopeptide repeat (TPR) domain predicted to mediate protein interaction. hsp90 is a common cellular target for CyP-40 and FKBP52. Deletion mutants of CyP-40 fused to glutathione S-transferase were immobilized on glutathione-agarose and then used in a rapid hsp90 retention assay to define regions of the CyP-40 C terminus that are important for hsp90 binding. Our evidence suggests that the TPR domain is not sufficient for stable association of CyP-40 with hsp90 and requires the participation of flanking acidic and basic residues clustered at the N- and C-terminal ends, respectively. Both microdomains are characterized by alpha-helical structures with segregated hydrophobic and charged residues. Corresponding regions were identified in FKBP52. By preincubating myometrial cytosol with lysates containing bacterially expressed FKBP52, we have shown that FKBP52 competes with CyP-40 for hsp90 binding. Our results raise the possibility of a mutually exclusive association of CyP-40 and FKBP52 with hsp90. This would lead to separate immunophilin-hsp90-receptor complexes and place the estrogen receptor under the control of distinct immunophilin signaling pathways.
authors.affiliation: Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, 6009 Western Australia.
authors.forename: T
authors.initials: T
authors.lastname: Ratajczak
authors.forename: A
authors.initials: A
authors.lastname: Carrello
mesh_terms: D000591:Amino Acid Isomerases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D002417:Cattle; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins; D003600:Cytosol / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005982:Glutathione Transferase / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009215:Myometrium / Q000378:metabolism; D019696:Peptidylprolyl Isomerase; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D015183:Restriction Mapping; D017384:Sequence Deletion; D022021:Tacrolimus Binding Proteins
chemical_list: D002352:Carrier Proteins; D000081406:Peptidyl-Prolyl Isomerase F; D004268:DNA-Binding Proteins; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase; D000591:Amino Acid Isomerases; D021983:Cyclophilins; D022021:Tacrolimus Binding Proteins; D019696:Peptidylprolyl Isomerase