title: Posttranslational modification and conformational state of heat shock protein 90 differentially affect binding of chemically diverse small molecule inhibitors.
abstract: Heat shock protein 90 (Hsp90) is an essential molecular chaperone in eukaryotes that facilitates the conformational maturation and function of a diverse protein clientele, including aberrant and/or over-expressed proteins that are involved in cancer growth and survival. A role for Hsp90 in supporting the protein homeostasis of cancer cells has buoyed interest in the utility of Hsp90 inhibitors as anti-cancer drugs. Despite the fact that all clinically evaluated Hsp90 inhibitors target an identical nucleotide-binding pocket in the N domain of the chaperone, the precise determinants that affect drug binding in the cellular environment remain unclear, and it is possible that chemically distinct inhibitors may not share similar binding preferences. Here we demonstrate that two chemically unrelated Hsp90 inhibitors, the benzoquinone ansamycin geldanamycin and the purine analog PU-H71, select for overlapping but not identical subpopulations of total cellular Hsp90, even though both inhibitors bind to an amino terminal nucleotide pocket and prevent N domain dimerization. Our data also suggest that PU-H71 is able to access a broader range of N domain undimerized Hsp90 conformations than is geldanamycin and is less affected by Hsp90 phosphorylation, consistent with its broader and more potent anti-tumor activity. A more complete understanding of the impact of the cellular milieu on small molecule inhibitor binding to Hsp90 should facilitate their more effective use in the clinic.
authors.affiliation: Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA.
authors.forename: Kristin
authors.initials: K
authors.lastname: Beebe
authors.forename: Mehdi
authors.initials: M
authors.lastname: Mollapour
authors.forename: Bradley
authors.initials: B
authors.lastname: Scroggins
authors.forename: Chrisostomos
authors.initials: C
authors.lastname: Prodromou
authors.forename: Wanping
authors.initials: W
authors.lastname: Xu
authors.forename: Mari
authors.initials: M
authors.lastname: Tokita
authors.forename: Tony
authors.initials: T
authors.lastname: Taldone
authors.forename: Lester
authors.initials: L
authors.lastname: Pullen
authors.forename: Bettina K
authors.initials: BK
authors.lastname: Zierer
authors.forename: Min-Jung
authors.initials: MJ
authors.lastname: Lee
authors.forename: Jane
authors.initials: J
authors.lastname: Trepel
authors.forename: Johannes
authors.initials: J
authors.lastname: Buchner
authors.forename: Daniel
authors.initials: D
authors.lastname: Bolon
authors.forename: Gabriela
authors.initials: G
authors.lastname: Chiosis
authors.forename: Leonard
authors.initials: L
authors.lastname: Neckers
mesh_terms: D052117:Benzodioxoles / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D016227:Benzoquinones / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D001665:Binding Sites; D045744:Cell Line, Tumor; D057809:HEK293 Cells; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047029:Lactams, Macrocyclic / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D011687:Purines / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D052117:Benzodioxoles; D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D011687:Purines; C526550:9H-purine-9-propanamine, 6-amino-8-((6-iodo-1,3-benzodioxol-5-yl)thio)-N-(1-methylethyl)-; C001277:geldanamycin