title: A surface on the androgen receptor that allosterically regulates coactivator binding.
abstract: Current approaches to inhibit nuclear receptor (NR) activity target the hormone binding pocket but face limitations. We have proposed that inhibitors, which bind to nuclear receptor surfaces that mediate assembly of the receptor's binding partners, might overcome some of these limitations. The androgen receptor (AR) plays a central role in prostate cancer, but conventional inhibitors lose effectiveness as cancer treatments because anti-androgen resistance usually develops. We conducted functional and x-ray screens to identify compounds that bind the AR surface and block binding of coactivators for AR activation function 2 (AF-2). Four compounds that block coactivator binding in solution with IC(50) approximately 50 microM and inhibit AF-2 activity in cells were detected: three nonsteroidal antiinflammatory drugs and the thyroid hormone 3,3',5-triiodothyroacetic acid. Although visualization of compounds at the AR surface reveals weak binding at AF-2, the most potent inhibitors bind preferentially to a previously unknown regulatory surface cleft termed binding function (BF)-3, which is a known target for mutations in prostate cancer and androgen insensitivity syndrome. X-ray structural analysis reveals that 3,3',5-triiodothyroacetic acid binding to BF-3 remodels the adjacent interaction site AF-2 to weaken coactivator binding. Mutation of residues that form BF-3 inhibits AR function and AR AF-2 activity. We propose that BF-3 is a previously unrecognized allosteric regulatory site needed for AR activity in vivo and a possible pharmaceutical target.
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143, USA.
authors.forename: Eva
authors.initials: E
authors.lastname: Estébanez-Perpiñá
authors.forename: Leggy A
authors.initials: LA
authors.lastname: Arnold
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Arnold
authors.forename: Phuong
authors.initials: P
authors.lastname: Nguyen
authors.forename: Edson Delgado
authors.initials: ED
authors.lastname: Rodrigues
authors.forename: Ellena
authors.initials: E
authors.lastname: Mar
authors.forename: Raynard
authors.initials: R
authors.lastname: Bateman
authors.forename: Peter
authors.initials: P
authors.lastname: Pallai
authors.forename: Kevan M
authors.initials: KM
authors.lastname: Shokat
authors.forename: John D
authors.initials: JD
authors.lastname: Baxter
authors.forename: R Kiplin
authors.initials: RK
authors.lastname: Guy
authors.forename: Paul
authors.initials: P
authors.lastname: Webb
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Fletterick
mesh_terms: D000495:Allosteric Site / Q000235:genetics; D059002:Androgen Receptor Antagonists; D000818:Animals; D018360:Crystallography, X-Ray; D066298:In Vitro Techniques; D051379:Mice; D008958:Models, Molecular; D051958:Nuclear Receptor Coactivator 2 / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011944:Receptors, Androgen / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D059002:Androgen Receptor Antagonists; D051958:Nuclear Receptor Coactivator 2; D011944:Receptors, Androgen; D011994:Recombinant Proteins