title: Benzoflavone activators of the cystic fibrosis transmembrane conductance regulator: towards a pharmacophore model for the nucleotide-binding domain.
abstract: Our previous screen of flavones and related heterocycles for the ability to activate the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel indicated that UCCF-029, a 7,8-benzoflavone, was a potent activator. In the present study, we describe the synthesis and evaluation, using cell-based assays, of a series of benzoflavone analogues to examine structure-activity relationships and to identify compounds having greater potency for activation of both wild type CFTR and a mutant CFTR (G551D-CFTR) that causes cystic fibrosis in some human subjects. Using UCCF-029 as a structural guide, a panel of 77 flavonoid analogues was prepared. Analysis of the panel in FRT cells indicated that benzannulation of the flavone A-ring at the 7,8-position greatly improved compound activity and potency for several flavonoids. Incorporation of a B-ring pyridyl nitrogen either at the 3- or 4-position also elevated CFTR activity, but the influence of this structural modification was not as uniform as the influence of benzannulation. The most potent new analogue, UCCF-339, activated wild-type CFTR with a K(d) of 1.7 microM, which is more active than the previous most potent flavonoid activator of CFTR, apigenin. Several compounds in the benzoflavone panel also activated G551D-CFTR, but none were as active as apigenin. Pharmacophore modeling suggests a common binding mode for the flavones and other known CFTR activators at one of the nucleotide-binding sites, allowing for the rational development of more potent flavone analogues.
authors.affiliation: Department of Chemistry, University of California, Davis, CA 95616, USA.
authors.forename: Mark F
authors.initials: MF
authors.lastname: Springsteel
authors.forename: Luis J V
authors.initials: LJ
authors.lastname: Galietta
authors.forename: Tonghui
authors.initials: T
authors.lastname: Ma
authors.forename: Kolbot
authors.initials: K
authors.lastname: By
authors.forename: Gideon O
authors.initials: GO
authors.lastname: Berger
authors.forename: Hong
authors.initials: H
authors.lastname: Yang
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Dicus
authors.forename: Wonken
authors.initials: W
authors.lastname: Choung
authors.forename: Chao
authors.initials: C
authors.lastname: Quan
authors.forename: Anang A
authors.initials: AA
authors.lastname: Shelat
authors.forename: R Kiplin
authors.initials: RK
authors.lastname: Guy
authors.forename: A S
authors.initials: AS
authors.lastname: Verkman
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Kurth
authors.forename: Michael H
authors.initials: MH
authors.lastname: Nantz
mesh_terms: D000818:Animals; D047310:Apigenin; D001571:Benzoflavones / Q000138:chemical synthesis* / Q000494:pharmacology; D001665:Binding Sites; D002478:Cells, Cultured; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins; D008958:Models, Molecular; D008968:Molecular Conformation; D009711:Nucleotides / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D013329:Structure-Activity Relationship
chemical_list: D001571:Benzoflavones; C505032:CFTR protein, human; D005419:Flavonoids; D008164:Luminescent Proteins; D009711:Nucleotides; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D049452:Green Fluorescent Proteins; D047310:Apigenin