title: An ATP-site on-off switch that restricts phosphatase accessibility of Akt.
abstract: The protein serine-threonine kinase Akt undergoes a substantial conformational change upon activation, which is induced by the phosphorylation of two critical regulatory residues, threonine 308 and serine 473. Paradoxically, treating cells with adenosine 5'-triphosphate (ATP)-competitive inhibitors of Akt results in increased phosphorylation of both residues. We show that binding of ATP-competitive inhibitors stabilized a conformation in which both phosphorylated sites were inaccessible to phosphatases. ATP binding also produced this protection of the phosphorylated sites, whereas interaction with its hydrolysis product adenosine 5'-diphosphate (ADP) or allosteric Akt inhibitors resulted in increased accessibility of these phosphorylated residues. ATP-competitive inhibitors mimicked ATP by targeting active Akt. Forms of Akt activated by an oncogenic mutation or myristoylation were more potently inhibited by the ATP-competitive inhibitors than was wild-type Akt. These data support a new model of kinase regulation, wherein nucleotides modulate an on-off switch in Akt through conformational changes, which is disrupted by ATP-competitive inhibitors.
authors.affiliation: Genentech Inc., South San Francisco, CA 94080, USA. klin@gene.com
authors.forename: Kui
authors.initials: K
authors.lastname: Lin
authors.forename: Jie
authors.initials: J
authors.lastname: Lin
authors.forename: Wen-I
authors.initials: WI
authors.lastname: Wu
authors.forename: Joshua
authors.initials: J
authors.lastname: Ballard
authors.forename: Brian B
authors.initials: BB
authors.lastname: Lee
authors.forename: Susan L
authors.initials: SL
authors.lastname: Gloor
authors.forename: Guy P A
authors.initials: GP
authors.lastname: Vigers
authors.forename: Tony H
authors.initials: TH
authors.lastname: Morales
authors.forename: Lori S
authors.initials: LS
authors.lastname: Friedman
authors.forename: Nicholas
authors.initials: N
authors.lastname: Skelton
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Brandhuber
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000494:Allosteric Regulation; D001665:Binding Sites; D008958:Models, Molecular; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*
chemical_list: D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D051057:Proto-Oncogene Proteins c-akt; D010744:Phosphoric Monoester Hydrolases