title: The Akt activation inhibitor TCN-P inhibits Akt phosphorylation by binding to the PH domain of Akt and blocking its recruitment to the plasma membrane.
abstract: Persistently hyperphosphorylated Akt contributes to human oncogenesis and resistance to therapy. Triciribine (TCN) phosphate (TCN-P), the active metabolite of the Akt phosphorylation inhibitor TCN, is in clinical trials, but the mechanism by which TCN-P inhibits Akt phosphorylation is unknown. Here we show that in vitro, TCN-P inhibits neither Akt activity nor the phosphorylation of Akt S473 and T308 by mammalian target of rapamycin or phosphoinositide-dependent kinase 1. However, in intact cells, TCN inhibits EGF-stimulated Akt recruitment to the plasma membrane and phosphorylation of Akt. Surface plasmon resonance shows that TCN, but not TCN, binds Akt-derived pleckstrin homology (PH) domain (K(D): 690 nM). Furthermore, nuclear magnetic resonance spectroscopy shows that TCN-P, but not TCN, binds to the PH domain in the vicinity of the PIP3-binding pocket. Finally, constitutively active Akt mutants, Akt1-T308D/S473D and myr-Akt1, but not the transforming mutant Akt1-E17K, are resistant to TCN and rescue from its inhibition of proliferation and induction of apoptosis. Thus, the results of our studies indicate that TCN-P binds to the PH domain of Akt and blocks its recruitment to the membrane, and that the subsequent inhibition of Akt phosphorylation contributes to TCN-P antiproliferative and proapoptotic activities, suggesting that this drug may be beneficial to patients whose tumors express persistently phosphorylated Akt.
authors.affiliation: Drug Discovery Department, Moffitt Cancer Center, Tampa, FL 33612, USA.
authors.forename: N
authors.initials: N
authors.lastname: Berndt
authors.forename: H
authors.initials: H
authors.lastname: Yang
authors.forename: B
authors.initials: B
authors.lastname: Trinczek
authors.forename: S
authors.initials: S
authors.lastname: Betzi
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang
authors.forename: B
authors.initials: B
authors.lastname: Wu
authors.forename: N J
authors.initials: NJ
authors.lastname: Lawrence
authors.forename: M
authors.initials: M
authors.lastname: Pellecchia
authors.forename: E
authors.initials: E
authors.lastname: Schönbrunn
authors.forename: J Q
authors.initials: JQ
authors.lastname: Cheng
authors.forename: S M
authors.initials: SM
authors.lastname: Sebti
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D000073:Acenaphthenes / Q000378:metabolism* / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000378:metabolism / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D005784:Gene Amplification; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008565:Membrane Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D051057:Proto-Oncogene Proteins c-akt / Q000737:chemistry / Q000378:metabolism*; D012265:Ribonucleotides / Q000378:metabolism* / Q000494:pharmacology*; D015398:Signal Transduction; D020349:Surface Plasmon Resonance; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: D000073:Acenaphthenes; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; D012265:Ribonucleotides; C014205:triciribine phosphate; D004815:Epidermal Growth Factor; D064413:3-Phosphoinositide-Dependent Protein Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases