title: PI3K/AKT signaling inhibits NOTCH1 lysosome-mediated degradation.
abstract: The pathways of NOTCH and PI3K/AKT are dysregulated in about 60% and 48% of T-cell acute lymphoblastic leukemia (T-ALL) patients, respectively. In this context, they interact and cooperate in controlling tumor cell biology. Here, we propose a novel mechanism by which the PI3K/AKT pathway regulates NOTCH1 in T-ALL, starting from the evidence that the inhibition of PI3K/AKT signaling induced by treatment with LY294002 or transient transfection with a dominant negative AKT mutant downregulates NOTCH1 protein levels and activity, without affecting NOTCH1 transcription. We showed that the withdrawal of PI3K/AKT signaling was associated to NOTCH1 phosphorylation in tyrosine residues and monoubiquitination of NOTCH1 detected by Ubiquitin capture assay. Co-immunoprecipitation assay and colocalization analysis further showed that the E3 ubiquitin ligase c-Cbl interacts and monoubiquitinates NOTCH1, activating its lysosomal degradation. These results suggest that the degradation of NOTCH1 could represent a mechanism of control by which NOTCH1 receptors are actively removed from the cell surface. This mechanism is finely regulated by the PI3K/AKT pathway in physiological conditions. In pathological conditions characterized by PI3K/AKT hyperactivation, such as T-ALL, the excessive AKT signaling could lead to NOTCH1 signaling dysregulation. Therefore, a therapeutic strategy directed to PI3K/AKT in T-ALL could contemporaneously inhibit the dysregulated NOTCH1 signaling. © 2015 Wiley Periodicals, Inc.
authors.affiliation: Department of Health Science, Università Degli Studi Di Milano, via A. Di Rudinì 8, 20142, Milan, Italy.
authors.forename: Natalia
authors.initials: N
authors.lastname: Platonova
authors.affiliation: Department of Health Science, Università Degli Studi Di Milano, via A. Di Rudinì 8, 20142, Milan, Italy.
authors.forename: Teresa
authors.initials: T
authors.lastname: Manzo
authors.affiliation: Department of Health Science, Università Degli Studi Di Milano, via A. Di Rudinì 8, 20142, Milan, Italy.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Mirandola
authors.affiliation: Department of Health Science, Università Degli Studi Di Milano, via A. Di Rudinì 8, 20142, Milan, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Colombo
authors.affiliation: Department of Health Science, Università Degli Studi Di Milano, via A. Di Rudinì 8, 20142, Milan, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Calzavara
authors.affiliation: Department of Health Science, Università Degli Studi Di Milano, via A. Di Rudinì 8, 20142, Milan, Italy.
authors.forename: Emilia
authors.initials: E
authors.lastname: Vigolo
authors.affiliation: Department of Health Science, Università Degli Studi Di Milano, via A. Di Rudinì 8, 20142, Milan, Italy.
authors.forename: Greta Chiara
authors.initials: GC
authors.lastname: Cermisoni
authors.affiliation: Department of Health Science, Università Degli Studi Di Milano, via A. Di Rudinì 8, 20142, Milan, Italy.
authors.forename: Daria
authors.initials: D
authors.lastname: De Simone
authors.affiliation: Department of Health Science, Università Degli Studi Di Milano, via A. Di Rudinì 8, 20142, Milan, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Garavelli
authors.affiliation: Department of Health Science, Università Degli Studi Di Milano, via A. Di Rudinì 8, 20142, Milan, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Cecchinato
authors.affiliation: Department of Health Science, Università Degli Studi Di Milano, via A. Di Rudinì 8, 20142, Milan, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Lazzari
authors.affiliation: Department of Clinical Sciences and Community Health, Università Degli Studi Di Milano, Hematology, Fondazione Cà Granda IRCCS Policlinico, via F. Sforza, 35, 20122, Milan, Italy.
authors.forename: Antonino
authors.initials: A
authors.lastname: Neri
authors.affiliation: Department of Health Science, Università Degli Studi Di Milano, via A. Di Rudinì 8, 20142, Milan, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Chiaramonte