title: Activation of amyloid precursor protein processing by growth factors is dependent on Ras GTPase activity.
abstract: The β-amyloid peptide is generated by the proteolysis of the amyloid precursor protein (APP) by the action of β- and γ-secretase. The mechanisms underlying this process are poorly understood. Using a cell-based reporter gene assay we analysed the possible signals and pathways that could be involved in APP cleavage. We used the stable cell line HeLa AG that expresses the human APP(695) fused with the yeast transcription factor Gal4. This fusion protein is normally translocated into the plasma membrane and after APP-Gal4 cleavage, the AICD-Gal4 fragment released can activate the transcription of a luciferase reporter gene. Through this reporter system, we demonstrated that Ras GTPase, but not Ral and Rap, could promote APP-Gal4 cleavage. In addition HeLa AG cells stimulated with EGF or PDGF or overexpressing EGFR exhibit increased APP proteolysis in a Ras-dependent way. This process is also dependent on γ-secretase activity, being abolished by the γ-secretase inhibitor DAPT.
authors.affiliation: Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza Della Scienza 2, 20126, Milan, Italy.
authors.forename: Loredana
authors.initials: L
authors.lastname: Amigoni
authors.forename: Michela
authors.initials: M
authors.lastname: Ceriani
authors.forename: Fiorella
authors.initials: F
authors.lastname: Belotti
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Minopoli
authors.forename: Enzo
authors.initials: E
authors.lastname: Martegani
mesh_terms: D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D016564:Amyloid beta-Protein Precursor; D036341:Intercellular Signaling Peptides and Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D066246:ErbB Receptors; D018631:ras Proteins