title: Platelet-derived growth factor induces the beta-gamma-secretase-mediated cleavage of Alzheimer's amyloid precursor protein through a Src-Rac-dependent pathway.
abstract: The beta-amyloid peptide (Abeta) present in the senile plaques of Alzheimer's disease derives from the cleavage of a membrane protein, named APP, driven by two enzymes, known as beta- and gamma-secretases. The mechanisms regulating this cleavage are not understood. We have developed an experimental system to identify possible extracellular signals able to trigger the cleavage of an APP-Gal4 fusion protein, which is detected by measuring the expression of the CAT gene transcribed under the control of the Gal4 transcription factor, which is released from the membrane upon the cleavage of APP-Gal4. By using this assay, we purified a protein contained in the C6 cell-conditioned medium, which activates the cleavage of APP-Gal4 and which we demonstrated to be PDGF-BB. The APP-Gal4 processing induced by PDGF is dependent on the gamma-secretase activity, being abolished by an inhibitor of this enzyme, and is the consequence of the activation of a pathway downstream of the PDGF-receptor, which includes the non-receptor tyrosine kinase Src and the small G-protein Rac1. These findings are confirmed by the observation that a constitutively active form of Src increases Abeta generation and that, in cells stably expressing APP, the generation of A is strongly decreased by the Src tyrosine kinase inhibitor PP2.
authors.affiliation: Dipartimento di Biochimica e Biotecnologie Mediche, Università degli Studi di Napoli Federico II, Napoli 80131, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Gianni
authors.forename: Nicola
authors.initials: N
authors.lastname: Zambrano
authors.forename: Marida
authors.initials: M
authors.lastname: Bimonte
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Minopoli
authors.forename: Luc
authors.initials: L
authors.lastname: Mercken
authors.forename: Fabio
authors.initials: F
authors.lastname: Talamo
authors.forename: Andrea
authors.initials: A
authors.lastname: Scaloni
authors.forename: Tommaso
authors.initials: T
authors.lastname: Russo
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism*; D000645:Ammonium Sulfate / Q000494:pharmacology; D053829:Amyloid Precursor Protein Secretases; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D016282:Aspartic Acid Endopeptidases; D000077214:Becaplermin; D015153:Blotting, Western; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D003183:Complement C6 / Q000378:metabolism; D017077:Culture Media, Conditioned / Q000494:pharmacology; D010450:Endopeptidases / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D009474:Neurons / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D011485:Protein Binding; D020574:Proto-Oncogene Proteins c-sis; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013997:Time Factors; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D016564:Amyloid beta-Protein Precursor; D003183:Complement C6; D017077:Culture Media, Conditioned; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D011993:Recombinant Fusion Proteins; D000077214:Becaplermin; D015500:Chloramphenicol O-Acetyltransferase; D017479:Receptors, Platelet-Derived Growth Factor; D019061:src-Family Kinases; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; D020744:rac GTP-Binding Proteins; D000645:Ammonium Sulfate