title: Reduced amyloidogenic processing of the amyloid beta-protein precursor by the small-molecule Differentiation Inducing Factor-1.
abstract: The detection of cell cycle proteins in Alzheimer's disease (AD) brains may represent an early event leading to neurodegeneration. To identify cell cycle modifiers with anti-Abeta properties, we assessed the effect of Differentiation-Inducing Factor-1 (DIF-1), a unique, small-molecule from Dictyostelium discoideum, on the proteolysis of the amyloid beta-protein precursor (APP) in a variety of different cell types. We show that DIF-1 slows cell cycle progression through G0/G1 that correlates with a reduction in cyclin D1 protein levels. Western blot analysis of DIF-treated cells and conditioned medium revealed decreases in the levels of secreted APP, mature APP, and C-terminal fragments. Assessment of conditioned media by sandwich ELISA showed reduced levels of Abeta40 and Abeta42, also demonstrating that treatment with DIF-1 effectively decreases the ratio of Abeta42 to Abeta40. In addition, DIF-1 significantly diminished APP phosphorylation at residue T668. Interestingly, site-directed mutagenesis of APP residue Thr668 to alanine or glutamic acid abolished the effect of DIF-1 on APP proteolysis and restored secreted levels of Abeta. Finally, DIF-1 prevented the accumulation of APP C-terminal fragments induced by the proteasome inhibitor lactacystin, and calpain inhibitor N-acetyl-leucyl-leucyl-norleucinal (ALLN). Our findings suggest that DIF-1 affects G0/G1-associated amyloidogenic processing of APP by a gamma-secretase-, proteasome- and calpain-insensitive pathway, and that this effect requires the presence of residue Thr668.
authors.affiliation: Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA. myre@chgr.mgh.harvard.edu
authors.forename: Michael A
authors.initials: MA
authors.lastname: Myre
authors.forename: Kevin
authors.initials: K
authors.lastname: Washicosky
authors.forename: Robert D
authors.initials: RD
authors.lastname: Moir
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Tesco
authors.forename: Rudolph E
authors.initials: RE
authors.lastname: Tanzi
authors.forename: Wilma
authors.initials: W
authors.lastname: Wasco
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D016229:Amyloid beta-Peptides / Q000378:metabolism; D016564:Amyloid beta-Protein Precursor / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D016466:CHO Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002460:Cell Line / Q000187:drug effects / Q000378:metabolism; D045744:Cell Line, Tumor / Q000187:drug effects / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D019938:Cyclin D1 / Q000096:biosynthesis; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005910:Glioma / Q000473:pathology; D006588:Hexanones / Q000494:pharmacology*; D006801:Humans; D006843:Hydrocarbons, Chlorinated / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology; D007976:Leupeptins / Q000494:pharmacology; D051379:Mice; D010446:Peptide Fragments / Q000378:metabolism; D061988:Proteasome Inhibitors; D011687:Purines / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D000077546:Roscovitine; D013912:Threonine / Q000737:chemistry
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D001552:Benzazepines; C490570:Differentiation-inducing factor-1, Dictyostelium; D006588:Hexanones; D006843:Hydrocarbons, Chlorinated; D007211:Indoles; D007976:Leupeptins; D010446:Peptide Fragments; D061988:Proteasome Inhibitors; D011687:Purines; D011993:Recombinant Fusion Proteins; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42); C119620:kenpaullone; D000077546:Roscovitine; C063261:acetylleucyl-leucyl-norleucinal; C067713:lactacystin; D019938:Cyclin D1; D013912:Threonine; D000111:Acetylcysteine