title: Astrocytes and microglia but not neurons preferentially generate N-terminally truncated Aβ peptides.
abstract: The neuropathological hallmarks of Alzheimer's disease include extracellular neuritic plaques and neurofibrillary tangles. The neuritic plaques contain β-amyloid peptides (Aβ peptides) as the major proteinaceous constituent and are surrounded by activated microglia and astrocytes as well as dystrophic neurites. N-terminally truncated forms of Aβ peptides are highly prevalent in neuritic plaques, including Aβ 3-x beginning at Glu eventually modified to pyroglutamate (Aβ N3pE-x), Aβ 2-x, Aβ 4-x, and Aβ 5-x. The precise origin of the different N-terminally modified Aβ peptides currently remains unknown. To assess the contribution of specific cell types to the formation of different N-terminally truncated Aβ peptides, supernatants from serum-free primary cell cultures of chicken neurons, astrocytes, and microglia, as well as human astrocytes, were analyzed by Aβ-ELISA and one- and two-dimensional SDS-urea polyacrylamide gel electrophoresis followed by immunoblot analysis. To evaluate the contribution of β- and γ-secretase to the generation of N-terminally modified Aβ, cultured astrocytes were treated with membrane-anchored "tripartite β-secretase (BACE1) inhibitors" and the γ-secretase inhibitor DAPT. Neurons, astrocytes, and microglia each exhibited cell type-specific patterns of secreted Aβ peptides. Neurons predominantly secreted Aβ peptides that begin at Asp1, whereas those released from astrocytes and microglia included high proportions of N-terminally modified Aβ peptides, presumably including Aβ 2/3-x and 4/5-x. The inhibition of BACE1 reduced the amount of Aβ 1-x in cell culture supernatants but not the amount of Aβ 2-x.
authors.affiliation: Department of Psychiatry and Psychotherapy, Friedrich-Alexander-University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
authors.forename: Timo Jan
authors.initials: TJ
authors.lastname: Oberstein
authors.affiliation: Department of Psychiatry and Psychotherapy, Friedrich-Alexander-University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Spitzer
authors.affiliation: Department of Psychiatry and Psychotherapy, Friedrich-Alexander-University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany; Department of Psychiatry and Psychotherapy, LVR-Klinikum, Medical Faculty, University of Duisburg-Essen, D-45147 Essen, Germany.
authors.forename: Hans-Wolfgang
authors.initials: HW
authors.lastname: Klafki
authors.affiliation: Department of Chemistry, Technische Universität Dresden, Bergstr. 66, D-01069 Dresden, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Linning
authors.affiliation: Department of Psychiatry and Psychotherapy, Friedrich-Alexander-University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany; II Medizinische Klinik, Klinikum rechts der Isar, Technische Universität München, Ismaningerstr 22, D-81675 Munich, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Neff
authors.affiliation: Department of Chemistry, Technische Universität Dresden, Bergstr. 66, D-01069 Dresden, Germany.
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Knölker
authors.affiliation: Department of Psychiatry and Psychotherapy, Friedrich-Alexander-University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
authors.forename: Piotr
authors.initials: P
authors.lastname: Lewczuk
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center (UMG), Georg-August-University, D-37075 Göttingen, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Wiltfang
authors.affiliation: Department of Psychiatry and Psychotherapy, Friedrich-Alexander-University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Kornhuber
authors.affiliation: Department of Psychiatry and Psychotherapy, Friedrich-Alexander-University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany. Electronic address: manuel.maler@uk-erlangen.de.
authors.forename: Juan Manuel
authors.initials: JM
authors.lastname: Maler
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001921:Brain / Q000166:cytology; D002478:Cells, Cultured; D002642:Chick Embryo; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D047468:Immunoprecipitation; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010446:Peptide Fragments; D058225:Plaque, Amyloid; D013997:Time Factors; D016875:tau Proteins / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; D016875:tau Proteins; D016282:Aspartic Acid Endopeptidases
keywords: Alzheimer's disease; Astrocytes; Aβ; BACE; Extracellular; Intracellular; Microglia; N-terminally truncated; Neurons; Secretase