Normal Cellular Processing of the β-Amyloid Precursor Protein Results in the Secretion of the Amyloid β Peptide and Related Molecules

Authors

  • CHRISTIAN HAASS,

    Corresponding author
    1. Department of Neurology and Program in Neuroscience, Harvard Medical School, and Center for Neurologic Diseases, Brigham and Women's Hospital, Boston, Massachusetts 02115 USA
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  • ALBERT Y. HUNG,

    1. Department of Neurology and Program in Neuroscience, Harvard Medical School, and Center for Neurologic Diseases, Brigham and Women's Hospital, Boston, Massachusetts 02115 USA
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  • MICHAEL G. SCHLOSSMACHER,

    1. Department of Neurology and Program in Neuroscience, Harvard Medical School, and Center for Neurologic Diseases, Brigham and Women's Hospital, Boston, Massachusetts 02115 USA
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    • This work was supported by NIH grants 06173 (LEAD Award) and AG 07911 to D.J.S. and grants from the Deutsche Forschungsgemcinschaft to C.H. and Merck Sharp and Dohme Research Laboratories to A.Y.H.

  • TILMAN OLTERSDORF,

    1. Athena Neuroscience Inc., South San Francisco, California 94090 USA
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  • DAVID B. TEPLOW,

    1. Department of Neurology and Program in Neuroscience, Harvard Medical School, and Center for Neurologic Diseases, Brigham and Women's Hospital, Boston, Massachusetts 02115 USA
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  • DENNIS J. SELKOE

    1. Department of Neurology and Program in Neuroscience, Harvard Medical School, and Center for Neurologic Diseases, Brigham and Women's Hospital, Boston, Massachusetts 02115 USA
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  • Present address: Research Unit of Experimental Neuropathology, Austrian Academy of Science, Vienna A 1090 Austria

Send correspondence to: Christian Haass, Department of Neurology and Program in Neuroscience, Harvard Medical School; and Center for Neurologic Diseases, Brigham and Women's Hospital, Boston, MA 02115 USA; TEL: 617–732–6454; FAX: 617–732–7787.

Abstract

Alzheimer's disease is characterized by the extracellular deposition in the brain and its blood vessels of insoluble aggregates of the amyloid β peptide (Aβ). This peptide is derived from a large integral membrane protein, the β-amyloid precursor protein (βAPP), by proteolytic processing. The Aβ has previously been found only in the brains of patients with Alzheimer's disease or advanced aging. We describe here the finding that Aβ is produced continuously by normal processing in tissue culture cells. Aβ and closely related peptides were identified in the media of cells transfected with cDNAs coding for βAPP in a variety of cell lines and primary tissue cultured cells. The identity of these peptides was confirmed by epitope mapping and radiosequencing. Peptides of a molecular weight of ∼3 and ∼4 kDa are described. The 4 kDa range contains mostly the Aβ and two related peptides starting N-terminal to the beginning of Aβ. In the 3 kDa range, the majority of peptides start at the secretase site; in addition, two longer peptides were found starting at amino acid F(4) and E(11) of the Aβ sequence. To identify the processing pathways which lead to the secretion of these peptides, we used a variety of drugs known to interfere with certain cell biological pathways. We conclude that lysosomes may not play a predominant role in the formation of 3 and 4 kDa peptides. We show that an acidic environment is necessary to create the N-terminus of the Aβ and postulate that alternative secretory cleavage might result in the formation of the N-terminus of Aβ and related peptides. This cleavage takes place either in late Golgi, at the cell-surface or in early endosomes, but not in lysosomes. The N-terminus of most of the 3 kDa peptides is created by secretory cleavage on the cell surface or within late Golgi.

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