Alzheimer disease (AD) is characterized by the accumulation of amyloid plaques, which are predominantly composed of amyloid-β peptide1. Two principal physiological pathways either prevent or promote amyloid-β generation from its precursor, β-amyloid precursor protein (APP), in a competitive manner1. Although APP processing has been studied in great detail, unknown proteolytic events seem to hinder stoichiometric analyses of APP metabolism in vivo2. Here we describe a new physiological APP processing pathway, which generates proteolytic fragments capable of inhibiting neuronal activity within the hippocampus. We identify higher molecular mass carboxy-terminal fragments (CTFs) of APP, termed CTF-η, in addition to the long-known CTF-α and CTF-β fragments generated by the α- and β-secretases ADAM10 (a disintegrin and metalloproteinase 10) and BACE1 (β-site APP cleaving enzyme 1), respectively. CTF-η generation is mediated in part by membrane-bound matrix metalloproteinases such as MT5-MMP, referred to as η-secretase activity. η-Secretase cleavage occurs primarily at amino acids 504–505 of APP695, releasing a truncated ectodomain. After shedding of this ectodomain, CTF-η is further processed by ADAM10 and BACE1 to release long and short Aη peptides (termed Aη-α and Aη-β). CTFs produced by η-secretase are enriched in dystrophic neurites in an AD mouse model and in human AD brains. Genetic and pharmacological inhibition of BACE1 activity results in robust accumulation of CTF-η and Aη-α. In mice treated with a potent BACE1 inhibitor, hippocampal long-term potentiation was reduced. Notably, when recombinant or synthetic Aη-α was applied on hippocampal slices ex vivo, long-term potentiation was lowered. Furthermore, in vivo single-cell two-photon calcium imaging showed that hippocampal neuronal activity was attenuated by Aη-α. These findings not only demonstrate a major functionally relevant APP processing pathway, but may also indicate potential translational relevance for therapeutic strategies targeting APP processing.

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The authors thank S. Lammich, N. Exner and H. Steiner for critical comments. We thank A. Sülzen, N. Astola, S. Diederich, E. Grießinger and J. Gobbert for technical help. The APPPS1-21 colony was established from a breeding pair provided by M. Jucker. MT1-MMP−/− mouse brains were obtained from Z. Zhou. MT5-MMP−/− mouse brains were obtained from I. Farinas. We thank H. Jacobsen for the BACE1 inhibitor RO5508887. This work was supported by the European Research Council under the European Union’s Seventh Framework Program (FP7/2007–2013)/ERC grant agreement no. 321366-Amyloid (advanced grant to C.H.). The work of D.R.T. was supported by AFI (grant 13803). The research leading to these results has received funding (F.M. and D.H.) from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement no. 318987 [TOPAG]. We thank J. Cox and M. Mann for critical discussions and the mass spectrometry infrastructure. We also acknowledge support by grants from Deutsche Forschungsgemeinschaft (MU 1457/9-1, 9-2 to U.M.) and the ERA-Net Neuron (01EW1305A to U.M.). Further support came from the ATIP/AVENIR program (Centre national de la recherche scientifique, CNRS) to H.M.; the French Fondation pour la Coopération Scientifique – Plan Alzheimer (Senior Innovative Grant 2010) to M.C. and H.M., and the French Government (National Research Agency, ANR) through the “Investments for the Future” LABEX SIGNALIFE: program reference ANR-11-LABX-0028-01 to S.K. M.A.B. was supported by the Langmatz Stiftung. F.J.L. is a Wellcome Trust Investigator. In vivo BACE1 inhibition experiments with APP transgenic mice were performed together with reMYND (Bio-Incubator, 3001 Leuven-Heverlee, Belgium).

Author information


  1. Biomedical Center (BMC), Ludwig-Maximilians-University Munich, 81377 Munich, Germany

    • Michael Willem
    • , Anna Daria
    • , Heike Hampel
    • , Veronika Müller
    • , Camilla Giudici
    • , Brigitte Nuscher
    •  & Christian Haass
  2. German Center for Neurodegenerative Diseases (DZNE) Munich, 81377 Munich, Germany

    • Sabina Tahirovic
    • , Saak V. Ovsepian
    • , Andrea Wenninger-Weinzierl
    • , Elisabeth Kremmer
    • , Jochen Herms
    •  & Christian Haass
  3. Department of Psychiatry and Psychotherapy, Technische Universität München, 81675 Munich, Germany

    • Marc Aurel Busche
  4. Institute of Neuroscience, Technische Universität München, 80802 Munich, Germany

    • Marc Aurel Busche
    •  & Arthur Konnerth
  5. Munich Cluster for Systems Neurology (SyNergy), Ludwig-Maximilians-University Munich, 81377 Munich, Germany

    • Marc Aurel Busche
    • , Elisabeth Kremmer
    • , Arthur Konnerth
    •  & Christian Haass
  6. Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Centre National de la Recherche Scientifique (CNRS), Université de Nice Sophia Antipolis, UMR 7275, 06560 Valbonne, France

    • Magda Chafai
    • , Scherazad Kootar
    •  & Hélène Marie
  7. Max Planck Institute of Biochemistry, Martinsried 82152, Germany

    • Daniel Hornburg
    •  & Felix Meissner
  8. Gurdon Institute, Cambridge Stem Cell Institute & Department of Biochemistry, University of Cambridge, Cambridge CB2 1QN, UK

    • Lewis D. B. Evans
    • , Steven Moore
    •  & Frederick J. Livesey
  9. Institute of Molecular Immunology, German Research Center for Environmental Health, 81377 Munich, Germany

    • Elisabeth Kremmer
  10. Department of Neurology, Clinical Neuroscience Unit, University of Bonn, 53127 Bonn, Germany

    • Michael T. Heneka
  11. German Center for Neurodegenerative Diseases (DZNE) Bonn, 53175 Bonn, Germany

    • Michael T. Heneka
  12. Institute of Pathology - Laboratory for Neuropathology, University of Ulm, 89081 Ulm, Germany

    • Dietmar R. Thal
  13. Department of Public Health/Geriatrics, Uppsala University, 751 85 Uppsala, Sweden

    • Vilmantas Giedraitis
    •  & Lars Lannfelt
  14. Institute for Pharmacy and Molecular Biotechnology IPMB, Functional Genomics, University of Heidelberg, 69120 Heidelberg, Germany

    • Ulrike Müller


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M.W. and C.H. designed the study and interpreted the results. M.W. generated all biochemical data together with H.H., V.M., B.N. and C.G. S.T., supported by A.W.-W., provided primary neuronal cultures, performed and analysed immunohistological stainings, and together with A.D. performed LCM. D.R.T. provided and analysed human brain sections. M.T.H. provided CSF samples. U.M. provided APP-knockout mice. E.K. produced new monoclonal antibodies. D.H. and F.M. designed and conducted mass spectrometry and data analysis. L.D.B.E., S.M. and F.J.L. carried out BACE1 inhibition of human neurons. H.M. together with M.C. and S.K. performed all electrophysiological recordings (LTP) in vitro and analysis in relation to application of peptides. S.V.O. and J.H. performed all electrophysiological recordings (LTP) in vitro in relation to the BACE1 inhibitor tests. M.A.B and A.K. performed all Ca2+-imaging experiments in vivo and analysis. M.W. and C.H. wrote the manuscript with input from the other authors. Correspondence and requests for materials should be addressed to M.W. and C.H.

Competing interests

M.W. and C.H. have filed a patent for analytical and therapeutic use of Aη peptides.

Corresponding authors

Correspondence to Michael Willem or Christian Haass.

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