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EMBO Mol Med. 2012 Mar;4(3):171-9. doi: 10.1002/emmm.201100195. Epub 2012 Jan 23.

β- but not γ-secretase proteolysis of APP causes synaptic and memory deficits in a mouse model of dementia.

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  • 1Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA.

Abstract

A mutation in the BRI2/ITM2b gene causes loss of BRI2 protein leading to familial Danish dementia (FDD). BRI2 deficiency of FDD provokes an increase in amyloid-β precursor protein (APP) processing since BRI2 is an inhibitor of APP proteolysis, and APP mediates the synaptic/memory deficits in FDD. APP processing is linked to Alzheimer disease (AD) pathogenesis, which is consistent with a common mechanism involving toxic APP metabolites in both dementias. We show that inhibition of APP cleavage by β-secretase rescues synaptic/memory deficits in a mouse model of FDD. β-cleavage of APP yields amino-terminal-soluble APPβ (sAPPβ) and β-carboxyl-terminal fragments (β-CTF). Processing of β-CTF by γ-secretase releases amyloid-β (Aβ), which is assumed to cause AD. However, inhibition of γ-secretase did not ameliorate synaptic/memory deficits of FDD mice. These results suggest that sAPPβ and/or β-CTF, rather than Aβ, are the toxic species causing dementia, and indicate that reducing β-cleavage of APP is an appropriate therapeutic approach to treating human dementias. Our data and the failures of anti-Aβ therapies in humans advise against targeting γ-secretase cleavage of APP and/or Aβ.

PMID:
22170863
PMCID:
PMC3376850
DOI:
10.1002/emmm.201100195
[PubMed - indexed for MEDLINE]
Free PMC Article
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