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Authors: Bauer, Charlotte | Pardossi-Piquard, Raphaëlle | Dunys, Julie | Roy, Maggie | Checler, Frédéric

Article Type: Research Article

Abstract: Proteolytic degradation has emerged as a key pathway involved in controlling levels of the Alzheimer's disease (AD)-associated amyloid-β peptides (Aβ) in the brain. The ectopeptidase, neprilysin (NEP), has been reported as the major Aβ-degrading enzyme in mice and human brains. We have previously shown that NEP expression and activity are regulated by AICD, the intracellular domain of the amyloid-β protein precursor (AβPP) generated by γ-secretase. Thus, NEP transcription, expression, and enzymatic activity are dramatically reduced in fibroblasts devoid of AβPP (the precursor of AICD) or lacking both presenilin (PS) 1 and 2 (two parent proteins contributing to AICD formation). We …demonstrate here that NEP expression and activity are influenced by a number of cell passages and density, and we confirm a drastic reduction of NEP expression and activity in AβPP and PS null fibroblasts examined at similar passages and cell densities. Furthermore, Imatinib (Gleevec), a known tyrosine kinase inhibitor was recently shown to elevate AICD in H4 human neuroglioma cells, and this was accompanied by concomitant increases of NEP protein, mRNA levels, and activity. However, the demonstration of a causal link between Imatinib and AICD levels was still lacking. We show here an Imatinib-dependent effect on NEP expression and activity in murine fibroblasts and establish that Imatinib-induced modulation of NEP was abolished by the depletion of AβPP or its homologues APLP1 and APLP2, thereby confirming that Imatinib-mediated control of NEP could indeed be accounted for its effect on AICD. Show more

Keywords: AβPP-null fibroblasts, AICD, cell aging, cell density, HEK293 cells, imatinib, neprilysin, PS null fibroblasts, secretase

DOI: 10.3233/JAD-2011-110746

Citation: Journal of Alzheimer's Disease, vol. 27, no. 3, pp. 511-520, 2011

Authors: Flammang, Brice | Pardossi-Piquard, Raphaëlle | Sevalle, Jean | Debayle, Delphine | Dabert-Gay, Anne-Sophie | Thévenet, Aurélie | Lauritzen, Inger | Checler, Frédéric

Article Type: Research Article

Abstract: One of the major pathological hallmarks of brains affected with Alzheimer's disease (AD) is the senile plaque, an extracellular deposit mainly composed of a set of highly insoluble peptides of various lengths (39–43 amino acids) referred to as amyloid-β (Aβ) peptides. Aβ peptides are derived from combined proteolytic cleavages undergone on the amyloid-β protein precursor (AβPP) by a set of enzymes called secretases. Several lines of anatomical and biological evidence suggest that Aβ peptides would not account for all pathological stigmata and molecular dysfunctions taking place in AD. In amyloidogenic and non-amyloidogenic pathways, AβPP first undergoes β- or α-secretases-mediated cleavages …yielding C99 and C83, respectively. These two membrane-embedded C-terminal fragments are both potential targets of subsequent γ-secretase-mediated proteolysis. The latter cleavage not only generates either p3 or Aβ peptides but similarly gives rise to an AβPP IntraCellular Domain (AICD fragment) that could modulate the transcription of several genes linked to AD pathology. It is therefore striking that AICD theoretically derives from both amyloidogenic and non-amyloidogenic AβPP processing pathways. Here we show that AICD predominantly derives from C99 by means of recombinant substrates and transiently transfected cells expressing C99. Our data suggest a preferred pathogenic pathway for AICD production and suggests that this fragment, in addition to C99 and Aβ peptides, could contribute to AD pathology. Show more

Keywords: AICD, Alzheimer's disease, amyloid-β, amyloidogenic pathway, C83, C99, secretases

DOI: 10.3233/JAD-2012-112186

Citation: Journal of Alzheimer's Disease, vol. 30, no. 1, pp. 145-153, 2012