Phospho-eIF2α level is important for determining abilities of BACE1 reduction to rescue cholinergic neurodegeneration and memory defects in 5XFAD mice

PLoS One. 2010 Sep 23;5(9):e12974. doi: 10.1371/journal.pone.0012974.


β-Site APP-cleaving enzyme 1 (BACE1) initiates amyloid-β (Aβ) generation and thus represents a prime therapeutic target in treating Alzheimer's disease (AD). Notably, increasing evidence indicates that BACE1 levels become elevated in AD brains as disease progresses; however, it remains unclear how the BACE1 upregulation may affect efficacies of therapeutic interventions including BACE1-inhibiting approaches. Here, we crossed heterozygous BACE1 knockout mice with AD transgenic mice (5XFAD model) and compared the abilities of partial BACE1 reduction to rescue AD-like phenotypes at earlier (6-month-old) and advanced (15-18-month-old) stages of disease, which expressed normal (∼100%) and elevated (∼200%) levels of BACE1, respectively. BACE1(+/-) deletion rescued memory deficits as tested by the spontaneous alternation Y-maze task in 5XFAD mice at the earlier stage and prevented their septohippocampal cholinergic deficits associated with significant neuronal loss. Importantly, BACE1(+/-) deletion was no longer able to rescue memory deficits or cholinergic neurodegeneration in 5XFAD mice at the advanced stage. Moreover, BACE1(+/-) deletion significantly reduced levels of Aβ42 and the β-secretase-cleaved C-terminal fragment (C99) in 6-month-old 5XFAD mouse brains, while these neurotoxic β-cleavage products dramatically elevated with age and were not affected by BACE1(+/-) deletion in 15-18-month-old 5XFAD brains. Interestingly, although BACE1(+/-) deletion lowered BACE1 expression by ∼50% in 5XFAD mice irrespective of age in concordance with the reduction in gene copy number, BACE1 equivalent to wild-type controls remained in BACE1(+/-)·5XFAD mice at the advanced age. In accord, phosphorylation of the translation initiation factor eIF2α, an important mediator of BACE1 elevation, was dramatically increased (∼9-fold) in 15-18-month-old 5XFAD mice and remained highly upregulated (∼6-fold) in age-matched BACE1(+/-)·5XFAD mice. Together, our results indicate that partial reduction of BACE1 is not sufficient to block the phospho-eIF2α-dependent BACE1 elevation during the progression of AD, thus limiting its abilities to reduce cerebral Aβ/C99 levels and rescue memory deficits and cholinergic neurodegeneration.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alzheimer Disease / genetics
  • Alzheimer Disease / metabolism*
  • Alzheimer Disease / pathology*
  • Alzheimer Disease / psychology
  • Amyloid Precursor Protein Secretases / genetics
  • Amyloid Precursor Protein Secretases / metabolism*
  • Animals
  • Aspartic Acid Endopeptidases / genetics
  • Aspartic Acid Endopeptidases / metabolism*
  • Cholinergic Fibers / metabolism
  • Cholinergic Fibers / pathology*
  • Disease Models, Animal
  • Eukaryotic Initiation Factor-2 / genetics
  • Eukaryotic Initiation Factor-2 / metabolism*
  • Female
  • Humans
  • Male
  • Memory*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mice, Transgenic
  • Nerve Degeneration
  • Phosphorylation


  • Eukaryotic Initiation Factor-2
  • Amyloid Precursor Protein Secretases
  • Aspartic Acid Endopeptidases
  • Bace1 protein, mouse