Alzheimer's disease is characterised by the accumulation of amyloid-b peptide, which is cleaved from the copper-binding amyloid-b precursor protein. Recent in vivo and in vitro studies have illustrated the importance of copper in Alzheimer's disease neuropathogenesis and suggested a role for amyloid-b precursor protein and amyloid-b in copper homeostasis. Amyloid-b precursor protein is a member of a multigene family, including amyloid precursor-like proteins-1 and -2. The copper-binding domain is similar among amyloid-b precursor protein family members, suggesting an overall conservation in its function or activity. Here, we demonstrate that double knockout of amyloid-b precursor protein and amyloid precursor-like protein-2 expression results in significant increases in copper accumulation in mouse primary cortical neurons and embryonic fibroblasts. In contrast, over-expression of amyloid-b precursor protein in transgenic mice results in significantly reduced copper levels in primary cortical neurons. These findings provide cellular neuronal evidence for the role of amyloid-b precursor protein in copper homeostasis and support the existing hypothesis that amyloid-b precursor protein and amyloid precursor-like protein-2 are copper-binding proteins with functionally interchangeable roles in copper homeostasis. Keywords: Alzheimer's disease, amyloid precursor-like protein 2, amyloid precursor protein, cortical neurons, gene knockout-out mice, neuronal copper homeostasis. The amyloid-b precursor protein (APP) of Alzheimer's disease is a type 1 transmembrane cuproprotein. The proteolytic processing of APP by secretases yields the amyloid-b peptide (Ab), the primary constituent of the amyloid plaque (Haass and Selkoe 1993). APP is a member of a multigene family that contains the paralogues amyloid precursor-like protein 1 and 2 (APLP1 and APLP2) (Wasco et al. 1992(Wasco et al. , 1993. Orthologues have been identified in a diverse range of species including Drosophila melanogaster, Xenopus laevis and Caenorhabditis elegans (Rosen et al. 1989;Okado and Okamoto 1992;Daigle and Li 1993). APP has a primary copper-binding domain, located in the N-terminal cysteinerich region next to the growth factor-like domain, and a secondary copper-binding domain, which is generated in Ab after proteolytic processing of APP (Hesse et al. 1994;Atwood et al. 2000). Both APP and Ab can strongly bind copper, as Cu(II), and reduce it to Cu(I) in vitro (Multhaup et al. 1996;Huang et al. 1999). Elevated copper concentrations reduce Ab production and increase secretion of APP in a cell line transfected with human APP cDNA (Borchardt et al. 1999). More recently, reports show that increased brain copper levels cause a decrease in Ab production in APP transgenic mouse models in vivo (Bayer et al. 2003;Phinney et al. 2003), while severely depleted cellular copper decreases APP gene expression (Bellingham et al. 2004).The copper-binding region is well conserved amongst the different APP-gene family members (Simons et al. 2002; Received Jun...

The b-amyloid protein (Ab) is the major protein component of amyloid plaques found in the Alzheimer brain. Although there is a loss of acetylcholinesterase (AChE) from both cholinergic and non-cholinergic neurones in the brain of Alzheimer patients, the level of AChE is increased around amyloid plaques. Previous studies using P19 cells in culture and transgenic mice which overexpress human Ab have suggested that this increase may be due to a direct action of Ab on AChE expression in cells adjacent to amyloid plaques. The aim of the present study was to examine the mechanism by which Ab increases levels of AChE in primary cortical neurones. Ab 1)42 was more potent than Ab 1)40 in its ability to increase AChE in primary cortical neurones. The increase in AChE was unrelated to the toxic effects of the Ab peptides. The effect of Ab 1)42 on AChE was blocked by inhibitors of a7 nicotinic acetylcholine receptors (a7 nAChRs) as well as by inhibitors of L-or N-type voltagedependent calcium channels (VDCCs), whereas agonists of a7 nAChRs (choline, nicotine) increased the level of AChE. The results demonstrate that the effect of Ab 1)42 on AChE is due to an agonist effect of Ab 1)42 on the a7 nAChR.

The identification of biochemical markers of Alzheimer's disease (AD) may help in the diagnosis of the disease. Previous studies have shown that Abeta(1-42) is decreased, and tau and phospho-tau are increased in AD cerebrospinal fluid (CSF). Our own studies have identified glycosylated isoforms of acetylcholinesterase (Glyc-AChE) and butyrylcholinesterase (Glyc-BuChE) that are increased in AD CSF. Glyc-AChE is increased in APP (SW) Tg2576 transgenic mice prior to amyloid plaque deposition, which suggests that Glyc-AChE may be an early marker of AD. The aim of this study was to determine whether Glyc-AChE or Glyc-BuChE is increased in CSF at early stages of AD and to compare the levels of these markers with those of Abeta(1-42), tau and phospho-tau. Lumbar CSF was obtained ante mortem from 106 non-AD patients, including 15 patients with mild cognitive impairment (MCI), and 102 patients with probable AD. Glyc-AChE, tau and phospho-tau were significantly increased in the CSF of AD patients compared to non-neurological disease (NND) controls. Abeta(1-42) was lower in the AD patients than in NND controls. A positive correlation was found between the levels of Glyc-AChE or Glyc-BuChE and disease duration. However, there was no clear correlation between the levels of tau, phospho-tau or Abeta(1-42) and disease duration. The results suggest that Glyc-AChE and Glyc-BuChE are unlikely to be early markers of AD, although they may have value as markers of disease progression.