Stable Complexes Involving Acetylcholinesterase and Amyloid-β Peptide Change the Biochemical Properties of the Enzyme and Increase the Neurotoxicity of Alzheimer’s Fibrils (original) (raw)
Related papers
1998
Brain acetylcholinesterase (AChE) forms stable complexes with amyloid- peptide (A) during its assembly into filaments, in agreement with its colocalization with the A deposits of Alzheimer's brain. The association of the enzyme with nascent A aggregates occurs as early as after 30 min of incubation. Analysis of the catalytic activity of the AChE incorporated into these complexes shows an anomalous behavior reminiscent of the AChE associated with senile plaques, which includes a resistance to low pH, high substrate concentrations, and lower sensitivity to AChE inhibitors. Furthermore, the toxicity of the AChE-amyloid complexes is higher than that of the A aggregates alone. Thus, in addition to its possible role as a heterogeneous nucleator during amyloid formation, AChE, by forming such stable complexes, may increase the neurotoxicity of A fibrils and thus may determine the selective neuronal loss observed in Alzheimer's brain.
FEBS Letters, 1999
Alzheimer's disease (AD) is a neurodegenerative disorder whose hallmark is the presence of senile plaques and neurofibrillary tangles. Senile plaques are mainly composed of amyloid L L-peptide (AL L) fibrils and several proteins including acetylcholinesterase (AChE). AChE has been previously shown to stimulate the aggregation of AL L 1À40 into amyloid fibrils. In the present work, the neurotoxicity of different amyloid aggregates formed in the absence or presence of AChE was evaluated in rat pheochromocytoma PC12 cells. Stable AChE-AL L complexes were found to be more toxic than those formed without the enzyme, for AL L 1À40 and AL L 1À42 , but not for amyloid fibrils formed with AL L Val183Ala , a synthetic variant of the AL L 1À40 peptide. Of all the AChE-AL L complexes tested the one containing the AL L 1À40 peptide was the most toxic. When increasing concentrations of AChE were used to aggregate the AL L 1À40 peptide, the neurotoxicity of the complexes increased as a function of the amount of enzyme bound to each complex. Our results show that AChE-AL L 1À40 aggregates are more toxic than those of AChE-AL L 1À42 and that the neurotoxicity depends on the amount of AChE bound to the complexes, suggesting that AChE may play a key role in the neurodegeneration observed in Alzheimer brain.
Journal of Molecular Biology, 1997
Acetylcholinesterase (AChE), an enzyme involved in the hydrolysis of the neurotransmitter acetylcholine, consistently colocalizes with the amyloid deposits characteristic of Alzheimer's disease and may contribute to the generation of amyloid proteins and/or physically affect ®bril assembly. In order to identify the structural domains of the amyloid-b-peptide (Ab) involved in the aggregation induced by AChE, we have studied the effect of this cholinergic enzyme on Ab peptide fragments of different sizes. AChE enhanced the aggregation of the Ab(12-28) and Ab(25-35) peptides but not of the Ab(1-16) fragment. The inductive effect of AChE on the aggregation of Ab(12-28) was abolished by the presence of either Ab(1-16) or Ab(9-21). The effect of the enzyme was also analysed using two different mutant fragments, possessing a low and the other a high capacity for ®brillogenesis. The fragments used were Ab(12-28) Val18 3 Ala and Ab(12-28) Glu22 3 Gln , respectively. AChE was able to promote the aggregation of these fragments in a very speci®c way and both mutant peptides were able to form amyloid ®brils, as revealed by negative staining under the electron microscope. Binding assays indicated that AChE was bound to Ab(12-28), as well as to the Ab(1-16) peptide. AChE was seen to form strong complexes with the Ab(12-28) ®brils as such complexes stained positively for both thio¯avine-T and AChE activity, were resistant to high ionic strength treatment, and were partially sensitive to detergents, suggesting that hydrophobic interactions may play a role in the stabilization of the AChE-Ab complex. Our results suggest that such amyloid-AChE complexes are formed when AChE interacts with the growing amyloid ®brils and accelerates the assembly of Ab peptides. This is consistent with the fact that AChE is known to be present within Ab deposits including the pre-amyloid diffuse and mature senile plaques found in Alzheimer's brain.
Journal of Molecular Biology, 1997
Acetylcholinesterase (AChE), an enzyme involved in the hydrolysis of the neurotransmitter acetylcholine, consistently colocalizes with the amyloid deposits characteristic of Alzheimer's disease and may contribute to the generation of amyloid proteins and/or physically affect ®bril assembly. In order to identify the structural domains of the amyloid-b-peptide (Ab) involved in the aggregation induced by AChE, we have studied the effect of this cholinergic enzyme on Ab peptide fragments of different sizes. AChE enhanced the aggregation of the Ab(12-28) and Ab(25-35) peptides but not of the Ab(1-16) fragment. The inductive effect of AChE on the aggregation of Ab(12-28) was abolished by the presence of either Ab(1-16) or Ab(9-21). The effect of the enzyme was also analysed using two different mutant fragments, possessing a low and the other a high capacity for ®brillogenesis. The fragments used were Ab(12-28) Val18 3 Ala and Ab(12-28) Glu22 3 Gln , respectively. AChE was able to promote the aggregation of these fragments in a very speci®c way and both mutant peptides were able to form amyloid ®brils, as revealed by negative staining under the electron microscope. Binding assays indicated that AChE was bound to Ab(12-28), as well as to the Ab(1-16) peptide. AChE was seen to form strong complexes with the Ab(12-28) ®brils as such complexes stained positively for both thio¯avine-T and AChE activity, were resistant to high ionic strength treatment, and were partially sensitive to detergents, suggesting that hydrophobic interactions may play a role in the stabilization of the AChE-Ab complex. Our results suggest that such amyloid-AChE complexes are formed when AChE interacts with the growing amyloid ®brils and accelerates the assembly of Ab peptides. This is consistent with the fact that AChE is known to be present within Ab deposits including the pre-amyloid diffuse and mature senile plaques found in Alzheimer's brain.
Journal of Molecular Biology, 1997
Acetylcholinesterase (AChE), an enzyme involved in the hydrolysis of the neurotransmitter acetylcholine, consistently colocalizes with the amyloid deposits characteristic of Alzheimer's disease and may contribute to the generation of amyloid proteins and/or physically affect ®bril assembly. In order to identify the structural domains of the amyloid-b-peptide (Ab) involved in the aggregation induced by AChE, we have studied the effect of this cholinergic enzyme on Ab peptide fragments of different sizes. AChE enhanced the aggregation of the Ab(12-28) and Ab(25-35) peptides but not of the Ab(1-16) fragment. The inductive effect of AChE on the aggregation of Ab(12-28) was abolished by the presence of either Ab(1-16) or Ab(9-21). The effect of the enzyme was also analysed using two different mutant fragments, possessing a low and the other a high capacity for ®brillogenesis. The fragments used were Ab(12-28) Val18 3 Ala and Ab(12-28) Glu22 3 Gln , respectively. AChE was able to promote the aggregation of these fragments in a very speci®c way and both mutant peptides were able to form amyloid ®brils, as revealed by negative staining under the electron microscope. Binding assays indicated that AChE was bound to Ab(12-28), as well as to the Ab(1-16) peptide. AChE was seen to form strong complexes with the Ab(12-28) ®brils as such complexes stained positively for both thio¯avine-T and AChE activity, were resistant to high ionic strength treatment, and were partially sensitive to detergents, suggesting that hydrophobic interactions may play a role in the stabilization of the AChE-Ab complex. Our results suggest that such amyloid-AChE complexes are formed when AChE interacts with the growing amyloid ®brils and accelerates the assembly of Ab peptides. This is consistent with the fact that AChE is known to be present within Ab deposits including the pre-amyloid diffuse and mature senile plaques found in Alzheimer's brain.
Crosslinking of amyloid-β peptide to brain acetylcholinesterase
Molecular and Chemical Neuropathology, 1998
Acetylcholinesterase (ACHE) is the enzyme responsible for the hydrolysis of the neurotransmitter acetylcholine in the central nervous system. Recently, we have found that AChE promotes the assembly of amyloid-[~ peptides (A~) into Alzheimer fibrils. The action of AChE on the state of aggregation of the A~ peptide supposes a near neighbor relationship between these two molecules. In the present work, we have studied A~-AChE interactions using the crosslinker reagent disuccinimidyl suberate (DSS), in the presence of [125I]-A~ peptide. The A~-AChE complexes formed by crosslinking were then analyzed by SDS-PAGE and autoradiography. We observed the formation of [12sI] A~-labeled complexes of 70, 160, 250, and 300 kDa corresponding to monomers, dimers, tetramers, and oligomers of ACHE, respectively crosslinked with the A~ peptide. Our results suggest that AChE and the A~ peptide may be involved in physiologically relevant interactions, related to the pathogenesis of Alzheimer disease (AD).
Molecular interactions of acetylcholinesterase with senile plaques
Journal of Physiology-Paris, 1998
Acetylcholinesterase (AChE) present in Alzheimer plaques is resistant to low pH, anti-ChE inhibitors and high substrate concentrations in comparison with the free enzyme. Kinetic and pharmacological studies of AChE-amyloid complexes indicate that steric hindrance by the amyloid over the gorge and the peripheral site of AChE is responsible for these effects. (OElsevier. Paris) Resume-Interactions mobkulaires de I'acetylcholinestkrase avec les plaques skniles. L'ac6tylcholinestkase (AChE), prkente dans les plaques seniles de la maladie d'Alzheimer, est rtkistante au baa pH, aux inhibiteurs et aux hautes concentrations de substrar. Les Ctudeb cinktiques et pharmacologiques des fibres du complexe amyloide-AChE indiquent que l'encombrement stkrique de I'amylo'ide au niveau de la gorge et du site periphktique de 1'AChE est responsable de ces effets. (bElsevier, Paris) AChE / amyloid plaques I AChE-Af3-amyloid fibril complexes / Alzheimer's disease