Aβ(25–35) and its C‐ and/or N‐blocked derivatives: Copper driven structural features and neurotoxicity

Abstract

The toxic properties of beta-amyloid protein, Abeta(1-42), the major component of senile plaques in Alzheimer's disease, depend on nucleation-dependent oligomerization and aggregation. In addition, Abeta(1-42) toxicity is favored by the presence of trace metals, which affect the secondary structure of the peptide. A peptide comprising 11 residues within Abeta(1-42) [Abeta(25-35)] aggregates and retains the neurotoxic activity of Abeta(1-42). We have used both Abeta(25-35) and its C-amidated or N-acetylated/C-amidated derivatives to investigate the role of copper(II) in modulating the conformation and aggregation state as well as the neurotoxic properties of amyloid peptides. Electrospray ionization mass spectrometry (ESI-MS) and electron paramagnetic resonance (EPR) measurements were performed to verify the formation of copper(II)/Abeta(25-35) complexes and to determine the coordination mode, respectively. Abeta(25-35) and its derivatives were analyzed by circular dichroism spectroscopy to assess their secondary structure, subjected to thioflavine-T (Th-T) binding assay to reveal beta-sheet structured aggregates formation, and imaged by scanning force microscopy. Toxicity was assessed on mature cultures of rat cortical neurons. We found that beta-sheet-structured species of Abeta(25-35) were neurotoxic, whereas the random-coil-structured derivatives were devoid of effect. Interestingly, copper promoted the random-coil/beta-sheet transition of Abeta(25-35), with ensuing peptide toxicity, but it induced the toxicity of the N-acetylated/C-amidated derivative without affecting peptide folding. Moreover, copper did not influence either the folding or the activity of the C-amidated Abeta(25-35), suggesting that blockade of the C-terminus of Abeta peptides might be sufficient to prevent Abeta toxicity.

Targeting Group II Metabotropic Glutamate (mGlu) Receptors for the Treatment of Psychosis Associated with Alzheimer's Disease: Selective Activation of mGlu2 Receptors Amplifies β-Amyloid Toxicity in Cultured Neurons, Whereas Dual Activation of mGlu2 and mGlu3 Receptors Is Neuroprotective

“…Rat cortical cultures, both pure neuronal and mixed neuron-glial types, were challenged either with soluble aggregates of the active A␤ fragment, A␤(25-35), (Giuffrida et al, 2007) or oligomers of the full-length A␤(1-42) . A␤(25-35) and A␤(1-42) were used at concentrations of 25 M and 100 nM, respectively, which induced a similar extent of neuronal death (35-45%) over a 24-h period.…”

The use of mass spectrometry to study amyloid‐β peptides

“…5) (Giuffrida et al, 2007;Damante et al, 2008), Zn (Zirah et al, 2003;Damante et al, 2009;Drochioiu et al, 2009), Fe(II) and Fe(III) (Drochioiu, 2009). The latter complexes are so strong that it has been suggested that Ab could compete for iron against other iron-containing proteins such as transferrin to greatly interfere with this metal homeostasis (Jiang et al, 2009).…”

Th17 Cell-Mediated Neuroinflammation Is Involved in Neurodegeneration of Aβ1-42-Induced Alzheimer’s Disease Model Rats

“…Before Aβ 1–42 (Sigma-Aldrich, USA) was used, it was firstly incubated in sterile saline at 37°C for 7 days to allow the change in an assembly state of the peptide with ensuing toxicity [18]. The incubated Aβ 1–42 solutions generally contain both fibril-like structures and different-sized oligomers [19]. Rats, which had been deeply anesthetized with pentobarbital (55 mg/kg, i.p.)…”