Abeta(25-35) and its C- and/or N-blocked derivatives: copper driven structural features and neurotoxicity

J Neurosci Res. 2007 Feb 15;85(3):623-33. doi: 10.1002/jnr.21135.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyloid beta-Peptides / chemical synthesis
  • Amyloid beta-Peptides / chemistry
  • Amyloid beta-Peptides / toxicity*
  • Animals
  • Cerebral Cortex / drug effects
  • Cerebral Cortex / pathology
  • Circular Dichroism
  • Copper / toxicity*
  • Electron Spin Resonance Spectroscopy
  • Microscopy, Atomic Force
  • Models, Animal
  • Neurons / drug effects
  • Neurons / pathology
  • Neurotoxins
  • Peptide Fragments / chemical synthesis
  • Peptide Fragments / chemistry
  • Peptide Fragments / toxicity*
  • Protein Conformation
  • Rats
  • Spectrometry, Mass, Electrospray Ionization

Substances

  • Amyloid beta-Peptides
  • Neurotoxins
  • Peptide Fragments
  • amyloid beta-protein (25-35)
  • Copper