Abeta(25-35) and its C- and/or N-blocked derivatives: copper driven structural features and neurotoxicity.
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.
Giuffrida
Maria Laura
ML
PhD Program in Neurobiology, Faculty of Medicine, University of Catania, Catania, Italy.
Grasso
Giulia
G
Ruvo
Menotti
M
Pedone
Carlo
C
Saporito
Angela
A
Marasco
Daniela
D
Pignataro
Bruno
B
Cascio
Claudia
C
Copani
Agata
A
Rizzarelli
Enrico
E
D016229:Amyloid beta-Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000633:toxicity*; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000473:pathology; D002942:Circular Dichroism; D003300:Copper / Q000633:toxicity*; D004578:Electron Spin Resonance Spectroscopy; D018625:Microscopy, Atomic Force; D023421:Models, Animal; D009474:Neurons / Q000187:drug effects / Q000473:pathology; D009498:Neurotoxins; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry / Q000633:toxicity*; D011487:Protein Conformation; D051381:Rats; D021241:Spectrometry, Mass, Electrospray Ionization
D016229:Amyloid beta-Peptides; D009498:Neurotoxins; D010446:Peptide Fragments; C074636:amyloid beta-protein (25-35); D003300:Copper