title: Abeta(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.
authors.affiliation: PhD Program in Neurobiology, Faculty of Medicine, University of Catania, Catania, Italy.
authors.forename: Maria Laura
authors.initials: ML
authors.lastname: Giuffrida
authors.forename: Giulia
authors.initials: G
authors.lastname: Grasso
authors.forename: Menotti
authors.initials: M
authors.lastname: Ruvo
authors.forename: Carlo
authors.initials: C
authors.lastname: Pedone
authors.forename: Angela
authors.initials: A
authors.lastname: Saporito
authors.forename: Daniela
authors.initials: D
authors.lastname: Marasco
authors.forename: Bruno
authors.initials: B
authors.lastname: Pignataro
authors.forename: Claudia
authors.initials: C
authors.lastname: Cascio
authors.forename: Agata
authors.initials: A
authors.lastname: Copani
authors.forename: Enrico
authors.initials: E
authors.lastname: Rizzarelli
mesh_terms: 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
chemical_list: D016229:Amyloid beta-Peptides; D009498:Neurotoxins; D010446:Peptide Fragments; C074636:amyloid beta-protein (25-35); D003300:Copper