Eilat Hanan

Inhibitory effect of monoclonal antibodies on Alzheimer's β-amyloid peptide aggregation

In vitro aggregation of β-amyloid peptide induced by incubating the peptide for 3 h at 37°C, was investigated via immunocomplexation with a panel of monoclonal anti-bodies raised against various β-amyloid fragments Some of these monoclonal antibodies prevented the formation of β-amyloid and this effect may be related to the localization of the antibody binding sites. Monoclonal antibodies 6C6 and 10D5, and AMY-33, which recognize epitopes spanning the amino acid residues 1–28 of β-amyloid peptide, inhibited its aggregation by 40%–90% when compared with aggregation occurring in the absence of the respective antibodies. The antibodies, 2H3 and 1C2, directed to the regions comprisingpeptides 1–12 and 13–28, respectively, had a considerably low effect. Identifying the “aggregating epitopes” as sequences that are related to the sites where protein aggregation is initiated and preparing monoclonal antibodies against these regions may facilitate the under-standing and prevention of protein aggregation processes....

Helix-coil transition of PrP106–126: Molecular dynamic study

A set of 34 molecular dynamic (MD) simulations totaling 305 ns of simulation time of the prion protein‐derived peptide PrP106–126 was performed with both explicit and implicit solvent models. The objective of these simulations is to investigate the relative stability of the α‐helical conformation of the peptide and the mechanism for conversion from the helix to a random‐coil structure. At neutral pH, the wild‐type peptide was found to lose its initial helical structure very fast, within a few nanoseconds (ns) from the beginning of the simulations. The helix breaks up in the middle and then unwinds to the termini. The spontaneous transition into the random coil structure is governed by the hydrophobic interaction between His111 and Val122. The A117V mutation, which is linked to GSS disease, was found to destabilize the helix conformation of the peptide significantly, leading to a complete loss of helicity approximately 1 ns faster than in the wild‐type. Furthermore, the A117V mutant exhibits a different mechanism for helix‐coil conversion, wherein the helix begins to break up at the C‐terminus and then gradually to unwind towards the N‐terminus. In most simulations, the mutation was found to speed up the conversion through an additional hydrophobic interaction between Met112 and the mutated residue Val117, an interaction that did not exist in the wild‐type peptide. Finally, the β‐sheet conformation of the wild‐type peptide was found to be less stable at acidic pH due to a destabilization of the His111–Val122, since at acidic pH this histidine is protonated and is unlikely to participate in hydrophobic interaction. Proteins 2001;45:382–396.

Antiaggregating antibody raised against human PrP 106-126 recognizes pathological and normal isoforms of the whole prion protein

Antibodies to the prion protein (PrP) have been critical to the neuropathological and biochemical characterization of PrP-related degenerative diseases in humans and animals. Although PrP is highly conserved evolutionarily, there is some sequence divergence among species; as a consequence, anti-PrP antibodies have a wide spectrum of reactivity when challenged with PrP from diverse species. We have produced an antibody [monoclonal antibody (mAb) 2-40] raised against a synthetic peptide corresponding to residues (106-126 of human PrP and have characterized it by epitope mapping, Western immunoblot analysis, and immunohistochemistry. The antibody recognizes not only human PrP isoforms but also pathological PrP from all species tested (i.e., sheep, hamsters, and mice). Together with the fact that it recognizes the whole PrP in both cellular and scrapie isoforms, mAb 2-40 may be helpful in studying conformational changes of the PrP, as well as establishing a possible connection between human and animal diseases.