NR ARSX
AU Satheeshkumar,K.S.; Murali,J.; Jayakumar,R.
TI Assemblages of prion fragments: novel model systems for understanding amyloid toxicity.
QU Journal of Structural Biology 2004 Nov; 148(2): 176-93
PT journal article
AB We report the conformational and toxic properties of two novel fibril-forming prion amyloid sequences, GAVVGGLG (PrP(119-126)) and VVGGLGG (PrP(121-127)). The conformational preferences of these fragments were studied in differing microenvironments of TFE/water mixtures and SDS solution. Interestingly, with an increase in TFE concentration, PrP(119-126) showed a helical conformational propensity, whereas PrP(121-127) adopted a more random coil structure. In 5% SDS, PrP(119-126) showed more alpha-helical content than in TFE solution, and PrP(121-127) exhibited a predominantly random coil conformation. However, both peptides took a random coil conformation in water, and over time the random coil transformed into a beta-sheet structure with a significant percentage of helical conformation and beta-turn structure in PrP(119-126) and PrP(121-127), respectively, as observed with CD spectroscopy. The aged fibrils of PrP(119-126) were insoluble in SDS, and PrP(121-127) was extractable with SDS solution. These fibrils were characterized by transmission electron microscopy. Both PrP(119-126) and PrP(121-127) formed stable monolayer's consisting of multimeric assemblages at the air-water interface. Monomeric PrP(119-126) was more toxic to astrocytes than the control Abeta peptide; however, the fibrillar form of PrP(119-126) was less toxic to astrocytes. PrP(121-127) elicited moderate toxicity in both soluble and fibrillar forms on astrocytes. Furthermore, quenching experiments using acroyl-labeled PrP(119-126) and PrP(121-127) with eosin-labeled synaptosomal membrane revealed that these prion fragments bind to anion-exchange protein. The binding of PrP(119-126) and PrP(121-127) with a membrane microdomain (lipid raft) was also analyzed using pyrenated derivatives. We conclude that the formation of PrP(119-126) and PrP(121-127) fibrils is a concentration-dependent process that involves coil to sheet conversion with aging. PrP(119-126), the sequence with intrinsic helical propensity, is more toxic in monomer form, and the fibril formation in this case seems to be protective to cells. For PrP(121-127), the SDS-soluble fibrils are more cytotoxic, indicating that a higher order assemblage structure is required for cytotoxic activity of this peptide.
MH Amyloid/*chemistry/toxicity; Amyloid beta-Protein/chemistry; Animals; Astrocytes/metabolism; Chromatography, Gel; Chromatography, Ion Exchange; Circular Dichroism; Disease Models, Animal; Lipids/chemistry; Membrane Microdomains; Microscopy, Electron, Transmission; Peptide Fragments/chemistry; Peptides/chemistry; Prions/*chemistry; Protein Binding; Protein Conformation; Protein Structure, Secondary; Protein Structure, Tertiary; Pyrenes/chemistry; Rats; Rats, Wistar; Sodium Dodecyl Sulfate/chemistry; Spectrometry, Fluorescence; Spectroscopy, Fourier Transform Infrared; Synaptosomes/metabolism; Temperature; Tetrazolium Salts/pharmacology; Thiazoles/pharmacology
AD Bioorganic and Neurochemistry Laboratory, Central Leather Research Institute, Adyar, Chennai 600 020, India.
SP englisch
PO USA