title: Solution state characterization of amyloid beta-derived diffusible ligands.
abstract: A growing body of evidence suggests that soluble oligomeric forms of the amyloid beta peptide known as amyloid-derived diffusible ligands (ADDLs) are the toxic species responsible for neurodegeneration associated with Alzheimer's disease. Accurate biophysical characterization of ADDL preparations is hampered by the peptide's strong tendency to self-associate and the effect of factors such as ionic strength, temperature, and pH on its behavior. In addition, amyloid peptides are known to interact with common laboratory excipients, specifically detergents, further complicating the results from standard analytical methods such as denaturing polyacrylamide gel electrophoresis. We have studied the solution behavior of various amyloid peptide preparations using analytical ultracentrifugation and size exclusion chromatography coupled with multiangle laser light scattering. Our results indicate that ADDL preparations exist in solution primarily as a binary mixture of a monomeric peptide and high-molecular mass oligomers. We relate our findings to previously described characterizations utilizing atomic force microscopy and electrophoretic methods and demonstrate that low-molecular mass oligomers identified by gel electrophoresis likely represent artifacts induced by the peptide's interaction with detergent, while atomic force microscopy results are likely skewed by differential binding of monomeric and oligomeric peptide species. Finally, we confirm that only the high-molecular mass oligomeric components of an ADDL preparation are capable of binding to subpopulations of primary hippocampal neurons in vitro.
authors.affiliation: Department of Vaccine & Biologics Research, Merck Research Laboratories, West Point, Pennsylvania 19486, USA. robert_hepler@merck.com
authors.forename: Robert W
authors.initials: RW
authors.lastname: Hepler
authors.forename: Karen M
authors.initials: KM
authors.lastname: Grimm
authors.forename: Deborah D
authors.initials: DD
authors.lastname: Nahas
authors.forename: Robert
authors.initials: R
authors.lastname: Breese
authors.forename: Elizabeth Chen
authors.initials: EC
authors.lastname: Dodson
authors.forename: Paul
authors.initials: P
authors.lastname: Acton
authors.forename: Paul M
authors.initials: PM
authors.lastname: Keller
authors.forename: Mark
authors.initials: M
authors.lastname: Yeager
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.forename: Paul
authors.initials: P
authors.lastname: Shughrue
authors.forename: Gene
authors.initials: G
authors.lastname: Kinney
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Joyce
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000378:metabolism* / Q000633:toxicity / Q000648:ultrastructure; D000818:Animals; D002478:Cells, Cultured; D002850:Chromatography, Gel; D008024:Ligands; D018625:Microscopy, Atomic Force; D008970:Molecular Weight; D009474:Neurons / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism* / Q000633:toxicity / Q000648:ultrastructure; D011485:Protein Binding; D051381:Rats; D012996:Solutions
chemical_list: D016229:Amyloid beta-Peptides; D008024:Ligands; D010446:Peptide Fragments; D012996:Solutions; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42)