Abstract
Understanding how amyloid-β peptide interacts with living cells on a molecular level is critical to development of targeted treatments for Alzheimer's disease. Evidence that oligomeric Aβ interacts with neuronal cell membranes has been provided, but the mechanism by which membrane binding occurs and the exact stoichiometry of the neurotoxic aggregates remain elusive. Physiologically relevant experimentation is hindered by the high Aβ concentrations required for most biochemical analyses, the metastable nature of Aβ aggregates, and the complex variety of Aβ species present under physiological conditions. Here we use single molecule microscopy to overcome these challenges, presenting direct optical evidence that small Aβ(1-40) oligomers bind to living neuroblastoma cells at physiological Aβ concentrations. Single particle fluorescence intensity measurements indicate that cell-bound Aβ species range in size from monomers to hexamers and greater, with the majority of bound oligomers falling in the dimer-to-tetramer range. Furthermore, while low-molecular weight oligomeric species do form in solution, the membrane-bound oligomer size distribution is shifted towards larger aggregates, indicating either that bound Aβ oligomers can rapidly increase in size or that these oligomers cluster at specific sites on the membrane. Calcium indicator studies demonstrate that small oligomer binding at physiological concentrations induces only mild, sporadic calcium leakage. These findings support the hypothesis that small oligomers are the primary Aβ species that interact with neurons at physiological concentrations.
Highlights
Soluble oligomeric forms of the 39-to-42 residue amyloid-b peptide, the primary component of Alzheimer’s disease plaques, may be a key player in synaptic dysfunction and cell death [1,2,3]
Efforts to pinpoint the neurotoxic aggregates have been complicated by the finding that at physiological concentrations, Ab exists as a mixture of metastable species [6,7,8]
Ab-membrane interactions are complex and variable; externalized Ab may bind to specific cellular receptors or protein complexes (e.g. NMDA receptors [9,10] and a7 nicotinic acetylcholine receptors [11]), associate with phosphatidylserine in the membrane [12], or bind to and insert directly into the lipid bilayer [13,14,15]
Summary
Soluble oligomeric forms of the 39-to-42 residue amyloid-b peptide, the primary component of Alzheimer’s disease plaques, may be a key player in synaptic dysfunction and cell death [1,2,3]. Studying this system at physiological peptide concentrations presents challenges. Oligomeric forms of Ab have repeatedly been shown to be a stronger indicator of disease state in humans than plaque load [4,5,21,22]. In one widely cited study, chemically purified oligomers were shown to induce instantaneous calcium leakage in cultured neuroblastoma cells [19]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call