High-Affinity Binding of Monomeric but Not Oligomeric Amyloid-β to Ganglioside GM1 Containing Nanodiscs

Abstract

The interaction of the amyloid-β protein (Aβ) with neuronal cell membranes plays a crucial role in Alzheimer's disease. Aβ undergoes structural changes upon binding to ganglioside GM1 containing membranes leading to altered molecular characteristics of the protein. The physiological role of the Aβ interaction with the ganglioside GM1 is still unclear. In order to further elucidate the molecular requirements of Aβ membrane binding, we tested different nanodiscs varying in their lipid composition, regarding the charge of the headgroups as well as ganglioside GM1 concentration. Nanodiscs are excellent model membrane systems for studying protein membrane interactions, and we show here their suitability to investigate the membrane interaction of Aβ. In particular, we set out to investigate whether the binding activity of GM1 to Aβ is specific for the assembly state of Aβ and compared the binding affinities of monomeric with oligomeric Aβ. Using fluorescence titration experiments, we demonstrate high-affinity binding of Aβ(1-40) to GM1 containing nanodiscs, with dissociation constants, K, in the range from 25 to 41 nM, in a GM1 concentration-dependent manner. Biolayer interferometry experiments confirmed the high-affinity binding of monomeric Aβ(1-40) (K of 24 nM to 49 nM) as well as of Aβ(1-42) (K of 30 nM) to GM1 containing nanodiscs, and no binding to phospholipid containing nanodiscs. Interestingly, and in contrast to monomeric Aβ, neither oligomeric Aβ(1-40) nor oligomeric Aβ(1-42) binds to GM1 nanodiscs. To the best of our knowledge, this is the first report of a loss of function for monomeric Aβ upon aggregation.

Structural insights from lipid-bilayer nanodiscs link α-Synuclein membrane-binding modes to amyloid fibril formation

“…Notably, NDs have been used before to study the effect of calcium ions on the membrane interaction of αS 32 , as well as lipid and monomer specificity of the Alzheimer-associated Aβ peptide 33 . In general, NDs are very homogeneous, stable in a wide buffer range 34 , and allow the preparations of well-defined lipid mixtures with an accurate estimate of the bilayer size 35 , charge 36 , and lipid molarity 37 .…”

Evidence that glial cells attenuate G47R transthyretin accumulation in the central nervous system

“…. Just as Aβ binds to the GM1 ganglioside in the membrane to become the seed for amyloid formation, we propose that TTR G47R binds to the basement membranes to accelerate ATTR accumulation in the subarachnoid area. ATTR deposition spreads in the tissue but is retained and degraded by the ubiquitin proteasome system of glial cells on the brain surface.…”

“…Amyloidogenic proteins such as Aβ protein and TTR variants are misfolded after translation, causing them to self‐aggregate through mechanisms that are poorly understood in vivo. It is known that in the presence of membranes, amyloidogenic proteins produce amyloids more easily due to interactions with biological membranes . The basement membrane is an extracellular matrix, which covers the basal aspect of most cells and contributes to various functions, including establishment of the tissue structure support and clearance of Aβ .…”

“…It is known that in the presence of membranes, amyloidogenic proteins produce amyloids more easily due to interactions with biological membranes. [12][13][14][15][16][17] The basement membrane is an extracellular matrix, which covers the basal aspect of most cells and contributes to various functions, including establishment of the tissue structure support and clearance of Aβ. 18 TTR variants form fibrils at the basement membranes of the myocardium and blood vessels, which cause cytotoxicity.…”

Alzheimer’s Amyloid-Beta Intermediates Generated by Polymer-Nanodiscs

“…5,6,7 Recent studies have further shown gangliosides (GM), sphingomyelin (SM) and cholesterol to be the major modulators of Aβ oligomerization. 8,9 Although, recent studies proposed the catalytic activities of lipidmembrane on Aβ deposition and aggregation, the exact function of these lipids is not yet fully understood. 9,10 Herein, we have investigated the roles of membrane composition in modulating Aβ's aggregation using polymethacrylate (PMA) copolymer encased lipid-nanodiscs in an attempt to trap and characterize structure and toxicity of Aβ intermediates.…”