The interaction of the amyloid-â protein (Aâ) with neuronal cell membranes plays a crucial role in Alzheimer's disease. Aâ undergoes structural changes upon binding to ganglioside GM1 containing membranes leading to altered molecular characteristics of the protein. The physiological role of the Aâ interaction with the ganglioside GM1 is still unclear. In order to further elucidate the molecular requirements of Aâ 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 Aâ. In particular, we set out to investigate whether the binding activity of GM1 to Aâ is specific for the assembly state of Aâ and compared the binding affinities of monomeric with oligomeric Aâ. Using fluorescence titration experiments, we demonstrate high-affinity binding of Aâ(1-40) to GM1 containing nanodiscs, with dissociation constants, KD, in the range from 25 to 41 nM, in a GM1 concentration-dependent manner. Biolayer interferometry experiments confirmed the high-affinity binding of monomeric Aâ(1-40) (KD of 24 nM to 49 nM) as well as of Aâ(1-42) (KD of 30 nM) to GM1 containing nanodiscs, and no binding to phospholipid containing nanodiscs. Interestingly, and in contrast to monomeric Aâ, neither oligomeric Aâ(1-40) nor oligomeric Aâ(1-42) binds to GM1 nanodiscs. To the best of our knowledge, this is the first report of a loss of function for monomeric Aâ upon aggregation.
Alzheimer Disease Amyloid beta-Peptides