Quantitative Attribution of the Protective Effects of Aminosterols against Protein Aggregates to Their Chemical Structures and Ability to Modulate Biological Membranes

Abstract

Natural aminosterols are promising drug candidates against neurodegenerative diseases, like Alzheimer and Parkinson, and one relevant protective mechanism occurs via their binding to biological membranes and displacement or binding inhibition of amyloidogenic proteins and their cytotoxic oligomers. We compared three chemically different aminosterols, finding that they exhibited different (i) binding affinities, (ii) charge neutralizations, (iii) mechanical reinforcements, and (iv) key lipid redistributions within membranes of reconstituted liposomes. They also had different potencies (EC50) in protecting cultured cell membranes against amyloid-β oligomers. A global fitting analysis led to an analytical equation describing quantitatively the protective effects of aminosterols as a function of their concentration and relevant membrane effects. The analysis correlates aminosterol-mediated protection with well-defined chemical moieties, including the polyamine group inducing a partial membrane-neutralizing effect (79 ± 7%) and the cholestane-like tail causing lipid redistribution and bilayer mechanical resistance (21 ± 7%), linking quantitatively their chemistry to their protective effects on biological membranes.

Leveraging Machine Learning-Guided Molecular Simulations Coupled with Experimental Data to Decipher Membrane Binding Mechanisms of Aminosterols

“…1) allowed us to obtain the corresponding K D values (Figure 5C). The K D values obtained with this LUVs composition were comparable to those obtained in a previous work with a very similar lipid composition, except a lower concentration of CHOL 63 . SQ was confirmed to have a higher increase of fluorescence upon LUV binding, and a higher affinity for LUVs, as showed by the lower K D value of 0.013 ± 0.002 mg/ml (corresponding to a ΔG value of -27.36 ± 0.69 kJ mol -1 ), compared to 0.034 ± 0.004 mg/ml for TRO (corresponding to a ΔG value of -24.93 ± 0.47 kJ mol -1 ).…”

“…We performed binding experiments incubating 10 μM of each labelled aminosterol for 15 min with increasing concentrations of unlabeled LUVs. Both TRO and SQ displayed a significant increase in fluorescence emission in the presence of LUVs (Figure 5C), as previously observed 63 and fitting the data points to a standard binding curve (Eq. 1) allowed us to obtain the corresponding K D values (Figure 5C).…”

“…Both TRO and SQ displayed a significant increase in fluorescence emission in the presence of LUVs (Figure 5C), as previously observed 63 and fitting the data points to a standard binding curve (Eq. 1) allowed us to obtain the corresponding KD values (Figure 5C).…”

“…In addition, both aminosterols demonstrated to interact with the neuronal cell membrane, thereby offering protection against the toxicity induced by oligomers responsible of AD and PD 15,17,[39][40][41][42]61,62 . In particular, they were shown to change the lipid distribution within the membrane bilayer, to increase the mechanical resistance force, and to reduce the natural membrane negative charge 17,63 . Examining the molecular interactions between the aminosterol The binding affinity of the aminosterol molecules can be more precisely estimated through the application of enhanced sampling methods that leverage CVs to simplify the complexity of the molecular system and allow a more detailed exploration of molecular interactions and transitions.…”

Squalamine reverses age-associated changes of firing patterns of myenteric sensory neurons and vagal fibres

“…Numerous studies have shown that once integrated into a membrane the spatial organization of lipids within the membrane, fluidity, and tensile strength are altered 37 . Because squalamine electrostatically reduces the overall surface charge of the membrane, the function of membrane proteins positioned by electrostatic forces can be affected.…”