Bioengineering mitochondrial membranes using drug-like compounds to combat diseases of protein misfolding

Abstract

Misfolding and aggregation events of amyloid-β (Aβ) in Alzheimer's disease (AD) and human islet amyloid polypeptide (hIAPP) in type 2 diabetes mellitus (T2DM), are central drivers to disease pathogenesis. These peptides, characterised by their intrinsically disordered nature, assemble into oligomeric species which display a pronounced tendency to interact with, and disrupt biological membranes. Furthermore, lipid bilayers also drive peptide misfolding and influence aggregation kinetics, thereby exacerbating disease pathology. Mitochondrial membranes, uniquely enriched with cardiolipin (CL), are primary targets of amyloid-induced toxicity; and thus present an attractive target for drug development. In this study, fluorescence polarisation membrane fluidity assays were performed on mito-mimetic liposomes (15% CL content) incubated with a diverse group of small-molecule compounds, to evaluate their effects on bilayer organisation. Following this, the research focuses on the incorporation of two promising compounds, the synthetic small-molecule anle138b, and the natural ubiquinone Coenzyme Q10 (CoQ10), into the CL-enriched vesicles, to generate ‘bioengineered’ mitochondrial liposomes. Remarkably, through thioflavin T and leakage assays, the study demonstrates the ability of these ‘bioengineered’ liposomes to mitigate peptide aggregation of Aβ and hIAPP while simultaneously enhancing membrane resilience against disruption by these toxic peptide species. Furthermore, a notable observation emerged, revealing a correlation between the presence of a more rigid acyl chain environment (induced by compound incorporation) and the reduction of peptide-induced bilayer destabilisation. Overall, the findings of this investigation suggest anle138b and CoQ10 as promising therapeutic agents for protein misfolding disorders, specifically through their unique integration into mitochondrial membranes. This study presents an opportunity for targeted therapeutic strategies aimed at preserving mitochondrial membrane integrity by altering the physico-chemical properties of bilayers and in turn restricting the destructive effects of peptide-membrane interactions.