Blocking huntingtin oligomers from binding lipid membranes improves phenotype in a C. elegans model of Huntington's disease.

Abstract

As protein aggregation is the defining hallmark of all amyloid diseases, a common therapeutic strategy is to develop molecules that inhibit aggregation. However, this approach has yielded limited success. Many amyloid proteins directly interact with lipid membranes. These interactions promote distinct aggregation pathways and often result in membrane damage leading to toxicity. As a result, directly targeting the ability of amyloids to bind lipid membranes represents a novel therapeutic strategy. As a proof of principle, the interaction between lipid membranes and mutant huntingtin (htt) aggregates was used to test this strategy. Using a colorimetric lipid binding assay over 1200 compounds were screened for their ability to block htt/lipid binding. The screen was set up to only identify compounds that directly interacted with htt, not the lipid membrane. Two promising compounds Ro-90-7501 and Benzamil hydrochloride were identified. Validation was achieved via two additional methods, a calcein dye leakage assay and in situ atomic force microscopy (AFM). As these compounds directly interact with htt, ThT and AFM assays were performed to assess their impact on aggregation. Ro-90-7501 had a slight inhibitory effect on fibril formation, but aggregate morphologies were unchanged. Benzamil did not inhibit fibril formation; however, oligomer precursors were significantly smaller when exposed to Benzamil. Molecular dynamic simulations (MD) revealed that the two compounds have unique mechanisms of interaction with htt aggregates. Having established that the compound prevented htt from binding membranes, a C. elegans model of Huntington's disease was used to determine if this strategy could alleviate phenotype. Despite have a minimal impact on punctate formation, both compounds reduced a thrashing deficit in animals caused by mutant htt expression, suggesting that this strategy reduces htt toxicity.