Engineering a membrane protein chaperone to ameliorate the proteotoxicity of mutant huntingtin

Abstract Toxic protein aggregates are associated with various neurodegenerative diseases, including Huntington’s disease (HD). Since no current treatment delays the progression of HD, we developed a mechanistic approach to preventing mutant huntingtin (mHttex1) aggregation. Here, we engineered the ATP-independent cytosolic chaperone PEX19, which targets peroxisomal membrane proteins to peroxisomes, to remove mHttex1 aggregates. Using yeast toxicity-based screening with a random mutant library, we identified two yeast PEX19 (scPEX19) variants and engineered equivalent mutations into human PEX19 (hsPEX19). These variants prevented mHttex1 aggregationin vitroand in cellular HD models. The mutated hydrophobic residue in the α4 helix ofhsPEX19 variants binds to the N17 domain of mHttex1, thereby inhibiting the initial aggregation process. Overexpression of thehsPEX19-FV variant rescues HD-associated phenotypes in primary striatal neurons and inDrosophila. Overall, our data reveal that engineering ATP-independent membrane protein chaperones is a promising therapeutic approach for rational targeting of mHttex1 aggregation in HD.