Pathway Platform for Aggregation & Trafficking Diseases

It is clear that protein misfolding is a significant cause of disease. However, the cellular mechanisms responsible for protein toxicity and mistrafficking of mutant cargo proteins are poorly understood. Consequently, most small molecule discovery efforts have targeted the misfolded protein, thereby identifying “pharmacological chaperones”, ligands that bind the mutant protein to facilitate its folding. At FoldRx, we have implemented a novel discovery strategy targeting the cellular machinery that interacts with misfolded proteins. We have developed a pathway screening platform that rapidly identifies small molecule modulators of critical pathways of either proteotoxicty or trafficking and have successfully translated these modulators to disease-relevant cellular assays. Because the pathways and processes essential for protein folding, proteotoxicity, quality control, and trafficking are highly conserved, we perform our initial screens in the yeast Saccharomyces cerevisiae. We have used our proprietary technology for yeast cell-based assays to discover lead molecules with potential utility in multiple protein misfolding diseases.

Pathway assays for aggregation diseases

In many neurodegenerative diseases, misfolding and aggregation of a specific protein is observed. In Parkinson’s disease, α-synuclein misfolds. When expressed in yeast, α-synuclein produces many of the same phenotypes observed in diseases cells, including copy-number dependent toxicity, proteasome impairment, and generation of reactive oxygen species.. FoldRx has used α-synuclein expressing yeast to identify compounds that restore growth. Some of these lead molecules also mitigate α-synuclein toxicity in assays using human cell lines. We are currently optimizing these leads to identify disease-modifying agents for the treatment of Parkinson’s disease.

FoldRx’s discovery platform has been applied to two additional proteins associated with neurodegeneration, huntingtin (Huntington’s disease) and TDP-43 (amyotrophic lateral sclerosis and frontal temporal lobar degeneration). Expression of huntingtin in yeast inhibits growth; this toxicity increases in severity with the length of the polyQ repeat and with the age of the cells. Expression of TDP-43 is also toxic. This approach may be applicable to additional toxic proteins, including tau (Alzheimer’s disease) and islet amyloid polypeptide (type 2 diabetes).

Pathway assays for trafficking diseases

Recent studies suggest that the folding and secretory capacity of the ER is regulated, and it is our hypothesis that stimulation of ER function is a promising therapeutic strategy for treating a variety of protein misfolding diseases. FoldRx has developed a high throughput assay to detect small molecules that enhance endoplasmic reticulum (ER) to Golgi trafficking and has shown that they correct the trafficking of the misfolded secretory protein ΔF508-CFTR, the mutant protein that is main cause of cystic fibrosis. This approach is readily adaptable to other disease-causing mutant cargo proteins, including variants of α₁-antitrypsin (emphysema), hERG (long QT syndrome), and glucocerebrosidase (Gaucher’s disease).