Yeast-based screening of natural product extracts results in the identification of prion inhibitors from a marine sponge

One of the major medical challenges of the twenty-first century is the treatment of incurable and fatal neurodegenerative disorders caused by misfolded prion proteins. Since the discovery of these diseases a number of studies have been conducted to identify small molecules for their treatment, however to date no curative treatment is available. These studies can be highly expensive and time consuming, but more recent experimental approaches indicate a significant application for yeast prions in these studies. We therefore used yeast prions to optimize previous high-throughput methods for the cheaper, easier and more rapid screening of natural extracts. Through this approach we aimed to identify natural yeast-prion inhibitors that could be useful in the development of novel treatment strategies for neurodegenerative disorders. We screened 500 marine invertebrate extracts from temperate waters in Australia allowing the identification of yeast-prion inhibiting extracts. Through the bioassay-driven chemical investigation of an active Suberites sponge extract, a group of bromotyrosine derivatives were identified as potent yeast-prion inhibitors. This study outlines the importance of natural products and yeast prions as a first-stage screen for the identification of new chemically diverse and bioactive compounds.

Interdependence of amyloid formation in yeast: implications for polyglutamine disorders and biological functions

In eukaryotic cells amyloid aggregates may incorporate various functionally unrelated proteins. In mammalian diseases this may cause amyloid toxicity, while in yeast this could contribute to prion phenotypes. Insolubility of amyloids in the presence of strong ionic detergents, such as SDS or sarcosyl, allows discrimination between amorphous and amyloid aggregates. Here, we used this property of amyloids to study the interdependence of their formation in yeast. We observed that SDS-resistant polymers of proteins with extended polyglutamine domains caused the appearance of SDS or sarcosyl-insoluble polymers of three tested chromosomally-encoded Q/N-rich proteins, Sup35, Rnq1 and Pub1. These polymers were non-heritable, since they could not propagate in the absence of polyglutamine polymers. Sup35 prion polymers caused the appearance of non-heritable sarcosyl-resistant polymers of Pub1. Since eukaryotic genomes encode hundreds of proteins with long Q/N-rich regions, polymer interdependence suggests that conversion of a single protein into polymer form may significantly affect cell physiology by causing partial transfer of other Q/N-rich proteins into a non-functional polymer state.