Prion diseases are a group of aggressive, lethal and incurable neurodegenerative disorders. The hallmark pathological event in these maladies is the misfolding, aggregation and brain deposition of [unreadable]scrapie[unreadable] Prion protein (PrPSc), which leads to spongiform degeneration of brain neurons. Unfortunately, a major gap exists in our understanding of how the conformational conversion of PrP ultimately kills neurons. Recent in vitro studies suggest that molecular chaperones may be key factors mediating PrP conversion and neuronal dysfunction. However, the functional relevance of this finding is unknown. My central hypothesis is that targeted expression of molecular chaperones can suppress PrP misfolding and PrP-mediated neurodegeneration. To that end, I created a novel and powerful Drosophila model of sporadic prion disease in which wild type PrP from Hamster converts into PrPSc[unreadable]like conformations and causes spongiform degeneration. Supporting my hypothesis, human Hsp70 prevents PrP misfolding and protects against PrP-dependent neurotoxicity in transgenic flies. The overall goal of this project is to define the role of molecular chaperones in PrP misfolding by a multidisciplinary approach that combines the power of Drosophila genetics with mammalian cellular systems and mice. My specific aims are: 1) Genetic, biochemical and pharmacological approaches to study Hsp70 protection against PrP misfolding and neurotoxicity in Drosophila;2) Determination of the ability of the Unfolded Protein Response components XBP1s and Grp58 to suppress PrP misfolding and neurotoxicity in Drosophila;3) Role of molecular chaperones in prion replication in simplified mammalian systems, and 4) Potential therapeutic role of Hsp70 in mouse models of prion diseases. I anticipate that our studies will contribute to better understand the molecular basis underlying PrP conversion. In addition, by exploring the role of chaperone-inducing compounds in flies and mice, I may discover effective and innovative therapeutic interventions for treating these devastating and yet incurable diseases.