Research Outline :
Currently the lab has three main research themes:
1- Recognition and processing of substrates by Hsp104:
One of our main goals is to understand how Hsp104 recognizes which proteins are misfolded and aggregated and how it extracts these proteins from the aggregate for resolubilization and refolding. One approach we have taken is to use large arrays of peptides derived from proteins that can be refolded by Hsp104 to identify those segments of protein that are most likely detected by Hsp104 as it polices the cell for aggregated proteins. We have used selected peptides to probe the peptide binding properties of Hsp104 and hope to eventually understand how ATP-driven conformation changes in Hsp104 coupled to peptide interactions, lead to the extraction and refolding of aggregated proteins. We are using a similar approach to determine how Hsp104 may traffic through the nuclear pore complex during heat shock without the help of nuclear import receptors.
2-Interactions of chaperones with prions:
Prions are infectious proteins that are capable of propagating themselves by promoting the conversion of normal form of the same protein into the infectious form. The formation of protein aggregates is one of the hallmarks of the pathogenic proteins. In yeast, prions are responsible for a novel form of inheritance at the level of protein conformation rather than through normal, Mendelian inheritance of allelic genes. Not surprisingly, chaperones including Hsp104 influence the stability of prions. We are studying these interactions and have recently extended our interests to include mammalian prions that are implicated in Transmissible Spongiform Encephalopathies (TSEs) including Mad Cow Disease or BSE.
3-Protein-protein interactions in PrP function, biogenesis, and misfolding:
PrP is a glycophosphatidyl inositol-anchoured cell surface protein that in its native form has a neuroprotective effect in the brain. When a healthy animal is infected with prions— a misfolded, aggregated form of PrP called PrPSc— the infectious form templates the conversion of normal PrP to the abnormal form causing neurodegeneration. We are interested in taking new approaches to discovering novel proteins that may interact with PrP and influence its normal function and its folding stability at the cell surface or in other subcellular organelles. We are using yeast membrane two-hybrid screens to identify candidate interactors and then verifying the functional consequences of the identified interaction. As a complementary approach, we have engineered novel forms of PrP that accumulate in organelles that normal PrP visits only transiently. These are being used to identify critical interactions that may influence the folding of newly synthesized PrP or PrP that is in the process of recycling through endocytic compartments. These interactions may profoundly influence the function of PrP in health and disease.