Donald John Tipper PhD
|Institution||University of Massachusetts Medical School|
|Department||Microbiology and Physiological Systems|
|Address||University of Massachusetts Medical School|
55 Lake Avenue North, S6-228
Worcester MA 01655
|Institution||UMMS - Programs, Centers and Institutes|
|Department||Bacterial Genetics and Pathogenesis|
Ph. D. (1959) University of Birmingham (UK)
Yeast Molecular Genetics
The relationship between prion protein sequence and disease. Use of yeast as a model system for analysis of determinants of their transmembrane topology.
My laboratory uses yeast for the molecular genetic analysis of determinants of transmembrane (TM) protein topology. Both prion diseases and far more prevalent diseases such as Alzheimer's and cystic fibrosis result from errors in folding, membrane insertion, localization or processing of TM proteins. Although the topogenic signals that determine the topology of insertion are quite well understood (and have been extensively studied in yeast by my lab), the mechanisms for response to these signals are unknown. A long term goal is to characterize these mechanisms by the analysis of yeast mutants defective in responses to these signals. Our primary focus, however, is to use these techniques to analyze the relationship between mutations in the mammalian prion protein (PrP), membrane insertion and pathogenesis.
Misfolded forms of PrP appear to be both the infectious agent of prion diseases and the primary cause of the neurotoxicity that leads to slowly lethal destruction of the brain. About 10% of human prion disease are familial, caused by mutations in the PrP gene. Recent studies show that, in at least one class of such mutants, neurotoxicity correlates with increased production of a normally rare transmembrane (TM) form of PrP, called PrPCtm, that may be the actual toxic form in all prion disease. We have shown that yeast is an efficient system for analysis of the relationship between pathogenic PrP mutations and TM topology. Using PrP as a model, we are collaborating in analysis of a previously unidentified component of the mammalian protein translocation apparatus that helps to control the topology of insertion of PrP and, presumably, other translocated proteins.
- Determine the mechanism of PrPCtm production by constructing PrP mutants with N-terminal glycosylation sites and analyzing their modification in yeast and in vitro.
- Test the role of PrPCtm in prion pathology by determining the effects of changing the charged topogenic signals in PrP on transmembrane insertion and pathogenicity.
- Isolate new pio mutants and determine their effects on normal yeast TM proteins.
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