Protein folding, assembly and the regulation of intracellular protein transport.

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My main interests are in the field of intracellular protein trafficking. My research has focused on the mechanisms of selective capture of proteins from their site of synthesis at the endoplasmic reticulum (ER) into COPII vesicles, which convey proteins to the Golgi apparatus. We use the the budding yeast, Saccharomyces cerevisiae, as a model system to understand this process, using a combination of genetics and biochemical reconstitution of intracellular transport events. Capture of proteins into ER-derived vesicles is a critical junction between the folding and assembly of newly synthesized proteins and their forward transport through the secretory pathway. To prevent “proteotoxicity” associated with aberrant secretion of improperly assembled proteins, cells employ a quality control pathway that ensures that only properly assembled proteins are packaged into vesicles for delivery to downstream compartments. Although we now understand the molecular interactions that drive uptake of cargo proteins into ER-derived vesicles, we know very little about how cells regulate this process in the context of protein folding, nor how perturbations in this regulation may contribute to cellular pathologies.

Current research is aimed at addressing the fundamental question of how cells regulate cargo selection in the context of protein folding and assembly to prevent inappropriate export of aberrant proteins. The basic question can be posed as follows: when transmembrane proteins display cytoplasmic sorting signals that interact directly with the COPII coat machinery that drives vesicle formation from the ER, how is that interaction regulated to prevent the packaging of an unfolded or unassembled protein? We use a range of biochemical and genetic techniques, including an in vitro vesicle budding assay that reconsititutes this process using purified proteins as well as a number of genetic screens and selections.

• genetic screens to identify mutations that bypass the ER quality control checkpoint and allow the secretion of a misfolded cargo protein
• biochemical identification of proteins that may regulate ER export through association with COPII vesicle coat components
• characterization of the interplay between protein folding and ER export using a chimeric misfolded substrate protein that also contains a strong ER export signal
• high-throughput chemical screen to identify compounds that restore the trafficking of a misfolded cargo protein that is ER-retained and/or degraded