Faculty

The long-term goal of our laboratory is to understand the mechanisms and regulation of exocytic transport from the Golgi and endosomes, a fundamental process in all eukaryotic cells. Most of the conserved genes required for membrane and protein trafficking were first identified in genetic screens using the yeast Saccharomyces cerevisiae, and yeast is a well-established model in the study of intracellular transport. However, the branching of exocytic transport routes in both yeast and mammalian cells has made it difficult to identify the genes involved in exocytic cargo sorting and exit from the Golgi and endosomes, and these transport steps are still poorly understood.  In addition to partially redundant exocytic pathways, there is likely to be redundancy in both the machineries and the regulatory mechanisms that function in traffic to the cell surface. Such complexity is not unexpected in fine-tuned processes that respond to external cues to regulate cell surface growth and cell proliferation, and which also regulate the temporal and spatial placement of cell surface components in polarized cells. The likely partial redundancy of most genes involved in the mechanisms and control of transport from late exocytic compartments needs to be considered when devising strategies to identify and study such genes. We used a classical yeast genetic strategy as well as a high-throughput chemical genetic strategy to identify genes that function in traffic from late exocytic compartments. Our strategies have identified a novel, conserved eukaryotic protein, Avl9, involved in late exocytic transport. We also identified pathway-specific chemical inhibitors of the late exocytic pathway.

We are analyzing the effects of our new chemical inhibitors, as well as the functions of the genes we identify, by light and electron microscopy, subcellular fractionation, and various transport assays in yeast and cultured mammalian cells. We are initially focusing on Avl9, a member of an ancient eukaryotic protein superfamily. These proteins, including orthologs of Avl9, are widely present in eukaryotes from ciliates to vertebrates, but the mechanisms by which they function, and in most cases even the processes in which they function, are unknown.  Our recent biochemical analysis indicates that Avl9 interacts with specific phospholipids in vitro, so it may have a function in regulating transport vesicle formation.

Defects in membrane traffic pathways, either blocks in transport or defects in the regulatory mechanisms that define when and where transport occurs, lead to a wide range of diseases including immune and neurological disorders, diabetes, and cancer. Furthermore, many intracellular pathogens hijack the host cell transport machinery for pathogen survival and spreading. Identifying and understanding the functions of the membrane traffic machinery will therefore allow us to better understand and combat many diseases.

Representative Publications

Search PubMed for articles by Edina Harsay.