- Graduate Students
Vesicle targeting and fusion are tightly regulated processes used by eukaryotic cells to transport cargo between membrane-bound subcellular compartments and to the plasma membrane for secretion. The proper function and specificity of these processes are crucial for maintenance of cellular integrity, normal growth, and for intercellular signaling events, such as neurotransmission.
We are interested in understanding the mechanistic basis for regulation of the spatial and temporal specificity of vesicle fusion, at the correct site on the target membrane. Many questions remain to be answered. For example, what marks the site of fusion on the target membrane? What checks to make sure that the correct vesicle docks at the right place? How are the membrane fusion proteins regulated to ensure that the wrong vesicle does not fuse? Our aim is to answer questions such as these through a multifaceted approach that combines biochemical, structural and biophysical techniques with yeast genetics, microscopy and cell biological methods. We are investigating proteins that regulate exocytosis in the model organism Saccharomyces cerevisiae. Because these proteins are conserved from yeast to man, these studies will advance our understanding of how secretion is regulated in all eukaryotic cells.
Our investigations mainly focus on the Exocyst complex, a protein complex essential for vesicle trafficking (exocytosis) in all eukaryotes. The proteins that form the Exocyst complex localize to secretory vesicles and to sites of active secretion at bud tips and mother-bud necks. These proteins are essential for cell viability, show physical and genetic interactions with the the membrane fusion proteins (SNAREs) and with each other, and their temperature-sensitive mutants have secretory blocks and accumulate secretory vesicles.
Our research has several aims: 1) biophysical and structural studies of the Exocyst proteins and their interactions with each other; 2) creation and testing of mutants in vivo, in order to elucidate the functions of the Exocyst proteins; 3) characterization of interactions between the Exocyst and other proteins required for exocytosis, such as the SNARE proteins, and regulators such as Sec1p and the small Rab GTPase Sec4p; and 4) genetic and proteomic identification of novel regulators of exocytosis and SNARE complex assembly. Additionally, we are characterizing the regulation of endocytosis by the Sec1-homolog Vps45p, through its interactions with the endosomal SNARE proteins.