PROJECT SUMMARY
Eukaryotic cells transport cargo between subcellular organelles, and to the plasma membrane for secretion,
using small membrane-bound vesicles are carriers. The regulation of vesicular transport and membrane fusion
processes are crucial for cellular morphology, growth, movement and secretion, including hormone release
and neurotransmission. Many essential proteins are required for these processes, including the SNARE
proteins and Sec1 that are involved in the membrane fusion process, the Rab and Rho GTPases, and the
exocyst octameric tethering complex. Exocyst has been implicated in a number of different functions involved
in recognition, tethering and quality control of SNARE assembly and fusion, but none of these are well
understood at the molecular level. We use a multidisciplinary strategy of biochemical, structural and
biophysical techniques, combined with genetics and cell biological methods, to understand the molecular
architecture and function of the exocyst complex, Sec1 and regulation of SNARE complex assembly and
fusion. We study the exocyst proteins from the model organism Saccharomyces cerevisiae to take advantage
of the wealth of genetic, cell biological and biochemical techniques available, but have expanded to exocyst
from other organisms. Our studies aim to address the following fundamental questions: How is the specificity of
vesicle targeting and fusion achieved? How do exocyst and Sec1 function to regulate SNAREs? What are the
roles for different partner proteins and lipids? What happens when exocyst and Sec1 functions are
dysregulated? Because these proteins are conserved from yeast to human neurons, this research will advance
our knowledge of how secretion and growth are regulated in all eukaryotic cells. We will also illuminate the
molecular consequences of disease-associated dysfunction.