Viktor Jiracek, University of Utah
The nervous system is responsible for cognition, memory, and motor function. Neurons communicate with each other at intercellular connections called synapses. It is at these locations that vesicles fuse with the plasma membrane and release their contents into the space between the neurons (synaptic cleft). SNARE proteins (synaptobrevin, syntaxin and SNAP-25) facilitate synaptic vesicle fusion by winding together in a four-helix bundle forcing the mixture of opposing membranes. After exocytosis, the cell regenerates vesicles by a process called endocytosis. This process involves the budding of membrane back into the cytoplasm re-forming a functional synaptic vesicle. This progression from vesicle fusion to internalization is termed the “synaptic vesicle cycle” and is coordinated by a long list of molecular players. The SNARE proteins are classically considered to be unique to exocytosis. However, preliminary results from Erik Jorgensen’s lab have implicated SNAP-25 in endocytosis. Although we have evidence that SNAP-25 is required for endocytosis, the molecular mechanism is completely unknown. In this proposal we use forward genetics in the model organism C. elegans to identify novel protein interactions required for SNAP-25 mediated endocytosis. We have designed three suppressor screens that are predicted to target the role of SNAP-25 in exocytosis, endocytosis and general function. The first two screens use crippled forms of SNAP-25 (hypomorphs) while the last screen uses a deletion allele of the SNAP-25 gene (null mutation). With these screens we hope to precisely identify the molecular players involved in SNAP-25 mediated endocytosis versus exocytosis.