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Show RESEARCH POSTERS ON THE HILL SPRING 2007 101 Molecular Events at Brain Synapses: Does Syntaxin Form a Rosette? Katharine Osborn and Erik Jorgensen Department of Biology The exact intracellular mechanism for the release of a neurotrans-mitter at the pre-synaptic membrane of a neuron has not yet been discovered. It has been shown, however, that a vesicle sequestering the neurotransmitter is docked, primed, and fused to the plasma membrane, thus releasing the chemical messenger. We also know that three proteins from the SNARE family play a central role in the three-step process of exocytosis. Synaptobrevin, one protein containing the SNARE motif, is located on the vesicle. SNAP-25 and syntaxin are the two complementary SNARE proteins that localize to the target membrane. Despite the functional importance of the SNARE proteins, their role in the molecular mechanism of exocytosis is unknown. One hypothesis for the mechanism of exocytosis involves syntaxin molecules forming a rosette configuration on the inside of the post-synaptic membrane with which the vesicle will come into contact. Further, we hypothesize that the connecting of syntaxin proteins forms the rosette configuration. Syntaxin is primarily made up of two protein domains. The SNARE domain consists of the trunk of the protein, and three folded alpha helices, called the Habc domain, make up the upper portion of the protein. We are investigating whether the rosette is formed by the Habc domain of one syntaxin molecule attaching to the SNARE domain of an adjacent syntaxin molecule. We are testing our hypothesis by constructing chimeric syntaxin molecules consisting of both yeast and nematode sequences to be expressed in our model organism, C.elegans. If the syntaxin protein expressed has the Habc domain of yeast and the SNARE domain of nematode, we postulate that there will do no exo-cytosis of neurotransmitter because the Habc domain will be unable to attach to the adjacent SNARE domain, thus no rosette will form, and there will be no fusion of the vesicle to the pre-synaptic membrane. We will also investigate whether other combinations of yeast and nematode syntaxin proteins allow or prevent excytosis to occur in the neurons of C. elegans Our objective is to further the understanding of the function of the SNARE protein, syntaxin, so that the knowledge can be used to better realize its importance in neuronal signaling. This research is supported with funding from The National Institute of Health. Katharine Osborne is supported by funding from The University of Utah, Department of Biology, Bioscience Undergraduate Research Program. |