Membrane trafficking contributes to the intracellular organization of all eukaryotic cells, and to the specialized functions of many cell types. The membranous compartments of the secretory and endocytic pathways exhibit distinct biochemical properties related to the specific functions that they perform. This intracellular organization is maintained, in part, by transport vesicles that shuttle membrane and soluble cargo from one intracellular compartment of another. In specialized cell types, such as epithelial cells, vesicular trafficking plays and important role in the maintenance of cell surface polarity that is essential for vectorial transport and secretory functions. Furthermore, the regulation of certain membrane trafficking events, for example those underlying the regulated secretion of neurotransmitter at the synapse, play important roles in intercellular communication. The long-term objective of the proposed research is an understanding of the molecular mechanisms responsible for these intracellular membrane trafficking events. Such an understanding will ultimately provide insight into a wide variety of cellular processes. The strategy to be employed in approaching this objective is the biochemical and functional characterization of a family of proteins, the syntaxins, that have been proposed to act as receptors for intracellular membrane transport vesicles. Particular emphasis will be focused on the role of syntaxin 1 in synaptic vesicle docking and fusion. The proposed research will address the following specific aims: 1. Biochemical characterization of the interaction between membrane of the syntaxin family and other specific components of the intracellular membrane trafficking machinery. 2. Identification of the signal(s) within the syntaxins responsible for localization to different intracellular membrane compartments. 3. Functional characterization of the role of syntaxins in constitutive and regulated secretion from PC12 cells.
