Nerve cells communicate with each other by secreting chemical messengers known as neurotransmitters. Exocytosis, a form of secretion, is a cellular process which involves the fusion of membranes, resulting in the discharge of substances from cells. Though poorly understood, the mechanism of exocytosis is of fundamental importance for understanding synaptic transmission and intercellular communication between cells. The goal of this research project is to ascertain the steps involved in the regulation of exocytosis that occur in neuronal and paraneuronal cells. Dr. Holz will examine the role of annexins, a class of lipoproteins, in the process of exocytosis. Previous results suggest that annexins play a significant role in the normal secretory pathway. Experiments using cultured chromaffin cells will be used to determine if annexins interact with granule, a specialized cell product involved in secretion, and to test the possibility that annexins may regulate the binding of granule to the plasma membrane. Results of these studies are likely to be applicable to the understanding of presynaptic events in synaptic transmission.