Studies of Single Exocytotic Events
Manfred Lindau

Many cell types release pre-formed compounds stored in secretory vesicles or granules by fusion of these vesicles with the plasma membrane. This process is called exocytosis. The substances released by exocytosis include neurotransmitters and hormones from neurons and endocrine cells, histamine from mast cells, and cytotoxic proteins or various enzymes from granulocytes. Our goal is to understand the mechanism of biological membrane fusion.

To study this process we investigate single fusion events using electrophysiological methods (patch-clamp, amperometry), microscopy imaging, and micromechanical manipulations using optical tweezers. These methods enable us to study the forces which develop when vesicles dock at the target membrane. They allow us to characterize the opening and expansion of the fusion pore connecting the intravesicular lumen to the extracellular space by its electrical conductance. They furthermore allow us to measure the time course of transmitter release during exocytosis of a single vesicle and to relate this time course to the dynamics of the fusion pore. Using molecular biological techniques and artificial membranes reconstituted from pure lipids and proteins, we hope to reveal a detailed picture of the exocytotic fusion machinery. Measurements of single fusion pores will be as significant for the understanding of fusion as single channel recordings were instrumental for an understanding of ion channel function.

This exploration will involve an introductory lecture and a lab tour with demonstrations and opportunities to talk to the graduate students and post-docs in the lab.