Biophysical Measurements of SNARE Protein Interactions and Movements
Synapses communicate information between neurons by releasing a package of chemical activator (transmitter) packaged in vesicles docked at the presynaptic cell membrane. The trace shows a recording of FRET (fluorescence resonance energy transfer) reporting interactions between two fluorescently labeled proteins -- VAMP in vesicles and SNAP-25 in the membrane -- that with syntaxin form the SNARE complex of vesicles docked at the membrane. These events are illustrated: Presynaptic electrical signals (30 Hz stimulation) open calcium channels, calcium enters and activates the vesicular protein synaptotagmin which interacts with SNARE proteins (sharp transient increase in FRET) and the plasma membrane to fuse the vesicle with the membrane by exocytosis, releasing transmitter. The proteins migrate laterally in the membrane, then dissociate (drop in FRET) before the recovery of vesicle membrane and protein by endocytosis. Vesicles are refilled with transmitter, and dock at vacant release sites to reform SNARE complexes (recovery of FRET to resting level) in readiness for further activity.
Quicktime video available below.
Design: Prof. Robert Zucker (©2006)
Experimental Data: Dr. Ismail Hafez (2005)
Animation: Russell English (2007)
Audio: Thanks to Richard Wagner (Walkürenritt, 1856)