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Liposomes, Exosomes, and Virosomes: From Modeling Complex
Membrane Processes to Medical Diagnostics and Drug Delivery
Poster Abstracts
65
40-POS
Board 20
Interaction of Complexin with SNARE Proteins Depends on the Lipid Environment of the
Membrane
Binyong Liang
1,2
, Alex J. Kreutzberger
1,2
, Volker Kiessling
1,2
, Rafal Zdanowicz
1,3
, David S.
Cafiso
1,3
, Lukas K. Tamm
1,2
.
2
University of Virginia, Charlottesville, VA, USA,
3
University of Virginia, Charlottesville, VA,
USA.
1
University of Virginia, Charlottesville, VA, USA,
Fusion of synaptic vesicles with the presynaptic membrane is mediated by SNAREs and several
SNARE-interacting proteins. Complexin is a soluble protein, which binds strongly to fully
assembled neuronal SNARE complexes. Complexin is required for Ca2+-triggered fast fusion at
nerve terminals; however, its mechanism of action remains elusive and controversial. Inhibitory
and fusion-promoting effects have been reported and attributed to different domains of
complexin. In addition, preferential binding of complexin to charged and highly curved
membranes has been postulated to also contribute to its regulatory effect.
We have used solution NMR and EPR spectroscopy, isothermal titration calorimetry, fluorescent
anisotropy, and TIRF microscopy to probe multiple interactions between complexin and SNARE
proteins in different complexes in a number of membrane-mimetic systems. Based on the
molecular details revealed by NMR and EPR, and thermodynamic and kinetic measurements
performed by ITC and fluorescence anisotropy, respectively, we present a model of how
complexin effects SNARE-mediated membrane fusion in a physiological lipid environment.