Re-examining how complexin inhibits neurotransmitter release.
Complexins play activating and inhibitory functions in neurotransmitter release. The complexin accessory helix inhibits release and was proposed to insert into SNARE complexes to prevent their full assembly. This model was supported by 'superclamp' and 'poor-clamp' mutations that enhanced or decreased the complexin-I inhibitory activity in cell-cell fusion assays, and by the crystal structure of a superclamp mutant bound to a synaptobrevin-truncated SNARE complex. NMR studies now show that the complexin-I accessory helix does not insert into synaptobrevin-truncated SNARE complexes in solution, and electrophysiological data reveal that superclamp mutants have slightly stimulatory or no effects on neurotransmitter release, whereas a poor-clamp mutant inhibits release. Importantly, increasing or decreasing the negative charge of the complexin-I accessory helix inhibits or stimulates release, respectively. These results suggest a new model whereby the complexin accessory helix inhibits release through electrostatic (and perhaps steric) repulsion enabled by its location between the vesicle and plasma membranes.DOI: http://dx.doi.org/10.7554/eLife.02391.001.
NeuroCure Cluster of Excellence, Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Thorsten
T
Trimbuch
Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.
Junjie
J
Xu
Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.
David
D
Flaherty
Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.
Diana R
DR
Tomchick
Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States jose@arnie.swmed.edu.
Josep
J
Rizo
NeuroCure Cluster of Excellence, Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany christian.rosenmund@charite.de.
Christian
C
Rosenmund
D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004926:Escherichia coli / Q000235:genetics; D005822:Genetic Vectors / Q000235:genetics; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D006801:Humans; D016086:Lentivirus / Q000235:genetics; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D008958:Models, Molecular; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000737:chemistry; D011401:Promoter Regions, Genetic; D050683:R-SNARE Proteins / Q000235:genetics / Q000378:metabolism; D051381:Rats; D016704:Synapsins / Q000235:genetics / Q000378:metabolism; D013572:Synaptic Vesicles / Q000378:metabolism; D050827:Syntaxin 1 / Q000235:genetics / Q000378:metabolism
D033942:Adaptor Proteins, Vesicular Transport; D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; D009587:Nitrogen Isotopes; D050683:R-SNARE Proteins; D016704:Synapsins; D050827:Syntaxin 1; C095992:complexin I
membrane fusion; protein interactions; synaptic vesicle exocytosis