Munc18-1 binding to the neuronal SNARE complex controls synaptic vesicle priming.
Munc18-1 and soluble NSF attachment protein receptors (SNAREs) are critical for synaptic vesicle fusion. Munc18-1 binds to the SNARE syntaxin-1 folded into a closed conformation and to SNARE complexes containing open syntaxin-1. Understanding which steps in fusion depend on the latter interaction and whether Munc18-1 competes with other factors such as complexins for SNARE complex binding is critical to elucidate the mechanisms involved. In this study, we show that lentiviral expression of Munc18-1 rescues abrogation of release in Munc18-1 knockout mice. We describe point mutations in Munc18-1 that preserve tight binding to closed syntaxin-1 but markedly disrupt Munc18-1 binding to SNARE complexes containing open syntaxin-1. Lentiviral rescue experiments reveal that such disruption selectively impairs synaptic vesicle priming but not Ca(2+)-triggered fusion of primed vesicles. We also find that Munc18-1 and complexin-1 bind simultaneously to SNARE complexes. These results suggest that Munc18-1 binding to SNARE complexes mediates synaptic vesicle priming and that the resulting primed state involves a Munc18-1-SNARE-complexin macromolecular assembly that is poised for Ca(2+) triggering of fusion.
Deák
Ferenc
F
Howard Hughes Medical Institute, Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Xu
Yi
Y
Chang
Wen-Pin
WP
Dulubova
Irina
I
Khvotchev
Mikhail
M
Liu
Xinran
X
Südhof
Thomas C
TC
Rizo
Josep
J
D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000648:ultrastructure; D002478:Cells, Cultured; D005822:Genetic Vectors / Q000235:genetics; D046911:Macromolecular Substances / Q000378:metabolism; D008561:Membrane Fusion / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D051938:Munc18 Proteins / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D017354:Point Mutation / Q000235:genetics; D017729:Presynaptic Terminals / Q000378:metabolism* / Q000648:ultrastructure; D011485:Protein Binding / Q000235:genetics; D051381:Rats; D050600:SNARE Proteins / Q000378:metabolism* / Q000648:ultrastructure; D013570:Synaptic Membranes / Q000378:metabolism* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000235:genetics; D013572:Synaptic Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D050827:Syntaxin 1 / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D033942:Adaptor Proteins, Vesicular Transport; D046911:Macromolecular Substances; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins; D050600:SNARE Proteins; C497938:Stxbp1 protein, mouse; D050827:Syntaxin 1; C095992:complexin I