A protein assembly-disassembly pathway in vitro that may correspond to sequential steps of synaptic vesicle docking, activation, and fusion.
The SNARE hypothesis holds that a transport vesicle chooses its target for fusion when a soluble NSF attachment protein (SNAP) receptor on the vesicle (v-SNARE) pairs with its cognate t-SNARE at the target membrane. Three synaptosomal membrane proteins have previously been identified: syntaxin, SNAP-25 (t-SNAREs), and vesicle-associated membrane protein (VAMP) (v-SNARE); all assemble with SNAPs and NSF into 20S fusion particles. We now report that in the absence of SNAP and NSF, these three SNAREs form a stable complex that can also bind synaptotagmin. Synaptotagmin is displaced by alpha-SNAP, suggesting that these two proteins share binding sites on the SNARE complex and implying that synaptotagmin operates as a "clamp" to prevent fusion from proceeding in the absence of a signal. The alpha-SNAP-SNARE complex can bind NSF, and NSF-dependent hydrolysis of ATP dissociates the complex, separating syntaxin, SNAP-25, and VAMP. ATP hydrolysis by NSF may provide motion to initiate bilayer fusion.
Söllner
T
T
Program in Cellular Biochemistry and Biophysics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
Bennett
M K
MK
Whiteheart
S W
SW
Scheller
R H
RH
Rothman
J E
JE
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D000954:Antigens, Surface / Q000302:isolation & purification; D001921:Brain / Q000378:metabolism; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins / Q000378:metabolism; D002417:Cattle; D005089:Exocytosis; D005455:Fluorescent Antibody Technique; D008561:Membrane Fusion; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins; D008954:Models, Biological; D052066:N-Ethylmaleimide-Sensitive Proteins; D009419:Nerve Tissue Proteins / Q000302:isolation & purification / Q000378:metabolism*; D016716:PC12 Cells; D013572:Synaptic Vesicles / Q000378:metabolism*; D050825:Synaptosomal-Associated Protein 25; D050857:Synaptotagmins; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins
D000954:Antigens, Surface; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins; D050857:Synaptotagmins; D000251:Adenosine Triphosphatases; D052066:N-Ethylmaleimide-Sensitive Proteins