The small GTP-binding protein Rab3A regulates a late step in synaptic vesicle fusion.
The Rab family of low-molecular-mass GTP-binding proteins are thought to guide membrane fusion between a transport vesicle and the target membrane, and to determine the specificity of docking. The docking and fusion of vesicles is, however, a complex multistep reaction, and the precise point at which Rab proteins act in these sequential processes is unknown. In brain, the Rab protein Rab3A is specific to synaptic vesicles, whose exocytosis can be monitored with submillisecond resolution by following synaptic transmission. We have now determined the precise point at which Rab3A acts in the sequence of synaptic vesicle docking and fusion by using electrophysiological analysis of neurotransmitter release in Rab3A-deficient mice. Unexpectedly, the size of the readily releasable pool of vesicles is normal, whereas Ca2+-triggered fusion is altered in the absence of Rab3A in that a more-than-usual number of exocytic events occur within a brief time after arrival of the nerve impulse.
Geppert
M
M
Max Planck Institute for Experimental Medicine, Gottingen, Germany.
Goda
Y
Y
Stevens
C F
CF
Südhof
T C
TC
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005089:Exocytosis; D019204:GTP-Binding Proteins / Q000502:physiology*; D066298:In Vitro Techniques; D008561:Membrane Fusion; D051379:Mice; D018345:Mice, Knockout; D018377:Neurotransmitter Agents / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism; D013569:Synapses / Q000502:physiology*; D013570:Synaptic Membranes / Q000502:physiology; D009435:Synaptic Transmission; D013572:Synaptic Vesicles / Q000502:physiology*; D020692:rab3 GTP-Binding Proteins
D018691:Excitatory Amino Acid Antagonists; D018377:Neurotransmitter Agents; D016194:Receptors, N-Methyl-D-Aspartate; D016291:Dizocilpine Maleate; D015763:2-Amino-5-phosphonovalerate; D019204:GTP-Binding Proteins; D020692:rab3 GTP-Binding Proteins; D002118:Calcium