Identification of the minimal protein domain required for priming activity of Munc13-1.
Most nerve cells communicate with each other through synaptic transmission at chemical synapses. The regulated exocytosis of neurotransmitters, hormones, and peptides occurs at specialized membrane areas through Ca2+-triggered fusion of secretory vesicles with the plasma membrane . Prior to fusion, vesicles are docked at the plasma membrane and must then be rendered fusion-competent through a process called priming. The molecular mechanism underlying this priming process is most likely the formation of the SNARE complex consisting of Syntaxin 1, SNAP-25, and Synaptobrevin 2. Members of the Munc13 protein family consisting of Munc13-1, -2, -3, and -4 were found to be absolutely required for this priming process . In the present study, we identified the minimal Munc13-1 domain that is responsible for its priming activity. Using Munc13-1 deletion constructs in an electrophysiological gain-of-function assay of chromaffin-granule secretion, we show that priming activity is mediated by the C-terminal residues 1100-1735 of Munc13-1, which contains both Munc13-homology domains and the C-terminal C2 domain. Priming by Munc13-1 appears to require its interaction with Syntaxin 1 because point mutants that do not bind Syntaxin 1 do not prime chromaffin granules.
Stevens
David R
DR
Physiologisches Institut, Universität des Saarlandes, Kirrberger Str. 8, D-66421 Homburg/Saar, Germany.
Wu
Zheng-Xing
ZX
Matti
Ulf
U
Junge
Harald J
HJ
Schirra
Claudia
C
Becherer
Ute
U
Wojcik
Sonja M
SM
Brose
Nils
N
Rettig
Jens
J
D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D019439:Chromaffin Cells; D002837:Chromaffin Granules / Q000378:metabolism; D004594:Electrophysiology; D049452:Green Fluorescent Proteins; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D009435:Synaptic Transmission / Q000235:genetics* / Q000502:physiology; D013572:Synaptic Vesicles / Q000378:metabolism*; D050827:Syntaxin 1 / Q000378:metabolism
D009419:Nerve Tissue Proteins; D050827:Syntaxin 1; C503321:Unc13a protein, mouse; D049452:Green Fluorescent Proteins; D002118:Calcium