[HTML][HTML] Contact-induced clustering of syntaxin and munc18 docks secretory granules at the exocytosis site

NR Gandasi, S Barg - Nature communications, 2014 - nature.com
Nature communications, 2014nature.com
Docking of secretory vesicles at the plasma membrane is a poorly understood prerequisite
for exocytosis. Current models propose raft-like clusters containing syntaxin as docking
receptor, but direct evidence for this is lacking. Here we provide quantitative measurements
of several exocytosis proteins (syntaxin, SNAP25, munc18, munc13 and rab3) at the insulin
granule release site and show that docking coincides with rapid de novo formation of
syntaxin1/munc18 clusters at the nascent docking site. Formation of such clusters prevents …
Abstract
Docking of secretory vesicles at the plasma membrane is a poorly understood prerequisite for exocytosis. Current models propose raft-like clusters containing syntaxin as docking receptor, but direct evidence for this is lacking. Here we provide quantitative measurements of several exocytosis proteins (syntaxin, SNAP25, munc18, munc13 and rab3) at the insulin granule release site and show that docking coincides with rapid de novo formation of syntaxin1/munc18 clusters at the nascent docking site. Formation of such clusters prevents undocking and is not observed during failed docking attempts. Overexpression of syntaxins’ N-terminal Habc-domain competitively interferes with both cluster formation and successful docking. SNAP25 and munc13 are recruited to the docking site more than a minute later, consistent with munc13’s reported role in granule priming rather than docking. We conclude that secretory vesicles dock by inducing syntaxin1/munc18 clustering in the target membrane, and find no evidence for preformed docking receptors.
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