Ying Lai, Jiajie Diao, Yanxin Liu, Yuji Ishitsuka, Zengliu Su, Klaus Schulten,
Taekjip Ha, and Yeon-Kyun Shin.
Fusion pore formation and expansion induced by Ca2+ and
synaptotagmin 1.
Proceedings of the National Academy of Sciences, USA,
110:1333-1338, 2013.
(PMC: 3557091)
LAI2013
Fusion pore formation and expansion, crucial steps for neurotransmitter release and
vesicle recycling in SNARE-dependent vesicle fusion, have not been well studied in vitro
due to the lack of a reliable content mixing fusion assay. Using methods detecting the
inter-vesicular mixing of small and large cargoes at a single vesicle level, we found that
the neuronal SNARE complexes have the capacity to drive membrane hemifusion. However,
efficient fusion pore formation and expansion require synaptotagmin 1 and Ca2+. Real-
time measurements show that pore expansion detected by content mixing of large DNA
cargoes occurs much slower than initial pore formation that transmits small cargoes. Slow
pore expansion perhaps provides a time window for vesicles to escape the full collapse
fusion pathway via alternative mechanisms such as kiss-and-run. The results also show
that complexin 1 stimulates pore expansion significantly, which could put bias between
two pathways of vesicle recycling.
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