Preferential sharing of recycling vesicles rather than reserve pool vesicles between adjacent synapses

L Shalev, D Gitler

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Neuronal transmission relies on the synaptic vesicle cycle,
which incorporates all mechanisms supplying vesicles for
fusion at the plasma membrane. The various segments of
this cycle are controlled by a large group of pre-synaptic
proteins, of which synapsin is one of the most abundant.
The synapsins are a multigene family of phospho-proteins
which reversibly bind to synaptic vesicles, to each other,
and to the cytoskeleton, thus managing the reserve pool of
vesicles. Recent studies have shown that vesicles are not
confined to individual presynaptic terminals as is widely
believed. Rather, it was observed that functional vesicles
move between adjacent synaptic boutons, effectively forming a large super-pool of shared vesicles.
We focused on the phenomenon of vesicle mobility along
axons using Fluorescence Recovery After Photobleaching
(FRAP) to investigate how synaptic vesicle clustering by
the synapsins affects vesicle sharing between synapses.
Synaptophysin I-EGFP (Syp-EGPF) expression was utilized to label the complete vesicle population, while FM 1-
43 served to specifically label the recycling pool. We show
that FRAP of Syp-EGPF is faster in synapsin-devoid
neurons as compared to wild type ones, suggesting that a
decrease in vesicle clustering due to the absence of
synapsin increases the rate of vesicle mobility between
synapses. Moreover, in WT neurons FRAP of FM 1-43 is
faster as compared to FRAP of Syp-EGFP, while in synapsindevoid neurons no such difference was observed. These
results indicate that the recycling pool is more motile than the
reserve pool, and that synapsin affects mostly the mobility of
the latter. Our results further imply that the super pool of
vesicles draws vesicles more easily from the recycling pool
than from the more tightly bound reserve pool.
Original languageEnglish
StatePublished - 2011


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