[Abstract Title]. - Society for Neuroscience

Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 236.6/D6
Topic: B.06.a. Docking and fusion
Support: NIH Grant MH064070
Title: Relationship between vesicle pools, release probability, and the prevalence of rapid vesicle
retrieval (kiss and run)
Authors: Q. ZHANG, *R. W. TSIEN;
Dept Molec & Cell Physiol, Stanford Univ. Sch. Med., Stanford, CA
Abstract: There is growing evidence for the existence of non-classical fusion (modes generally
termed “kiss-and-run”, K&R) in various secretory systems, but the cellular basis and biological
impact of K&R are far from clear. We have developed a quantum dot (Qdot)-based approach to
monitor the fate of individual synaptic vesicles as they undergo K&R or classical full collapse
fusion (FCF). After loading a single vesicle with an indivisible probe, we could identify a
vesicle‟s pool of origin with a hypertonic sucrose challenge, then track the fate of the once-used
vesicle during subsequent electrical stimulation. This allowed us to clarify the basis of a
progressive change in the prevalence of K&R during electrical stimulation, falling from 65% to
5% at steady state. We prefaced the electrical stimulation with a hypertonic challenge to provoke
a restricted turnover of the readily releasable pool (RRP). The hypertonic challenge produced a
mixture of Qdot signals corresponding to K&R and FCF events that were similar in amplitude,
time course and prevalence to those evoked at the start of electrical stimulation on its own. More
than half of the hypertonicity-induced events were K&R. However, in the wake of the hypertonic
challenge and RRP release, subsequent electrical stimulation evoked only a low, flat level of
K&R usage (~5%). Thus, RRP vesicles show a much higher prevalence of K&R than reserve
pool vesicles, and the gradual change in prevalence reflects usage of the RRP. Put differently,
RRP residents acquired an enhanced propensity to undergo K&R, enabling their subsequent
reuse. However, the readiness for K&R can be dissipated. Interestingly, we found that a loading
procedure that targeted RRP vesicles led to preferential loading of vesicles releasable by
subsequent hypertonic challenges, supporting the idea of a preferential recycling of RRP vesicles
back to their pool of origin.
Disclosures: Q. Zhang, None; R.W. Tsien , None.
Poster
236. Neurotransmitter Release: Docking and Fusion
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm