2025-10-17 中国科学院(CAS)
<関連情報>
- https://english.cas.cn/newsroom/research_news/life/202510/t20251017_1089587.shtml
- https://www.science.org/doi/10.1126/science.ads7954
「キス・シュリンク・ラン」はシナプス小胞のエキソサイトーシスと超高速リサイクリングのメカニズムを統合する “Kiss-shrink-run” unifies mechanisms for synaptic vesicle exocytosis and hyperfast recycling
Chang-Lu Tao, Chong-Li Tian, Yun-Tao Liu, Zhen-Hang Lu, […] , and Guo-Qiang Bi
Science Published:16 Oct 2025
DOI: https://doi.org/10.1126/science.ads7954
Editor’s summary
Neurons transmit signals through synaptic vesicle release, but the nanoscale dynamics of this process have been unclear. Tao et al. revealed these dynamics in hippocampal synapses using optogenetics and time-resolved cryo–electron tomography (see the Perspective by Lichter). Their innovative approach captures synaptic vesicle exocytosis at millisecond resolution, identifying the “kiss-shrink-run” pathway in which synaptic vesicles briefly contact the presynaptic membrane, shrink significantly, and then detach for rapid recycling. This mechanism unifies competing neurotransmitter release models and elucidates the underpinnings of synaptic efficiency and reliability. —Stella M. Hurtley
Structured Abstract
INTRODUCTION
Synaptic vesicle (SV) exocytosis is triggered by an action potential and leads to neurotransmitter release. As such, SV exocytosis is fundamental to neuronal communication. However, the structural and biophysical mechanisms underlying SV exocytosis remain incompletely understood. In particular, questions remain regarding the dynamic interactions between the SV membrane, the presynaptic membrane, and the protein complexes involved. This gap has fueled a long-standing debate over the existence of transient “kiss-and-run” fusion versus irreversible “full-collapse” fusion in central synapses.
RATIONALE
Resolving this debate requires techniques that can achieve nanometer spatial resolution and millisecond temporal resolution. To address this need, we developed a time-resolved, cellular cryo–electron tomography (cryo-ET) method to image intact synapses in cultured rat hippocampal neurons. This approach integrated optogenetic stimulation for synaptic activation and plunge-freezing at millisecond intervals. It also provided high three-dimensional spatial resolution, enabling accurate vesicle size measurements and detailed structural analysis of vesicle–plasma membrane interactions. Using this technique, we acquired more than 1000 tomograms of entire excitatory synapses, frozen at various time points from 0 to 300 ms post–action potential. This large dataset facilitated rigorous statistical analysis of vesicle states and subtomogram averaging to visualize fusion-pore structures.
RESULTS
Near the presynaptic active zones, we observed two distinct SV populations with diameters centered at ~29 and ~41 nm. These SVs were mainly categorized into seven distinct structural states: tethered (large and small), semifused (large and small), pore-opened (large and small), and Ω-shaped (small). Notably, the population of small SVs decreased markedly after neural network inactivity with 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and was completely absent when vesicle exocytosis was blocked by tetanus toxin.
Time-resolved cryo-ET revealed a sequence of transitions among these vesicle states. In the resting condition, large SVs were primarily tethered to the plasma membrane (docking). Within 4 ms post–action potential, docked SVs transitioned to large semifused SVs (priming) that transiently “kiss” the plasma membrane. These primed SVs then formed pore-opened SVs with a ~4-nm lipidic fusion pore flanked by putative soluble NSF attachment protein receptor (SNARE) complexes. These fused SVs rapidly shrank to small pore-opened SVs with approximately half the surface area of the original large SVs. Most shrunken SVs subsequently closed their fusion pores and converted into small semifused SVs.
By 70 ms, small semifused SVs detached from the presynaptic membrane (“run-away”), whereas the remaining shrunken, pore-opened SVs fully collapsed into the plasma membrane. After 100 ms, the run-away SVs began to migrate to the periphery of the SV cluster, and the resulting expanded presynaptic membrane began to be retrieved through ultrafast endocytosis.
CONCLUSION
Our study identifies a kiss-shrink-run pathway as the dominant biophysical mechanism for SV exocytosis and rapid recycling in hippocampal synapses. This kiss-shrink-run mechanism reconciles the kiss-and-run and full-collapse models of neurotransmission and provides a unified explanation for the high efficiency and fidelity of synaptic transmission. Our integrative methodology also establishes a general framework for probing membrane dynamics and molecular interactions in situ with high spatiotemporal precision.
Kiss-shrink-run mechanism of SV release revealed by time-resolved cryo-ET.
A millisecond-precision time-resolved cryo-ET system, involving plunge-freezing coupled with optogenetic stimulation (top left), captured distinct intermediate states of SV exocytosis in intact hippocampal synapses (top right). With population analysis and subtomogram averaging, a kiss-shrink-run sequence was revealed as the prominent SV exocytosis and recycling pathway in hippocampal synapses (bottom). AP, action potential.
Abstract
Synaptic vesicle (SV) exocytosis underpins neuronal communication, yet its nanoscale dynamics remain poorly understood owing to limitations in visualizing rapid events in situ. Here, we used optogenetics-coupled, time-resolved cryo–electron tomography to capture SV exocytosis in rat hippocampal synapses. Within 4 milliseconds of synaptic activation, SVs transiently “kiss” the plasma membrane, forming a ~4-nanometer lipidic fusion pore flanked by putative soluble NSF-attachment protein receptor (SNARE) complexes and then rapidly “shrink” to approximately half of their original surface area. By 70 milliseconds, most shrunken SVs recycle via a “run-away” pathway, whereas others collapse into the presynaptic membrane. Ultrafast endocytosis retrieves the expanded presynaptic membrane after 100 milliseconds. These findings reveal a “kiss-shrink-run” mechanism of SV exocytosis and hyperfast recycling, reconciling conflicting models and elucidating the efficiency and fidelity of synaptic transmission.
