Synaptophysin sustains presynaptic performance by preserving vesicular synaptobrevin‐II levels

Citations Over TimeTop 10% of 2019 papers

Abstract

The two most abundant molecules on synaptic vesicles (SVs) are synaptophysin and synaptobrevin-II (sybII). SybII is essential for SV fusion, whereas synaptophysin is proposed to control the trafficking of sybII after SV fusion and its retrieval during endocytosis. Despite controlling key aspects of sybII packaging into SVs, the absence of synaptophysin results in negligible effects on neurotransmission. We hypothesised that this apparent absence of effect may be because of the abundance of sybII on SVs, with the impact of inefficient sybII retrieval only revealed during periods of repeated SV turnover. To test this hypothesis, we subjected primary cultures of synaptophysin knockout neurons to repeated trains of neuronal activity, while monitoring SV fusion events and levels of vesicular sybII. We identified a significant decrease in both the number of SV fusion events (monitored using the genetically encoded reporter vesicular glutamate transporter-pHluorin) and vesicular sybII levels (via both immunofluorescence and Western blotting) using this protocol. This revealed that synaptophysin is essential to sustain both parameters during periods of repetitive SV turnover. This was confirmed by the rescue of presynaptic performance by the expression of exogenous synaptophysin. Importantly, the expression of exogenous sybII also fully restored SV fusion events in synaptophysin knockout neurons. The ability of additional copies of sybII to fully rescue presynaptic performance in these knockout neurons suggests that the principal role of synaptophysin is to mediate the efficient retrieval of sybII to sustain neurotransmitter release.

Related Papers

• → Synaptophysin sustains presynaptic performance by preserving vesicular synaptobrevin‐II levels(2019)56 cited
• → The V Sector of the V-ATPase, Synaptobrevin, and Synaptophysin Are Associated on Synaptic Vesicles in a Triton X-100-resistant, Freeze-thawing Sensitive, Complex(1996)141 cited
• → Vesicle-associated membrane protein-2 (synaptobrevin-2) forms a complex with synaptophysin(1995)132 cited
• → Activity-dependent changes of the presynaptic synaptophysin-synaptobrevin complex in adult rat brain(2001)63 cited
• → Cd2+- and K+-evoked ACh release induce different synaptophysin and synaptobrevin immunolabelling at the frog neuromuscular junction(1995)11 cited