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The best-supported functional model is that synaptophysin regulates synaptic
vesicle protein trafficking and retrieval during endocytosis, with particularly
strong evidence for a selective role in synaptobrevin/VAMP2 retrieval.
"The best-supported functional model is that synaptophysin is a **regulator of synaptic vesicle protein trafficking and retrieval during endocytosis**, with particularly strong evidence for a **selective role in synaptobrevin/VAMP2 retrieval**"
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Knockout studies show synaptophysin is not strictly essential for
neurotransmitter release, indicating redundancy and/or context dependence.
"knockout studies show synaptophysin is **not strictly essential for neurotransmitter release**, indicating redundancy and/or context-dependent roles"
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Synaptophysin is not required for overall exocytosis or recycling pool size but
is required for kinetically efficient endocytosis and to mitigate
activity-dependent synaptic depression during sustained stimulation.
"synaptophysin is not required for overall exocytosis or recycling pool size, but is required for **kinetically efficient endocytosis** and to mitigate activity-dependent synaptic depression during sustained stimulation"
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In cultured hippocampal synapses, post-stimulus recovery after stimulation was
faster in wild-type than in synaptophysin knockout neurons (time constant 5.60 s
WT vs 12.8 s syp-/-), consistent with slowed vesicle retrieval in the absence of
synaptophysin.
"post-stimulus recovery after stimulation was faster in wild-type than synaptophysin knockout neurons (**time constant 5.60 s WT vs 12.8 s syp−/−**), consistent with slowed vesicle retrieval/reacidification dynamics in the absence of synaptophysin"
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In synaptophysin knockout neurons, sybII-pHluorin was stranded on the cell
surface and retrieval kinetics were significantly impaired; re-expression of
synaptophysin rescued retrieval, supporting a cargo-specific organizer/chaperone
role for synaptobrevin-2 during synaptic vesicle recycling.
"In synaptophysin knockout neurons, sybII-pHluorin was **stranded on the cell surface** and retrieval kinetics were significantly impaired; re-expression of synaptophysin rescued retrieval"
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Other cargo reporters (vGLUT-pHluorin and syt-pHluorin) were still retrieved but
with slower kinetics, while bulk vesicle turnover by FM dye was unchanged,
indicating synaptophysin is a cargo-specific factor rather than a universal
endocytosis factor.
"Other cargo reporters (vGLUT-pHluorin and syt-pHluorin) were still retrieved but with slower kinetics"
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Reviews describe synaptophysin as a synaptic vesicle cholesterol-binding protein,
with cholesterol content influencing the synaptophysin-synaptobrevin interaction.
"Reviews describe synaptophysin as a synaptic vesicle **cholesterol-binding** protein and report that cholesterol content influences the synaptophysin–synaptobrevin interaction"
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The synaptophysin-VAMP2 complex is considered a hallmark of synaptic vesicle
maturation; reported partners also include dynamin and AP-1 gamma-adaptin,
consistent with roles in vesicle budding/fission and sorting.
"The SYP–VAMP2 complex is considered a hallmark of synaptic vesicle maturation and depends on membrane cholesterol"
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Loss of SYP causes VAMP dispersion along axons, trapping at the plasma membrane
and impaired vesicle endocytosis; however, conventional knockout mice lack an
overt global neurotransmission phenotype.
"Loss of SYP causes **VAMP dispersion along axons**, trapping at the plasma membrane and impaired vesicle endocytosis; however, conventional knockout mice lack an overt global neurotransmission phenotype"
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Synaptophysin localizes predominantly to the synaptic vesicle membrane and is
widely used as a marker of synapse density, synaptogenesis, and neuronal
maturation.
"SYP localizes predominantly to the **synaptic vesicle membrane** in presynaptic terminals and is widely used as a marker of synapse density, synaptogenesis, and neuronal maturation"
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Open Targets curation links SYP to neurodevelopmental phenotypes including
X-linked non-syndromic intellectual disability / neurodevelopmental delay.
"Open Targets curation links **SYP** to neurodevelopmental phenotypes including **X-linked non-syndromic intellectual disability / neurodevelopmental delay**"