Dynamic Partitioning of Synaptic Vesicle Pools by the SNARE-Binding Protein Tomosyn

Cazares, Victor A.; Njus, Meredith M.; Manly, Amanda; Saldate, Johnny J.; Subramani, Arasakumar; Ben-Simon, Yoav; Sutton, Michael A.; Ashery, Uri; Stuenkel, Edward L.

doi:10.1523/jneurosci.1297-16.2016

Cited by 32 publications

(33 citation statements)

References 109 publications

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“…elegans DCVs [21] as well as the direct interaction of rat tomosyn with the vesicular proteins Syt-1 [41] and Rab3 [29]. To differentiate between immobile synapses and mobile organelles, we performed live imaging of EYFP-tomosyn-m1 puncta and observed that many tomosyn-1 puncta moved along the neurite (typical example in Fig 3A–3C).…”

Section: Resultsmentioning

confidence: 99%

Tomosyn associates with secretory vesicles in neurons through its N- and C-terminal domains

et al. 2017

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The secretory pathway in neurons requires efficient targeting of cargos and regulatory proteins to their release sites. Tomosyn contributes to synapse function by regulating synaptic vesicle (SV) and dense-core vesicle (DCV) secretion. While there is large support for the presynaptic accumulation of tomosyn in fixed preparations, alternative subcellular locations have been suggested. Here we studied the dynamic distribution of tomosyn-1 (Stxbp5) and tomosyn-2 (Stxbp5l) in mouse hippocampal neurons and observed a mixed diffuse and punctate localization pattern of both isoforms. Tomosyn-1 accumulations were present in axons and dendrites. As expected, tomosyn-1 was expressed in about 75% of the presynaptic terminals. Interestingly, also bidirectional moving tomosyn-1 and -2 puncta were observed. Despite the lack of a membrane anchor these puncta co-migrated with synapsin and neuropeptide Y, markers for respectively SVs and DCVs. Genetic blockade of two known tomosyn interactions with synaptotagmin-1 and its cognate SNAREs did not abolish its vesicular co-migration, suggesting an interplay of protein interactions mediated by the WD40 and SNARE domains. We hypothesize that the vesicle-binding properties of tomosyns may control the delivery, pan-synaptic sharing and secretion of neuronal signaling molecules, exceeding its canonical role at the plasma membrane.

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Section: Resultsmentioning

confidence: 99%

Tomosyn associates with secretory vesicles in neurons through its N- and C-terminal domains

et al. 2017

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“…In addition, comparison of WT and Rab27 KO lysates demonstrated no significant differences in synaptic protein expression levels, except for the V‐SNARE domain containing protein Tomosyn‐1. Tomosyn‐1, which is reported to act as a negative regulator on presynaptic release (Hatsuzawa, Lang, Fasshauer, Bruns, & Jahn, 2003; Yizhar et al., 2004), be subject to CDK5 phosphorylation and interact with Rab GTPases (Cazares et al., 2016), was reduced by approximately 62% (WT, 0.6259 ± 0.07; KO = 0.2389 ± 0.18).…”

Section: Resultsmentioning

confidence: 99%

“…One known effector of Rab3 is RIM1 which has been reported to form a trimeric complex containing Rab3 and Munc13 (Castillo et al., 2002; Schoch et al., 2002), a protein essential for exocytotic activity in mammalian glutaminergic neurons. The KO of Rab27B exhibited negligible effect on expression of the array of synaptic proteins that were assessed, with the exception of tomosyn‐1, a v‐SNARE containing protein that serves as a negative regulator of exocytosis (Hatsuzawa et al., 2003; Yizhar et al., 2004) and regulator of SV distribution between functionally defined resting and recycling SV pools in hippocampal neurons (Cazares et al., 2016). Tomosyn‐1 also serves as an effector of Rab3, and perhaps Rab27, GTPases in regulating SV pool dynamics (Cazares et al., 2016).…”

Section: Discussionmentioning

confidence: 99%

Actions of Rab27B‐GTPase on mammalian central excitatory synaptic transmission

Njus

Murphy

et al. 2020

Physiol Rep

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Members of the Rab3 gene family are considered central to membrane trafficking of synaptic vesicles at mammalian central excitatory synapses. Recent evidence, however, indicates that the Rab27B-GTPase, which is highly homologous to the Rab3 family, is also enriched on SV membranes and co-localize with Rab3A and Synaptotagmin at presynaptic terminals. While functional roles of Rab3A have been well-established, little functional information exists on the role of Rab27B in synaptic transmission.Here we report on functional effects of Rab27B at SC-CA1 and DG-MF hippocampal synapses. The data establish distinct functional actions of Rab27B and demonstrate functions of Rab27B that differ between SC-CA1 and DG-MF synapses. Rab27B knockout reduced frequency facilitation compared to wild-type (WT) controls at the DG/MF-CA3 synaptic region, while increasing facilitation at the SC-CA1 synaptic region. Remarkably, Rab27B KO resulted in a complete elimination of LTP at the MF-CA3 synapse with no effect at the SC-CA1 synapse. These actions are similar to those previously reported for Rab3A KO. Specificity of action on LTP to Rab27B was confirmed as LTP was rescued in response to lentiviral infection and expression of human Rab27B, but not to GFP, in the DG in the Rab27B KO mice. Notably, the effect of Rab27B KO on MF-CA3 LTP occurred in spite of continued expression of Rab3A in the Rab27B KO. Overall, the results provide a novel perspective in suggesting that Rab27B and Rab3A act synergistically, perhaps via sequential effector recruitment or signaling for presynaptic LTP expression in this hippocampal synaptic region. K E Y W O R D Sneurotransmission, RabGTPase, synapse

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“…Sro7p has also been reported to disrupt cell polarity via suppression of a small GTPase Rho3p (48). Similar to the yeast homolog, tomosyn has recently been shown to interact with the GTP-bound state of Rab3A to partition synaptic vesicle pools (49).…”

Section: Discussionmentioning

confidence: 99%

STXBP5/tomosyn regulates the small RhoA GTPase to control the dendritic stability of neurons and the surface expression of AMPA receptors

Shen

Kilander

Bridi

et al. 2019

Preprint

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Tomosyn, a protein encoded by syntaxin-1-binding protein 5 (STXBP5) gene, has a wellestablished presynaptic role in the inhibition of neurotransmitter release and the reduction of synaptic transmission by its conical interaction with the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) machinery. The postsynaptic role of tomosyn in dendritic arborization, spine stability, and trafficking of ionotropic glutamate receptors remains to be elucidated. We used short hairpin RNA (shRNA) to knock down tomosyn in mouse primary neurons to evaluate the postsynaptic cellular function and molecular signaling regulated by tomosyn. Knockdown of tomosyn led to an increase of RhoA GTPase activity accompanied by compromised dendritic arborization, loss of dendritic spines, decreased surface expression of AMPA receptors, and reduced miniature excitatory postsynaptic current (mEPSC) frequency.Inhibiting RhoA signaling was sufficient to rescue the abnormal dendritic morphology and the surface expression of AMPA receptors. The function of tomosyn regulating RhoA is mediated through the N-terminal WD40 motif, where two variants each carrying a single nucleotide mutation in this region, were found in individuals with autism spectrum disorder (ASD). We demonstrated that these variants displayed loss-of-function phenotypes. Unlike the wild-type tomosyn, these two variants failed to restore the reduced dendritic complexity, spine density, as well as decreased surface expression of AMPA receptors in tomosyn knockdown neurons. This study uncovers a critical role of tomosyn, independent of its interaction with the SNARE machinery, in maintaining neuronal function by inhibiting RhoA activity. Further analysis of tomosyn variants also provides a potential mechanism for explaining cellular pathology in ASD. Significance StatementThis study unveils a vital role of tomosyn in the maintenance of neuronal morphology, basal synaptic transmission, and AMPA receptor surface expression that is distinct from its presynaptic role. Tomosyn affects dendritic stability and glutamate receptor trafficking via the regulation of the Rho signaling pathway and this interaction is likely independent of the interaction with the dendritic SNARE complex, such as syntaxin-4. The WD40 domain of tomosyn is necessary to conduct the Rho regulation and two autism-associated variants localized at the WD40 domain perturb this function. The current study reveals a novel molecular link between dendritic stability and synaptic function, which could advance a greater understanding of the cellular pathologies involved in neurodevelopmental disorders, such as ASD.

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Dynamic Partitioning of Synaptic Vesicle Pools by the SNARE-Binding Protein Tomosyn

Cited by 32 publications

References 109 publications

Tomosyn associates with secretory vesicles in neurons through its N- and C-terminal domains

Tomosyn associates with secretory vesicles in neurons through its N- and C-terminal domains

Actions of Rab27B‐GTPase on mammalian central excitatory synaptic transmission

STXBP5/tomosyn regulates the small RhoA GTPase to control the dendritic stability of neurons and the surface expression of AMPA receptors

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