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Synaptotagmin 1 directs repetitive release by coupling vesicle exocytosis to the Rab3 cycle.

Cheng Y, Wang J, Wang Y, Ding M - Elife (2015)

Bottom Line: How this harmonization is achieved is not known.In the absence of Ca(2+), synaptotagmin 1 binds to Rab3 GTPase activating protein (GAP) and inhibits the GTP hydrolysis of Rab3 protein.In the presence of Ca(2+), synaptotagmin 1 releases Rab3 GAP and promotes membrane disassociation of Rab3.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.

ABSTRACT
In response to Ca(2+) influx, a synapse needs to release neurotransmitters quickly while immediately preparing for repeat firing. How this harmonization is achieved is not known. In this study, we found that the Ca(2+) sensor synaptotagmin 1 orchestrates the membrane association/disassociation cycle of Rab3, which functions in activity-dependent recruitment of synaptic vesicles. In the absence of Ca(2+), synaptotagmin 1 binds to Rab3 GTPase activating protein (GAP) and inhibits the GTP hydrolysis of Rab3 protein. Rab3 GAP resides on synaptic vesicles, and synaptotagmin 1 is essential for the synaptic localization of Rab3 GAP. In the presence of Ca(2+), synaptotagmin 1 releases Rab3 GAP and promotes membrane disassociation of Rab3. Without synaptotagmin 1, the tight coupling between vesicle exocytosis and Rab3 membrane disassociation is disrupted. We uncovered the long-sought molecular apparatus linking vesicle exocytosis to Rab3 cycling and we also revealed the important function of synaptotagmin 1 in repetitive synaptic vesicle release.

No MeSH data available.


Related in: MedlinePlus

Localization of RBG-1 on synaptic vesicles requires SNT-1.(A and B) mCherry::RBG-1 has a punctate distribution in wild type (A) but accumulates in cell bodies (yellow arrows) in unc-104 mutants (B). (C) mCherry::RBG-1 (red) is co-localized with SNB-1::GFP puncta (green). (D) In snt-1 mutants, mCherry::RBG-1 loses its punctate localization and becomes diffuse in axons, while SNB-1::GFP retains its punctate pattern. (E) mCherry::RBG-1 retains its punctate distribution and is co-localized with SNB-1::GFP in rab-3 mutants. Scale bars, 5 µm.DOI:http://dx.doi.org/10.7554/eLife.05118.009
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fig5: Localization of RBG-1 on synaptic vesicles requires SNT-1.(A and B) mCherry::RBG-1 has a punctate distribution in wild type (A) but accumulates in cell bodies (yellow arrows) in unc-104 mutants (B). (C) mCherry::RBG-1 (red) is co-localized with SNB-1::GFP puncta (green). (D) In snt-1 mutants, mCherry::RBG-1 loses its punctate localization and becomes diffuse in axons, while SNB-1::GFP retains its punctate pattern. (E) mCherry::RBG-1 retains its punctate distribution and is co-localized with SNB-1::GFP in rab-3 mutants. Scale bars, 5 µm.DOI:http://dx.doi.org/10.7554/eLife.05118.009

Mentions: As the catalytic subunit of Rab3 GAP, RBG-1 can interact with RAB-3 (Figure 4—figure supplement 1F). To understand how SNT-1 inhibits RAB-3 GTP hydrolysis, we examined the sub-cellular localization of RBG-1. We created a functional mCherry::RBG-1 construct and injected it into rbg-1 mutant animals. In wild-type animals, the mCherry::RBG-1 signal displayed a punctate expression pattern along the ventral and dorsal cords. Double staining further showed that the mCherry::RBG-1 puncta co-localized with the SV marker SNB-1::GFP (Figure 5C). Next, we tested whether the punctate localization of RBG-1 relies on the UNC-104-based intracellular transport system like other SV-associated proteins. We found that in unc-104 mutants, the mCherry::RBG-1 puncta no longer appeared in the putative synaptic region; instead they were retained in the cell bodies (Figure 5B). Together, the data above suggest that RBG-1 is localized on SVs.10.7554/eLife.05118.009Figure 5.Localization of RBG-1 on synaptic vesicles requires SNT-1.


Synaptotagmin 1 directs repetitive release by coupling vesicle exocytosis to the Rab3 cycle.

Cheng Y, Wang J, Wang Y, Ding M - Elife (2015)

Localization of RBG-1 on synaptic vesicles requires SNT-1.(A and B) mCherry::RBG-1 has a punctate distribution in wild type (A) but accumulates in cell bodies (yellow arrows) in unc-104 mutants (B). (C) mCherry::RBG-1 (red) is co-localized with SNB-1::GFP puncta (green). (D) In snt-1 mutants, mCherry::RBG-1 loses its punctate localization and becomes diffuse in axons, while SNB-1::GFP retains its punctate pattern. (E) mCherry::RBG-1 retains its punctate distribution and is co-localized with SNB-1::GFP in rab-3 mutants. Scale bars, 5 µm.DOI:http://dx.doi.org/10.7554/eLife.05118.009
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4374511&req=5

fig5: Localization of RBG-1 on synaptic vesicles requires SNT-1.(A and B) mCherry::RBG-1 has a punctate distribution in wild type (A) but accumulates in cell bodies (yellow arrows) in unc-104 mutants (B). (C) mCherry::RBG-1 (red) is co-localized with SNB-1::GFP puncta (green). (D) In snt-1 mutants, mCherry::RBG-1 loses its punctate localization and becomes diffuse in axons, while SNB-1::GFP retains its punctate pattern. (E) mCherry::RBG-1 retains its punctate distribution and is co-localized with SNB-1::GFP in rab-3 mutants. Scale bars, 5 µm.DOI:http://dx.doi.org/10.7554/eLife.05118.009
Mentions: As the catalytic subunit of Rab3 GAP, RBG-1 can interact with RAB-3 (Figure 4—figure supplement 1F). To understand how SNT-1 inhibits RAB-3 GTP hydrolysis, we examined the sub-cellular localization of RBG-1. We created a functional mCherry::RBG-1 construct and injected it into rbg-1 mutant animals. In wild-type animals, the mCherry::RBG-1 signal displayed a punctate expression pattern along the ventral and dorsal cords. Double staining further showed that the mCherry::RBG-1 puncta co-localized with the SV marker SNB-1::GFP (Figure 5C). Next, we tested whether the punctate localization of RBG-1 relies on the UNC-104-based intracellular transport system like other SV-associated proteins. We found that in unc-104 mutants, the mCherry::RBG-1 puncta no longer appeared in the putative synaptic region; instead they were retained in the cell bodies (Figure 5B). Together, the data above suggest that RBG-1 is localized on SVs.10.7554/eLife.05118.009Figure 5.Localization of RBG-1 on synaptic vesicles requires SNT-1.

Bottom Line: How this harmonization is achieved is not known.In the absence of Ca(2+), synaptotagmin 1 binds to Rab3 GTPase activating protein (GAP) and inhibits the GTP hydrolysis of Rab3 protein.In the presence of Ca(2+), synaptotagmin 1 releases Rab3 GAP and promotes membrane disassociation of Rab3.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.

ABSTRACT
In response to Ca(2+) influx, a synapse needs to release neurotransmitters quickly while immediately preparing for repeat firing. How this harmonization is achieved is not known. In this study, we found that the Ca(2+) sensor synaptotagmin 1 orchestrates the membrane association/disassociation cycle of Rab3, which functions in activity-dependent recruitment of synaptic vesicles. In the absence of Ca(2+), synaptotagmin 1 binds to Rab3 GTPase activating protein (GAP) and inhibits the GTP hydrolysis of Rab3 protein. Rab3 GAP resides on synaptic vesicles, and synaptotagmin 1 is essential for the synaptic localization of Rab3 GAP. In the presence of Ca(2+), synaptotagmin 1 releases Rab3 GAP and promotes membrane disassociation of Rab3. Without synaptotagmin 1, the tight coupling between vesicle exocytosis and Rab3 membrane disassociation is disrupted. We uncovered the long-sought molecular apparatus linking vesicle exocytosis to Rab3 cycling and we also revealed the important function of synaptotagmin 1 in repetitive synaptic vesicle release.

No MeSH data available.


Related in: MedlinePlus