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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

snt-1 is require for RAB-3 synaptic vesicle localization.(A) Multiple snt-1 alleles show the diffuse GFP::RAB-3 phenotype. White arrows indicate the cell bodies. (B) GFP::RAB-3 expressed pan-neuronally under the control of the Prab-3 promoter displays punctate distribution. (C) GFP::RAB-3 is diffuse in all Prab-3-expressing cells. Red boxed areas are enlarged in panels underneath the image taken from a whole animal (B′, B″, B‴, C′, C″ and C‴). (D) The diffuse GFP::RAB-3 phenotype in snt-1 mutants is rescued by expressing wild-type snt-1 gene pan-neuronally using the Psnt-1 promoter or in DD, VD, and AS neurons using the Phmr-1 promoter. Scale bar, 5 µm.DOI:http://dx.doi.org/10.7554/eLife.05118.004
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fig1s1: snt-1 is require for RAB-3 synaptic vesicle localization.(A) Multiple snt-1 alleles show the diffuse GFP::RAB-3 phenotype. White arrows indicate the cell bodies. (B) GFP::RAB-3 expressed pan-neuronally under the control of the Prab-3 promoter displays punctate distribution. (C) GFP::RAB-3 is diffuse in all Prab-3-expressing cells. Red boxed areas are enlarged in panels underneath the image taken from a whole animal (B′, B″, B‴, C′, C″ and C‴). (D) The diffuse GFP::RAB-3 phenotype in snt-1 mutants is rescued by expressing wild-type snt-1 gene pan-neuronally using the Psnt-1 promoter or in DD, VD, and AS neurons using the Phmr-1 promoter. Scale bar, 5 µm.DOI:http://dx.doi.org/10.7554/eLife.05118.004

Mentions: snt-1 encodes the synaptotagmin 1 homologue in C. elegans (Nonet et al., 1993). Neuronal synaptotagmins function as Ca2+ sensors for synaptic exocytosis, but their role in Rab3 localization has not been revealed. To determine whether loss of snt-1 function indeed leads to the diffuse RAB-3 phenotype, we examined other snt-1 alleles. We found that the n2665, md220, md125, and md172 alleles of snt-1 all display a diffuse GFP::RAB-3 phenotype similar to md290 (Figure 1—figure supplement 1A). Both the snt-1 and rab-3 genes are broadly expressed in the nervous system (Nonet et al., 1993, 1997). To determine whether snt-1 influences RAB-3 in all neurons, we examined RAB-3 localization with a pan-neuronal marker Prab-3::GFP::RAB-3. In wild-type animals, GFP::RAB-3 displays a punctate pattern, while in snt-1 mutants, GFP::RAB-3 is completely diffuse in neuronal processes, including the nerve ring, ventral cord, and dorsal cord regions (Figure 1—figure supplement 1B,C). These data indicate that the effect of snt-1 on RAB-3 localization is widely preserved in the nervous system. In addition, the diffuse GFP::RAB-3 phenotype was fully rescued when wild-type snt-1 was introduced into mutant animals (Figure 1—figure supplement 1D), suggesting that SNT-1 is indeed essential for localization of RAB-3 on SVs.


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

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

snt-1 is require for RAB-3 synaptic vesicle localization.(A) Multiple snt-1 alleles show the diffuse GFP::RAB-3 phenotype. White arrows indicate the cell bodies. (B) GFP::RAB-3 expressed pan-neuronally under the control of the Prab-3 promoter displays punctate distribution. (C) GFP::RAB-3 is diffuse in all Prab-3-expressing cells. Red boxed areas are enlarged in panels underneath the image taken from a whole animal (B′, B″, B‴, C′, C″ and C‴). (D) The diffuse GFP::RAB-3 phenotype in snt-1 mutants is rescued by expressing wild-type snt-1 gene pan-neuronally using the Psnt-1 promoter or in DD, VD, and AS neurons using the Phmr-1 promoter. Scale bar, 5 µm.DOI:http://dx.doi.org/10.7554/eLife.05118.004
© Copyright Policy
Related In: Results  -  Collection

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

fig1s1: snt-1 is require for RAB-3 synaptic vesicle localization.(A) Multiple snt-1 alleles show the diffuse GFP::RAB-3 phenotype. White arrows indicate the cell bodies. (B) GFP::RAB-3 expressed pan-neuronally under the control of the Prab-3 promoter displays punctate distribution. (C) GFP::RAB-3 is diffuse in all Prab-3-expressing cells. Red boxed areas are enlarged in panels underneath the image taken from a whole animal (B′, B″, B‴, C′, C″ and C‴). (D) The diffuse GFP::RAB-3 phenotype in snt-1 mutants is rescued by expressing wild-type snt-1 gene pan-neuronally using the Psnt-1 promoter or in DD, VD, and AS neurons using the Phmr-1 promoter. Scale bar, 5 µm.DOI:http://dx.doi.org/10.7554/eLife.05118.004
Mentions: snt-1 encodes the synaptotagmin 1 homologue in C. elegans (Nonet et al., 1993). Neuronal synaptotagmins function as Ca2+ sensors for synaptic exocytosis, but their role in Rab3 localization has not been revealed. To determine whether loss of snt-1 function indeed leads to the diffuse RAB-3 phenotype, we examined other snt-1 alleles. We found that the n2665, md220, md125, and md172 alleles of snt-1 all display a diffuse GFP::RAB-3 phenotype similar to md290 (Figure 1—figure supplement 1A). Both the snt-1 and rab-3 genes are broadly expressed in the nervous system (Nonet et al., 1993, 1997). To determine whether snt-1 influences RAB-3 in all neurons, we examined RAB-3 localization with a pan-neuronal marker Prab-3::GFP::RAB-3. In wild-type animals, GFP::RAB-3 displays a punctate pattern, while in snt-1 mutants, GFP::RAB-3 is completely diffuse in neuronal processes, including the nerve ring, ventral cord, and dorsal cord regions (Figure 1—figure supplement 1B,C). These data indicate that the effect of snt-1 on RAB-3 localization is widely preserved in the nervous system. In addition, the diffuse GFP::RAB-3 phenotype was fully rescued when wild-type snt-1 was introduced into mutant animals (Figure 1—figure supplement 1D), suggesting that SNT-1 is indeed essential for localization of RAB-3 on SVs.

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