Diverse modes of synaptic signaling, regulation, and plasticity distinguish two classes of C. elegans glutamatergic neurons

High Calcium ◽

Vesicle Exocytosis ◽

Synaptic Dynamics

AbstractSynaptic vesicle release properties vary between neuronal cell types, but in most cases the molecular basis of this heterogeneity is unknown. Here, we compare in vivo synaptic properties of two neuronal classes in the C. elegans central nervous system, using VGLUT-pHluorin to monitor synaptic vesicle exocytosis and retrieval in intact animals. We show that the glutamatergic sensory neurons AWCON and ASH have distinct synaptic dynamics associated with tonic and phasic synaptic properties, respectively. Exocytosis in ASH and AWCON is differentially affected by SNARE-complex regulators that are present in both neurons: phasic ASH release is strongly dependent on UNC-13, whereas tonic AWCON release relies upon UNC-18 and on the protein kinase C homolog PKC-1. Exocytosis and retrieval each have two timescales in AWCON but one major timescale in ASH. Strong stimuli that elicit high calcium levels also increase exocytosis and retrieval rates in AWCON, generating distinct tonic and evoked synaptic modes. These results highlight the differential deployment of shared presynaptic proteins in neuronal cell type-specific functions.

Diverse modes of synaptic signaling, regulation, and plasticity distinguish two classes of C. elegans glutamatergic neurons

eLife ◽

10.7554/elife.31234 ◽

2017 ◽

Vol 6 ◽

Cited By ~ 6

Author(s):

Donovan Ventimiglia ◽

Cornelia I Bargmann

Keyword(s):

Synaptic Vesicle ◽

Neuronal Cell ◽

Cell Types ◽

Snare Complex ◽

C Elegans ◽

High Calcium ◽

Vesicle Exocytosis ◽

Synaptic Dynamics

Synaptic vesicle release properties vary between neuronal cell types, but in most cases the molecular basis of this heterogeneity is unknown. Here, we compare in vivo synaptic properties of two neuronal classes in the C. elegans central nervous system, using VGLUT-pHluorin to monitor synaptic vesicle exocytosis and retrieval in intact animals. We show that the glutamatergic sensory neurons AWCON and ASH have distinct synaptic dynamics associated with tonic and phasic synaptic properties, respectively. Exocytosis in ASH and AWCON is differentially affected by SNARE-complex regulators that are present in both neurons: phasic ASH release is strongly dependent on UNC-13, whereas tonic AWCON release relies upon UNC-18 and on the protein kinase C homolog PKC-1. Strong stimuli that elicit high calcium levels increase exocytosis and retrieval rates in AWCON, generating distinct tonic and evoked synaptic modes. These results highlight the differential deployment of shared presynaptic proteins in neuronal cell type-specific functions.

SNARE Complex Oligomerization by Synaphin/Complexin Is Essential for Synaptic Vesicle Exocytosis

Cell ◽

10.1016/s0092-8674(01)00229-x ◽

2001 ◽

Vol 104 (3) ◽

pp. 421-432 ◽

Cited By ~ 111

Author(s):

Hiroshi Tokumaru ◽

Keiko Umayahara ◽

Lorenzo L Pellegrini ◽

Toru Ishizuka ◽

Hideo Saisu ◽

...

Keyword(s):

Synaptic Vesicle ◽

Snare Complex ◽

Sphingosine Facilitates SNARE Complex Assembly and Activates Synaptic Vesicle Exocytosis

Neuron ◽

10.1016/j.neuron.2009.04.024 ◽

2009 ◽

Vol 62 (5) ◽

pp. 683-694 ◽

Cited By ~ 100

Author(s):

Frédéric Darios ◽

Catherine Wasser ◽

Anastasia Shakirzyanova ◽

Artur Giniatullin ◽

Kerry Goodman ◽

...

Keyword(s):

Synaptic Vesicle ◽

Snare Complex ◽

Complex Assembly ◽

rbSec1A and B colocalize with syntaxin 1 and SNAP-25 throughout the axon, but are not in a stable complex with syntaxin.

The Journal of Cell Biology ◽

10.1083/jcb.129.1.105 ◽

1995 ◽

Vol 129 (1) ◽

pp. 105-120 ◽

Cited By ~ 186

Author(s):

E P Garcia ◽

P S McPherson ◽

T J Chilcote ◽

K Takei ◽

P De Camilli

Keyword(s):

Snare Complex ◽

Stable Complex ◽

C Elegans ◽

Neuronal Protein ◽

Neurotransmitter Secretion ◽

Biochemical Studies ◽

Vesicle Exocytosis ◽

Alternatively Spliced ◽

Affinity Interaction

rbSec1 is a mammalian neuronal protein homologous to the yeast SEC1 gene product which is required for exocytosis. Mutations in Sec1 homologues in the nervous systems of C. elegans and D. melanogaster lead to defective neurotransmitter secretion. Biochemical studies have shown that recombinant rbSec1 binds syntaxin 1 but not SNAP-25 or synaptobrevin/VAMP, the two proteins which together with syntaxin 1 form the synaptic SNARE complex. In this study we have examined the subcellular localization of rbSec1 and the degree of interaction between rbSec1 and syntaxin 1 in situ. rbSec1, which we show here to be represented by two alternatively spliced isoforms, rbSec1A and B, has a widespread distribution in the axon and is not restricted to the nerve terminal. This distribution parallels the localization of syntaxin 1 and SNAP-25 along the entire axonal plasmalemma. rbSec1 is found in a soluble and a membrane-associated form. Although a pool of rbSec1 is present on the plasmalemma, the majority of membrane-bound rbSec1 is not associated with syntaxin 1. We also show that rbSec1 is not part of the synaptic SNARE complex or of the syntaxin 1/SNAP-25 complex we show to be present in non-synaptic regions of the axon. Thus, in spite of biochemical studies demonstrating the high affinity interaction of rbSec1 and syntaxin 1, our results indicate that rbSec1 and syntaxin 1 are not stably associated. They also suggest that the function of rbSec1, syntaxin 1, and SNAP-25 is not restricted to synaptic vesicle exocytosis at the synapse.

Complexin-1 regulated transition in the assembly of single neuronal SNARE complex

10.1101/2021.06.07.447331 ◽

2021 ◽

Author(s):

Hao Tongrui ◽

Feng Nan ◽

Gong Fan ◽

Liu Jiaquan ◽

Lu Ma ◽

...

Keyword(s):

Synaptic Vesicle ◽

Molecular Mechanism ◽

Optical Tweezers ◽

Neurotransmitter Release ◽

Snare Complex ◽

Snare Proteins ◽

Sensitive Factor ◽

Vesicle Exocytosis ◽

Vesicle Pool

Neurotransmitter release is mediated by the synaptic vesicle exocytosis. Important proteins in this process have been identified including the molecular machine Synaptic-soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins, and other regulators. Complexin (Cpx) is one of the vital regulators in this process. The functions of Cpx are proposed to maintain a proper primed vesicle pool by preventing its premature depletion, which facilitates the vesicle fusion in the presence of Ca2+. However, the molecular mechanism remains unclear. Using dual-trap optical tweezers, we detected the interaction of complexin-1 (CpxI) with SNARE. We found that the CpxI stabilizes partially folded SNARE complexes by competing with C-terminal of Vamp protein and interacting with the C-terminal of t-SNARE complex.

Role of C2 domain proteins during synaptic vesicle exocytosis

Biochemical Society Transactions ◽

10.1042/bst0380213 ◽

2010 ◽

Vol 38 (1) ◽

pp. 213-216 ◽

Cited By ~ 21

Author(s):

Sascha Martens

Keyword(s):

Membrane Fusion ◽

Synaptic Vesicle ◽

Synaptic Vesicles ◽

Calcium Concentration ◽

Membrane Curvature ◽

Snare Complex ◽

C2 Domain ◽

C2 Domains ◽

Neurotransmitter release is mediated by the fusion of synaptic vesicles with the presynaptic plasma membrane. Fusion is triggered by a rise in the intracellular calcium concentration and is dependent on the neuronal SNARE (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor) complex. A plethora of molecules such as members of the MUNC13, MUNC18, complexin and synaptotagmin families act along with the SNARE complex to enable calcium-regulated synaptic vesicle exocytosis. The synaptotagmins are localized to synaptic vesicles by an N-terminal transmembrane domain and contain two cytoplasmic C2 domains. Members of the synaptotagmin family are thought to translate the rise in intracellular calcium concentration into synaptic vesicle fusion. The C2 domains of synaptotagmin-1 bind membranes in a calcium-dependent manner and in response induce a high degree of membrane curvature, which is required for its ability to trigger membrane fusion in vitro and in vivo. Furthermore, members of the soluble DOC2 (double-C2 domain) protein family have similar properties. Taken together, these results suggest that C2 domain proteins such as the synaptotagmins and DOC2s promote membrane fusion by the induction of membrane curvature in the vicinity of the SNARE complex. Given the widespread expression of C2 domain proteins in secretory cells, it is proposed that promotion of SNARE-dependent membrane fusion by the induction of membrane curvature is a widespread phenomenon.

Epileptic Phenotypes Associated With SNAREs and Related Synaptic Vesicle Exocytosis Machinery

Frontiers in Neurology ◽

10.3389/fneur.2021.806506 ◽

2022 ◽

Vol 12 ◽

Author(s):

Elisa Cali ◽

Clarissa Rocca ◽

Vincenzo Salpietro ◽

Henry Houlden

Keyword(s):

Synaptic Vesicle ◽

Neurodevelopmental Disorder ◽

Febrile Seizures ◽

Autism Spectrum ◽

Snare Complex ◽

Protein Receptor ◽

Genes Encoding ◽

Associated Proteins ◽

SNAREs (soluble N-ethylmaleimide sensitive factor attachment protein receptor) are an heterogeneous family of proteins that, together with their key regulators, are implicated in synaptic vesicle exocytosis and synaptic transmission. SNAREs represent the core component of this protein complex. Although the specific mechanisms of the SNARE machinery is still not completely uncovered, studies in recent years have provided a clearer understanding of the interactions regulating the essential fusion machinery for neurotransmitter release. Mutations in genes encoding SNARE proteins or SNARE complex associated proteins have been associated with a variable spectrum of neurological conditions that have been recently defined as “SNAREopathies.” These include neurodevelopmental disorder, autism spectrum disorder (ASD), movement disorders, seizures and epileptiform abnormalities. The SNARE phenotypic spectrum associated with seizures ranges from simple febrile seizures and infantile spasms, to severe early-onset epileptic encephalopathies. Our study aims to review and delineate the epileptic phenotypes associated with dysregulation of synaptic vesicle exocytosis and transmission, focusing on the main proteins of the SNARE core complex (STX1B, VAMP2, SNAP25), tethering complex (STXBP1), and related downstream regulators.

Synaptotagmin VII Regulates Ca2+-Dependent Exocytosis of Lysosomes in Fibroblasts

The Journal of Cell Biology ◽

10.1083/jcb.148.6.1141 ◽

2000 ◽

Vol 148 (6) ◽

pp. 1141-1150 ◽

Cited By ~ 206

Author(s):

Iñigo Martinez ◽

Sabyasachi Chakrabarti ◽

Turid Hellevik ◽

Jennifer Morehead ◽

Kimberly Fowler ◽

...

Keyword(s):

Synaptic Vesicle ◽

Rat Kidney ◽

Transmembrane Proteins ◽

Cell Types ◽

C2 Domains ◽

Vesicle Exocytosis ◽

Normal Rat ◽

Recombinant Fragments ◽

C2a Domain

Synaptotagmins (Syts) are transmembrane proteins with two Ca2+-binding C2 domains in their cytosolic region. Syt I, the most widely studied isoform, has been proposed to function as a Ca2+ sensor in synaptic vesicle exocytosis. Several of the twelve known Syts are expressed primarily in brain, while a few are ubiquitous (Sudhof, T.C., and J. Rizo. 1996. Neuron. 17: 379–388; Butz, S., R. Fernandez-Chacon, F. Schmitz, R. Jahn, and T.C. Sudhof. 1999. J. Biol. Chem. 274:18290–18296). The ubiquitously expressed Syt VII binds syntaxin at free Ca2+ concentrations ([Ca2+]) below 10 μM, whereas other isoforms require 200–500 μM [Ca2+] or show no Ca2+-dependent syntaxin binding (Li, C., B. Ullrich, Z. Zhang, R.G.W. Anderson, N. Brose, and T.C. Sudhof. 1995. Nature. 375:594–599). We investigated the involvement of Syt VII in the exocytosis of lysosomes, which is triggered in several cell types at 1–5 μM [Ca2+] (Rodríguez, A., P. Webster, J. Ortego, and N.W. Andrews. 1997. J. Cell Biol. 137:93–104). Here, we show that Syt VII is localized on dense lysosomes in normal rat kidney (NRK) fibroblasts, and that GFP-tagged Syt VII is targeted to lysosomes after transfection. Recombinant fragments containing the C2A domain of Syt VII inhibit Ca2+-triggered secretion of β-hexosaminidase and surface translocation of Lgp120, whereas the C2A domain of the neuronal- specific isoform, Syt I, has no effect. Antibodies against the Syt VII C2A domain are also inhibitory in both assays, indicating that Syt VII plays a key role in the regulation of Ca2+-dependent lysosome exocytosis.