scholarly journals Superfluous Role of Mammalian Septins 3 and 5 in Neuronal Development and Synaptic Transmission

2008 ◽  
Vol 28 (23) ◽  
pp. 7012-7029 ◽  
Author(s):  
Christopher W. Tsang ◽  
Michael Fedchyshyn ◽  
John Harrison ◽  
Hong Xie ◽  
Jing Xue ◽  
...  
Keyword(s):  
Synaptic Transmission ◽  
Synaptic Vesicle ◽  
Hippocampal Neurons ◽  
Neuronal Development ◽  
Synapse Formation ◽  
Vesicle Traffic ◽  
Axon Development ◽  
Central Synapses ◽  
Synaptic Vesicle Fusion

ABSTRACT The septin family of GTPases, first identified for their roles in cell division, are also expressed in postmitotic tissues. SEPT3 (G-septin) and SEPT5 (CDCrel-1) are highly expressed in neurons, enriched in presynaptic terminals, and associated with synaptic vesicles. These characteristics suggest that SEPT3 or SEPT5 might be important for synapse formation, maturation, or synaptic vesicle traffic. Since Sept5 −/− mice do not show any overt neurological phenotypes, we generated Sept3 −/− and Sept3 −/− Sept5 −/− mice and found that SEPT3 and SEPT5 are not essential for development, fertility, or viability. Changes in the expression of septins were noted in the absence of SEPT3, SEPT5, and both septins. SEPT5 association with other septins in brain tissue was unaffected by the removal of SEPT3. No abnormalities were observed in the gross morphology and synapses of the hippocampus. Similarly, axon development and synapse formation were unaffected in vitro. In cultured hippocampal neurons, the size of the recycling synaptic vesicle pool was unaltered in the absence of SEPT3. Furthermore, synaptic transmission at two different central synapses was not significantly affected in Sept3 −/− Sept5 −/− mice. These results indicate that SEPT3 and SEPT5 are dispensable for neuronal development as well as for synaptic vesicle fusion and recycling.

scholarly journals Persistence of quantal synaptic vesicle recycling following dynamin depletion

2020 ◽  
Author(s):  
Olusoji A.T. Afuwape ◽  
Natali L. Chanaday ◽  
Merve Kasap ◽  
Lisa M. Monteggia ◽  
Ege T. Kavalali
Keyword(s):  
Synaptic Vesicle ◽  
Hippocampal Neurons ◽  
Endocytic Pathway ◽  
Fluorescent Reporter ◽  
Vesicle Recycling ◽  
Presynaptic Boutons ◽  
Critical Curvature ◽  
Central Synapses ◽  
Synaptic Vesicle Fusion ◽  
Modest Effect

AbstractDynamins are GTPases required for pinching vesicles off the plasma membrane once a critical curvature is reached during endocytosis. Here, we probed dynamin function in central synapses by depleting all three dynamin isoforms in postnatal hippocampal neurons. We found a decrease in the propensity of evoked neurotransmission as well as a reduction in synaptic vesicle numbers. Using the fluorescent reporter vGluT1-pHluorin, we observed that compensatory endocytosis after 20 Hz stimulation was arrested in ~40% of presynaptic boutons, while remaining synapses showed only a modest effect suggesting the existence of a dynamin-independent endocytic pathway in central synapses. Surprisingly, we found that the retrieval of single synaptic vesicles, after either evoked or spontaneous fusion, was largely impervious to disruption of dynamins. Overall, our results suggest that classical dynamin-dependent endocytosis is not essential for retrieval of synaptic vesicle proteins after quantal single synaptic vesicle fusion.

Spastin Interacts with CRMP2 to Regulate Neurite Outgrowth by Controlling Microtubule Dynamics through Phosphorylation Modifications

2020 ◽  
Vol 19 ◽  
Author(s):  
Sumei Li ◽  
Jifeng Zhang ◽  
Jiaqi Zhang ◽  
Jiong Li ◽  
Longfei Cheng ◽  
...  
Keyword(s):  
Neurite Outgrowth ◽  
Hippocampal Neurons ◽  
Neuronal Development ◽  
Phosphorylation Site ◽  
Microtubule Dynamics ◽  
Microtubule Assembly ◽  
C Terminus ◽  
Mediator Protein ◽  
Branch Formation

Aims: Our work aims to revealing the underlying microtubule mechanism of neurites outgrowth during neuronal development, and also proposes a feasible intervention pathway for reconstructing neural network connections after nerve injury. Background: Microtubule polymerization and severing are the basis for the neurite outgrowth and branch formation. Collapsin response mediator protein 2 (CRMP2) regulates axonal growth and branching as a binding partner of the tubulin heterodimer to promote microtubule assembly. And spastin participates in the growth and regeneration of neurites by severing microtubules into small segments. However, how CRMP2 and spastin cooperate to regulate neurite outgrowth by controlling the microtubule dynamics needs to be elucidated. Objective: To explore whether neurite outgrowth was mediated by coordination of CRMP2 and spastin. Method: Hippocampal neurons were cultured in vitro in 24-well culture plates for 4 days before being used to perform the transfection. Calcium phosphate was used to transfect the CRMP2 and spastin constructs and their control into the neurons. An interaction between CRMP2 and spastin was examined by using pull down, CoIP and immunofluorescence colocalization assays. And immunostaining was also performed to determine the morphology of neurites. Result: We first demonstrated that CRMP2 interacted with spastin to promote the neurite outgrowth and branch formation. Furthermore, our results identified that phosphorylation modification failed to alter the binding affinities of CRMP2 for spastin, but inhibited their binding to microtubules. CRMP2 interacted with the MTBD domain of spastin via its C-terminus, and blocking the binding sites of them inhibited the outgrowth and branch formation of neurites. In addition, we confirmed one phosphorylation site S210 at spastin in hippocampal neurons and phosphorylation spastin at site S210 promoted the neurite outgrowth but not branch formation by remodeling microtubules. Conclusion: Taken together, our data demonstrated that the interaction of CRMP2 and spastin is required for neurite outgrowth and branch formation and their interaction is not regulated by their phosphorylation.

scholarly journals BDNF mobilizes synaptic vesicles and enhances synapse formation by disrupting cadherin–β-catenin interactions

2006 ◽  
Vol 174 (2) ◽  
pp. 289-299 ◽  
Author(s):  
Shernaz X. Bamji ◽  
Beatriz Rico ◽  
Nikole Kimes ◽  
Louis F. Reichardt
Keyword(s):  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Hippocampal Neurons ◽  
Molecular Mechanisms ◽  
Synapse Formation ◽  
Time Lapse ◽  
Synapse Density ◽  
Vesicle Mobility ◽  
Small Clusters ◽  
Vertebrate Central Nervous System

Neurons of the vertebrate central nervous system have the capacity to modify synapse number, morphology, and efficacy in response to activity. Some of these functions can be attributed to activity-induced synthesis and secretion of the neurotrophin brain-derived neurotrophic factor (BDNF); however, the molecular mechanisms by which BDNF mediates these events are still not well understood. Using time-lapse confocal analysis, we show that BDNF mobilizes synaptic vesicles at existing synapses, resulting in small clusters of synaptic vesicles “splitting” away from synaptic sites. We demonstrate that BDNF's ability to mobilize synaptic vesicle clusters depends on the dissociation of cadherin–β-catenin adhesion complexes that occurs after tyrosine phosphorylation of β-catenin. Artificially maintaining cadherin–β-catenin complexes in the presence of BDNF abolishes the BDNF-mediated enhancement of synaptic vesicle mobility, as well as the longer-term BDNF-mediated increase in synapse number. Together, this data demonstrates that the disruption of cadherin–β-catenin complexes is an important molecular event through which BDNF increases synapse density in cultured hippocampal neurons.

scholarly journals The Caenorhabditis elegans unc-64 Locus Encodes a Syntaxin That Interacts Genetically with Synaptobrevin

1998 ◽  
Vol 9 (6) ◽  
pp. 1235-1252 ◽  
Author(s):  
Owais Saifee ◽  
Liping Wei ◽  
Michael L. Nonet
Keyword(s):  
Caenorhabditis Elegans ◽  
Synaptic Vesicle ◽  
Acetylcholinesterase Inhibitor ◽  
Coiled Coil ◽  
Vesicle Fusion ◽  
Loss Of Function ◽  
Hydrophobic Membrane ◽  
Coiled Coil Domain ◽  
Synaptic Vesicle Fusion

We describe the molecular cloning and characterization of theunc-64 locus of Caenorhabditis elegans. unc-64 expresses three transcripts, each encoding a molecule with 63–64% identity to human syntaxin 1A, a membrane- anchored protein involved in synaptic vesicle fusion. Interestingly, the alternative forms of syntaxin differ only in their C-terminal hydrophobic membrane anchors. The forms are differentially expressed in neuronal and secretory tissues; genetic evidence suggests that these forms are not functionally equivalent. A complete loss-of-function mutation in unc-64 results in a worm that completes embryogenesis, but arrests development shortly thereafter as a paralyzed L1 larva, presumably as a consequence of neuronal dysfunction. The severity of the neuronal phenotypes of C. elegans syntaxin mutants appears comparable to those ofDrosophila syntaxin mutants. However, nematode syntaxin appears not to be required for embryonic development, for secretion of cuticle from the hypodermis, or for the function of muscle, in contrast to Drosophila syntaxin, which appears to be required in all cells. Less severe viable unc-64 mutants exhibit a variety of behavioral defects and show strong resistance to the acetylcholinesterase inhibitor aldicarb. Extracellular physiological recordings from pharyngeal muscle of hypomorphic mutants show alterations in the kinetics of transmitter release. The lesions in the hypomorphic alleles map to the hydrophobic face of the H3 coiled-coil domain of syntaxin, a domain that in vitro mediates physical interactions with similar coiled-coil domains in SNAP-25 and synaptobrevin. Furthermore, the unc-64 syntaxin mutants exhibit allele-specific genetic interactions with mutants carrying lesions in the coiled-coil domain of synaptobrevin, providing in vivo evidence for the significance of these domains in regulating synaptic vesicle fusion.

scholarly journals Simultaneous lipid and content mixing assays for in vitro reconstitution studies of synaptic vesicle fusion

2017 ◽  
Vol 12 (9) ◽  
pp. 2014-2028 ◽  
Author(s):  
Xiaoxia Liu ◽  
Alpay Burak Seven ◽  
Junjie Xu ◽  
Victoria Esser ◽  
Lijing Su ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Vesicle Fusion ◽  
In Vitro Reconstitution ◽  
Synaptic Vesicle Fusion

scholarly journals Deletion of the Nucleotide Exchange Factor Vav3 Enhances Axonal Complexity and Synapse Formation but Tampers Activity of Hippocampal Neuronal Networks In Vitro

2020 ◽  
Vol 21 (3) ◽  
pp. 856
Author(s):  
David Wegrzyn ◽  
Christine Wegrzyn ◽  
Kerry Tedford ◽  
Klaus-Dieter Fischer ◽  
Andreas Faissner
Keyword(s):  
Hippocampal Neurons ◽  
Synapse Formation ◽  
Synergistic Effects ◽  
Neuronal Morphology ◽  
Network Activity ◽  
Nucleotide Exchange ◽  
Double Knockout ◽  
Nucleotide Exchange Factor ◽  
Key Events

Vav proteins activate GTPases of the RhoA subfamily that regulate the cytoskeleton and are involved in adhesion, migration, differentiation, polarity and the cell cycle. While the importance of RhoA GTPases for neuronal morphology is undisputed, their regulation is less well understood. In this perspective, we studied the consequences of the deletion of Vav2, Vav3 and Vav2 and 3 (Vav2−/−, Vav3−/−, Vav2−/−/3−/−) for the development of embryonic hippocampal neurons in vitro. Using an indirect co-culture system of hippocampal neurons with primary wild-type (WT) cortical astrocytes, we analysed axonal and dendritic parameters, structural synapse numbers and the spontaneous network activity via immunocytochemistry and multielectrode array analysis (MEA). Here, we observed a higher process complexity in Vav3−/−, but not in Vav2−/− neurons after three and five days in vitro (DIV). Furthermore, an enhanced synapse formation was observed in Vav3−/− after 14 days in culture. Remarkably, Vav2−/−/3−/− double knockout neurons did not display synergistic effects. Interestingly, these differences were transient and compensated after a cultivation period of 21 days. Network analysis revealed a diminished number of spontaneously occurring action potentials in Vav3−/− neurons after 21 DIV. Based on these results, it appears that Vav3 participates in key events of neuronal differentiation.

scholarly journals Reconstituted synaptotagmin I mediates vesicle docking, priming, and fusion

2011 ◽  
Vol 195 (7) ◽  
pp. 1159-1170 ◽  
Author(s):  
Zhao Wang ◽  
Huisheng Liu ◽  
Yiwen Gu ◽  
Edwin R. Chapman
Keyword(s):  
Synaptic Transmission ◽  
Membrane Fusion ◽  
Synaptic Vesicle ◽  
Cytoplasmic Domain ◽  
Snare Proteins ◽  
Antagonist Activity ◽  
Vesicle Docking ◽  
Synaptotagmin I ◽  
Target Membrane

The synaptic vesicle protein synaptotagmin I (syt) promotes exocytosis via its ability to penetrate membranes in response to binding Ca2+ and through direct interactions with SNARE proteins. However, studies using full-length (FL) membrane-embedded syt in reconstituted fusion assays have yielded conflicting results, including a lack of effect, or even inhibition of fusion, by Ca2+. In this paper, we show that reconstituted FL syt promoted rapid docking of vesicles (<1 min) followed by a priming step (3–9 min) that was required for subsequent Ca2+-triggered fusion between v- and t-SNARE liposomes. Moreover, fusion occurred only when phosphatidylinositol 4,5-bisphosphate was included in the target membrane. This system also recapitulates some of the effects of syt mutations that alter synaptic transmission in neurons. Finally, we demonstrate that the cytoplasmic domain of syt exhibited mixed agonist/antagonist activity during regulated membrane fusion in vitro and in cells. Together, these findings reveal further convergence of reconstituted and cell-based systems.

Sign in / Sign up

Export Citation Format

Share Document