scholarly journals Activity-dependent endoplasmic reticulum Ca2+ uptake depends on Kv2.1-mediated endoplasmic reticulum/plasma membrane junctions to promote synaptic transmission

2021 ◽  
Author(s):  
Lauren C. Panzera ◽  
Ben Johnson ◽  
In Ha Cho ◽  
Michael M. Tamkun ◽  
Michael B. Hoppa
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Synaptic Transmission ◽  
Electrical Activity ◽  
Synaptic Vesicle ◽  
Cell Biology ◽  
Neuronal Cell ◽  
Critical Pathway ◽  
Critical Function ◽  
Vesicle Exocytosis

The endoplasmic reticulum (ER) forms a continuous and dynamic network throughout a neuron, extending from dendrites to axon terminals, and axonal ER dysfunction is implicated in several neurological disorders. In addition, tight junctions between the ER and plasma membrane (PM) are formed by several molecules including Kv2 channels, but the cellular functions of many ER-PM junctions remain unknown. Dynamic Ca2+ uptake into the ER during electrical activity plays an essential role in synaptic transmission as failure to allow rapid ER Ca2+ filling during stimulation activates stromal interaction molecule 1 (STIM1) and decreases both presynaptic Ca2+ influx and synaptic vesicle exocytosis. Our experiments demonstrate that Kv2.1 channels are necessary for enabling ER Ca2+ uptake during electrical activity as genetic depletion of Kv2.1 rendered both the somatic and axonal ER unable to accumulate Ca2+ during electrical stimulation. Moreover, our experiments show that the loss of Kv2.1 in the axon impairs synaptic vesicle fusion during stimulation via a mechanism unrelated to modulation of membrane voltage. Thus, our data demonstrate that the non-conducting role of Kv2.1 in forming stable junctions between the ER and PM via ER VAMP-associated protein (VAP) binding couples ER Ca2+ uptake with electrical activity. Our results further suggest that Kv2.1 has a critical function in neuronal cell biology for Ca2+-handling independent of voltage and reveals a novel and critical pathway for maintaining ER lumen Ca2+ levels and efficient neurotransmitter release. Taken together these findings reveal an essential non-classical role for both Kv2.1 and the ER-PM junctions in synaptic transmission.

scholarly journals Structural changes after transmitter release at the frog neuromuscular junction.

1981 ◽  
Vol 88 (3) ◽  
pp. 564-580 ◽  
Author(s):  
J E Heuser ◽  
T S Reese
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Structural Changes ◽  
Frog Neuromuscular Junction ◽  
Vesicle Membrane ◽  
Intramembrane Particles ◽  
Synaptic Vesicle Exocytosis ◽  
Quick Freezing ◽  
Vesicle Exocytosis ◽  
Active Zones

The sequence of structural changes that occur during synaptic vesicle exocytosis was studied by quick-freezing muscles at different intervals after stimulating their nerves, in the presence of 4-aminopyridine to increase the number of transmitter quanta released by each stimulus. Vesicle openings began to appear at the active zones of the intramuscular nerves within 3-4 ms after a single stimulus. The concentration of these openings peaked at 5-6 ms, and then declined to zero 50-100 ms late. At the later times, vesicle openings tended to be larger. Left behind at the active zones, after the vesicle openings disappeared, were clusters of large intramembrane particles. The larger particles in these clusters were the same size as intramembrane particles in undischarged vesicles, and were slightly larger than the particles which form the rows delineating active zones. Because previous tracer work had shown that new vesicles do not pinch off from the plasma membrane at these early times, we concluded that the particle clusters originate from membranes of discharged vesicles which collapse into the plasmalemma after exocytosis. The rate of vesicle collapse appeared to be variable because different stages occurred simultaneously at most times after stimulation; this asynchrony was taken to indicate that the collapse of each exocytotic vesicle is slowed by previous nearby collapses. The ultimate fate of synaptic vesicle membrane after collapse appeared to be coalescence with the plasma membrane, as the clusters of particles gradually dispersed into surrounding areas during the first second after a stimulus. The membrane retrieval and recycling that reverse this exocytotic sequence have a slower onset, as has been described in previous reports.

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

2017 ◽  
Author(s):  
Donovan Ventimiglia ◽  
Cornelia I. Bargmann
Keyword(s):  
Synaptic Vesicle ◽  
Neuronal Cell ◽  
Cell Types ◽  
Snare Complex ◽  
C Elegans ◽  
Synaptic Vesicle Exocytosis ◽  
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.

scholarly journals Caveolin-1 deficiency impairs synaptic transmission in hippocampal neurons

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Soulmee Koh ◽  
Wongyoung Lee ◽  
Sang Myun Park ◽  
Sung Hyun Kim
Keyword(s):  
Synaptic Transmission ◽  
Synaptic Vesicle ◽  
Hippocampal Neurons ◽  
Membrane Dynamics ◽  
Synaptic Membrane ◽  
Cellular Mechanisms ◽  
Caveolin 1 ◽  
Synaptic Vesicle Exocytosis ◽  
Vesicle Dynamics ◽  
Vesicle Exocytosis

AbstractIn addition to providing structural support, caveolin-1 (Cav1), a component of lipid rafts, including caveolae, in the plasma membrane, is involved in various cellular mechanisms, including signal transduction. Although pre-synaptic membrane dynamics and trafficking are essential cellular processes during synaptic vesicle exocytosis/synaptic transmission and synaptic vesicle endocytosis/synaptic retrieval, little is known about the involvement of Cav1 in synaptic vesicle dynamics. Here we demonstrate that synaptic vesicle exocytosis is significantly impaired in Cav1–knockdown (Cav1–KD) neurons. Specifically, the size of the synaptic recycled vesicle pool is modestly decreased in Cav1–KD synapses and the kinetics of synaptic vesicle endocytosis are somewhat slowed. Notably, neurons rescued by triple mutants of Cav1 lacking palmitoylation sites mutants show impairments in both synaptic transmission and retrieval. Collectively, our findings implicate Cav1 in activity-driven synaptic vesicle dynamics—both exocytosis and endocytosis—and demonstrate that palmitoylation of Cav1 is important for this activity.

scholarly journals Isoflurane inhibits synaptic vesicle exocytosis through reduced Ca2+ influx, not Ca2+-exocytosis coupling

2015 ◽  
Vol 112 (38) ◽  
pp. 11959-11964 ◽  
Author(s):  
Joel P. Baumgart ◽  
Zhen-Yu Zhou ◽  
Masato Hara ◽  
Daniel C. Cook ◽  
Michael B. Hoppa ◽  
...  
Keyword(s):  
Synaptic Transmission ◽  
Synaptic Vesicle ◽  
Hippocampal Neurons ◽  
Volatile Anesthetic ◽  
Selective Inhibition ◽  
Nerve Terminals ◽  
General Anesthetics ◽  
Single Action ◽  
Presynaptic Mechanisms ◽  
Vesicle Exocytosis

Identifying presynaptic mechanisms of general anesthetics is critical to understanding their effects on synaptic transmission. We show that the volatile anesthetic isoflurane inhibits synaptic vesicle (SV) exocytosis at nerve terminals in dissociated rat hippocampal neurons through inhibition of presynaptic Ca2+ influx without significantly altering the Ca2+ sensitivity of SV exocytosis. A clinically relevant concentration of isoflurane (0.7 mM) inhibited changes in [Ca2+]i driven by single action potentials (APs) by 25 ± 3%, which in turn led to 62 ± 3% inhibition of single AP-triggered exocytosis at 4 mM extracellular Ca2+ ([Ca2+]e). Lowering external Ca2+ to match the isoflurane-induced reduction in Ca2+ entry led to an equivalent reduction in exocytosis. These data thus indicate that anesthetic inhibition of neurotransmitter release from small SVs occurs primarily through reduced axon terminal Ca2+ entry without significant direct effects on Ca2+-exocytosis coupling or on the SV fusion machinery. Isoflurane inhibition of exocytosis and Ca2+ influx was greater in glutamatergic compared with GABAergic nerve terminals, consistent with selective inhibition of excitatory synaptic transmission. Such alteration in the balance of excitatory to inhibitory transmission could mediate reduced neuronal interactions and network-selective effects observed in the anesthetized central nervous system.

Some Contributions of Phosphatase and 3,3'-Diaminobenzidine Cytochemistry to Cell Biology

1977 ◽  
Vol 35 ◽  
pp. 420-423
Author(s):  
Alex B. Novikoff
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Cell Biology ◽  
Mammalian Cells ◽  
Structure And Function ◽  
Cell Organelles ◽  
Thiamine Pyrophosphatase ◽  
The Status ◽  
Dab Cytochemistry ◽  
And Function

This presentation will highlight cytochemical studies that have illuminated some aspects of structure and function of the endoplasmic reticulum (ER); these have been reviewed recently (1, 2). Phosphatase (Pase) cytochemistry has led to the formulation of new questions regarding secretory mechanisms in a number of endocrine and exocrine cells; it has also made the status of GERL as a distinct organelle considerably firmer. 3,31-diaminobenzidine (DAB) cytochemistry has revealed the presence of an organelle apparently ubiquitous in mammalian cells, the anucleoid peroxisomes(microperoxisomes). DAB cytochemistry has been utilized recently by Gonatas et al. (3) to demonstrate that internalized plasma membrane is transported to GERL.Our initial use of Pase cytochemistry to visualize cell organelles included nucleoside diphosphatase (NDPase), thiamine pyrophosphatase (TPPase), and acid Pase (AcPase). NDPase hydrolyzes the diphosphates of inosine, uridine, and guanosine but not cytidine or adenine diphosphates. Since the work of Yamasaku and Hayaishi (4) we have used TPPase and NDPase interchangeably.

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

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Donovan Ventimiglia ◽  
Cornelia I Bargmann
Keyword(s):  
Synaptic Vesicle ◽  
Neuronal Cell ◽  
Cell Types ◽  
Snare Complex ◽  
C Elegans ◽  
Synaptic Vesicle Exocytosis ◽  
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.

scholarly journals A common human brain-derived neurotrophic factor polymorphism leads to sustained depression of excitatory synaptic transmission by isoflurane in hippocampus

2022 ◽  
Author(s):  
Riley A. Williams ◽  
Kenneth W. Johnson ◽  
Francis S. Lee ◽  
Hugh C. Hemmings ◽  
Jimcy Platholi
Keyword(s):  
Synaptic Plasticity ◽  
Synaptic Transmission ◽  
Synaptic Vesicle ◽  
Neurotrophic Factor ◽  
Brain Derived Neurotrophic Factor ◽  
Synaptic Function ◽  
Excitatory Synaptic Transmission ◽  
Neurological Dysfunction ◽  
Synaptic Vesicle Exocytosis ◽  
Vesicle Exocytosis

Multiple presynaptic and postsynaptic targets have been identified for the reversible neurophysiological effects of general anesthetics on synaptic transmission and neuronal excitability. However, the synaptic mechanisms involved in persistent depression of synaptic transmission resulting in more prolonged neurological dysfunction following anesthesia are less clear. Here, we show that brain-derived neurotrophic factor (BDNF), a growth factor implicated in synaptic plasticity and dysfunction, enhances glutamate synaptic vesicle exocytosis, and that attenuation of vesicular BDNF release by isoflurane contributes to transient depression of excitatory synaptic transmission in mice. This reduction in synaptic vesicle exocytosis was irreversible in neurons that release less endogenous BDNF due to a polymorphism (BDNF Val66Met) compared to wild-type mouse hippocampal neurons following isoflurane exposure. These effects were prevented by exogenous application of BDNF. Our findings identify a role for a common human BDNF single nucleotide polymorphism (Val66Met; rs6265) in persistent changes of synaptic function following isoflurane exposure. These persistent alterations in excitatory synaptic transmission have important implications for the role of genotype in anesthetic effects on synaptic plasticity and neurocognitive function.

Triple Fixation For Electron Microscopy

1968 ◽  
Vol 26 ◽  
pp. 90-91 ◽  
Author(s):  
M. A. Hayat
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Electron Beam ◽  
Plasma Membrane ◽  
Myelin Sheath ◽  
Good Deal ◽  
Granular Structure ◽  
Oxidizing Agent ◽  
Fixation Technique ◽  
Large Clusters

Potassium permanganate has been successfully employed to study membranous structures such as endoplasmic reticulum, Golgi, plastids, plasma membrane and myelin sheath. Since KMnO4 is a strong oxidizing agent, deposition of manganese or its oxides account for some of the observed contrast in the lipoprotein membranes, but a good deal of it is due to the removal of background proteins either by dehydration agents or by volatalization under the electron beam. Tissues fixed with KMnO4 exhibit somewhat granular structure because of the deposition of large clusters of stain molecules. The gross arrangement of membranes can also be modified. Since the aim of a good fixation technique is to preserve satisfactorily the cell as a whole and not the best preservation of only a small part of it, a combination of a mixture of glutaraldehyde and acrolein to obtain general preservation and KMnO4 to enhance contrast was employed to fix plant embryos, green algae and fungi.

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