scholarly journals Variable priming of a docked synaptic vesicle

2016 ◽  
Vol 113 (8) ◽  
pp. E1098-E1107 ◽  
Author(s):  
Jae Hoon Jung ◽  
Joseph A. Szule ◽  
Robert M. Marshall ◽  
Uel J. McMahan
Keyword(s):  
Normal Distribution ◽  
Synaptic Vesicle ◽  
Contact Area ◽  
Active Zone ◽  
Neuromuscular Junctions ◽  
Dynamic Equilibrium ◽  
Nerve Impulse ◽  
Complete Fusion ◽  
Contact Areas ◽  
Fusion Probability

The priming of a docked synaptic vesicle determines the probability of its membrane (VM) fusing with the presynaptic membrane (PM) when a nerve impulse arrives. To gain insight into the nature of priming, we searched by electron tomography for structural relationships correlated with fusion probability at active zones of axon terminals at frog neuromuscular junctions. For terminals fixed at rest, the contact area between the VM of docked vesicles and PM varied >10-fold with a normal distribution. There was no merging of the membranes. For terminals fixed during repetitive evoked synaptic transmission, the normal distribution of contact areas was shifted to the left, due in part to a decreased number of large contact areas, and there was a subpopulation of large contact areas where the membranes were hemifused, an intermediate preceding complete fusion. Thus, fusion probability of a docked vesicle is related to the extent of its VM–PM contact area. For terminals fixed 1 h after activity, the distribution of contact areas recovered to that at rest, indicating the extent of a VM–PM contact area is dynamic and in equilibrium. The extent of VM–PM contact areas in resting terminals correlated with eccentricity in vesicle shape caused by force toward the PM and with shortness of active zone material macromolecules linking vesicles to PM components, some thought to include Ca2+ channels. We propose that priming is a variable continuum of events imposing variable fusion probability on each vesicle and is regulated by force-generating shortening of active zone material macromolecules in dynamic equilibrium.

scholarly journals Hypothesis Relating the Structure, Biochemistry and Function of Active Zone Material Macromolecules at a Neuromuscular Junction

2022 ◽  
Vol 13 ◽  
Author(s):  
Joseph A. Szule
Keyword(s):  
Membrane Fusion ◽  
Synaptic Vesicle ◽  
Active Zone ◽  
Structural Integrity ◽  
Neuromuscular Junctions ◽  
Vesicle Trafficking ◽  
Material Structure ◽  
Neurotransmitter Secretion ◽  
Active Zones ◽  
And Function

This report integrates knowledge of in situ macromolecular structures and synaptic protein biochemistry to propose a unified hypothesis for the regulation of certain vesicle trafficking events (i.e., docking, priming, Ca2+-triggering, and membrane fusion) that lead to neurotransmitter secretion from specialized “active zones” of presynaptic axon terminals. Advancements in electron tomography, to image tissue sections in 3D at nanometer scale resolution, have led to structural characterizations of a network of different classes of macromolecules at the active zone, called “Active Zone Material’. At frog neuromuscular junctions, the classes of Active Zone Material macromolecules “top-masts”, “booms”, “spars”, “ribs” and “pins” direct synaptic vesicle docking while “pins”, “ribs” and “pegs” regulate priming to influence Ca2+-triggering and membrane fusion. Other classes, “beams”, “steps”, “masts”, and “synaptic vesicle luminal filaments’ likely help organize and maintain the structural integrity of active zones. Extensive studies on the biochemistry that regulates secretion have led to comprehensive characterizations of the many conserved proteins universally involved in these trafficking events. Here, a hypothesis including a partial proteomic atlas of Active Zone Material is presented which considers the common roles, binding partners, physical features/structure, and relative positioning in the axon terminal of both the proteins and classes of macromolecules involved in the vesicle trafficking events. The hypothesis designates voltage-gated Ca2+ channels and Ca2+-gated K+ channels to ribs and pegs that are connected to macromolecules that span the presynaptic membrane at the active zone. SNARE proteins (Syntaxin, SNAP25, and Synaptobrevin), SNARE-interacting proteins Synaptotagmin, Munc13, Munc18, Complexin, and NSF are designated to ribs and/or pins. Rab3A and Rabphillin-3A are designated to top-masts and/or booms and/or spars. RIM, Bassoon, and Piccolo are designated to beams, steps, masts, ribs, spars, booms, and top-masts. Spectrin is designated to beams. Lastly, the luminal portions of SV2 are thought to form the bulk of the observed synaptic vesicle luminal filaments. The goal here is to help direct future studies that aim to bridge Active Zone Material structure, biochemistry, and function to ultimately determine how it regulates the trafficking events in vivo that lead to neurotransmitter secretion.

scholarly journals Synaptic vesicle exocytosis captured by quick freezing and correlated with quantal transmitter release.

1979 ◽  
Vol 81 (2) ◽  
pp. 275-300 ◽  
Author(s):  
J E Heuser ◽  
T S Reese ◽  
M J Dennis ◽  
Y Jan ◽  
L Jan ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Neuromuscular Junctions ◽  
Freeze Fracture ◽  
Nerve Impulse ◽  
Biological Tissues ◽  
Synaptic Vesicle Exocytosis ◽  
Capacitance Method ◽  
Quick Freezing ◽  
Vesicle Exocytosis ◽  
Cold Metal

We describe the design and operation of a machine that freezes biological tissues by contact with a cold metal block, which incorporates a timing circuit that stimulates frog neuromuscular junctions in the last few milliseconds before thay are frozen. We show freeze-fracture replicas of nerve terminals frozen during transmitter discharge, which display synpatic vesicles caught in the act of exocytosis. We use 4-aminopyridine (4-AP) to increase the number of transmitter quanta discharged with each nerve impulse, and show that the number of exocytotic vesicles caught by quick-freezing increases commensurately, indicating that one vesicle undergoes exocytosis for each quantum that is discharged. We perform statistical analyses on the spatial distribution of synaptic vesicle discharge sites along the "active zones" that mark the secretory regions of these nerves, and show that individual vesicles fuse with the plasma membrane independent of one another, as expected from physiological demonstrations that quanta are discharged independently. Thus, the utility of quick-freezing as a technique to capture biological processes as evanescent as synaptic transmission has been established. An appendix describes a new capacitance method to measure freezing rates, which shows that the "temporal resolution" of our quick-freezing technique is 2 ms or better.

Amyloid Precursor Protein Knockout Diminishes Synaptic Vesicle Proteins at the Presynaptic Active Zone in Mouse Brain

2014 ◽  
Vol 11 (10) ◽  
pp. 971-980 ◽  
Author(s):  
Melanie Laßek ◽  
Jens Weingarten ◽  
Amparo Acker-Palmer ◽  
Sandra Bajjalieh ◽  
Ulrike Muller ◽  
...  
Keyword(s):  
Amyloid Precursor Protein ◽  
Synaptic Vesicle ◽  
Mouse Brain ◽  
Active Zone ◽  
Precursor Protein ◽  
Presynaptic Active Zone ◽  
Vesicle Proteins

scholarly journals Coordinated bi-directional trafficking of synaptic vesicle and active zone proteins in peripheral nerves

2021 ◽  
Vol 559 ◽  
pp. 92-98
Author(s):  
Judyta K. Juranek ◽  
Konark Mukherjee ◽  
Reinhard Jahn ◽  
Jia-Yi Li
Keyword(s):  
Synaptic Vesicle ◽  
Peripheral Nerves ◽  
Active Zone

scholarly journals The DISABLED protein functions in CLATHRIN-mediated synaptic vesicle endocytosis and exoendocytic coupling at the active zone

2011 ◽  
Vol 108 (25) ◽  
pp. E222-E229 ◽  
Author(s):  
F. Kawasaki ◽  
J. Iyer ◽  
L. L. Posey ◽  
C. E. Sun ◽  
S. E. Mammen ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Active Zone ◽  
The Disabled ◽  
Protein Functions

scholarly journals Synaptic vesicle dynamics in mouse rod bipolar cells

2008 ◽  
Vol 25 (4) ◽  
pp. 523-533 ◽  
Author(s):  
QUN-FANG WAN ◽  
ALEJANDRO VILA ◽  
ZHEN-YU ZHOU ◽  
RUTH HEIDELBERGER
Keyword(s):  
Synaptic Vesicle ◽  
Time Constant ◽  
Active Zone ◽  
Bipolar Cell ◽  
Visual Information ◽  
Membrane Surface ◽  
Bipolar Cells ◽  
Calcium Dependent ◽  
Vesicle Dynamics ◽  
Rod Bipolar Cells

AbstractTo better understand synaptic signaling at the mammalian rod bipolar cell terminal and pave the way for applying genetic approaches to the study of visual information processing in the mammalian retina, synaptic vesicle dynamics and intraterminal calcium were monitored in terminals of acutely isolated mouse rod bipolar cells and the number of ribbon-style active zones quantified. We identified a releasable pool, corresponding to a maximum of ≈35 vesicles/ribbon-style active zone. Following depletion, this pool was refilled with a time constant of ≈7 s. The presence of a smaller, rapidly releasing pool and a small, fast component of refilling was also suggested. Following calcium channel closure, membrane surface area was restored to baseline with a time constant that ranged from 2 to 21 s depending on the magnitude of the preceding Ca2+ transient. In addition, a brief, calcium-dependent delay often preceded the start of onset of membrane recovery. Thus, several aspects of synaptic vesicle dynamics appear to be conserved between rod-dominant bipolar cells of fish and mammalian rod bipolar cells. A major difference is that the number of vesicles available for release is significantly smaller in the mouse rod bipolar cell, both as a function of the total number per neuron and on a per active zone basis.

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