scholarly journals Adhesion energy can regulate vesicle fusion and stabilize partially fused states

2012 ◽  
Vol 9 (72) ◽  
pp. 1555-1567 ◽  
Author(s):  
Rong Long ◽  
Chung-Yuen Hui ◽  
Anand Jagota ◽  
Maria Bykhovskaia
Keyword(s):  
Metastable State ◽  
Synaptic Vesicles ◽  
Membrane Curvature ◽  
Fusion Process ◽  
Synaptic Membrane ◽  
Adhesion Forces ◽  
Molecular Adhesion ◽  
Strong Adhesion ◽  
Molecular Machinery ◽  
Molecular Components

Release of neurotransmitters from nerve terminals occurs by fusion of synaptic vesicles with the plasma membrane, and this process is highly regulated. Although major molecular components that control docking and fusion of vesicles to the synaptic membrane have been identified, the detailed mechanics of this process is not yet understood. We have developed a mathematical model that predicts how adhesion forces imposed by docking and fusion molecular machinery would affect the fusion process. We have computed the membrane stress that is produced by adhesion-driven vesicle bending and find that it is compressive. Further, our computations of the membrane curvature predict that strong adhesion can create a metastable state with a partially opened pore that would correspond to the ‘kiss and run’ release mode. Our model predicts that the larger the vesicle size, the more likely the metastable state with a transiently opened pore. These results contribute to understanding the mechanics of the fusion process, including possible clamping of the fusion by increasing molecular adhesion, and a balance between ‘kiss and run’ and full collapse fusion modes.

scholarly journals ELECTRON MICROSCOPE OBSERVATIONS ON SYNAPTIC VESICLES IN SYNAPSES OF THE RETINAL RODS AND CONES

1956 ◽  
Vol 2 (3) ◽  
pp. 307-318 ◽  
Author(s):  
Eduardo De Robertis ◽  
Carlos M. Franchi
Keyword(s):  
Electron Microscope ◽  
Synaptic Vesicles ◽  
Sharp Decrease ◽  
Albino Rabbit ◽  
Synaptic Membrane ◽  
Complete Darkness ◽  
Rods And Cones ◽  
Retinal Rods ◽  
Filamentous Material ◽  
Rod Cell

The submicroscopic organization of the rod and cone synapses of the albino rabbit has been investigated with the use of the electron microscope. The most common rod synapse consists of an enlarged expansion of the rod fiber (the so called spherule) into which the dendritic postsynaptic fiber of the bipolar cell penetrates and digitates. The membrane surrounding the terminal consists of a double layer, the external of which is interpreted as belonging to the intervening glial cells. The synaptic membrane has a pre- and a postsynaptic layer with a total thickness of 180 to 300 A. The presynaptic layer is frequently denser and is intimately associated with the adjacent synaptic vesicles. The synaptic membrane shows processes constituted by foldings of the presynaptic layer. The entire spherule is filled with synaptic vesicles varying in diameter between 200 and 650 A with a mean of 386 A. In addition, the spherule contains a few large vacuoles near the rod fiber, interpreted as endoplasmic reticulum, and a matrix in which with high resolution a fine filamentous material can be observed. The postsynaptic fiber is homogeneous and usually does not show synaptic vesicles. In animals maintained in complete darkness for 24 hours vesicles appear to accumulate near the synaptic membrane and its processes. After 9 days there is a sharp decrease in size of the synaptic vesicles. A special rod synapse in which the dendritic postsynaptic expansion penetrates directly into the rod cell body has been identified. In line with Cajal's classification this type of synapse could be considered as a somatodendritic one. The cone synapse has a much larger terminal with a more complex relationship with the postsynaptic fiber. However, the same components recognized in the rod synapse can be observed. In animals maintained for 9 days in complete darkness there is also a considerable diminution in size of the synaptic vesicles.

scholarly journals Carbohydrate–carbohydrate interaction provides adhesion force and specificity for cellular recognition

2004 ◽  
Vol 165 (4) ◽  
pp. 529-537 ◽  
Author(s):  
Iwona Bucior ◽  
Simon Scheuring ◽  
Andreas Engel ◽  
Max M. Burger
Keyword(s):  
Adhesion Force ◽  
Species Specificity ◽  
Live Cells ◽  
Sponge Cell ◽  
Cell Recognition ◽  
Adhesion Forces ◽  
Cellular Recognition ◽  
Strong Adhesion ◽  
Species Specific ◽  
Cell Cell

The adhesion force and specificity in the first experimental evidence for cell–cell recognition in the animal kingdom were assigned to marine sponge cell surface proteoglycans. However, the question whether the specificity resided in a protein or carbohydrate moiety could not yet be resolved. Here, the strength and species specificity of cell–cell recognition could be assigned to a direct carbohydrate–carbohydrate interaction. Atomic force microscopy measurements revealed equally strong adhesion forces between glycan molecules (190–310 piconewtons) as between proteins in antibody–antigen interactions (244 piconewtons). Quantitative measurements of adhesion forces between glycans from identical species versus glycans from different species confirmed the species specificity of the interaction. Glycan-coated beads aggregated according to their species of origin, i.e., the same way as live sponge cells did. Live cells also demonstrated species selective binding to glycans coated on surfaces. These findings confirm for the first time the existence of relatively strong and species-specific recognition between surface glycans, a process that may have significant implications in cellular recognition.

scholarly journals Complexin cooperates with Bruchpilot to tether synaptic vesicles to the active zone cytomatrix

2019 ◽  
Vol 218 (3) ◽  
pp. 1011-1026 ◽  
Author(s):  
Nicole Scholz ◽  
Nadine Ehmann ◽  
Divya Sachidanandan ◽  
Cordelia Imig ◽  
Benjamin H. Cooper ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Active Zone ◽  
Synaptic Vesicles ◽  
Snare Complex ◽  
C Terminus ◽  
Unknown Protein ◽  
Transmission Part ◽  
Molecular Components ◽  
In Vivo Screen

Information processing by the nervous system depends on neurotransmitter release from synaptic vesicles (SVs) at the presynaptic active zone. Molecular components of the cytomatrix at the active zone (CAZ) regulate the final stages of the SV cycle preceding exocytosis and thereby shape the efficacy and plasticity of synaptic transmission. Part of this regulation is reflected by a physical association of SVs with filamentous CAZ structures via largely unknown protein interactions. The very C-terminal region of Bruchpilot (Brp), a key component of the Drosophila melanogaster CAZ, participates in SV tethering. Here, we identify the conserved SNARE regulator Complexin (Cpx) in an in vivo screen for molecules that link the Brp C terminus to SVs. Brp and Cpx interact genetically and functionally. Both proteins promote SV recruitment to the Drosophila CAZ and counteract short-term synaptic depression. Analyzing SV tethering to active zone ribbons of cpx3 knockout mice supports an evolutionarily conserved role of Cpx upstream of SNARE complex assembly.

Neurotransmitter Release

2017 ◽  
Author(s):  
Peggy Mason
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Active Zone ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Synaptic Cleft ◽  
Fusion Pore ◽  
Synaptic Membrane ◽  
Specialized Region ◽  
Synaptic Vesicle Fusion

The biochemical and physiological processes of neurotransmitter release from an active zone, a specialized region of synaptic membrane, are examined. Synaptic vesicles containing neurotransmitters are docked at the active zone and then primed for release by SNARE complexes that bring them into extreme proximity to the plasma membrane. Entry of calcium ions through voltage-gated calcium channels triggers synaptic vesicle fusion with the synaptic terminal membrane and the consequent diffusion of neurotransmitter into the synaptic cleft. Release results when the fusion pore bridging the synaptic vesicle and plasma membrane widens and neurotransmitter from the inside of the synaptic vesicle diffuses into the synaptic cleft. Membrane from the active zone membrane is endocytosed, and synaptic vesicle proteins are then reassembled into recycled synaptic vesicles, allowing for more rounds of neurotransmitter release.

scholarly journals SOME FEATURES OF THE SUBMICROSCOPIC MORPHOLOGY OF SYNAPSES IN FROG AND EARTHWORM

1955 ◽  
Vol 1 (1) ◽  
pp. 47-58 ◽  
Author(s):  
Eduardo D. P. De Robertis ◽  
H. Stanley Bennett
Keyword(s):  
Electron Micrographs ◽  
Nerve Cord ◽  
Synaptic Vesicles ◽  
Sympathetic Ganglia ◽  
Synaptic Membrane ◽  
Presynaptic Membrane ◽  
Close Relationship

Electron micrographs are presented of synaptic regions encountered in sections of frog sympathetic ganglia and earthworm nerve cord neuropile. Pre- and postsynaptic neuronal elements each appear to have a membrane 70 to 100 A thick, separated from each other over the synaptic area by an intermembranal space 100 to 150 A across. A granular or vesicular component, here designated the synaptic vesicles, is encountered on the presynaptic side of the synapse and consists of numerous oval or spherical bodies 200 to 500 A in diameter, with dense circumferences and lighter centers. Synaptic vesicles are encountered in close relationship to the synaptic membrane. In the earthworm neuropile elongated vesicles are found extending through perforations or gaps in the presynaptic membrane, with portions of vesicles appearing in the intermembranal space. Mitochondria are encountered in the vicinity of the synapse, and in the frog, a submicroscopic filamentary component can be seen in the presynaptic member extending up to the region where the vesicles are found, but terminating short of the synapse itself.

scholarly journals Submicroscopic Changes in Visual Cells of the Rabbit Induced by Iodoacetate

1959 ◽  
Vol 5 (2) ◽  
pp. 245-250 ◽  
Author(s):  
Arnaldo Lasansky ◽  
Eduardo De Robertis
Keyword(s):  
Body Weight ◽  
Synaptic Vesicles ◽  
Single Injection ◽  
Synaptic Membrane ◽  
Visual Cells ◽  
Rod Cells ◽  
Complete Destruction ◽  
Cone Cells ◽  
The Matrix ◽  
Myelin Figures

Alterations produced by iodoacetate in visual cells have been studied under the electron microscope. Lesions of the outer segments of the rods are visible as early as 3 hours after a single injection of 20 mg. iodoacetate per kg. body weight. After 6 hours the changes are more marked and consist then of disorganization, vesiculation, and lysis of the rod sacs. The inner segments of most rod cells show swelling and vacuolization of the matrix, the endoplasmic reticulum, and the Golgi complex. The mitochondria of the ellipsoid show a tendency to disintegrate. In some inner segments the changes consist primarily in an increase in density of the matrix and deposition of a granular material. The rod synapses are also affected, showing lysis of the synaptic vesicles and alterations of the synaptic membrane. With a second injection of 20 mg. iodoacetate per kg. body weight, all these changes become more marked and lead to complete destruction of the rod cells. The cones seem more resistant than the rods. A single injection produces no visible changes in the outer or inner segments of the cones. At cone synapses, however, there are changes consisting of fusion of synaptic vesicles and other membranous material to form large concentric membranes characteristic of myelin figures. A second dose of the drug causes complete destruction of the cone cells. All these, and other submicroscopic changes, are discussed in relation to various hypotheses put forward to explain the mode of action of iodoacetate on visual cells. The pronounced alterations of submicroscopic intracellular membranes suggest that the locus of action of iodoacetate may be a component widely dispersed throughout the visual cells and related, in some way, to the maintenance of these lipoprotein structures.

MODELING TUMOR CELL POPULATION DYNAMICS BASED ON MOLECULAR ADHESION ASSUMPTIONS

2004 ◽  
Vol 12 (03) ◽  
pp. 273-288 ◽  
Author(s):  
WIESLAW GRYGIERZEC ◽  
ANDREAS DEUTSCH ◽  
WALTER SCHUBERT ◽  
MANUELA FRIEDENBERGER ◽  
LARS PHILIPSEN
Keyword(s):  
Population Dynamics ◽  
Tumor Cell ◽  
Cell Population ◽  
Adhesion Forces ◽  
Protein Patterns ◽  
Cell Population Dynamics ◽  
Tumor Cell Population ◽  
Molecular Adhesion ◽  
Ca Model ◽  
Adhesion Process

A model of cell population dynamics based on molecular adhesion is explained and discussed in this paper. We consider cancer cells experiencing interactions due to adhesion forces. In the cells' membranes there are proteins directly involved in adhesion. These proteins in the membrane are assembled in complex patterns called Combinatorial Protein Patterns (CPP). The goal of this work is to understand the mechanisms governing the adhesion process — in particular distinguishing CPPs involved in interactions. On the basis of experimental observation we have constructed an asynchronous cellular automaton (CA) model that simulates protein network dynamics in a population of cells.

Investigations of the Relationship Between Acetylcholine Synthesis and the Recycling of Synaptic Vesicles

1976 ◽  
Vol 34 ◽  
pp. 4-5
Author(s):  
Francine M. Benes ◽  
Russell J. Barrnett
Keyword(s):  
Synaptic Vesicles ◽  
Neuromuscular Junctions ◽  
Synaptic Membrane ◽  
Frog Neuromuscular Junction ◽  
Acetylcholine Synthesis ◽  
The Reformation ◽  
Key Factor ◽  
Choline Acetylase ◽  
Series Of Experiments ◽  
Biochemical Analyses

It is well established that synaptic vesicles fuse with the pre-synaptic membrane during stimulation, and are reformed during a period of rest. These events have been correlated with the depletion and resynthesis of stores of acetylcholine (Ach) in the frog neuromuscular junction. Thus, choline acetylase (ChAc) activity appears to be a key factor in the metabolism of the transmitter Ach pool. The present work inquires into the possible interrelationship of the above events; that is, whether the reformation of vesicles after depletion by stimulation is associated with the activity of ChAc. Therefore, a series of experiments on frog neuromuscular junctions were performed in which the data from biochemical analyses of acetylcholine synthesis and from the morphometric determination of vesicle numbers were compared.

Ultrastructural localization of calcium-binding sites in the electrocyte of Electrophorus electricus (L.)

1979 ◽  
Vol 38 (1) ◽  
pp. 97-104
Author(s):  
T.C. De Araujo Jorge ◽  
W. De Souza ◽  
R.D. Machado
Keyword(s):  
Plasma Membrane ◽  
Binding Sites ◽  
Calcium Binding ◽  
Synaptic Vesicles ◽  
Ultrastructural Localization ◽  
Synaptic Membrane ◽  
Electrophorus Electricus ◽  
Calcium Binding Sites

Calcium-binding sites were detected in the electrocyte of Electrophorus electricus (L.) using the Oschman & Wall technique, in which CaCl2 was added to the fixative and washing solutions. Deposits were seen scattered along the plasma membrane of the electrocyte, inside mitochondria, associated with the post-synaptic membrane and the membrane of synaptic vesicles.

The Synaptology of the Granule Cells of the Olfactory Bulb

1970 ◽  
Vol 7 (1) ◽  
pp. 125-155
Author(s):  
J. L. PRICE ◽  
T. P. S POWELL
Keyword(s):  
Olfactory Bulb ◽  
Synaptic Vesicles ◽  
Granule Cells ◽  
Mitral Cell ◽  
Synaptic Membrane ◽  
Quantitative Evidence ◽  
Axon Terminals ◽  
Quantitative Measurements ◽  
Asymmetrical Synapse ◽  
Cell Somata

The synapses related to the granule cells of the olfactory bulb of rat brain have been studied in aldehyde-fixed material. The synapses can be divided into three classes: (1) those which have asymmetrical synaptic membrane thickenings and spheroidal synaptic vesicles; (2) those with symmetrical synaptic thickenings and flattened vesicles; and (3) the reciprocal synapses, one half of which (from mitral to granule cell) has an asymmetrical synaptic thickening associated with spheroidal vesicles, while the other half (from granule to mitral cell) has a symmetrical synaptic thickening and flattened vesicles. Qualitative observations, supported by preliminary quantitative measurements, suggest that it may be possible to divide both the spheroidal and flattened-vesicle types into two further varieties, on the basis of size, The smaller variety of spheroidal vesicles is found in most axon terminals, while the larger spheroidal vesicles are present in mitral cell dendrites and in some of the axon terminals. The flattened vesicles associated with symmetrical synapses which are oriented on to the granule cells are smaller than the spheroidal vesicles, but the flattened vesicles in the spines and gemmules of the granule cells are the same size or larger than the spheroidal vesicles. The division of flattened vesicles into two sizes is supported by statistical analysis of measurements of these vesicles, but because of difficulty in identifying the axon terminals with asymmetrical synapses there is no quantitative evidence for such a division of spheroidal vesicles. The asymmetrical synapses are found predominantly on spines, gemmules, and dendritic varicosities, although they are occasionally present on shafts of dendrites and on the cell somata. The symmetrical synapses are almost completely restricted to the shafts of the peripheral processes and the deep dendrites, and to the cell somata; only very rarely are synapses of this type found on spines, and then always in conjunction with an asymmetrical synapse.

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