In our brain, information is passed from one neuron to the next at a structure called synapse. At a chemical synapse, a chemical is released from the signal-sending neuron or presynaptic neuron. This neurotransmitter then crosses the synaptic cleft to bind to receptors in the target neuron or postsynaptic neuron. An extensive molecular machinery is at work: for example, vesicles filled with neurotransmitter dock at “docking sites” in the pre-synaptic active zone before they fuse and release the neurotransmitter into the synapse.
A study co-led by Ryuichi Shigemoto, Professor at the Institute of Science and Technology Austria (IST Austria), with Alain Marty, Professor at Université Paris Descartes, uncovers that a single docking site may use a single cluster of calcium channels and that both the number of docking sites and the number of calcium clusters change in parallel with brain age.
This establishes the first clear link between the morphology and function of docking sites. The study was published today in PNAS.
At a chemical synapse, signal transmission requires an elaborate sequence of events. It starts when an electrical signal, the action potential, reaches the synaptic terminal of the presynaptic neuron. This causes voltage-gated calcium channel to open. Calcium ions rapidly stream into the presynaptic terminal and the calcium concentration in the presynaptic terminal rises. This allows synaptic vesicles filled with neurotransmitter to fuse with the plasma membrane and release the neurotransmitters into the synaptic cleft. Speed is essential in information transmission.
Therefore, before the action potential even arrives at the presynaptic terminal, vesicles containing neurotransmitter line up in a fusion-ready state at docking sites in the presynaptic terminal. When the action potential reaches the presynaptic terminal, the vesicles can rapidly fuse and release the neurotransmitter.
Functionally, docking sites limit the maximum number of vesicles that can be released at each action potential, this determines the strength of the synapse. Until now, a clear link between the functional aspect of docking sites and their morphological aspect as sites where vesicles dock could not be established in the mammalian brain.
Shigemoto and colleagues used a high-resolution electron microscopy technique to look closely at the presynaptic terminal of a particular synapse in the mouse. They found that the number of functional docking sites matches the number of clusters of voltage-gated calcium channels in the presynaptic terminal.
In addition, the number of docking sites and the number of calcium clusters change in parallel with brain age and synaptic size. This led the researchers to a major conclusion, as Shigemoto explains: “Based on our results, we suggest that for each docking site, there is a corresponding cluster of voltage-gated calcium channels. We propose a model in which each cluster of calcium channels is surrounded by enough free space to allow one synaptic vesicle to fuse in any direction.”
Ryuichi Shigemoto joined IST Austria as Professor in 2013. He and his group investigate the functional roles of ion channels and neurotransmitter receptors in neurons and glia using morphological, electrophysiological and molecular biological techniques. Shigemoto received an ERC Advanced Grant in 2016. Walter Kaufmann, Staff Scientist in IST Austria’s Electron Microscopy Facility, performed part of the research for the current study.
Bernhard Wenzl | idw - Informationsdienst Wissenschaft
If Machines Could Smell ...
19.07.2019 | Fraunhofer-Institut für Produktionstechnik und Automatisierung IPA
Algae-killing viruses spur nutrient recycling in oceans
18.07.2019 | Rutgers University
Adjusting the thermal conductivity of materials is one of the challenges nanoscience is currently facing. Together with colleagues from the Netherlands and Spain, researchers from the University of Basel have shown that the atomic vibrations that determine heat generation in nanowires can be controlled through the arrangement of atoms alone. The scientists will publish the results shortly in the journal Nano Letters.
In the electronics and computer industry, components are becoming ever smaller and more powerful. However, there are problems with the heat generation. It is...
Scientists have visualised the electronic structure in a microelectronic device for the first time, opening up opportunities for finely-tuned high performance electronic devices.
Physicists from the University of Warwick and the University of Washington have developed a technique to measure the energy and momentum of electrons in...
Scientists at the University Würzburg and University Hospital of Würzburg found that megakaryocytes act as “bouncers” and thus modulate bone marrow niche properties and cell migration dynamics. The study was published in July in the Journal “Haematologica”.
Hematopoiesis is the process of forming blood cells, which occurs predominantly in the bone marrow. The bone marrow produces all types of blood cells: red...
For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.
Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...
An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".
The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...
24.06.2019 | Event News
29.04.2019 | Event News
17.04.2019 | Event News
19.07.2019 | Physics and Astronomy
19.07.2019 | Physics and Astronomy
19.07.2019 | Earth Sciences