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
Researchers identify how bacterium survives in oxygen-poor environments
22.11.2017 | Columbia University
Researchers discover specific tumor environment that triggers cells to metastasize
22.11.2017 | University of California - San Diego
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
22.11.2017 | Medical Engineering
22.11.2017 | Materials Sciences
22.11.2017 | Health and Medicine