Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Loose coupling between calcium channels and sensors: A key mechanism underlying synaptic plasticity

07.02.2014
Science paper by IST Austria scientists reports first evidence for “microdomain” coupling at a mature central synapse and explores the implications for synaptic plasticity

In research published in this week’s online edition of Science (DOI: 10.1126/science.1244811), postdoc Nicholas Vyleta and Professor Peter Jonas of the Institute of Science and Technology Austria (IST Austria) uncover the existence of loose coupling between calcium channels and release sensors of exocytosis at a mature central synapse in the rodent brain. The researchers show that loose coupling provides a framework for presynaptic plasticity, a hallmark of synaptic signaling in hippocampal microcircuits.



Information transmission at the synapse between neurons is a highly complex, but at the same time very fast, series of events. When a voltage change, the so-called action potential, reaches the synaptic terminal in the presynaptic neuron, calcium flows through voltage-gated calcium channels into the presynaptic neuron. This influx leads to a rise in the intracellular calcium concentration. Calcium then binds to a calcium sensor in the presynaptic terminal, which in turn triggers the release of vesicles containing neurotransmitters into the synapse. The released neurotransmitter binds to postsynaptic receptors, leading to a response in the postsynaptic neuron. The coupling between calcium channels and sensors of exocytosis is key in determining the speed, timing and probability of synaptic transmission. Two forms of coupling occur in the brain: in tight, or „nanodomain“ coupling, channels and sensors are located very close to each other, with 10 to 20 nm distance, while in loose, or „microdomain“ coupling, channel and sensor are further apart, in the region of around 100 nm.

Previous research suggests that loose coupling occurs in synapses during early development, while tight coupling is observed in the mature central nervous system. In their current paper, Vyleta and Jonas ask whether, given the advantages of tight coupling – including the speed, temporal precision, fidelity and energy efficiency of synaptic transmission – any synapse in the mature central nervous system makes use of loose coupling? And if it does so, what are the consequences for the function of synaptic transmission?

A specific synapse in the hippocampus, the mossy fiber synapse on CA3 pyramidal neurons, which is accessible to direct recording using the patch-clamp method and shows a high degree of plasticity, was the focus in this research. To investigate whether loose or tight coupling occurs in this synapse, Vyleta and Jonas made use of calcium chelators, which capture calcium ions on their way from the source to the sensor, to investigate the timescale and distance of coupling. If only the fast-acting chelator, BAPTA, can inhibit exocytosis and synaptic transmission, but the slow chelator EGTA cannot, tight coupling is at work, while in loose coupling, both fast and slow chelators can inhibit transmission. As both fast and slow chelators suppress transmission in the synapse under investigation, results suggest loose coupling between channels and sensors, with a mean coupling distance of around 75 nm.

Why does loose coupling, which is likely slower and has less fidelity than tight coupling, exist in the mossy fiber-pyramidal neuron synapse? Further results by Vyleta and Jonas show that due to loose coupling, fast endogenous calcium buffers in the synapse can act as a brake on transmission, controlling how likely the initial release of neurotransmitter is. Loose coupling provides the time frame for endogenous buffers to act on synaptic transmission. The saturation of endogenous buffers after repeated stimulation may also promote facilitation, the phenomenon in which impulses are more likely to generate action potentials when they closely follow a prior impulse.

The new findings challenge the view that loose coupling is a developmental phenomenon, demonstrating instead that coupling is regulated in a synapse-specific way. Loose coupling is predominantly used at dynamic and plastic synapses, both in the developing and the mature brain. Together with fast endogenous calcium buffers, loose channel-sensor coupling may provide the molecular framework for presynaptic plasticity, a hallmark of hippocampal neurons.

Oliver Lehmann | EurekAlert!
Further information:
http://www.ist.ac.at

More articles from Life Sciences:

nachricht Moth takes advantage of defensive compounds in Physalis fruits
26.08.2016 | Max-Planck-Institut für chemische Ökologie

nachricht Designing ultrasound tools with Lego-like proteins
26.08.2016 | California Institute of Technology

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Streamlining accelerated computing for industry

PyFR code combines high accuracy with flexibility to resolve unsteady turbulence problems

Scientists and engineers striving to create the next machine-age marvel--whether it be a more aerodynamic rocket, a faster race car, or a higher-efficiency jet...

Im Focus: X-ray optics on a chip

Waveguides are widely used for filtering, confining, guiding, coupling or splitting beams of visible light. However, creating waveguides that could do the same for X-rays has posed tremendous challenges in fabrication, so they are still only in an early stage of development.

In the latest issue of Acta Crystallographica Section A: Foundations and Advances , Sarah Hoffmann-Urlaub and Tim Salditt report the fabrication and testing of...

Im Focus: Piggyback battery for microchips: TU Graz researchers develop new battery concept

Electrochemists at TU Graz have managed to use monocrystalline semiconductor silicon as an active storage electrode in lithium batteries. This enables an integrated power supply to be made for microchips with a rechargeable battery.

Small electrical gadgets, such as mobile phones, tablets or notebooks, are indispensable accompaniments of everyday life. Integrated circuits in the interiors...

Im Focus: UCI physicists confirm possible discovery of fifth force of nature

Light particle could be key to understanding dark matter in universe

Recent findings indicating the possible discovery of a previously unknown subatomic particle may be evidence of a fifth fundamental force of nature, according...

Im Focus: Wi-fi from lasers

White light from lasers demonstrates data speeds of up to 2 GB/s

A nanocrystalline material that rapidly makes white light out of blue light has been developed by KAUST researchers.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

The energy transition is not possible without Geotechnics

25.08.2016 | Event News

New Ideas for the Shipping Industry

24.08.2016 | Event News

A week of excellence: 22 of the world’s best computer scientists and mathematicians in Heidelberg

12.08.2016 | Event News

 
Latest News

Symmetry crucial for building key biomaterial collagen in the lab

26.08.2016 | Health and Medicine

Volcanic eruption masked acceleration in sea level rise

26.08.2016 | Earth Sciences

Moth takes advantage of defensive compounds in Physalis fruits

26.08.2016 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>