Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

"Kiss-and-Run" Rules the Inner Lives of Neurons

05.06.2003


Neurons transmit chemical signals in a fleeting “kiss-and-run” process, which in large part determines how quickly neurons can fire, according to new studies by Howard Hughes Medical Institute researchers.

The transfer of information between nerve cells occurs when chemicals called neurotransmitters are released into the synapse, the junction between neurons. Electrical impulses in the neuron cause tiny vesicles loaded with neurotransmitters to move to the tip of the nerve terminal where they are released.

In an article published in the June 5, 2003, issue of the journal Nature, HHMI investigator Charles F. Stevens and Sunil Gandhi, both at The Salk Institute, reported that they have devised a technique that permits them to visualize individual vesicles after they have released their cargo. The new findings are significant, said the researchers, because they answer questions about the rate at which synaptic vesicles can be recycled. This rate determines how much information nerve cells can transmit.



Stevens and Gandhi have identified three distinct ways in which a used vesicle can be retrieved from the surface of the nerve cell once it has released its cargo. The fastest of these, called the “kiss-and-run” mode, takes less than a second; the slower “compensatory” mode takes up to 21 seconds; and the “stranded” mode leaves the vesicle stuck at the surface until the next nerve impulse triggers its retrieval.

According to Stevens, the latest findings settle lingering questions about how vesicle retrieval occurs. Early electron microscopy images of vesicles in synapses were interpreted as either a kiss-and-run model or one in which the vesicle is completely incorporated into the cell membrane, to be drawn back into the cell.

“The advance that we have made is to figure out a way of imaging individual vesicles so that we can measure the time course of single-vesicle events and immediately answer these questions,” said Stevens.

The optical recording technique devised by Stevens and Gandhi involves genetically modifying a gene for one type of vesicle protein to incorporate a special form of green fluorescent protein. This modified fluorescent protein, developed by other researchers, does not fluoresce under acidic conditions normally present in vesicles fully loaded with neurotransmitter. However, when the vesicle releases its payload, the interior becomes less acidic and the vesicle glows a bright green.

Thus, said Stevens, by imaging individual vesicles in cell cultures of neurons, it is now possible to detect how and when vesicles release their cargo at the synaptic membrane.

“Among the minor observations we made was that vesicles can re-acidify themselves in less than half a second,” said Stevens. “We also observed that the proteins in the vesicle are maintained together, so that when a vesicle is taken back in from the membrane, the same proteins are still there, even if the vesicle had been fused with the membrane for quite a while.

“And the third thing that was surprising is that all vesicles across different preparations have basically the same number of these tagged protein molecules,” said Stevens. “This means that they are either saturated or there is some mechanism for counting the proteins.”

The major observations from their studies, said Stevens, are that are three modes of vesicle release and retrieval from the membrane. “One is what you could call classical, when the vesicle opens to the outside world, stays open for about eight seconds, and then is taken back in at random times extending out to twelve or fourteen seconds,” he said. This finding confirms previous theories about modes of vesicle recycling, he said.

“However, sometimes if the vesicle failed to be re-internalized to be reused again by about fourteen or fifteen milliseconds, sometimes it got stuck there,” said Stevens. In this “stranded” mode, the vesicle remained stuck until another nerve impulse caused it to be zipped into the interior of the neuron to be recycled. Presumably, stranding occurs because vesicle recycling depends somehow on the level of calcium in the nerve cell, which rises precipitously during a nerve impulse, and drops afterward, said Stevens.

“The third recycling mode we observed was a kiss-and run-mode that happened very rapidly, in less than half a second,” said Stevens. “Also, we showed experimentally that in this mode there was a `fusion pore’ formed where the vesicle contacted the membrane,” he said.

Stevens and Gandhi also found that vesicles appear to adjust their mode of recycling based on the probability that a given synapse will trigger the release of a vesicle’s cargo. Vesicles in synapses with a low-release probability are more likely to use the rapid kiss-and-run mode, he said, while those vesicles in a higher-probability synapse use the slower compensatory mode.

Future studies will seek to determine the molecules responsible for recycling and how structures such as the fusion pore form. The researchers will also explore the role of calcium in recycling, as well as the advantages to the nerve cell of using the kiss-and-run recycling mode.

Jim Keeley | HHMI

More articles from Life Sciences:

nachricht New switch decides between genome repair and death of cells
27.09.2016 | University of Cologne - Universität zu Köln

nachricht A blue stoplight to prevent runaway photosynthesis
27.09.2016 | National Institute for Basic Biology

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: First quantum photonic circuit with electrically driven light source

Optical quantum computers can revolutionize computer technology. A team of researchers led by scientists from Münster University and KIT now succeeded in putting a quantum optical experimental set-up onto a chip. In doing so, they have met one of the requirements for making it possible to use photonic circuits for optical quantum computers.

Optical quantum computers are what people are pinning their hopes on for tomorrow’s computer technology – whether for tap-proof data encryption, ultrafast...

Im Focus: OLED microdisplays in data glasses for improved human-machine interaction

The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.

“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...

Im Focus: Artificial Intelligence Helps in the Discovery of New Materials

With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.

Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...

Im Focus: Complex hardmetal tools out of the 3D printer

For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.

Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...

Im Focus: Launch of New Industry Working Group for Process Control in Laser Material Processing

At AKL’16, the International Laser Technology Congress held in May this year, interest in the topic of process control was greater than expected. Appropriately, the event was also used to launch the Industry Working Group for Process Control in Laser Material Processing. The group provides a forum for representatives from industry and research to initiate pre-competitive projects and discuss issues such as standards, potential cost savings and feasibility.

In the age of industry 4.0, laser technology is firmly established within manufacturing. A wide variety of laser techniques – from USP ablation and additive...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Laser use for neurosurgery and biofabrication - LaserForum 2016 focuses on medical technology

27.09.2016 | Event News

Experts from industry and academia discuss the future mobile telecommunications standard 5G

23.09.2016 | Event News

ICPE in Graz for the seventh time

20.09.2016 | Event News

 
Latest News

New switch decides between genome repair and death of cells

27.09.2016 | Life Sciences

Nanotechnology for energy materials: Electrodes like leaf veins

27.09.2016 | Physics and Astronomy

‘Missing link’ found in the development of bioelectronic medicines

27.09.2016 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>