Think fast! Scientists unlock nerve speed secret

Jul 17, 2006

In the second it takes you to read these words, tens of thousands of vesicles in your optic nerves are released in sequence, opening tiny surface pores to pass chemical signals to the next cell down the line, telling your brain what you're seeing and your eyes where to move.

Thanks to two new studies – including one spearheaded by an undergraduate biochemistry student at Rice University and published online today by Nature Structural and Molecular Biology – scientists have defined the function of a key protein that nerve cells use to pass information quickly.

Like all cells in our bodies, nerve cells are encased in a membrane, a thin layer of fatty tissue that walls off the outside world from the cell's interior. And like other cells, nerve cells use a complex system of proteins as sensors, switches and activators to scan the outside world and decide when to open membrane doorways to take in food, expel waste and export chemical products to the rest of the body.

Many studies suggest that a group of proteins called SNAREs act like the cell's loading dock managers, deciding when to open the door to release shipments of chemical freight. SNAREs form a docking bay for cartons of chemicals encased in their own fatty membranes.

"Nerve cells are one of the few cells in our bodies in which vesicles are prepositioned at the cell membrane, because they have to be ready to release neurotransmitter to the next nerve cell at a moment's notice," said principal researcher James McNew, assistant professor of biochemistry and cell biology.

SNAREs are a key player in membrane fusion. They oversee the merger of the cell's outer membrane with the membrane encasing the chemical freight, and they do it in such a way that the freight can be exported, but no outside cargo can enter.

"With nerve cells, we've known that SNAREs provide the mechanical energy for membrane fusion, and another protein called synaptotagmin is the actuator," McNew said. "We also knew there was a chemical brake in the system, something that held the pre-positioned vesicle in check, but poised for release. These new studies clearly show that the brake is a protein called complexin."

Rice's study, which was conducted in McNew's lab, largely by undergraduate Johanna Schaub, involved in vitro experiments on a synthetic and highly controlled complex of membranes and proteins. Via these experiments, Schaub was able to show that SNARE-driven membrane fusion – the act that opens the door for neurotransmitter to leave the neuronal cell – was inhibited by complexin.

"By halting fusion partway, complexin essentially shortens the response time for signal transmission," said Schaub, who will begin graduate school at Stanford University in the fall. "The nerve cell can almost instantaneously pass on its information."

McNew said the finding is independently confirmed by work published online June 22 by Science magazine. In that study, Columbia University's James Rothman and colleagues created mutant cells with SNAREs on the outside rather than the inside, and they used the cells to show that complexin could inhibit fusion that would otherwise be expected to proceed.

"Complexin is the brake," McNew said. "It says, 'Stop. Don't go any further until you get the signal from synaptotagmin.'"

Source: Rice University

Explore further: For cells, internal stress leads to unique shapes

add to favorites email to friend print save as pdf

Related Stories

A novel mechanism for fast regulation of gene expression

Mar 18, 2014

Our genome, we are taught, operates by sending instructions for the manufacture of proteins from DNA in the nucleus of the cell to the protein-synthesizing machinery in the cytoplasm. These instructions are ...

Unlocking the brain's secrets using sound

Jan 22, 2014

(Phys.org) —The brain is a reclusive organ. Neurons the cells that make up the brain, nerves, and spinal cord communicate with each other using electrical pulses known as action potentials, but their interactions are complicated ...

Recommended for you

Chimpanzees prefer firm, stable beds

37 minutes ago

Chimpanzees may select a certain type of wood, Ugandan Ironwood, over other options for its firm, stable, and resilient properties to make their bed, according to a study published April 16, 2014 in the open-access ...

For cells, internal stress leads to unique shapes

1 hour ago

From far away, the top of a leaf looks like one seamless surface; however, up close, that smooth exterior is actually made up of a patchwork of cells in a variety of shapes and sizes. Interested in how these ...

Adventurous bacteria

2 hours ago

To reproduce or to conquer the world? Surprisingly, bacteria also face this problem. Theoretical biophysicists at Ludwig-Maximilians-Universitaet (LMU) in Munich have now shown how these organisms should ...

User comments : 0

More news stories

Chimpanzees prefer firm, stable beds

Chimpanzees may select a certain type of wood, Ugandan Ironwood, over other options for its firm, stable, and resilient properties to make their bed, according to a study published April 16, 2014 in the open-access ...

For cells, internal stress leads to unique shapes

From far away, the top of a leaf looks like one seamless surface; however, up close, that smooth exterior is actually made up of a patchwork of cells in a variety of shapes and sizes. Interested in how these ...

IBM posts lower 1Q earnings amid hardware slump

IBM's first-quarter earnings fell and revenue came in below Wall Street's expectations amid an ongoing decline in its hardware business, one that was exasperated by weaker demand in China and emerging markets.