Navigation Links
Researchers get a grip on nervous system's receptors
Date:2/7/2011

A digital signal processing technique long used by statisticians to analyze data is helping Houston scientists understand the roots of memory and learning, Alzheimer's and Parkinson's diseases and stroke.

Researchers at Rice University and the University of Texas Health Science Center at Houston (UTHealth) reported today in the journal Nature Chemical Biology that single molecule fluorescence resonance energy transfer (FRET) techniques combined with wavelet transforms have given them a new view of the AMPA receptor, a glutamate receptor and a primary mediator of fast signal transmission in the central nervous system.

Scientists have long thought these receptor proteins, which bind to glutamate to activate the flow of ions through the nervous system, are more than simple "on-off" switches. A "cleft" in the AMPA protein that looks and acts like a C-clamp and that binds the neurotransmitter glutamate may, in reality, serve functions at positions between fully open (off) and fully closed (on).

"In the old days, the binding was thought to be like a Venus flytrap," said Christy Landes, a Norman Hackerman-Welch Young Investigator Assistant Professor of Chemistry at Rice and lead author of the new paper. "The trap sat there waiting for something to come into the cleft. A neurotransmitter would come in and -- oops! -- it snapped shut on the molecule it was binding to, the gate opened up and ions would flow. We have all sorts of high-quality X-ray crystallography studies to show us what the snapped-open and snapped-shut cleft looks like."

But X-ray images likely show the protein in its most stable -- not necessarily its most active -- conformation, she said. Spectroscopy also has its limits: If half the proteins in an assay are open and half are shut, the measured average is 50 percent, a useless representation of what's really going on.

The truth, Landes said, is that the clefts of AMPA receptors are constantly opening and closing, exploring their space for neurotransmitters. "We know these proteins are super dynamic whether glutamate is present or not," she said. "And we need to look at one protein at a time to avoid averaging."

But seeing single protein molecules go through the motions is well beyond the capability of standard optical tools. That led the researchers to employ a unique combination of technologies. Vasanthi Jayaraman, an associate professor in UTHealth's Department of Biochemistry and Molecular Biology who studies chemical signaling, started the process when she used the binding domain of the AMPA receptor and attached fluorescent dyes to the points of the cleft in a way that would not affect their natural function.

Single-molecule FRET allowed Landes and her team to detect the photons emitted by the dyes. "These experiments had to be done in a box inside a box inside a box in a dark room," she said. "In a short period of measurement, we might be counting 10 photons."

The trick, she said, was to excite only one dye, which would in turn activate the other. "The amount of light that comes out of the dyes has a direct relationship to the distance between the dyes," Landes said. "You excite one, you measure both, and the relative amount of light that comes out of the one you're not exciting depends on how close they are."

Detecting very small changes in the distance between the two points over a period of time required calculations involving wavelets, a tool Rice mathematicians helped develop in the '70s and '80s. (Another recent paper by Landes and Taylor on their wavelet optimization method appears here.)

Wavelets allowed the researchers to increase the resolution of FRET results by reducing shot noise -- distortion at a particular frequency -- from the data. It also allowed them to limit measurements to a distinct time span -- say, 100 milliseconds -- during which the AMPA receptor would explore a range of conformations. They identified four distinct conformations in an AMPA receptor bound to a GluA2 agonist (which triggers the receptor response). Other experiments that involved agonist-free AMPA or AMPA bound to mutated glutamate showed an even floppier receptor.

Knowing how cleft positions match up with the function is valuable, said Jayaraman, who hopes to extend the technique to other signaling proteins with the ultimate goal of designing drugs to manipulate proteins implicated in neurological diseases.

"It was a beautiful combination," she said of the experiments. "We had done a lot of work on this protein and figured out the basic things. What was lacking was this one critical aspect. Being able to collaborate with a physical chemist (Landes) who had the tools allowed us to get details about this protein we wouldn't have seen otherwise."

"Physical chemistry, for all of its existence, amounts to coming up with new tricks to be able to calculate things that nature would not have us calculate," Landes said. "I think our true contribution is to be able to analyze this noisy data to get to what's underneath."


'/>"/>

Contact: David Ruth
druth@rice.edu
713-348-6327
Rice University
Source:Eurekalert

Related medicine news :

1. Researchers map all the fragile sites of the yeast Saccharomyces cerevisiaes genome
2. UH Case Medical Center researchers publish promising findings for advanced cervical cancer
3. Researchers discover new way to kill pediatric brain tumors
4. Researchers Who Discovered First Genes for Stuttering will Present Findings to the National Stuttering Association
5. Researchers create drug to keep tumor growth switched off
6. Urine protein test might help diagnose kidney damage from lupus, UT Southwestern researchers find
7. GUMC researchers say flower power may reduce resistance to breast cancer drug tamoxifen
8. Clemson researchers develop hands-free texting application
9. Researchers find biomarkers in saliva for detection of early-stage pancreatic cancer
10. Researchers chart genomic map spanning over 2 dozen cancers
11. Researchers discover second protective role for tumor-suppressor
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/12/2016)... ... February 12, 2016 , ... The ... Zuckerberg San Francisco General Hospital on April 5-7. The series is a multi-day, ... new habits. The workshops cover a broad range of topics, including coaching skills, ...
(Date:2/12/2016)... ... , ... Every winter, someone is killed, injured or loses a home in ... part of the Allegheny Health Network, has partnered with Etna Volunteer Fire Department, ... Space” campaign. , “Space Heaters Need Space” aims to bring awareness to ...
(Date:2/12/2016)... NC (PRWEB) , ... February 12, 2016 , ... AssureVest ... surrounding areas, is initiating a charity drive that will raise funds earmarked to purchase ... John C. Tayloe Elementary School. , “My school is in a low-income area and ...
(Date:2/12/2016)... Vail, Colorado (PRWEB) , ... February 12, 2016 , ... ... 164 ASC Industry Physician Leaders to Know in 2016 . The list consists of ... leaders nominated physicians to establish this list. , An Ambulatory Surgery Center, also ...
(Date:2/12/2016)... ... February 12, 2016 , ... Young Asset Protection, a full ... of the latest charity campaign in their community enrichment program. Art Expression utilizes ... worthy cause are currently being accepted at: http://artexpressioninc.org/ . , Art Expression ...
Breaking Medicine News(10 mins):
(Date:2/11/2016)...  Kindred Biosciences, Inc. (NASDAQ: KIN ), a ... of pets, today announced the submission to FDA of ... Application (NADA) for Zimeta™ (dipyrone injection, KIND-012).  Positive topline ... for the control of pyrexia (fever) in horses were ... --> The Chemistry, Manufacturing, and Controls ...
(Date:2/11/2016)... 11, 2016  Governor Andrew M. Cuomo today announced ... jobs throughout Western New York . ... SUNY Polytechnic Institute, includes a major expansion of Athenex,s ... Buffalo , as well as the creation ... Dunkirk . The combined projects are ...
(Date:2/11/2016)... SAN FRANCISCO , Feb. 11, 2016 Potrero ... system, is pleased to announce the appointment of George ... San Antonio, TX , WellMed is ... servicing over 200,000 patients and HMO members in ... founding WellMed in 1990 out of his own internal medicine ...
Breaking Medicine Technology: