[ Back to EurekAlert! ] Public release date: 3-Mar-2011
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Contact: Tom Vasich
tmvasich@uci.edu
949-824-6455
University of California - Irvine

UCI researchers find new light-sensing mechanism in neurons

'Out of the blue' discovery marks new direction in phototransduction studies

IMAGE: This image shows blue-light sensing arousal neurons.

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Irvine, Calif. A UC Irvine research team led by Todd C. Holmes has discovered a second form of phototransduction light sensing in cells that is derived from vitamin B2. This discovery may reveal new information about cellular processes controlled by light.

For more than 100 years, it had been believed that the phototransduction process was solely based on a chemical derived from vitamin A called retinal. Phototransduction is the conversion of light signals into electrical signals in photoreceptive neurons and underlies both image-forming and non-image-forming light sensing.

In discovering this new light-sensing phototransduction mechanism, the UCI scientists found that phototransduction can also be mediated by a protein called cryptochrome, which uses a B2 vitamin chemical derivative for light sensing. Cryptochromes are blue-light photoreceptors found in circadian and arousal neurons that regulate slow biochemical processes, but this is the first time they have been linked to rapid phototransduction.

Their work appears March 3 on online Express site for the journal Science.

"This is totally novel mechanism that does not depend on retinal," said Holmes, a professor of physiology & biophysics. "This discovery opens whole new technology opportunities for adapting light-sensing proteins to drive medically relevant cellular activities."

This basic science breakthrough "which literally and figuratively came 'out of the blue,'" Holmes said has implications in the fast-growing field of optogenetics. Optogenetics combines optical and genetic research techniques to probe neural circuits at the high speeds needed to understand brain information processing. In one area, it is being used to understand how treatments such as deep brain massage can aid people with neurodegenerative diseases.

Holmes' team found that cryptochrome mediates phototransduction directly in fruit fly circadian and arousal neurons in response to blue-light wavelengths. The researchers also found that they could genetically express cryptochrome in neurons that are not ordinarily electrically responsive to light to make them light responsive.

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Keri Fogel, Kelly Parson and Nicole Dahm of UCI contributed to the study, which received National Institutes of Health support.

About the University of California, Irvine: Founded in 1965, UCI is a top-ranked university dedicated to research, scholarship and community service. Led by Chancellor Michael Drake since 2005, UCI is among the most dynamic campuses in the University of California system, with nearly 28,000 undergraduate and graduate students, 1,100 faculty and 9,000 staff. Orange County's largest employer, UCI contributes an annual economic impact of $4.2 billion. For more UCI news, visit www.today.uci.edu.

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