Compiled by BioPhotonics staff
IRVINE, Calif. – The discovery of a second form of phototransduction
light sensing in cells that is derived from vitamin B2 could reveal new information
about cellular processes controlled by light.
Phototransduction – the conversion of light signals into
electrical signals in photoreceptive neurons – was believed for many years
to be solely based on a chemical derived from vitamin A called retinal. Now, however,
scientists from the University of California have determined that phototransduction
also can be mediated “by cryptochrome, a protein that uses a B2 vitamin
chemical derivative for light sensing.
The image shows blue-light-sensing arousal neurons, which for the first time have been linked to rapid phototransduction. Courtesy of the University of California, Irvine.
Cryptochromes are blue-light photoreceptors found in circadian
and arousal neurons that help to regulate slow biochemical processes. For the first
time, these proteins have been linked to rapid phototransduction. The findings open
the door to opportunities to adapt light-sensing proteins that could drive medically
relevant cellular activities, the investigators say.
The breakthrough – “which literally and figuratively
came ‘out of the blue,’ ” said researcher Todd C. Holmes –
has implications in the field of optogenetics. It is currently being used to understand
how treatments like deep brain massage can aid people with neurodegenerative diseases.
The team found that cryptochrome mediates phototransduction directly
in fruit fly circadian and arousal neurons in response to wavelengths of blue light.
In addition, the investigators genetically expressed the protein in the neurons
that are not ordinarily electrically responsive to light to make them light responsive.
Their work appears in the March 3, 2011, online Express site for the journal Science.