Researchers have discovered a chemical reaction in the eye that may improve vision. A light-sensing pigment found in everything from bacteria to vertebrates can be biochemically manipulated to reset itself, an important therapeutic advantage.
This is according to the research from Case Western Reserve University School of Medicine. Researchers successfully used a modified form of vitamin A, called locked retinal, to induce the recycling mechanism and engage proteins central to human vision.
‘The newly discovered mechanism may enhance current approaches to treat retinal degenerative diseases and other nerve cell disorders’
The targeted proteins include light-sensing rhodopsin, which belongs to a family of proteins, G protein-coupled receptors, or GPCRs, that sit in cell membranes and transmit external cellular cues into internal cell signaling pathways. The discovery opens a new therapeutic opportunity for modified retinals that help improve vision, and offers a major improvement over current therapeutics designed to perturb cell signaling in the eye. "Our study demonstrates a complete transition from a one-way activation of a GPCR into a self-renewing, recycling activation mechanism by the mere addition of a cyclohexyl chemical group to the retinal. These findings exemplify the possibility of reprogramming GPCRs into self-renewing machines that can be controlled by external cues.
This biochemically induced function will be helpful in treating people with vision impairment, and opens up several avenues for more efficient GPCR-based therapeutics," said first author Sahil Gulati. "Our study shows how a chemical modification in the retinal can activate downstream visual signaling in a photocyclic manner. This chemical modification allows retinal to self-renew using thermal energy, and hence does not require any additional enzymes," Gulati said. The researchers discovered the self-renewing mechanism in bovine rhodopsin, which is exceptionally similar to human rhodopsin.
The researchers used purified proteins in their laboratory to show that their modified retinal binds to bovine rhodopsin and successfully activates specific human eye proteins in response to light, and when complete, it uses thermal energy to slowly return to its inactive form that can be repeatedly reactivated with light. The findings suggest that retinal molecules with the specific chemical structure could reversibly stimulate rhodopsin that drives human vision.
The newly discovered mechanism may enhance current approaches to treat retinal degenerative diseases and other nerve cell disorders. Researchers can biochemically tinker with the retinal and the retinal-bound rhodopsin molecules to improve their ability to turn on and off proteins in the eye. The study appears is the Proceedings of the National Academy of Sciences.