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A rat's eye lens with a developing cataract.
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Removing Damaged Proteins that Cloud Vision
By Rosalie Marion
August 2, 2005
Consuming a diet rich in antioxidants
found in fruits and vegetables could help stave off the breakdown of an
important mechanism through which eye lenses are cleared of damaged proteins,
according to research funded by the Agricultural Research Service. Efficient
removal or repair of damaged proteins within eye lenses is crucial to continued
Taylor and Fu Shang and their colleagues were the first to observe the
mechanism, called the ubiquitin-proteasome pathway, in cells within the eye's
lens, retina and cornea. They reported the findings in several peer-reviewed
Taylor is director of the
Nutrition and Vision Research, where he conducted the studies with Shang,
at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA)
at Tufts University in
When eye lenses accumulate too many damaged proteins, the resulting areas
that become cloudy or opaque are called cataracts. Although a successful
procedure for removing cataracts is available, cataract remains the leading
cause of blindness worldwide.
The ubiquitin-proteasome pathway helps balance a healthy concentration of
proteins within cells. Ubiquitin is an omnipresent protein that identifies
damaged proteins that are ripe for removal and attaches itself to them. These
"conjugated" proteins then latch onto proteasomes, or
protein-degrading enzymes, that in turn complete their function of clearing the
But highly active molecules, called free radicals, that damage cells
actually attack ubiquitin and other healthy proteins in the eye. Since a
healthy ubiquitin-proteasome pathway could be damaged by severe oxidative
stress, antioxidants, such as vitamins C and E, and antioxidant enzymes, such
as superoxide dismutase and catalase, may play an important role in protecting
Taylor and Shang are now examining ways in which antioxidant nutrients might
keep the pathway active longer.
more about this research in the August 2005 issue of Agricultural