Steve Wright <[EMAIL PROTECTED]> writes:
Tuesday April 14 9:45 AM EDT
Atomic pictures offer new hope for common cold cure
By Maggie Fox
WASHINGTON (Reuters) - Researchers said Monday they had created an image of
the doorway used by the cold virus to infect human cells and said their
finding could lead to a better treatment for the common cold.
They used a technique known as x-ray crystallography to make an atomic map
of the receptor, a kind of chemical doorway, that the virus uses to infect
cells.
Reporting in the Proceedings of the National Academy of Sciences, they said
their finding could possibly lead to a treatment for the common cold, which
is currently incurable.
"By solving the structure of this receptor, we can gain insights into the
chemical and biological activity that occurs when a cold virus infects a
human cell," Michael Rossmann, a biology professor at Indiana's Purdue
University who led one of the studies, said in a statement.
But treatment would not be as simple as just blocking the doorway. The
receptor is also used by the body's immune cells, Rossmann said.
The receptor is called ICAM-1, for intracellular adhesion molecule one. It
consists of a single protein and looks like a five-part arm extending from a
"shoulder" in the cell's outside membrane.
Rossmann's team has so far figured out the structure of the first two parts
of the arm, known as domains, at the "hand" end where the virus attaches.
Timothy Springer and colleagues at Harvard Medical School came up with
similar findings, also reported in the Proceedings of the National Academy
of Science.
"Our study shows that the very top of the ICAM-1 molecule is shaped somewhat
like a hand, with a thumb and three projections or fingers," said Jordi
Bella, a researcher at Purdue who worked on the study.
Usually, the receptor molecules help hold infection-fighting immune cells in
place while they do their work after an injury or trauma. But the rhinovirus
responsible for 70 percent of human colds -- rhinovirus-16 -- has hijacked
the receptor to get into the cells it infects.
"Normally white blood cells bind to the thumb-like projections," Bella said.
"But the virus binds to the three finger-like projections, and interacts
with the receptor to gain entry into the cell."
Rossmann, who first mapped the structure of the cold virus in 1986, said
humans and chimpanzees may have unique ICAM-1 receptors, which would explain
why only people and their close relatives, the chimps, catch colds.
"The shell of the rhinovirus has deep crevices or canyons capable of
interacting with the finger-like projections of the ICAM-1 receptor,"
Rossmann said.
"The virus probably has adapted itself to be able to attach to this
particular molecule in humans, so that they fit in exactly, similar to a
lock and key."
After it latches onto a cell, the rhinovirus wraps itself around it,
attaching to even more of the ICAM receptors and injecting its genetic
material into the cell.
"If scientists could prevent that interaction from occurring, either by a
drug or genetic engineering techniques, we could eliminate a large
percentage of colds in humans without interfering with the normal function
of the ICAM-1 receptor," Rossmann said.
Other viruses responsible for colds use other receptors, so any treatment
based on their findings would only work against the 70 percent of colds
caused by rhinovirus-16.
^REUTERS@
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