Cell Movement Studies Track Herpes to its Hideout
Many NIGMS-supported scientists focus on
individual cells the fundamental units of life. By studying
what happens inside, on, or around cells, researchers can reveal
life's most basic and essential activities how cells move,
divide, or communicate with each other.
Bearer's team injected herpes virus
particles into giant squid nerve cells to study how viruses
travel inside cells. The virus appears green because it is
labeled with a fluorescent protein. The round bead in the
middle of the cell is an oil droplet that marks the injection
site.
Photo: Elaine Bearer
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Take, for instance, the work of Elaine Bearer
of Brown University and her colleagues. Their studies of how cells
transport internal cargo revealed long-sought secrets about the
herpes virus.
Herpes is a major cause of infectious corneal
blindness as well as a host of other diseases ranging from cold
sores to life-threatening brain inflammation. The disease is especially
dangerous for infants and those with weakened immune systems.
Scientists already knew that even when a herpes
infection seems to have receded, the virus hides out in nerve cell
bodies, emerging periodically to cause new flare-ups. But until
Bearer's group made it clear, researchers didn't know exactly how
the virus travels from the nerve ending to the cell body.
The scientists track the virus as it travels in
giant squid nerve cells. These cells are research favorites because
they are enormous, making them easy to work with. Each cell is about
7 centimeters (2.75 inches) long and almost a millimeter wide
about the size of a small, straightened-out paper clip.
Bearer and her coworkers discovered that the virus
moves in one direction, and it travels at the same constant speed
as specialized cellular structures called organelles. The researchers
concluded that the virus takes over the nerve cells' own internal
transport machinery.
Other studies confirmed this, strongly suggesting
that the herpes virus plays the same trick in humans. Understanding
how the virus travels within nerve cells may lead to new treatments
for herpes infections. It also teaches us more about cellular transport,
a process that is essential to life.
Protein Fragments May Undergird
New Cystic Fibrosis Drug
Cystic fibrosis (CF) is one of the most common fatal genetic diseases
in the United States. Approximately 30,000 Americans have CF and
an estimated 8 million are carriers of it.
John Tomich of Kansas State University and his
colleagues designed protein fragments that may be the basis of a
new drug to treat CF. These fragments, called peptides, may substitute
for a protein that often malfunctions in those with the disease.
This protein is called cystic fibrosis transmembrane conductance
regulator, or CFTR.
CFTR is an "ion channel protein" that
controls the flow of chloride ions (a component of salt) into and
out of cells. When CFTR does not work properly, the balance of salt
inside cells is out of whack, leading to a buildup of abnormally
thick mucus that clogs the lungs, intestines, and pancreas. Those
with CF have trouble breathing and digesting food, and they frequently
suffer from persistent lung infections.
Tomich's team discovered that bits of a brain
protein similar in salt selectivity to CFTR can substitute for the
defective CFTR proteins. These brain peptides form chloride channels
that restore the salt balance in mice that have a genetic defect
similar to the one in most people with CF.
If researchers can develop a peptide that forms
chloride channels in those with cystic fibrosis, there's a chance
it could help treat the disease. Toward that end, Tomich's group
continues tweaking the brain peptides to improve their potential
as drugs, such as their ability to be delivered and absorbed by
cells. The scientists have already examined more than 100 variations
of the peptides. Tomich is also interested in using the same strategy
to treat other disorders, including stroke and epilepsy.
Rieder's research team uses fluorescent
dyes to label the dividing newt lung cells. The scientists
use newt lung cells in their studies because these cells are
large, easy to see into, and are biochemically similar to
human lung cells.
Photo: Conly Rieder
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Studies of Dividing Cells Uncloak Cancer Cause
One of the most dramatic activities that
cells accomplish is cell division, in which a cell must copy and
sort out evenly all of its genetic material (chromosomes), then
pinch itself in two. The complex dance performed by chromosomes
just before cell division fascinates Conly Rieder, a cell biologist
at The Wadsworth Center in Albany, New York. His team's work revealed
how asbestos, previously used in ceiling tiles and insulation, can
cause a wide variety of diseases, including lung cancer. By studying
dividing newt lung cells, Rieder and his coworkers discovered that
spear-like asbestos fibers can needle their way into the nucleus
of a cell, where they may snag, sever, or stab chromosomes. In rare
cases, the fibers may disturb chromosome sorting during cell division,
which can lead to cancer and other disorders. Once asbestos fibers
are lodged inside cells, they are passed on to each succeeding generation
of cells, continually increasing the risk of serious genetic damage.
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