Im****tant discovery that increases understanding of multiple sclerosis
15 Sep 2004
Scientists at the University of California, Santa Barbara have made an
im****tant discovery that will increase the understanding of multiple
sclerosis, a debilitating disease of the central nervous system in
which the myelin sheath, an insulating membrane surrounding the nerve
cells in the brain and spinal cord, start to unravel for reasons as
yet unknown.
In a paper appearing in today's issue (Sept. 14) of the Proceedings of
the National Academy of Science, several UC Santa Barbara researchers
describe the results of a study that shows why the unraveling occurs.
The myelin sheath is made up of a lipid bilayer (similar to those
making up the cell membrane) wrapped many times around the nerve axon
-- the part of a nerve cell through which impulses travel away from
the cell body.
One specific protein, called myelin basic protein, acts to hold the
myelin sheath together tightly around the axon. The axons serve as the
electrical wires that connect the nerve cells, and the myelin serves
as the insulation to keep the electrical impulses flowing quickly and
reliably.
"If the myelin breaks down, for whatever reason, the nerve electrical
impulses leak out, slow down, and generally don't work very well,"
says Joe Zasadzinski, professor of chemical engineering at UCSB.
Zasadzinski, with co-authors Jacob Israelachvili, professor of
chemical engineering, graduate student Yufang Hu and postdoctoral
fellow Ivo Doudevski, and Cynthia Husted, director of UCSB's Center
for the Study of Neurodegenerative Disorders write that "We have
discovered that in the progression of MS, there are small changes in
the lipid composition of myelin. There is less negatively-charged
lipid in the membrane and more neutral, or uncharged, lipids. Myelin
basic protein is positively charged and gets in between the bilayers
to link up the negatively-charged lipids and glue the myelin sheath
together."
The scientists explain that the tightest seal occurs when the amount
of negative charge from the lipids just match the amount of positive
charge from the protein. If there is too much of either one, then the
bilayers start to repel each other rather than bind.
"Although we can't say why the lipid composition changes, now with
this new knowledge, perhaps we can suggest methods of trying to treat
the unraveling before it gets too far along," Zasadzinski says.
Zasadzinski, Husted and Israelachvili also discovered that the myelin
basic protein acts as a patch to fill in any holes in the myelin
bilayers. "It is similar to the stuff you put in your tires to fix
punctures," Zasadzinski explains. "The myelin basic protein floats
around until it finds a hole, binds to the edge of the hole and then
pushes the lipids to fill in the hole, insuring good insulation from
the myelin sheath."
Joe Zasadzinski can be reached at 805-893-4769 Or
gorilla@[EMAIL PROTECTED]
Joan Magruder
joan.magruder@[EMAIL PROTECTED]
of California - Santa Barbara
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