Monday, November 06, 2006
LOS ANGELES, Nov. 3 (UPI) -- A newly discovered protein called Par-3 plays an important role in creating the myelin sheaths on nerves outside the spinal cord, and might help clinicians create treatments for serious neurological disorders like multiple sclerosis and other conditions like numbness and/or pain in the arms and legs from vitamin deficiencies, and diabetes.
Lead researcher Jonah Chan, of the Zilkha Neurogenetic Institute at the University of Southern California in Los Angeles, told United Press International that myelin sheaths insulate the nerves the way plastic coatings insulate electrical wires, and keep nerve impulses flowing in the right direction instead of shorting out before they reach their goal.
He said that, while scientists know a great deal about outside factors that affect nerve transmission, such as alcohol and environmental pollutants, the mechanisms inside the cell that transmit neural impulses have not been studied.
The team used innovative cell culture techniques pioneered by Richard Bunge at Washington University in St. Louis to perform their work. Since the myelin sheaths of peripheral nerves form soon after birth, Chan and his team used Bunge's techniques to purify neurons and myelin-producing Schwann cells from developing rats and mice, then placed both preparations in a culture dish. The team then watched while the Schwann cells created sheaths around the neurons. They noticed that, as soon as the long, thin exploring arm of a neuron, called an axon, made contact with a Schwann cell, a protein they later called Par-3 moved through the Schwann cell cytoplasm and stopped at the place where the two cells touched.
The protein drew other proteins, receptors on the Schwann cell's outer membrane, and certain molecules to the site so the Schwann cell could communicate with the axon more efficiently.
"Essentially, Par-3 set up a receiving station inside the Schwann cell that picked up signals from the neuron," Chan told UPI. "Once the signals were received, the Schwann cell began producing myelin and started wrapping the nerve."
Chan said being able to define the process might make it possible to modify it in the future.
"By understanding the fundamental mechanisms that are involved in the process of myelination, hopefully one day we will be able to tell a cell when and where to form myelin," Chan told UPI. "That's our ultimate goal."
Robert Fox, medical director of the Mellen Center for Multiple Sclerosis at the Cleveland Clinic said he was impressed with the study.
"Chan's work seems a very reasonable demonstration of how the myelin-making Schwann cell starts its interactions with the axon and creates the myelin sheath," Fox told UPI. "Up to this point in time, we've had a limited understanding of how this happens. This study provides some new information about the molecular mechanisms that produce myelination and could lead to treatments for peripheral neuropathies."
Details of the study appear in the November 3 issue of the journal Science.
Copyright 2006 by United Press International. All Rights Reserved.