Without nuts and bolts, bridges and buildings would be nothing more than piles of beams and girders. Like skyscrapers, cells have internal support systems, but instead of steel, cells use a variety of rod-like protein fibers for their microscopic cytoskeletons.

At the University of Chicago, scientists interested in skin disorders caused by a weakening of the cytoskeleton have long known that a group of bolt-like proteins called plakins, brace the intermediate filaments. Of the three filamentous systems of the cytoskeleton, intermediate filaments have a diameter that places them between the microfilaments (think of them as high tension wires) and microtubules (the I-beam of the cell).

Now, researchers led by Elaine Fuchs, PhD, Amgen Professor of Molecular Genetics & Cell Biology and Howard Hughes Investigator, report in the July 23 issue of Cell, that plakins bind to all three components of the cytoskeleton, providing an integrated bracing system that gives cells their strength and flexibility.

This important finding sheds new light on how nerve axons, which in humans can reach as much as a meter in length for a single neuron, maintain their rigidity and allow for the transport of neurotransmitter-filled vesicles from one end to the other.

"We have known for several years that plakins give intermediate filaments their mechanical strength by anchoring them to the actin cytoskeleton just inside the cellular membrane, and that plakins also can stabilize intercellular junctions by linking them to the cytoskeleton," says Fuchs "But now we are seeing how truly versatile these fascinating plakin proteins are in that some of them can bind to and stabilize microtubules."

An important component of the cytoskeleton, microtubules serve as the cellular highway for the transport of vesicles and other proteins. "Stabilizing microtubules is especially important for cells like neurons which need to transport vesicles over very long distances," Fuchs
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Contact: Sharon Parmet
sparmet@mcis.bsd.uchicago.edu
773-702-6241
University of Chicago Medical Center
23-Jul-1999