What is known about Lou Gehrig's disease, as it is commonly called, is that misfolded and damaged proteins clump together in cells to form aggregates and motor neurons die. But scientists have long debated whether or not the protein aggregates actually kill the cells.

Now a research team at Northwestern University, using mammalian neurons and live-cell time-lapse spectroscopy, has become the first to clearly link the presence of the ALS-associated mutant SOD1 protein aggregates with neuronal cell death. This evidence could help explain the disease process and eventually lead to new therapeutics.

In the study, published this month in the Journal of Cell Biology, the scientists looked one at a time at neuronal cells expressing the mutant SOD1 protein and found that in cells where the protein accumulated and aggregates formed, 90 percent of the cells went on to die. (They died between six and 24 hours after aggregates were visually detected.) Cells that did not form aggregates did not die.

The study also provides a new understanding of the structure and composition of the deadly aggregates -- one of the first studies to do so.

"We found that these aggregates are quite peculiar and very different from the aggregates formed in Huntington's disease," said Richard I. Morimoto, Bill A. and Gayle Cook Professor in Biological Sciences, who led the study. Morimoto is an expert in Huntington's disease and on the cellular response to damaged proteins.

"In Huntington's, the aggregate is very dense and impenetrable and binds irreversibly with other molecules in the cell," he said. "In ALS, the aggregates are amorphous, like a sponge. Other proteins can go through the structure and i
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Contact: Megan Fellman
fellman@northwestern.edu
847-491-3115
Northwestern University
26-Oct-2005