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Cells' chemical switchboard isolated.

Just as the ear funnels sounds to where nerve endings can sense them, tiny chambers located on cell surfaces gather chemical signals and convey them into the cells. Researchers first observed these structures in cell membranes in the late 1950s, but only now have scientists isolated them, says Michael P. Lisanti, a cell biologist with the Whitehead Institute for Biomedical Research in Cambridge, Mass. The chambers, called caveolae, or "tiny caves," keep cells in touch with their neighbors and with their environment, he says.

By accident, Lisanti and his colleagues discovered that a particular detergent could dissolve most of a cell, leaving behind caveolae and the cell's internal framework, or cytoskeleton. Then they found that in a sugar solution, the cytoskeleton sinks while the lipid-laden caveolae float. This makes them easy to isolate and study, Lisanti's group reports in the August Journal of Cell Biology (Vol. 122, No. 4).

Copies of a protein called caveolin cluster to help form caveolae, he adds. Other researchers had shown that a virus can alter this protein, causing cells to become cancerous. Scientists can now try to determine whether this change affects how cells respond to growth-stimulating substances, says Lisanti.

Lisanti's group has found that many other kinds of messenger molecules hang out in caveolae, leading Lisanti to call these cavities signaling organelles. This cellular switchboard may relay many chemical messages to the cell's interior. For example, these messenger molecules suggest that caveolae play a key role in calcium-based signal systems and those involving sugar-containing lipids, called glycolipids. The new findings indicate that some pathogens exploit this access. For instance, bacterial toxins that lead to cholera and whooping cough home in on the glycolipids, then exert toxic effects by modifying signal proteins also in these chambers, Lisanti notes.
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Title Annotation:caveolae on cell surface collects chemical signals and transmits them into the cell
Publication:Science News
Article Type:Brief Article
Date:Aug 28, 1993
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