NEWS OF THE WEEK SCIENCE
BREACHING THE INTESTINAL WALL Pathogen crosses intestinal barrier with help from a surface protein
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monocytogenes from contaminated food causes flulike symptoms. If untreated, these worsen to gastroenteritis, convulsions, even spontaneous abortions. From the mouth, the pathogen travels to the stomach, crosses the intestine, and spreads through the bloodstream. How it breaks through the intestine has been a subject of much research. A new study shows that the pathogen breaches the intestinal barrier through a surface protein that binds to a human protein on epithelial cells of the intestine. The work was carried out by Pascale Cossart and coworkers at the Pasteur Institute, in Paris [Science, 292,1722(2001)}. Previous in vitro studies had shown that the bacterial protein, called internalin, interacts with a receptor called E-cadherin on intestinal cells. Using animal models of the oral infection, the new study confirms that this protein-protein interaction is key to the pathogen's virulence. When the two proteins bind, the bacterium is "yanked inside the epithelial cells, which presumably lets the bacterium pass through the intestinal barrier and reach deeper tissue," B. Brett Finlay, a biotechnology professor at the University of British Columbia, tells C&EN. What's still unknown is how the bacterium finds E-cadherin, a protein that acts like a glue keeping epithelial cells together. Packed between cells, it is not readily accessible. One possibility is that cell-cell junctions may open briefly as cells migrate. Another is that some other proteins maybe destabilizing the barHTTP://PUBS.ACS.ORG/CEN
rier to provide access to E-cadherin. 'We are in the process of investigating this critical point," Cossart says. Internaliris uncompromising nature complicated the animal studies. Although the E-cadherin in humans binds internalin, those in rats and mice do not. The specificity originates from a difference of just one residue in the E-cadherins. Human E-cadherin has proline at position 16, the critical residue for binding internalin; in E-cadherins from rats and mice, glutamic acid occupies this position. For their animal models, the researchers turned to guinea pigs, which produce E-cadherin similar to that in humans, and to engi-
neered mice expressing human E-cadherin. They "are the first to make a transgenic mouse expressing a human receptor for a bacterial pathogen," Finlay notes in an accompanying Science commentary-MAUREEN ROUHI
DANGEROUS Listeria monocytogenes
EMPLOYMENT
ACS LaunchesJobSpectrum.org
W
ith the June 1 launch of JobSpectrum.org, the American Chemical Society is giving job seekers and recruiters another way to find each other. JobSpectrum.org is an employment site on the Web designed for the chemistry world. It aims to be comprehensive, and, as with other recruitment sites, it will be open to the public. The new service is a joint effort between the ACS Publications and Membership Divisions and is designed to complement the current ACS suite of career services and Chemical & Engineering News classified ads.
JobSpectrum.org is now accepting résumés and job postings. Résumés and open positions can be posted at http://www.jobspectrum.org. Services are free to job seekers. All recruitment
employers will be able to create a personal search agent that notifies them by e-mail when a résumé or job meeting their criteria is posted. C&EN will continue to pro-
Job Spectrum · org CHEMISTRY. CAREERS. C O N N E C T I O N S . announcements posted before Aug. 31 will be free as an introductory offer to employers. Job seekers will be able to search and apply for jobs online, and employers will be able to search the résumé database and receive online applications. In addition, job seekers and
vide the chemical enterprise with the most widely read print classified advertisements. C&EN classified ads are also posted online at http://pubs.acs.org/cen for two weeks for ACS members only and for two subsequent weeks at JobSpectrum.org. -LINDA RABER
C&EN
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4, 2001
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