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About turn - Is there genuine hope of treating malaria at last?

点击量:   时间:2017-10-12 04:02:14

By Oliver Klaffke THE parasite that causes malaria has let slip clues to how resistant strains evade the drug chloroquine. The results have already led to tests of a new drug that may kill off all strains, chloroquine resistant or not. Previous research had shown that chloroquine binds to a transporter molecule in the membranes of bacteria. Michael Lanzer and his colleagues at the University of Würzburg suspected that the malaria parasite, plasmodium, uses a similar membrane transporter to absorb the drug. The team studied one such membrane molecule, an ion transporter that pumps sodium and hydrogen ions in and out of the cells. Their experiments showed that chloroquine triggers the transport mechanism, which shunts the drug into the cell. The researchers found that this ion transporter is less active in plasmodium strains that are resistant to chloroquine. While the drug normally activates its own uptake, in resistant plasmodium strains it knocks on doors in vain. “Only a little chloroquine gets inside, leaving plasmodium unharmed,” Lanzer says. The findings fit with the discovery of a gene whose mutation could be behind chloroquine resistance (This Week, 13 December 1997, p 11). Lanzer believes the gene codes for the membrane transporter he studied. However, Thomas Wellems of the National Institute of Allergy and Infectious Diseases near Washington DC, one of the team that discovered the gene, is not sure that the protein the gene codes for is really a transporter. “It can be also found in the vesicles inside plasmodium,” he says. “That’s not the place you would expect a carrier.” He argues that the protein may have several functions. The findings suggest a new way of treating malaria. Although the ion transporter normally helps chloroquine to get inside the parasite and kill it, blocking the transporter completely should make the parasite unable to regulate ion exchange, and it would die. In collaboration with Lanzer’s group,