Receptor for anthrax toxin identified
A receptor for anthrax toxin on the surface of human
cells has been identified by American researchers. Identification of this
receptor, a 368-amino-acid protein, holds promise for developing new approaches
to treating anthrax, they say.
Dr Kenneth Bradley, McArdle Laboratory for Cancer
Research, University of Wisconsin, United States, and colleagues say that
the toxin secreted by Bacillus anthracis, which consists of three
protein components, helps the bacterium to evade the immune system. One
component of the toxin, protective antigen, binds to the extracellular
domain of the anthrax toxin receptor, enabling the rest of the toxin to
enter cells. They also found that, in vitro, a soluble version
of this domain protects cells from the toxin by inhibiting the toxin's
action (Nature 2001;414:225).
The researchers add that the receptor identified
can be used as a tool for identifying inhibitors of the protective antigen-receptor
interaction. "The identification of anthrax toxin receptor now allows
for a more detailed investigation of the mechanism of uptake by cells
of anthrax toxin," they say.
In a second study, Dr Andrew Pannifer, University
of Leicester, and colleagues analyse the structure of another component
of anthrax toxin, lethal factor, which, they say, is critical in the pathogenesis
of anthrax. The researchers say that lethal factor, an enzyme that inhibits
one or more signalling pathways in cells, is a "potential target for therapeutic
agents that would inhibit its catalytic activity or block its association
with protective antigen" (ibid, p229).
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