Anthrax toxin receptor proteins.

Anthrax toxin is a key virulence factor for Bacillus anthracis, the causative agent of anthrax. Here we discuss what is known about the anthrax toxin receptor (ATR), the cellular receptor for anthrax toxin, and how this information is being used to develop treatments for anthrax as well as to understand aspects of cancer. ATR was identified recently as a type I transmembrane protein with unknown function that contains an extracellular integrin-like inserted (I) domain. The ATR I domain contains the toxin binding site, and a soluble form of this domain was shown to serve as an effective antitoxin to protect cultured cells from toxin action. ATR is encoded by the tumor endothelial marker 8 (TEM8) gene, which is selectively up-regulated during blood vessel formation and in tumor vasculature, raising the possibility that this protein normally functions in angiogenesis. Therefore, identification of the cellular receptor for anthrax toxin has made possible new avenues of research in the areas of anthrax pathogenesis, antitoxin development, and cancer biology.