Targeted Silencing of Anthrax Toxin Receptors Protects against Anthrax Toxins

• Published in: The Journal of biological chemistry Vol. 289; no. 22; pp. 15730 - 15738
• Main Authors: Arévalo, Maria T., Navarro, Ashley, Arico, Chenoa D., Li, Junwei, Alkhatib, Omar, Chen, Shan, Diaz-Arévalo, Diana, Zeng, Mingtao
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 30.05.2014; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Anthrax - genetics; Anthrax - prevention & control; Anthrax Toxin; Antigens, Bacterial - metabolism; Antigens, Bacterial - toxicity; Bacterial Toxin; Bacterial Toxins - metabolism; Bacterial Toxins - toxicity; Biomarkers, Tumor - genetics; Biomarkers, Tumor - metabolism; Bioterrorism; Gene Regulation; HEK293 Cells; Humans; Macrophage; Macrophages - cytology; Macrophages - physiology; Mice; Microfilament Proteins; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; Receptor; Receptors, Cell Surface - genetics; Receptors, Cell Surface - metabolism; Receptors, Peptide - genetics; Receptors, Peptide - metabolism; RNA Interference (RNAi); RNA Silencing; RNA, Small Interfering - genetics; RNA Silencing; Anthrax Toxin; Receptor; RNA Interference (RNAi); Bacterial Toxin; Macrophage
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.538587

Anthrax spores can be aerosolized and dispersed as a bioweapon. Current postexposure treatments are inadequate at later stages of infection, when high levels of anthrax toxins are present. Anthrax toxins enter cells via two identified anthrax toxin receptors: tumor endothelial marker 8 (TEM8) and capillary morphogenesis protein 2 (CMG2). We hypothesized that host cells would be protected from anthrax toxins if anthrax toxin receptor expression was effectively silenced using RNA interference (RNAi) technology. Thus, anthrax toxin receptors in mouse and human macrophages were silenced using targeted siRNAs or blocked with specific antibody prior to challenge with anthrax lethal toxin. Viability assays were used to assess protection in macrophages treated with specific siRNA or antibody as compared with untreated cells. Silencing CMG2 using targeted siRNAs provided almost complete protection against anthrax lethal toxin-induced cytotoxicity and death in murine and human macrophages. The same results were obtained by prebinding cells with specific antibody prior to treatment with anthrax lethal toxin. In addition, TEM8-targeted siRNAs also offered significant protection against lethal toxin in human macrophage-like cells. Furthermore, silencing CMG2, TEM8, or both receptors in combination was also protective against MEK2 cleavage by lethal toxin or adenylyl cyclase activity by edema toxin in human kidney cells. Thus, anthrax toxin receptor-targeted RNAi has the potential to be developed as a life-saving, postexposure therapy against anthrax. Existing anthrax postexposure antibiotic treatments are inadequate because they do not clear the high levels of secreted anthrax toxins. Susceptible cells treated with anthrax toxin receptor-targeted siRNAs became resistant to anthrax toxin-mediated cytotoxicity. RNAi-targeted silencing of anthrax toxin receptors prevents toxins from entering target cells and inducing pathogenesis. Toxin receptor-targeted RNAi can be developed as a postexposure treatment against anthrax.