Anthrax toxin receptor 2 mediates Bacillus anthracis killing of macrophages following spore challenge

Banks, David J.; Barnajian, Moshe; Maldonado-Arocho, Francisco J.; Sánchez, Ana M.; Bradley, Kenneth A.

doi:10.1111/j.1462-5822.2005.00545.x

Cited by 80 publications

(99 citation statements)

References 44 publications

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“…As shown, the expression of ANTXR2 mRNA exceeds that of ANTXR1 mRNA by roughly 90-fold. This result is in qualitative agreement with recent finding by others [14,15].…”

Section: Assessment Of Mrna Levels Of Antxr1 and Antxr2 In Murine J77supporting

confidence: 83%

Transcriptional stimulation of anthrax toxin receptors by anthrax edema toxin and Bacillus anthracis Sterne spore

Hesek

Zeng

2007

Microbial Pathogenesis

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We used quantitative real-time RT-PCR to not only investigate the mRNA levels of anthrax toxin receptor 1 (ANTXR1) and 2 (ANTXR2) in the murine J774A.1 macrophage cells and different tissues of mice, but also evaluate the effect of anthrax edema toxin and Bacillus anthracis Sterne spores on the expression of mRNA of these receptors. The mRNA transcripts of both receptors was detected in J774A.1 cells and mouse tissues such as the lung, heart, kidney, spleen, stomach, jejunum, brain, skeleton muscle, and skin. The ANTXR2 mRNA level was significantly higher than that of ANTXR1 in J774A.1 cells and all tissues examined. The mRNA expression of both receptors in the lung was the highest among the tissues evaluated. Interestingly, the mRNA expression of both receptors in J774A.1 cells was up-regulated by edema toxin. In addition, ANTXR mRNA expression in the lung was down-regulated after subcutaneous inoculation of B. anthracis Sterne spores as well as after intranasal administration of anthrax toxin-based vaccine BioThrax™. These results suggest that anthrax edema toxin and B. anthracis Sterne spore are involved in the ANTXR mRNA regulation in host cells.

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“…As shown, the expression of ANTXR2 mRNA exceeds that of ANTXR1 mRNA by roughly 90-fold. This result is in qualitative agreement with recent finding by others [14,15].…”

Section: Assessment Of Mrna Levels Of Antxr1 and Antxr2 In Murine J77supporting

confidence: 83%

Transcriptional stimulation of anthrax toxin receptors by anthrax edema toxin and Bacillus anthracis Sterne spore

Hesek

Zeng

2007

Microbial Pathogenesis

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“…This peptide was isolated from a screen for its ability to bind ANTXR1, but the protection of R AW264.7 cells by AWPLSQLDHSYNfunctionalized liposomes suggested that this peptide also binds ANTXR2, because ANTXR2 is expressed in RAW264.7 cells (28). To test this possibility, we examined the binding of phage presenting the peptide AWPLSQLDHSYN to ANTXR1 and ANTXR2 by ELISA.…”

Section: Resultsmentioning

confidence: 99%

Polyvalent inhibitors of anthrax toxin that target host receptors

Basha

Rai

Poon

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Resistance of pathogens to antimicrobial therapeutics has become a widespread problem. Resistance can emerge naturally, but it can also be engineered intentionally, which is an important consideration in designing therapeutics for bioterrorism agents. Blocking host receptors used by pathogens represents a powerful strategy to overcome this problem, because extensive alterations to the pathogen may be required to enable it to switch to a new receptor that can still support pathogenesis. Here, we demonstrate a facile method for producing potent receptor-directed antitoxins. We used phage display to identify a peptide that binds both anthraxtoxin receptors and attached this peptide to a synthetic scaffold. Polyvalency increased the potency of these peptides by >50,000-fold in vitro and enabled the neutralization of anthrax toxin in vivo. This work demonstrates a receptor-directed anthrax-toxin inhibitor and represents a promising strategy to combat a variety of viral and bacterial diseases.antimicrobial resistance ͉ phage display ͉ therapeutics P athogens can develop resistance to drugs directed against microbial targets by modifying the drug, by lowering the concentration of drug that reaches the target, or by mutating the target (1, 2). There is also an increasing concern that therapeutics developed for bioterrorism agents may be rendered ineffective if the microbial target is altered intentionally. This problem could be overcome, however, by designing inhibitors that block host proteins used by the pathogen or its toxins to cause disease.Microbial pathogens and their products interact with host structures to facilitate colonization or to promote cellular uptake. Many of these interactions are polyvalent, meaning that they involve the simultaneous binding of multiple ligands on one entity to multiple receptors on another (3). The design of synthetic polyvalent (4-8) or oligovalent (9, 10) molecules also represents a promising approach to enhance the potency of inhibitors of microbial pathogens and toxins. Current examples of this approach have involved the design of molecules that bind directly to the pathogen or toxin. Inhibitors that bind host proteins would represent an effective way to attenuate virulence that may be less susceptible to resistance mechanisms, and the use of polyvalency could provide a significant enhancement in the potency of these inhibitors.ANTXR1 and ANTXR2 are host receptors that bind and internalize anthrax toxin (11,12). These proteins are likely important for anthrax pathogenesis because the toxin impairs the immune response and is responsible for the major symptoms and death associated with anthrax. Thus, blocking these receptors could represent a promising approach to anthrax therapy.ANTXR1 and ANTXR2 are widely expressed type I membrane proteins that bind components of the extracellular matrix (13). They both contain an extracellular I domain, which binds the protective antigen (PA) component of anthrax toxin. The two proteins are 40% identical overall and share 60% identity within ...

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“…In the initial stages of anthrax infection, toxin plays a role in facilitating spore germination (36)(37)(38). Once the vegetative infection is established, many cells are exposed to the toxin.…”

Section: Discussionmentioning

confidence: 99%

Receptor-specific requirements for anthrax toxin delivery into cells

Rainey

Wigelsworth

Ryan

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

119

157

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The three proteins that constitute anthrax toxin self-assemble into toxic complexes after one of these proteins, protective antigen (PA), binds to tumor endothelial marker 8 (TEM8) or capillary morphogenesis protein 2 (CMG2) cellular receptors. The toxin receptor complexes are internalized, and acidic endosomal pH triggers pore formation by PA and translocation of the catalytic subunits into the cytosol. In this study we show that the pH threshold for conversion of the PA prepore to the pore and for translocation differs by approximately a pH unit, depending on whether the TEM8 or CMG2 receptor is used. For TEM8-associated toxin, these events can occur at close to neutral pH values, and they show relatively low sensitivity to ammonium chloride treatment in cells. In contrast, with CMG2-associated toxin, these events require more acidic conditions and are highly sensitive to ammonium chloride. We show, furthermore, that PA dissociates from TEM8 and CMG2 upon pore formation. Our results are consistent with a model in which translocation depends on pore formation and pore formation, in turn, depends on release of PA from its receptor. We propose that because PA binds to CMG2 with much higher affinity than it does to TEM8, a lower pH is needed to attenuate CMG2 binding to allow pore formation. Our results suggest that toxin can form pores at different points in the endocytic pathway, depending on which receptor is used for entry.capillary morphogenesis protein 2 ͉ tumor endothelial marker 8 ͉ toxin entry B acillus anthracis, the causative agent of anthrax, secretes a toxin that is believed to be instrumental in causing anthrax disease symptoms leading to death. Anthrax toxin consists of three proteins, protective antigen (PA), which is a receptorbinding and pore-forming subunit; lethal factor (LF), which is a protease that cleaves mitogen-activated protein kinase kinase family members; and edema factor (EF), which is an adenylate cyclase that raises cAMP levels in cells (1). PA is synthesized as an 83-kDa protein (PA 83 ) for which two cell surface receptors have been identified: tumor endothelial marker 8 (TEM8) (2, 3) and capillary morphogenesis protein 2 (CMG2) (4). Two splice variant mRNAs derived from the TEM8 gene (sv1 and sv2) encode functional anthrax toxin receptors (2, 5). TEM8 expression has been documented in epithelium of the lung, intestine, and skin, the three routes of entry in anthrax infection (6). The CMG2 gene, which has been shown to be broadly expressed in different tissues (4), encodes three protein isoforms, two of which, CMG2 488 and CMG2 489 , are anthrax toxin receptors (4) (H.M.S., unpublished data).Receptor-bound PA 83 is cleaved by a cellular protease to generate a 20-kDa PA 20 subunit and a 63-kDa subunit (PA 63 ). The larger subunit assembles into the heptameric (PA 63 ) 7 prepore in lipid rafts (7-9). EF and LF bind to the prepore, and the toxin-receptor complexes are internalized by clathrindependent endocytosis and by other endocytic mechanisms (9, 10). These complexes are then exp...

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Anthrax toxin receptor 2 mediates Bacillus anthracis killing of macrophages following spore challenge

Cited by 80 publications

References 44 publications

Transcriptional stimulation of anthrax toxin receptors by anthrax edema toxin and Bacillus anthracis Sterne spore

Transcriptional stimulation of anthrax toxin receptors by anthrax edema toxin and Bacillus anthracis Sterne spore

Polyvalent inhibitors of anthrax toxin that target host receptors

Receptor-specific requirements for anthrax toxin delivery into cells

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