Figure 2.

Opposing effects of anthrolysin, LF and EF on host cell apoptosis. Anthrolysin secreted by B. anthracis binds surface TLR4 receptors with downstream signaling through either TRIF and PKR to promote apoptosis, or through MEK to inhibit apoptosis; the latter inhibitory effect is opposed by LF cleaving MEK, thus promoting apoptosis. EF signals through the PKA and CREB pathway which has benefit in delaying apoptosis until the phagocytic host cell reaches the lymph node, an optimal niche for germination with further toxin release. Glossary: PKR, protein kinase regulated by RNA; PKA protein kinase A; CREB, cAMP response-element-binding protein; TRIF, TIR-domain-containing adapter-inducing interferon-β.