ATP Depletion via Mitochondrial F₁F₀Complex by Lethal Factor is an Early Event inB. Anthracis-Induced Sudden Cell Death

Abstract

Bacillus anthracis' primary virulence factor is a tripartite anthrax toxin consisting of edema factor (EF), lethal factor (LF) and protective antigen (PA). In complex with PA, EF and LF are internalized via receptor-mediated endocytosis. EF is a calmodulindependent adenylate cyclase that induces tissue edema. LF is a zinc-metalloprotease that cleaves members of mitogen-activated protein kinase kinases. Lethal toxin (LT: PA plus LF)-induced death of macrophages is primarily attributed to expression of the sensitive Nalp1b allele, inflammasome formation and activation of caspase-1, but early events that initiate these processes are unknown. Here we provide evidence that an early essential event in pyroptosis of alveolar macrophages is LF-mediated depletion of cellular ATP. The underlying mechanism involves interaction of LF with F 1 F 0 -complex gamma and beta subunits leading to increased ATPase activity in mitochondria. In support, mitochondrial DNA-depleted MH-S cells have decreased F 1 F 0 ATPase activity due to the lack of F 0 6 and F 0 8 polypeptides and show increased resistance to LT. We conclude that ATP depletion is an important early event in LT-induced sudden cell death and its prevention increases survival of toxin-sensitive cells.

Pneumolysin induced mitochondrial dysfunction leads to release of mitochondrial DNA

“…Additionally, the T3SS effector VopE released by Vibrio cholerae also modulated mitochondrial dynamics by targeting of Miro GTPases 45 . The observation that enterohemorrhagic Escherichia coli hemolysin 46 , Helicobacter pylori effector protein VacA 47 , and Bacillus anthracis lethal factor 48 targeted mitochondria, thereby inducing malfunction of mitochondrial pathways critical for cell survival, further highlighted that mitochondria are primary targets for protein toxins released by human pathogenic bacteria.…”

Article Commentary: Increased Mitochondrial Activity in Anthrax-Induced Cell Death

“…In this issue, Boldogh and colleagues provide compelling evidence that LF enhances F 1 F 0 ATPase activity via directly interacting with β and γ subunits of the mitochondrial F 1 F 0 ATPase complex. The resultant ATPase activation leads to ATP depletion, a pivotal early event in cell death induced by LT. 5 Because the level of intracellular ATP plays an important role in rapid cytolysis (termed pyroptosis), including LT-induced cell death, Woodberry et al investigated the specific role of ATP depletion in cell death triggered by LT. First, they demonstrate that LT treatment causes ATP depletion and opening of the mitochondrial permeability transition pore (MPTP), followed by subsequent cell death in susceptible macrophages, but not in non-susceptible macrophages. The correlation between ATP depletion and MPTP opening led them to explore the possible direct interaction between LT and mitochondrial membrane protein complexes.…”

“…In this issue, Boldogh and colleagues provide compelling evidence that LF enhances F 1 F 0 ATPase activity via directly interacting with β and γ subunits of the mitochondrial F 1 F 0 ATPase complex. The resultant ATPase activation leads to ATP depletion, a pivotal early event in cell death induced by LT. 5 …”