ERK pathway reactivation prevents anthrax toxin lethality in mice

Area of Science:

• Molecular Biology
• Pathogen-Host Interactions
• Biochemistry

Background:

• Bacillus anthracis lethal toxin (LT) inactivates MEK signaling pathways, disrupting ERK, p38, and JNK, leading to severe tissue damage and mortality.
• Current therapies for LT-induced damage post-internalization are limited.

Purpose of the Study:

• To engineer MEK variants resistant to LT proteolysis.
• To evaluate the therapeutic potential of these MEK variants in protecting against LT-induced damage.
• To investigate strategies for reactivating LT-disrupted signaling pathways.

Main Methods:

• Construction of MEK variants with modified LT proteolytic sites (MEK2(P10V/A11D), MEK3(I27D), MEK6(I15D)).
• Expression of MEK variants in cells and assessment of pathway signaling and cell survival upon LT treatment.
• Evaluation of MEK variant transgenic mouse survival following LT or B. anthracis challenge.
• Investigation of receptor tyrosine kinase engagement and growth factor administration (EGF, GM-CSF, FGF2) for pathway reactivation.

Main Results:

• Engineered MEK variants demonstrated resistance to LT proteolysis.
• Sustained activation of ERK and p38 pathways was observed in cells expressing MEK variants, promoting cell survival.
• MEK variant transgenic mice exhibited increased survival rates when challenged with LT or B. anthracis.
• Reactivation of the LT-disrupted ERK pathway was achieved via upstream receptor tyrosine kinases and a cocktail of EGF, GM-CSF, and FGF2, significantly improving mouse survival.

Conclusions:

• LT-mediated disruption of ERK and p38 pathways is critical for anthrax pathogenesis.
• Modified MEK variants offer a promising strategy for limiting LT-induced damage.
• Growth factor administration represents a potential therapeutic approach to counteract LT effects and enhance survival in anthrax.