Outlining Core Pathways of Amyloid Toxicity in Bacteria with the RepA-WH1 Prionoid

Area of Science:

• Microbiology
• Biochemistry
• Molecular Biology

Background:

• Amyloid proteinopathies, like those caused by prionoids, can affect various organisms.
• The synthetic bacterial prionoid RepA-WH1 induces a transmissible amyloid proteinopathy in Escherichia coli.
• Previous studies suggest RepA-WH1 may form pores in lipid membranes, potentially explaining bacterial cell death.

Purpose of the Study:

• To investigate the mechanism of RepA-WH1 toxicity in Escherichia coli.
• To compare the effects of different RepA-WH1 mutant variants on bacterial viability and cellular processes.
• To elucidate the pathway leading to bacterial cell death induced by RepA-WH1.

Main Methods:

• Comparative analysis of cytotoxic RepA-WH1 mutant variants (A31V and ΔN37).
• Measurement of intracellular osmotic pressure and bacterial viability under aerobic and anaerobic conditions.
• Systems approaches including analysis of proton motive force (PMF)-dependent transport, respiratory dehydrogenase activity (NdhII), and oxidative stress responses.

Main Results:

• RepA-WH1(A31V) expression reduced intracellular osmotic pressure and compromised bacterial viability.
• Impairment of PMF-dependent ion transport (Fe3+) and ATP synthesis was observed.
• Induction of the PMF-independent respiratory dehydrogenase NdhII occurred, leading to increased hydrogen peroxide (H2O2) production.
• Key oxidative stress defense proteins (OxyR, KatE) were sequestered by RepA-WH1(A31V) amyloid aggregates, inhibiting cellular defense mechanisms.

Conclusions:

• RepA-WH1 toxicity involves a primary membrane damage event that compromises cellular energetics.
• This leads to a secondary oxidative stress response exacerbated by the aggregation-dependent inactivation of crucial defense proteins.
• The bacterial proteinopathy caused by RepA-WH1 shares hallmarks with human amyloid diseases, offering a model for studying these conditions.