A noncanonical polyamine from bacteria antagonizes animal mitochondrial function.

Area of Science:

• Microbiology
• Biochemistry
• Animal Physiology

Background:

• Polyamines from gut bacteria interact with human intestinal cells, potentially influencing Irritable Bowel Syndrome with Diarrhea (IBS-D) and inflammatory bowel diseases (IBD).
• Molecular mechanisms behind these interactions are often unclear due to limitations in studying polyamine functions in vivo.

Purpose of the Study:

• To develop novel methods for studying polyamine metabolism in bacteria and its effects on animal systems.
• To identify novel bioactive polyamine metabolites produced by gut bacteria and elucidate their mechanisms of action.

Main Methods:

• Development of a Caenorhabditis elegans-based screening platform.
• Application of a modified Liquid Chromatography-Mass Spectrometry (LC-MS) approach for polyamine metabolite profiling.
• In vivo studies in animal models to assess the bioactivity of identified metabolites.

Main Results:

• Discovery of N1-Aminopropylagmatine (N1-APA), a noncanonical polyamine intermediate, accumulating due to dysfunctional bacterial polyamine metabolism (in E. coli and B. subtilis).
• N1-APA is produced via spermidine synthase (SpeE) and is bioactive, antagonizing animal development and mitochondrial function.
• N1-APA is transported into intestinal cells via CATP-5 and functions similarly to deoxyhypusine synthase inhibitor GC7, inhibiting eIF5A hypusination and macrophage activation.

Conclusions:

• N1-APA is the first identified bioactive metabolite produced by bacteria that mimics the function of deoxyhypusine synthase inhibitors.
• This finding provides a potential mechanistic link between the loss of speB in gut microbes and the development of inflammatory bowel disease (IBD).
• The study highlights the importance of bacterial polyamine metabolism in host-microbe interactions and disease pathogenesis.