Enterococcus faecium secreted antigen A generates muropeptides to enhance host immunity and limit bacterial...

Area of Science:

• Microbiology
• Immunology
• Biochemistry

Background:

• Enterococcus faecium (E. faecium) enhances intestinal barrier function and pathogen tolerance.
• The precise biochemical mechanism behind E. faecium's beneficial effects was previously unknown.

Purpose of the Study:

• To elucidate the biochemical mechanism by which E. faecium and its enzyme SagA enhance intestinal barrier function and pathogen tolerance.
• To investigate the role of SagA's peptidoglycan hydrolase activity in activating host immune pathways.

Main Methods:

• Structural and biochemical studies of SagA.
• Analysis of E. faecium's peptidoglycan composition and remodeling activity.
• In vivo studies of E. faecium's effect on Clostridium difficile pathogenesis.

Main Results:

• E. faecium possesses unique peptidoglycan composition and remodeling activity mediated by SagA.
• SagA, a NlpC/p60-endopeptidase, generates smaller muropeptides that effectively activate nucleotide-binding oligomerization domain-containing protein 2 (NOD2).
• SagA secretion and its endopeptidase activity are crucial for enhancing probiotic activity against Clostridium difficile in vivo.

Conclusions:

• The peptidoglycan composition and hydrolase activity of specific gut bacteria can modulate host immune responses.
• E. faecium's SagA enzyme plays a key role in activating NOD2 signaling, thereby enhancing intestinal barrier function and pathogen tolerance.
• Targeting microbial hydrolase activity offers a potential strategy for improving host defense against enteric pathogens.