A c-di-AMP-controlled glutamine synthesis pathway promotes persistence of Staphylococcus aureus thymidine-dependent...

Area of Science:

• Microbiology
• Infectious Diseases
• Bacterial Pathogenesis

Background:

• Children with cystic fibrosis (CF) frequently harbor Staphylococcus aureus thymidine-dependent small-colony variants (TD-SCVs).
• TD-SCVs are linked to decreased lung function and increased respiratory issues in CF patients.
• The survival mechanisms of TD-SCVs in the thymidine-limited CF lung remain unclear.

Purpose of the Study:

• To investigate how TD-SCVs survive in the thymidine-limited environment of the CF lung.
• To elucidate the molecular pathways governing TD-SCV survival and growth.
• To identify potential therapeutic targets for combating S. aureus TD-SCV infections.

Main Methods:

• Studied TD-SCV glutamine uptake and de novo synthesis pathways.
• Investigated the role of cyclic di-AMP (c-di-AMP) in regulating glutamine synthesis.
• Utilized murine models to assess TD-SCV survival and growth.
• Examined the effect of GlnA inhibition on TD-SCV proliferation.

Main Results:

• TD-SCVs exhibit impaired glutamine uptake and rely on c-di-AMP-regulated de novo glutamine synthesis for survival.
• Transcription of the glutamine synthetase gene (glnA) is repressed by GlnR, PstA, and GlnA.
• Glutamine starvation increases c-di-AMP levels, relieving repression and promoting glutamine synthesis.
• Reduced c-di-AMP levels impair TD-SCV growth, which is rescued by glnA overexpression.
• Pharmacological inhibition of GlnA significantly hinders TD-SCV growth in vivo.

Conclusions:

• The study reveals the molecular mechanism of S. aureus TD-SCV survival in CF lungs, highlighting reliance on glutamine synthesis.
• Cyclic di-AMP (c-di-AMP) plays a crucial role in regulating glutamine synthesis in response to nutrient availability.
• Glutamine synthetase (GlnA) is identified as a promising therapeutic target for treating infections caused by antifolate-resistant bacteria like S. aureus TD-SCVs.