Sec and Tat Mediated Secretion Safeguards Mycobacterium tuberculosis Membrane Homeostasis

Area of Science:

• Microbiology
• Molecular Biology
• Cell Biology

Background:

• Protein secretion is crucial for Mycobacterium tuberculosis (Mtb) growth and virulence.
• The specific roles and organization of Mtb secretion pathways, including Sec, Tat, and ESX, are not fully understood.

Purpose of the Study:

• To curate a comprehensive list of secretory components and reactions in Mtb.
• To investigate the essentiality of SecA1 and Tat pathways for Mtb membrane homeostasis and survival.

Main Methods:

• Literature review, systematic queries, experimental data, and computational predictions were used to identify secretory components.
• CRISPR interference (CRISPRi) was employed for targeted depletion of SecA1 and TatAC.
• Label-free quantitative secretome and membrane proteomics analyses were performed.
• Electron microscopy was used to assess structural abnormalities.

Main Results:

• A curated list of 92 secretory components and 198 reactions across Sec, Tat, and ESX pathways was compiled.
• Depletion of SecA1 or TatAC significantly impaired Mtb in vitro growth and ex vivo survival.
• Secretome analysis revealed reduced substrate export and cytosolic protein enrichment upon SecA1/TatAC depletion, indicating membrane dysbiosis.
• Proteomics identified altered levels of metabolic and cell wall-associated proteins, suggesting compromised membrane integrity.
• Loss of SecA1/TatAC increased membrane permeability and caused structural defects, with TatAC depletion having a more pronounced effect.

Conclusions:

• The SecA1 and Tat pathways are essential for maintaining membrane homeostasis in Mycobacterium tuberculosis.
• These findings highlight the critical role of protein secretion pathways in Mtb viability.
• Essential secretory proteins represent promising therapeutic targets for combating tuberculosis.