Listeria monocytogenes Co-Opts the Host Exocyst Complex To Promote Internalin A-Mediated Entry

Area of Science:

• Microbiology
• Cell Biology
• Infectious Diseases

Background:

• Listeria monocytogenes invades intestinal cells via internalin A (InlA) binding to E-cadherin.
• Actin polymerization is known to be required for this entry process.
• The role of other host cell processes in Listeria internalization is not fully understood.

Purpose of the Study:

• To investigate whether host cell membrane trafficking processes, specifically polarized exocytosis, contribute to Listeria monocytogenes internalization.
• To determine the involvement of the exocyst complex in Listeria entry and E-cadherin function.

Main Methods:

• Live-cell imaging to observe exocytosis at sites of bacterial entry.
• Inhibition of N-ethylmaleimide-sensitive factor (NSF) to assess the role of exocytosis.
• RNA interference (RNAi) to deplete exocyst components (Sec6, Exo70, Exo84).
• Analysis of E-cadherin surface levels after exocyst depletion.

Main Results:

• Listeria monocytogenes internalization via InlA-E-cadherin interaction stimulates polarized exocytosis.
• Exocytosis is required for efficient Listeria entry, as shown by NSF inhibition.
• The exocyst component Exo70 is recruited to sites of Listeria entry.
• Depletion of exocyst proteins (Exo70, Exo84, Sec6) impairs Listeria entry without affecting E-cadherin levels.
• Homophilic E-cadherin interactions also trigger exocyst mobilization and exocytosis.

Conclusions:

• Ligation of E-cadherin by Listeria monocytogenes induces polarized exocytosis, which enhances bacterial uptake.
• The exocyst complex plays a crucial role in facilitating Listeria entry by promoting exocytosis.
• These findings suggest a potential role for the exocyst in regulating normal E-cadherin function in cell-cell adhesion.