WIPF2 promotes Shigella flexneri actin-based motility and cell-to-cell spread

Area of Science:

• Cell biology
• Microbiology
• Infectious diseases

Background:

• Shigella flexneri spreads between colonic epithelial cells via actin-based motility.
• This process involves N-WASP (neural Wiskott-Aldrich syndrome protein) and the ARP2/3 complex for actin nucleation.
• The role of WIP (Wiskott-Aldrich syndrome protein family member) proteins in this process is controversial.

Purpose of the Study:

• To investigate the role of WIP family members in Shigella flexneri dissemination within human colonic epithelial cells.
• To determine if WIPF2 is essential for bacterial actin-based motility and cell-to-cell spread.

Main Methods:

• Used the human colonic epithelial cell line HT-29.
• Depleted WIPF2 using genetic methods.
• Quantified bacterial motility, actin tail formation, and N-WASP recruitment.
• Assessed the formation and resolution of membrane protrusions.

Main Results:

• WIPF2 was the sole WIP family member expressed in HT-29 cells.
• WIPF2 depletion significantly impaired S. flexneri dissemination.
• Reduced numbers of motile bacteria with actin tails and decreased bacterial velocity were observed.
• N-WASP recruitment to bacteria and subsequent actin nucleation were diminished.
• Fewer membrane protrusions successfully resolved into vacuoles for pathogen escape.

Conclusions:

• WIPF2 is essential for efficient Shigella flexneri cell-to-cell spread in colonic epithelial cells.
• WIPF2 plays a critical role in facilitating N-WASP recruitment and activation at the bacterial pole, enabling actin-based motility.
• The findings clarify the controversial role of WIP proteins in pathogen dissemination.