Host PIK3C3 promotes Shigella flexneri spread from cell to cell through vacuole formation

Area of Science:

• Microbiology
• Cell Biology
• Infectious Diseases

Background:

• Shigella flexneri causes bacillary dysentery by invading colonic epithelial cells and spreading between them.
• This cell-to-cell spread involves actin-based motility, forming membrane protrusions that resolve into vacuole-like protrusions (VLPs) and eventually double-membrane vacuoles (DMVs).

Purpose of the Study:

• To identify host factors critical for Shigella flexneri cell-to-cell dissemination.
• To elucidate the role of PIK3C3 in the vacuole-like protrusion to double-membrane vacuole transition.

Main Methods:

• Utilized HT-29 cells and an infant rabbit model of shigellosis.
• Employed live-fluorescence confocal microscopy to track bacterial spread and vacuole dynamics.
• Investigated the role of PIK3C3 inhibition on infection foci size and bacterial dissemination.

Main Results:

• PIK3C3 was identified as essential for Shigella flexneri cell-to-cell spread, decreasing infection foci size upon inhibition.
• PIK3C3 is required for the efficient resolution of VLPs into DMVs, involving PtdIns(3)P accumulation and Dynamin 2 recruitment.
• PIK3C3 inhibition also impacted Listeria monocytogenes dissemination, specifically at the vacuole escape stage.

Conclusions:

• PIK3C3 plays a critical role in Shigella flexneri dissemination by facilitating VLP maturation into DMVs via PtdIns(3)P and Dynamin 2.
• PIK3C3 inhibition effectively reduces Shigella flexneri spread in both cellular and animal models.