VopX, a novel Vibrio cholerae T3SS effector, modulates host actin dynamics

Area of Science:

• Microbiology
• Cell Biology
• Pathogenesis

Background:

• Pathogenic Vibrio cholerae strains employ diverse virulence factors for colonization and disease, including type III secretion systems (T3SS).
• T3SS effectors are crucial for manipulating host cells, but their specific functions in V. cholerae remain incompletely understood.
• VopX is a T3SS effector identified in a non-O1/non-O139 V. cholerae strain, implicated in altering host cell cytoskeleton.

Purpose of the Study:

• To elucidate the molecular target and mechanism of the V. cholerae VopX effector protein.
• To translate findings from yeast models to mammalian systems for understanding VopX function in host-pathogen interactions.
• To investigate the role of VopX in modulating host cell cytoskeletal dynamics and bacterial adherence.

Main Methods:

• Overexpression of VopX in HeLa cells to observe cytoskeletal changes.
• Co-culture of V. cholerae strain AM-19226 with polarized Caco-2/BBE monolayers.
• In vitro biochemical assays to determine VopX's enzymatic activity.
• Analysis of VopX's interaction with RhoA and MAPK signaling pathways.

Main Results:

• VopX overexpression induced significant cell rounding in HeLa cells.
• Co-culture with V. cholerae AM-19226 led to increased stress fibers, focal adhesions, and Caco-2/BBE cell adherence in a VopX-dependent manner.
• VopX was identified as a guanine nucleotide exchange factor (GEF) for RhoA, activating a MAPK signaling cascade.

Conclusions:

• VopX promotes enhanced cell-extracellular matrix adhesion by modulating host cell cytoskeleton via RhoA/MAPK signaling.
• This mechanism likely prevents host cell detachment, facilitating sustained bacterial colonization by T3SS-positive V. cholerae.
• VopX represents a unique virulence strategy involving cytoskeletal remodeling for productive infection.