Epithelial microvilli establish an electrostatic barrier to microbial adhesion

Area of Science:

• Cell Biology
• Microbiology
• Immunology

Background:

• Microvilli are apical membrane extensions on polarized epithelial cells.
• M cells, specialized for particle capture, lack microvilli, suggesting a role for microvilli in barrier function.
• Hypothesis: Microvilli increase surface charge density, repelling microbes and augmenting the mucosal barrier.

Purpose of the Study:

• To investigate the role of microvilli in bacterial adhesion and uptake.
• To test if microvilli electrostatic charges repel microbes.
• To understand the host-pathogen relationship in the context of microvilli and electrostatic interactions.

Main Methods:

• Development of polarized intestinal epithelial cells with reduced microvilli (microvillus-minus, MVM cells).
• Assessment of microbial particle adhesion and uptake by MVM cells compared to microvillus-positive cells.
• Expression of enterohemorrhagic Escherichia coli O157:H7 effector protein Tir in epithelial cells.

Main Results:

• MVM cells exhibited significantly enhanced adhesion and uptake of microbial particles compared to control cells.
• Microbial adhesion showed a linear relationship with bacterial surface charge, supporting electrostatic repulsion by microvilli.
• Tir expression induced microvilli loss and increased microbial binding, demonstrating pathogen manipulation of host cell surface.

Conclusions:

• Microvilli function as a crucial component of the mucosal barrier by utilizing electrostatic repulsion to prevent microbial adhesion.
• Reduced microvilli density enhances susceptibility to microbial invasion.
• Pathogen strategies targeting electrostatic interactions, like Tir expression, can contribute to virulence by compromising the microvilli barrier.