Matrix stiffness regulates endosomal escape of uropathogenic E. coli

Area of Science:

• Microbiology
• Cell Biology
• Biophysics

Background:

• Uropathogenic E. coli (UPEC) invades bladder epithelial cells, escaping endosomes to form intracellular bacterial communities in vivo.
• In vitro models show UPEC trapped in endosomes, limiting proliferation, contrasting with in vivo observations.

Purpose of the Study:

• To investigate the role of extracellular matrix stiffness in UPEC endosomal escape and intracellular proliferation.
• To understand how substrate stiffness influences the actin cytoskeleton dynamics crucial for bacterial intracellular survival.

Main Methods:

• Utilized functionalized polyacrylamide substrates with varying stiffness to mimic physiological conditions.
• Investigated the involvement of the Rho GTPase RhoB and its effector PRK1 in the UPEC intracellular lifecycle.
• Quantified UPEC proliferation and endosomal escape in bladder epithelial cells cultured on substrates of different stiffness.

Main Results:

• Physiological substrate stiffness facilitated UPEC endosomal escape and rapid cytoplasmic proliferation.
• Inhibition of RhoB or PRK1 increased cytoplasmic bacterial growth, suggesting their role in limiting intracellular proliferation.
• RhoB protein levels were significantly reduced on substrates with physiological stiffness.

Conclusions:

• Tissue stiffness is a critical regulator of intracellular bacterial growth, influencing UPEC's ability to establish infection.
• The findings highlight the importance of the biophysical microenvironment in host-pathogen interactions.
• Cell culture models on stiffness-controlled substrates offer a valuable tool for studying uropathogen intracellular dynamics.