Rickettsia Sca4 Reduces Vinculin-Mediated Intercellular Tension to Promote Spread

Area of Science:

• Microbiology
• Cell Biology
• Pathogen-Host Interactions

Background:

• Spotted fever group (SFG) rickettsiae are human pathogens that infect vascular cells.
• Bacterial dissemination often relies on actin-based motility for cell-to-cell spread.
• SFG rickettsiae spread involves protrusion formation, engulfment, and vacuolar escape.

Purpose of the Study:

• To investigate the mechanism of cell-to-cell spread employed by SFG rickettsiae, specifically Rickettsia parkeri.
• To identify bacterial factors involved in SFG rickettsiae dissemination.
• To elucidate how Rickettsia parkeri manipulates host cell processes to spread through tissues.

Main Methods:

• Transposon mutagenesis was used to identify key bacterial effectors.
• Interaction studies were performed to map protein-protein interactions (Sca4, vinculin, α-catenin).
• Traction and monolayer stress microscopy were employed to analyze host cell mechanics.

Main Results:

• Rickettsia parkeri typically lacks actin tails during cell spread.
• The secreted effector Sca4 promotes protrusion engulfment by interacting with vinculin and disrupting vinculin-α-catenin binding.
• Sca4 reduces vinculin-dependent mechanotransduction at cell-cell junctions, lowering intercellular tension.

Conclusions:

• SFG rickettsiae, like Rickettsia parkeri, utilize a unique strategy for dissemination that does not rely on actin-based motility.
• The effector Sca4 plays a critical role in facilitating spread by reducing host intercellular tension.
• This mechanism represents a novel approach to manipulating host cytoskeletal forces for pathogen spread.