Caspase-11 and caspase-1 differentially modulate actin polymerization via RhoA and Slingshot proteins to promote...

Area of Science:

• Cellular Biology
• Immunology
• Microbiology

Background:

• Inflammasomes, including NOD-like receptors and caspase-1, are key immune signaling complexes.
• Caspase-1 and caspase-11 are implicated in phagolysosomal fusion, particularly during Legionella infection.
• The precise mechanisms by which these caspases influence intracellular trafficking remain incompletely understood.

Purpose of the Study:

• To elucidate the roles of caspase-11 and caspase-1 in regulating intracellular trafficking pathways.
• To investigate how these proteases modulate the actin cytoskeleton during pathogen vacuole dynamics.
• To determine the downstream targets and signaling cascades affected by caspase activity in Legionella infection.

Main Methods:

• Investigated the phosphorylation status of cofilin in response to Legionella infection.
• Utilized genetic knockouts of caspase-11 and caspase-1 to assess their necessity in trafficking.
• Examined the involvement of RhoA GTPase and Slingshot phosphatase in caspase-mediated cofilin regulation.

Main Results:

• Caspase-11 promotes cofilin phosphorylation via RhoA GTPase, while caspase-1 dephosphorylates cofilin through Slingshot phosphatase.
• Absence of caspase-11 leads to persistent actin polymerization, preventing phagolysosomal fusion.
• Absence of caspase-1 results in actin depolymerization, also averting phagolysosomal fusion.

Conclusions:

• Caspase-11 and caspase-1 exert opposing control over cofilin phosphorylation, a critical regulator of the actin cytoskeleton.
• These opposing actions converge on the actin machinery to precisely control vesicular trafficking, specifically phagolysosomal fusion.
• The interplay between caspase-11, caspase-1, and cofilin is essential for effective host defense against Legionella by mediating vacuole-lysosome fusion.