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Caspase-1 activity affects AIM2 speck formation/stability through a negative feedback loop

C Juruj1, V Lelogeais, R Pierini

  • 1International Center for Infectiology Research, Université de Lyon Lyon, France.

Frontiers in Cellular and Infection Microbiology
|May 1, 2013
PubMed

Insights

The AIM2 inflammasome detects cytosolic bacteria like Francisella. Caspase-1 activity negatively regulates AIM2 complex formation, revealing a novel feedback loop before cell death.

Area of Science:

  • Innate immunity
  • Molecular and cellular immunology
  • Microbiology

Background:

  • The inflammasome is a key innate immune complex that activates caspase-1, promoting inflammation and cell death.
  • AIM2 (Absent in Melanoma 2) is a cytosolic sensor that detects foreign DNA, initiating inflammasome assembly.
  • Francisella tularensis, a bacterium causing tularemia, resides in the host cytosol, making it a target for inflammasome surveillance.

Purpose of the Study:

  • To investigate the regulation of AIM2 inflammasome assembly during Francisella infection.
  • To identify potential feedback mechanisms controlling inflammasome activation and stability.

Main Methods:

  • Macrophage infection models using wild-type (WT), ASC knockout (ASC(KO)), and Caspase-1 knockout (Casp1(KO)) cells.
  • Confocal microscopy to visualize AIM2 speck formation kinetics.
  • Biochemical assays to confirm regulatory interactions.

Main Results:

  • Faster AIM2 speck formation was observed in ASC(KO) and Casp1(KO) macrophages compared to WT macrophages upon Francisella novicida infection.
  • Biochemical validation confirmed a negative feedback loop regulated by ASC/caspase-1 on AIM2 complex formation and stability.
  • This regulatory mechanism precedes pyroptosis and depends on caspase-1's catalytic activity.

Conclusions:

  • ASC and caspase-1 negatively regulate AIM2 inflammasome assembly and stability, forming a feedback loop.
  • This regulation occurs before pyroptosis and requires caspase-1 enzymatic activity.
  • Sublytic caspase-1 activity may delay the formation of stable AIM2 inflammasome complexes, influencing cell death pathways.
Keywords:
AIM2Francisella tularensiscaspase-1inflammasomeregulation

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