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Related Concept Videos

Caspases01:24

Caspases

Caspase, a family of cysteine proteases, serve as effectors in apoptosis. The ced3 gene in C.elegans was first identified to be involved in apoptosis. This gene encodes the ced-3 caspase that is similar to the interleukin-1-beta converting enzyme or ICE in mammals. In addition to apoptosis, caspases also function in the inflammatory response. Inflammatory caspases are essential in activating pro-inflammatory cytokines that recruit immune cells and block the replication of pathogens inside cells.
Allosteric Proteins-ATCase01:19

Allosteric Proteins-ATCase

Binding sites linkages can regulate a protein's function.  For example, enzyme activity is often regulated through a feedback mechanism where the end product of the biochemical process serves as an inhibitor.
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to  N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
The Intrinsic Apoptotic Pathway01:31

The Intrinsic Apoptotic Pathway

Internal cellular stress, such as cellular injury or hypoxia, triggers intrinsic apoptosis. The B-cell lymphoma 2 (Bcl-2) family of proteins are the primary regulators of the intrinsic apoptotic pathway. For example, during DNA damage, checkpoint proteins, such as Ataxia Telangiectasia Mutated (ATM protein) and Checkpoints Factor-2 (Chk2) proteins, are activated. These proteins phosphorylate p53 which further activates pro-apoptotic proteins, such as Bax, Bak, PUMA, and Noxa, and inhibits...
The JAK-STAT Signaling Pathway01:20

The JAK-STAT Signaling Pathway

Several cytokine receptors have tightly bound Janus kinase or JAK proteins attached at their cytosolic tail. Small signaling molecules such as cytokines, growth hormones, or prolactins bind to the cytokine receptors and initiate their dimerization. The dimerization brings the cytosolic JAKs together that trans-phosphorylate and activates each other. The activated JAKs now phosphorylate cytosolic tails of the cytokine receptors, which serve as binding sites for adaptor proteins such as  SH2...
Calmodulin-dependent Signaling01:16

Calmodulin-dependent Signaling

Calmodulin (CaM) is a calcium-binding protein in eukaryotes that controls various calcium-regulated cellular processes. It has four calcium-binding sites that bind calcium to form the calcium-calmodulin ( Ca2+-CaM) complex. GPCR stimulation increases the calcium levels in the cells that bind to CaM and induces a conformational change.
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
Regulation of the Unfolded Protein Response01:31

Regulation of the Unfolded Protein Response

Inositol-requiring kinase one or IRE1 is the most conserved eukaryotic unfolded protein response (UPR) receptor. It is a type I transmembrane protein kinase receptor with a distinctive site-specific RNase activity. As the binding mechanics of the misfolded proteins with the N-terminal domain of IRE-1 are unclear, three binding models — direct, indirect, and allosteric -- are proposed for receptor activation. Nevertheless, it is known that once a misfolded protein associates with IRE1, it...

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Updated: May 11, 2026

Lighting Up the Pathways to Caspase Activation Using Bimolecular Fluorescence Complementation
08:47

Lighting Up the Pathways to Caspase Activation Using Bimolecular Fluorescence Complementation

Published on: March 5, 2018

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
Summary
This summary is machine-generated.

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

Keywords:
AIM2Francisella tularensiscaspase-1inflammasomeregulation

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Related Experiment Videos

Last Updated: May 11, 2026

Lighting Up the Pathways to Caspase Activation Using Bimolecular Fluorescence Complementation
08:47

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Published on: March 5, 2018

Exploring Caspase Mutations and Post-Translational Modification by Molecular Modeling Approaches
05:56

Exploring Caspase Mutations and Post-Translational Modification by Molecular Modeling Approaches

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Measuring Caspase Activity Using a Fluorometric Assay or Flow Cytometry
05:29

Measuring Caspase Activity Using a Fluorometric Assay or Flow Cytometry

Published on: March 24, 2023

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.