Related Experiment Video

Updated: Aug 19, 2026

Visualization of Bacterial Toxin Induced Responses Using Live Cell Fluorescence Microscopy
14:29

Visualization of Bacterial Toxin Induced Responses Using Live Cell Fluorescence Microscopy

Published on: October 1, 2012

Proteolytic activation of bacterial toxins by eukaryotic cells is performed by furin and by additional cellular

V M Gordon1, K R Klimpel, N Arora

  • 1Laboratory of Microbial Ecology, National Institute of Dental Research, Bethesda, Maryland 20892.

Infection and Immunity
|January 1, 1995
PubMed

Insights

Furin activates anthrax toxin protective antigen (PA), Pseudomonas exotoxin A (PE), and diphtheria toxin (DT) by cleaving specific sites. Furin-deficient cells show resistance to PE and PA mutants, indicating furin

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Background:

  • Proteolytic cleavage is essential for activating bacterial toxins like anthrax toxin protective antigen (PA), Pseudomonas exotoxin A (PE), and diphtheria toxin (DT) before intoxication.
  • Furin, a proprotein convertase, has been previously implicated in the activation of PA and DT.
  • Understanding the specific proteases involved in toxin activation is crucial for developing targeted interventions.

Purpose of the Study:

  • To characterize the role of furin and other eukaryotic proteases in the activation of PA, PE, and DT.
  • To investigate the functional consequences of furin deficiency on cellular sensitivity to these toxins.

Main Methods:

  • Utilized Chinese hamster ovary (CHO) cells, including wild-type and furin-deficient variants, selected via chemical mutagenesis.
  • Assessed toxin potency (EC50) using PA cleavage site mutants and modified lethal factor constructs.
  • Performed in vitro cleavage assays with purified furin and analyzed toxin sensitivity in furin-deficient and furin-transfected cells.

Main Results:

  • In vitro studies confirmed that native PA and a specific PA mutant (RAAR) are substrates for furin.
  • Furin-deficient CHO cells exhibited resistance to PE and PA mutants but remained sensitive to DT and wild-type PA.
  • Transfection of furin-deficient cells with the furin gene restored sensitivity to PE and PA mutants.

Conclusions:

  • Furin plays a significant role in activating PA and PE, and potentially DT.
  • Additional cellular proteases contribute to the activation of DT and PA, suggesting a complex proteolytic network.
  • These findings highlight the importance of furin in bacterial toxin activation and provide insights for therapeutic strategies.

More Related Videos

Implementation of a Permeable Membrane Insert-based Infection System to Study the Effects of Secreted Bacterial Toxins on Mammalian Host Cells09:25

Implementation of a Permeable Membrane Insert-based Infection System to Study the Effects of Secreted Bacterial Toxins on Mammalian Host Cells

Published on: August 19, 2016

A Fluorogenic Peptide Cleavage Assay to Screen for Proteolytic Activity: Applications for coronavirus spike protein activation07:53

A Fluorogenic Peptide Cleavage Assay to Screen for Proteolytic Activity: Applications for coronavirus spike protein activation

Published on: January 9, 2019

Related Concept Videos

The Proteasome02:18

The Proteasome

Eukaryotic cells can degrade proteins through several pathways. One of the most important amongst these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
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.
The Proteasome01:13

The Proteasome

Eukaryotic cells can degrade proteins through several pathways. One of the most important among these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. This involves participation of a series of enzymes including— E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3 (ubiquitin...
The Proteasome Structure01:17

The Proteasome Structure

The ubiquitin-proteasome pathway is a well-known mechanism utilized by eukaryotic cells to remove cytoplasmic proteins that are misfolded, damaged, or no longer needed. In this pathway, the protein that needs to be eliminated undergoes a process called ubiquitination, where a chain of ubiquitin molecules is attached to the 48th lysine residue of the target protein. This ubiquitin modification helps the proteasome distinguish between a target protein and a healthy protein.
The proteasome is an...
Bacterial Toxins01:12

Bacterial Toxins

Bacterial toxins are sophisticated virulence factors that enable pathogenic bacteria to interact with, invade, and damage host tissues. These toxins fall broadly into two types: protein exotoxins, which are secreted into the environment and target specific host receptors, and lipopolysaccharide endotoxins, which are structural components of the bacterial outer membrane released primarily during bacterial lysis or membrane shedding. Exotoxins generally act more selectively, binding to cell...
Determinants of Bacterial Pathogenicity and Virulence01:20

Determinants of Bacterial Pathogenicity and Virulence

Pathogenic bacteria employ a variety of strategies to establish infections, including the secretion of extracellular enzymes that act as potent virulence factors. These enzymes facilitate bacterial colonization of host tissues and help evade immune surveillance. By targeting structural components of host tissues and interfering with immune mechanisms, these enzymes play a pivotal role in disease progression.Extracellular Enzymes Facilitating Tissue Invasion: Several bacterial pathogens secrete...