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Calpain-Mediated Processing of Adenylate Cyclase Toxin Generates a Cytosolic Soluble Catalytically Active N-Terminal

Kepa B Uribe1, Aitor Etxebarria, César Martín

  • 1Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica, Universidad del País Vasco UPV/EHU, Bilbao, Spain.

Plos One
|July 11, 2013
PubMed

Insights

Bordetella pertussis adenylate cyclase toxin (ACT) is processed by host calpain, a protease, within phagocytes. This cleavage releases a soluble AC domain, enabling targeted cAMP production and enhancing virulence.

Area of Science:

  • Microbiology
  • Cell Biology
  • Immunology

Background:

  • Bordetella pertussis causes whooping cough and uses virulence factors like adenylate cyclase toxin (ACT).
  • ACT is crucial for disease establishment by suppressing phagocytic cell functions.
  • Previously, ACT intoxication was thought to solely involve cAMP accumulation beneath the plasma membrane.

Purpose of the Study:

  • To investigate the precise mechanism of ACT-mediated host cell intoxication.
  • To identify host factors involved in ACT processing and its functional consequences.
  • To elucidate how ACT achieves specific targeting within host cells.

Main Methods:

  • Analysis of toxin-host cell interactions.
  • Detection of calcium influx and calpain activation.
  • Proteolytic cleavage assays and identification of processed toxin fragments.
  • Subcellular localization studies of the active toxin domain.

Main Results:

  • Toxin-triggered calcium rise activates host calpain within phagocytes.
  • Calpain proteolytically cleaves ACT, releasing a catalytically active soluble adenylate cyclase (AC) domain.
  • The soluble AC domain is trafficked to subcellular organelles.
  • This processing enhances toxin specificity and prevents widespread cAMP activation.

Conclusions:

  • Host calpain-mediated processing of ACT is a novel mechanism of bacterial virulence.
  • ACT generates distinct cAMP pools in specific subcellular locations, modulating host cell pathophysiology.
  • This finding offers new insights into the sophisticated strategies employed by B. pertussis to evade host defenses.

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